[GitHub] [pulsar] wolfstudy opened a new pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

wolfstudy opened a new pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741


   Signed-off-by: xiaolong.ran <rx...@apache.org>
   
   ### Modifications
   
   - Add window function context docs for repo


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[GitHub] [pulsar] Jennifer88huang commented on a change in pull request #7741: [Issue 5520][Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465425569



##########
File path: site2/website/versioned_docs/version-2.3.0/window-functions-context.md
##########
@@ -0,0 +1,528 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---

Review comment:
       please check all similar cases.

##########
File path: site2/website/versioned_docs/version-2.3.0/window-functions-context.md
##########
@@ -0,0 +1,528 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---

Review comment:
       ```suggestion
   ---
   id: version-2.3.0-window-functions-context
   title: Window Functions Context
   sidebar_label: "Window Functions: Context"
   original_id: window-functions-context
   ---
   ```




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[GitHub] [pulsar] Jennifer88huang commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465089393



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.

Review comment:
       How about refine it as follows?
   Routing is supported in Pulsar window functions. Pulsar window functions send messages to arbitrary topics as per the publish interface.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464977825



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->

Review comment:
       Same here.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464958876



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->

Review comment:
       Delete lines 48-49. When support and examples in other languages are available, we'll have them back.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464993659



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+When you want to publish as many results as you want, you can use the `context.publish()` interface.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.
+
+StreamNative Platform integrates with Apache BookKeeper `table service` to store the `state` for functions. For example, the `WordCount` function can store its `counters` state into BookKeeper table service via Pulsar Functions state APIs.
+
+States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar Function and shared between instances of that function.
+
+Currently, Pulsar window functions expose Java API to access, update, and manage states. These APIs are available in the context object when you use Java SDK functions.
+
+| Java API| Description
+|---|---
+|`incrCounter`|Increases a built-in distributed counter referred by key.
+|`getCounter`|Gets the counter value for the key.
+|`putState`|Updates the state value for the key.
+
+You can use the following APIs to access, update, and manage states in Java window functions. 
+
+#### incrCounter
+
+`incrCounter` API increases a built-in distributed counter referred by key.
+
+Applications uses the `incrCounter` API to change the counter of a given `key` by the given `amount`. If the `key` does not exist, a new key is created.

Review comment:
       ```suggestion
   Applications use the `incrCounter` API to change the counter of a given `key` by the given `amount`. If the `key` does not exist, a new key is created.
   ```




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[GitHub] [pulsar] wolfstudy commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

wolfstudy commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465053309



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+When you want to publish as many results as you want, you can use the `context.publish()` interface.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.
+
+StreamNative Platform integrates with Apache BookKeeper `table service` to store the `state` for functions. For example, the `WordCount` function can store its `counters` state into BookKeeper table service via Pulsar Functions state APIs.
+
+States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar Function and shared between instances of that function.

Review comment:
       Maybe we should use `Pulsar Function` in here




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[GitHub] [pulsar] Jennifer88huang commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465053865



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example

Review comment:
       which example?

##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,532 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+The `getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+
+### Get output topic
+
+The `getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+
+### Get tenant
+
+The `getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+
+### Get namespace
+
+The `getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+
+### Get function name
+
+The `getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+
+### Get function ID
+
+The `getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+
+### Get function version
+
+The `getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+
+### Get instance ID
+
+The `getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+
+### Get num instances
+
+The `getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+
+### Get output schema type
+
+The `getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+
+## User config
+
+When you run or update Pulsar Functions that are created using SDK, you can pass arbitrary key/value pairs to them with the `--user-config` flag. Key/value pairs **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+The `getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+The `getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+The `UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+You can use the `context.publish()` interface to publish as many results as you want.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.
+
+StreamNative Platform integrates with Apache BookKeeper `table service` to store the `state` for functions. For example, the `WordCount` function can store its `counters` state into BookKeeper table service via Pulsar Functions state APIs.
+
+States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar Function and shared between instances of that function.
+
+Currently, Pulsar window functions expose Java API to access, update, and manage states. These APIs are available in the context object when you use Java SDK functions.
+
+| Java API| Description
+|---|---
+|`incrCounter`|Increases a built-in distributed counter referred by key.
+|`getCounter`|Gets the counter value for the key.
+|`putState`|Updates the state value for the key.
+
+You can use the following APIs to access, update, and manage states in Java window functions. 
+
+#### incrCounter
+
+The `incrCounter` API increases a built-in distributed counter referred by key.
+
+Applications use the `incrCounter` API to change the counter of a given `key` by the given `amount`. If the `key` does not exist, a new key is created.
+
+```java
+    /**
+     * Increment the builtin distributed counter referred by key
+     * @param key The name of the key
+     * @param amount The amount to be incremented
+     */
+    void incrCounter(String key, long amount);
+```
+
+#### getCounter
+
+The `getCounter` API gets the counter value for the key.
+
+Applications can use the `getCounter` API to retrieve the counter of a given `key` changed by the `incrCounter` API.

