[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



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File path: site2/docs/window-functions-context.md
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@@ -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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