Configuring Asynchronous Execution Notification

Overview

Functions can be invoked synchronously or asynchronously. In asynchronous mode, FunctionGraph sends a response immediately after persisting a request. The request result cannot be known in real time. To retry when an asynchronous request fails or obtain asynchronous processing results, configure asynchronous settings.

Scenario

• Retry: By default, FunctionGraph does not retry if a function fails due to a code error. If your function needs retry, for example, if third-party services often fail to be invoked, configure retry to improve the success rate.
• Result notifications: FunctionGraph automatically notifies downstream services of the asynchronous execution result of a function for further processing. For example, storing execution failure information in OBS for cause analysis, or pushing execution success information to DIS or triggering the function again.

Procedure

1. Log in to the FunctionGraph console. In the navigation pane, choose Functions > Function List.
2. Click the function to be configured to go to the function details page.
3. Choose Configuration > Configure Async Notification. On the displayed page, click Edit next to Asynchronous Notification Policy.
   Figure 1 Configuring an asynchronous notification policy
   

4. Set parameters by referring to Table 1. For example, specify FunctionGraph for Target Service.
   Figure 2 Setting parameters
   

   Table 1 Parameter description

   Parameter	Description
   Asynchronous Execution Notification Policy	Max. Retries: maximum number of retries when asynchronous invocation fails. Value range: 0–3. Default value: 1. Max. Validity Period (s): maximum lifetime of a message in seconds. Value range: 1–86,400.
   Success Notification	Target Service: to which a notification will be sent if a function is executed successfully. FunctionGraph OBS DIS SMN
   Failure Notification	Target Service: to which a notification will be sent if a function fails to be executed. FunctionGraph OBS DIS SMN

5. Click OK.
   

   1. If a message indicating insufficient permissions is displayed when you configure asynchronous execution notification, add the FunctionGraph Administrator permission. For details, see Creating a User and Granting Permissions.
   2. Set an agency that allows FunctionGraph to access the target service.
   3. To avoid cyclic invocation, do not set two functions as asynchronous execution targets of each other.

Configuration Description

For details about how to set the target for asynchronous invocation, see Table 2. The following shows an example:

{
        "timestamp": "2020-08-20T12:00:00.000Z+08:00",
	"request_context": {
	        "request_id": "1167bf8c-87b0-43ab-8f5f-26b16c64f252",
	        "function_urn": "urn:fss:xx-xxxx-x:xxxxxxx:function:xxxx:xxxx:latest",
	        "condition": "",
	        "approximate_invoke_count": 0
	 },
	    "request_payload": "",
	    "response_context": {
	        "status_code": 200,
	        "function_error": ""
	  },
	 "response_payload": "hello world!"
}

Triggering the Function

The return value of a function in asynchronous mode cannot exceed 256 KB; otherwise, a null value is returned.

1. Create three functions test1, test2, and test3 based on Procedure. Configure the asynchronous policy for test1 as follows:
   • Success Notification
     • Target Service: Select FunctionGraph.
     • Function Name: Select test2.
     • Version/Alias: Retain the default value latest.
   • Failure Notification
     • Target Service: Select FunctionGraph.
     • Function Name: Select test3.
     • Version/Alias: Retain the default value latest.

2. Click the Code tab and configure a test event.

   Select Blank Template, copy the example code in Configuration Description to the code area, and click Create.

3. In the upper right corner of the FunctionGraph console, choose Tools > API Explorer. On the displayed API Explorer page, click FunctionGraph in the upper left corner.
4. In the API list on the left, choose Function Invocation > AsyncInvokeFunction. Set the parameters as follows:
   • Region: Choose the same region as in step 1.
   • function_urn: URN of the function. Enter the URN of test1.
   • Body: custom configuration. The format is string:JSON string, for example, aaa:123.

   Retain the default values for other parameters and click Debug.

   Figure 3 Parameters for AsyncInvokeFunction
   

Viewing the Asynchronous Execution Result of the Function

1. Return to the FunctionGraph console. In the navigation pane, choose Functions > Function List.
2. If the function test1 is successfully debugged in Triggering the Function, click the name of function test2 to go to the details page. If the debugging fails, click the name of function test3 to go to the details page.
3. Choose Monitoring > Logs to query running logs of function test2 or test3.