Review comment:
       ```suggestion
   Applications uses the `getCounter` API to retrieve the counter of a given `key` changed by the `incrCounter` API.
   ```

##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,532 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+The `getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+
+### Get output topic
+
+The `getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+
+### Get tenant
+
+The `getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+
+### Get namespace
+
+The `getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+
+### Get function name
+
+The `getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+
+### Get function ID
+
+The `getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+
+### Get function version
+
+The `getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+
+### Get instance ID
+
+The `getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+
+### Get num instances
+
+The `getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+
+### Get output schema type
+
+The `getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+
+## User config
+
+When you run or update Pulsar Functions that are created using SDK, you can pass arbitrary key/value pairs to them with the `--user-config` flag. Key/value pairs **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+The `getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+The `getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+The `UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+You can use the `context.publish()` interface to publish as many results as you want.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.
+
+StreamNative Platform integrates with Apache BookKeeper `table service` to store the `state` for functions. For example, the `WordCount` function can store its `counters` state into BookKeeper table service via Pulsar Functions state APIs.
+
+States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar Function and shared between instances of that function.
+
+Currently, Pulsar window functions expose Java API to access, update, and manage states. These APIs are available in the context object when you use Java SDK functions.
+
+| Java API| Description
+|---|---
+|`incrCounter`|Increases a built-in distributed counter referred by key.
+|`getCounter`|Gets the counter value for the key.
+|`putState`|Updates the state value for the key.
+
+You can use the following APIs to access, update, and manage states in Java window functions. 
+
+#### incrCounter
+
+The `incrCounter` API increases a built-in distributed counter referred by key.
+
+Applications use the `incrCounter` API to change the counter of a given `key` by the given `amount`. If the `key` does not exist, a new key is created.
+
+```java
+    /**
+     * Increment the builtin distributed counter referred by key
+     * @param key The name of the key
+     * @param amount The amount to be incremented
+     */
+    void incrCounter(String key, long amount);
+```
+
+#### getCounter
+
+The `getCounter` API gets the counter value for the key.
+
+Applications can use the `getCounter` API to retrieve the counter of a given `key` changed by the `incrCounter` API.
+
+```java
+    /**
+     * Retrieve the counter value for the key.
+     *
+     * @param key name of the key
+     * @return the amount of the counter value for this key
+     */
+    long getCounter(String key);
+```
+
+Except the `getCounter` API, Pulsar also exposes a general key/value API (`putState`) for functions to store general key/value state.
+
+#### putState
+
+The `putState` API updates the state value for the key.
+
+```java
+    /**
+     * Update the state value for the key.
+     *
+     * @param key name of the key
+     * @param value state value of the key
+     */
+    void putState(String key, ByteBuffer value);
+```
+
+### Example

Review comment:
       Where does this example belongs to?

##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+When you want to publish as many results as you want, you can use the `context.publish()` interface.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.

Review comment:
       please do not include "streamnative platform" related info in this PR. 
   Same comments for the following cases.

##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.

Review comment:
       What does this sentence mean?




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464979810



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.

Review comment:
       Maybe we can add a "The" at the beginning of this sentence. If you think this is better, then you can change all in this file.




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[GitHub] [pulsar] wolfstudy commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

wolfstudy commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465060778



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example

Review comment:
       Maybe we can delete `Example`?




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[GitHub] [pulsar] Jennifer88huang commented on pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668654550


   @wolfstudy thank you very much for contributing to the content. Could you please add Fixes #5520 in the description? And refine the PR title accordingly?
   Concerning line 28, I've left comments, please check, any issue feel free to contact me.


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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464992695



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+When you want to publish as many results as you want, you can use the `context.publish()` interface.
+
+This example shows that the `PublishFunction` class uses the built-in function in the context to publish messages to the `publishTopic` in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class PublishWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        String publishTopic = (String) context.getUserConfigValueOrDefault("publish-topic", "publishtopic");
+        String output = String.format("%s!", input);
+        context.publish(publishTopic, output);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## State storage
+
+Pulsar window functions use [Apache BookKeeper](https://bookkeeper.apache.org) as a state storage interface. StreamNative Platform installation (including the standalone installation) includes the deployment of BookKeeper bookies.
+
+StreamNative Platform integrates with Apache BookKeeper `table service` to store the `state` for functions. For example, the `WordCount` function can store its `counters` state into BookKeeper table service via Pulsar Functions state APIs.
+
+States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar Function and shared between instances of that function.

Review comment:
       ```suggestion
   States are key-value pairs, where the key is a string and the value is arbitrary binary data—counters are stored as 64-bit big-endian binary values. Keys are scoped to an individual Pulsar function and shared between instances of that function.
   ```




