doc-exports/docs/fg/umn/functiongraph_01_0390_03.html

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 SMN
   Failure Notification	Target Service: to which a notification will be sent if a function fails to be executed. FunctionGraph OBS SMN

5. Click OK.
   

   1. Set an agency that allows FunctionGraph to access the target service.
   2. 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!"
}

Table 2 Parameter description

Parameter	Description
timestamp	Time when the invocation starts.
request_context	Request context.
request_context.request_id	ID of an asynchronous invocation request.
request_context. function_urn	URN of the function that is to be executed asynchronously.
request_context.condition	Invocation error type.
request_context. approximate_invoke_count	Number of asynchronous invocation times. If the value is greater than 1, function execution has been retried.
request_payload	Original request payload.
response_context	Response context.
response_context.statusCode	Code returned after function invocation. If the code is not 200, a system error occurred.
response_context.function_error	Invocation error information.
response_payload	Payload returned after function execution.

Parent topic: Configuring Functions