Configuring Asynchronous Notification Policy

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 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: 1–86400.
   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!"
}