[GitHub] [pulsar] wolfstudy commented on a change in pull request #4725: [docs] Add functions-develop file for Pulsar Functions(new)

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wolfstudy commented on a change in pull request #4725: [docs] Add functions-develop file for Pulsar Functions(new)
URL: https://github.com/apache/pulsar/pull/4725#discussion_r304211821
 
 

 ##########
 File path: site2/docs/functions-develop.md
 ##########
 @@ -0,0 +1,570 @@
+---
+id: functions-develop
+title: Develop Pulsar Functions
+sidebar_label: Develop functions
+---
+
+This tutorial walks you through how to develop Pulsar Functions.
+
+## Available APIs
+In Java, Python, and Go, you have two options to write Pulsar Functions.
+
+Interface | Description | Use cases
+:---------|:------------|:---------
+Language-native interface | No Pulsar-specific libraries or special dependencies required (only core libraries from Java/Python/Go). | Functions that do not require access to the function [context](#context).
+Pulsar Function SDK for Java/Python/Go | Pulsar-specific libraries that provide a range of functionality not provided by "native" interfaces. | Functions that require access to the function [context](#context).
+
+<!--DOCUSAURUS_CODE_TABS-->
+<!--Java-->
+<!--Python-->
+In Python, the language-native function, which adds an exclamation point to all incoming strings and publishes the resulting string to a topic, has no external dependencies.
+
+```python
+def process(input):
+    return "{}!".format(input)
+```
+
+However, the function uses Pulsar Functions [SDK for Python](#python-sdk-functions):
+
+```python
+from pulsar import Function
+
+class DisplayFunctionName(Function):
+    def process(self, input, context):
+        function_name = context.function_name()
+        return "The function processing this message has the name {0}".format(function_name)
+```
+<!--Go-->
+The following example uses Pulsar Functions SDK.
+
+```
+import (
 
 Review comment:
   Sorry, Go Function does not support schema-related functions, so now Go Function's input and output can only be `[]byte`. 
   
   Here, this [code example](https://github.com/apache/pulsar/blob/master/pulsar-function-go/examples/inputFunc.go#L20-L36) might be more appropriate:
   ```
   package main
   
   import (
   	"context"
   	"fmt"
   
   	"github.com/apache/pulsar/pulsar-function-go/pf"
   )
   
   func HandleRequest(ctx context.Context, in []byte) error{
   	fmt.Println(string(in) + "!")
   	return nil
   }
   
   func main() {
   	pf.Start(HandleRequest)
   }
   ```

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