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464977153



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->

Review comment:
       Same here.




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[GitHub] [pulsar] wolfstudy merged pull request #7741: [Issue 5520][Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

wolfstudy merged pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741


   


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[GitHub] [pulsar] sijia-w commented on pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668551469


   @wolfstudy Left my comments, PTAL. Please keep the number and the first letter in "Pulsar Functions", "a function", etc. consistent.


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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464991494



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.

Review comment:
       Seems one sentence in two lines here.




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[GitHub] [pulsar] Jennifer88huang commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465089393



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.

Review comment:
       How about refine it as follows?
   Routing is supported in Pulsar Functions. Pulsar Functions send messages to arbitrary topics as per the publish interface.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464958876



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->

Review comment:
       Delete lines 48-49 & 63. When support and examples in other languages are available, we'll have them back.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464989312



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 

Review comment:
       ```suggestion
   When you run or update Pulsar Functions that are created using SDK, you can pass arbitrary key/value pairs to them with the `--user-config` flag. Key/value pairs **must** be specified as JSON. 
   ```




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[GitHub] [pulsar] sijia-w commented on pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668551872


   @Jennifer88huang  Left my comments. Your feedback is appreciated. Thanks.


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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464989312



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 

Review comment:
       ```suggestion
   When you run or update Pulsar Functions that are created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
   ```




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464976730



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->

Review comment:
       Same here. Lines 71-71 & 85.




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[GitHub] [pulsar] Jennifer88huang commented on pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

Jennifer88huang commented on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668920958


   Great job @wolfstudy. I checked the #5520, the feature was added since v2.3.0. So we need to apply the updates since v2.3.0. 


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[GitHub] [pulsar] wolfstudy commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

wolfstudy commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r465049852



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.

Review comment:
       OK will add it.




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[GitHub] [pulsar] sijia-w commented on a change in pull request #7741: [Function Doc] Add window function context docs for repo

[GitBox <gi...@apache.org>]

sijia-w commented on a change in pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#discussion_r464991958



##########
File path: site2/docs/window-functions-context.md
##########
@@ -0,0 +1,593 @@
+---
+id: window-functions-context
+title: Window Functions Context
+sidebar_label: "Window Functions: Context"
+---
+
+Java SDK provides access to a **window context object** that can be used by a window function. This context object provides a wide variety of information and functionality for Pulsar window functions as below.
+
+- [Spec](#spec)
+
+  * Names of all input topics and the output topic associated with the function.
+  * Tenant and namespace associated with the function.
+  * Pulsar window function name, ID, and version.
+  * ID of the Pulsar function instance running the window function.
+  * Number of instances that invoke the window function.
+  * Built-in type or custom class name of the output schema.
+  
+- [Logger](#logger)
+  
+  * Logger object used by the window function, which can be used to create window function log messages.
+
+- [User config](#user-config)
+  
+  * Access to arbitrary user configuration values.
+
+- [Routing](#routing)
+  
+  * Function to publish new messages to arbitrary topics.
+
+- [Metrics](#metrics)
+  
+  * Interface for recording metrics.
+
+- [State storage](#state-storage)
+  
+  * Interface for storing and retrieving state in [state storage](#state-storage).
+
+## Spec
+
+Spec contains the basic information of a function.
+
+### Get input topics
+
+`getInputTopics` method gets the **name list** of all input topics.
+
+This example demonstrates how to get the name list of all input topics in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInputTopicsWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Collection<String> inputTopics = context.getInputTopics();
+        System.out.println(inputTopics);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output topic
+
+`getOutputTopic` method gets the **name of a topic** to which the message is sent.
+
+This example demonstrates how to get the name of an output topic in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputTopicWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String outputTopic = context.getOutputTopic();
+        System.out.println(outputTopic);
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get tenant
+
+`getTenant` method gets the tenant name associated with the window function.
+
+This example demonstrates how to get the tenant name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetTenantWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String tenant = context.getTenant();
+        System.out.println(tenant);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get namespace
+
+`getNamespace` method gets the namespace associated with the window function.
+
+This example demonstrates how to get the namespace in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNamespaceWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String ns = context.getNamespace();
+        System.out.println(ns);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function name
+
+`getFunctionName` method gets the window function name.
+
+This example demonstrates how to get the function name in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNameOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionName = context.getFunctionName();
+        System.out.println(functionName);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function ID
+
+`getFunctionId` method gets the window function ID.
+
+This example demonstrates how to get the function ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetFunctionIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionID = context.getFunctionId();
+        System.out.println(functionID);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get function version
+
+`getFunctionVersion` method gets the window function version.
+
+This example demonstrates how to get the function version of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetVersionOfWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String functionVersion = context.getFunctionVersion();
+        System.out.println(functionVersion);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get instance ID
+
+`getInstanceId` method gets the instance ID of a window function.
+
+This example demonstrates how to get the instance ID in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetInstanceIDWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int instanceId = context.getInstanceId();
+        System.out.println(instanceId);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get num instances
+
+`getNumInstances` method gets the number of instances that invoke the window function.
+
+This example demonstrates how to get the number of instances in a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetNumInstancesWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        int numInstances = context.getNumInstances();
+        System.out.println(numInstances);
+
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+### Get output schema type
+
+`getOutputSchemaType` method gets the built-in type or custom class name of the output schema.
+
+This example demonstrates how to get the output schema type of a Java window function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+public class GetOutputSchemaTypeWindowFunction implements WindowFunction<String, Void> {
+
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        String schemaType = context.getOutputSchemaType();
+        System.out.println(schemaType);
+
+        return null;
+    }
+}
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Logger
+
+Pulsar window functions using Java SDK has access to an [SLF4j](https://www.slf4j.org/) [`Logger`](https://www.slf4j.org/api/org/apache/log4j/Logger.html) object that can be used to produce logs at the chosen log level.
+
+This example logs either a `WARNING`-level or `INFO`-level log based on whether the incoming string contains the word `danger` or not in a Java function.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+import org.slf4j.Logger;
+
+public class LoggingWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+        Logger log = context.getLogger();
+        for (Record<String> record : inputs) {
+            log.info(record + "-window-log");
+        }
+        return null;
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If you need your function to produce logs, specify a log topic when creating or running the function. 
+
+```bash
+bin/pulsar-admin functions create \
+  --jar my-functions.jar \
+  --classname my.package.LoggingFunction \
+  --log-topic persistent://public/default/logging-function-logs \
+  # Other function configs
+```
+
+You can access all logs produced by `LoggingFunction` via the `persistent://public/default/logging-function-logs` topic.
+
+## Metrics
+
+Pulsar window functions can publish arbitrary metrics to the metrics interface which can be queried. 
+
+> **Note**
+>
+> If a Pulsar window function uses the language-native interface for Java, that function is not able to publish metrics and stats to Pulsar.
+
+You can record metrics using the context object on a per-key basis. 
+
+This example sets a metric for the `process-count` key and a different metric for the `elevens-count` key every time the function processes a message in a Java function. 
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import java.util.Collection;
+import org.apache.pulsar.functions.api.Record;
+import org.apache.pulsar.functions.api.WindowContext;
+import org.apache.pulsar.functions.api.WindowFunction;
+
+
+/**
+ * Example function that wants to keep track of
+ * the event time of each message sent.
+ */
+public class UserMetricWindowFunction implements WindowFunction<String, Void> {
+    @Override
+    public Void process(Collection<Record<String>> inputs, WindowContext context) throws Exception {
+
+        for (Record<String> record : inputs) {
+            if (record.getEventTime().isPresent()) {
+                context.recordMetric("MessageEventTime", record.getEventTime().get().doubleValue());
+            }
+        }
+
+        return null;
+    }
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## User config
+
+When you run or update Pulsar Functions created using SDK, you can pass arbitrary key/values to them with the `--user-config` flag. Key/values **must** be specified as JSON. 
+
+This example passes a user configured key/value to a function.
+
+```bash
+bin/pulsar-admin functions create \
+  --name word-filter \
+ --user-config '{"forbidden-word":"rosebud"}' \
+  # Other function configs
+```
+
+### API
+You can use the following APIs to get user-defined information for window functions.
+#### getUserConfigMap
+
+`getUserConfigMap` API gets a map of all user-defined key/value configurations for the window function.
+
+
+```java
+/**
+     * Get a map of all user-defined key/value configs for the function.
+     *
+     * @return The full map of user-defined config values
+     */
+    Map<String, Object> getUserConfigMap();
+```
+
+
+#### getUserConfigValue
+
+`getUserConfigValue` API gets a user-defined key/value.
+
+```java
+/**
+     * Get any user-defined key/value.
+     *
+     * @param key The key
+     * @return The Optional value specified by the user for that key.
+     */
+    Optional<Object> getUserConfigValue(String key);
+```
+
+#### getUserConfigValueOrDefault
+
+`getUserConfigValueOrDefault` API gets a user-defined key/value or a default value if none is present.
+
+```java
+/**
+     * Get any user-defined key/value or a default value if none is present.
+     *
+     * @param key
+     * @param defaultValue
+     * @return Either the user config value associated with a given key or a supplied default value
+     */
+    Object getUserConfigValueOrDefault(String key, Object defaultValue);
+```
+
+### Example
+
+This example demonstrates how to access key/value pairs provided to Pulsar window functions.
+
+Java SDK context object enables you to access key/value pairs provided to Pulsar window functions via the command line (as JSON). 
+
+>**Tip**
+>
+> For all key/value pairs passed to Java window functions, both the `key` and the `value` are `String`. To set the value to be a different type, you need to deserialize it from the `String` type.
+
+This example passes a key/value pair in a Java window function.
+
+```bash
+bin/pulsar-admin functions create \
+   --user-config '{"word-of-the-day":"verdure"}' \
+  # Other function configs
+ ```
+
+This example accesses values in a Java window function.
+
+`UserConfigFunction` function logs the string `"The word of the day is verdure"` every time the function is invoked (which means every time a message arrives). The user config of `word-of-the-day` is changed **only** when the function is updated with a new config value via 
+multiple ways, such as the command line tool or REST API.
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+
+```java
+import org.apache.pulsar.functions.api.Context;
+import org.apache.pulsar.functions.api.Function;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+
+public class UserConfigWindowFunction implements WindowFunction<String, String> {
+    @Override
+    public String process(Collection<Record<String>> input, WindowContext context) throws Exception {
+        Optional<Object> whatToWrite = context.getUserConfigValue("WhatToWrite");
+        if (whatToWrite.get() != null) {
+            return (String)whatToWrite.get();
+        } else {
+            return "Not a nice way";
+        }
+    }
+
+}
+```
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+If no value is provided, you can access the entire user config map or set a default value.
+
+```java
+// Get the whole config map
+Map<String, String> allConfigs = context.getUserConfigMap();
+
+// Get value or resort to default
+String wotd = context.getUserConfigValueOrDefault("word-of-the-day", "perspicacious");
+```
+
+## Routing
+
+When you want to publish as many results as you want, you can use the `context.publish()` interface.

Review comment:
       ```suggestion
   You can use the `context.publish()` interface to publish as many results as you want.
   ```




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[GitHub] [pulsar] sijia-w removed a comment on pull request #7741: [Function Doc] Add window function context docs for repo

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sijia-w removed a comment on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668551872


   @Jennifer88huang  Left my comments. Your feedback is appreciated. Thanks.


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[GitHub] [pulsar] sijia-w edited a comment on pull request #7741: [Function Doc] Add window function context docs for repo

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sijia-w edited a comment on pull request #7741:
URL: https://github.com/apache/pulsar/pull/7741#issuecomment-668551469


   @wolfstudy Left my comments, PTAL. Please keep the number and the first letter in "Pulsar Functions", "a function", etc. consistent.
   @Jennifer88huang  Left my comments. Your feedback is appreciated. Thanks.


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