Configure an Alibaba Cloud service trigger

How it works

When you create a trigger on the Function Compute console, Function Compute automatically creates an event rule named FunctionName-TriggerName on the default event bus in EventBridge. After the trigger is created, you can view its information in the Function Compute console and view the automatically created event rule on the EventBridge console. When an event of a specified type from the event source is delivered to the event bus, the function associated with the trigger is invoked.

Usage notes

• You can create a maximum of 10 event rules on the default event bus in EventBridge. If this limit is reached, you cannot create more triggers for Alibaba Cloud services.

• You cannot use Serverless Devs to create triggers for Alibaba Cloud services.

Prerequisites

• EventBridge: Activate EventBridge and grant permissions

• Function Compute: Create a function

Step 1: Create a trigger

1. Log on to the Function Compute console. In the left-side navigation pane, click Functions.

2. In the top navigation bar, select a region. On the Functions page, click the function that you want to manage.

3. On the Function Details page, click the Configurations tab. In the left-side navigation pane, click Triggers. Then, click Create Trigger.

4. In the Create Trigger panel, configure the parameters and click OK.

   Parameter	Actions	Example
   Trigger Type	Select ECS.	ECS
   Name	Enter a custom name for the trigger.	ecs-trigger
   Version or Alias	The default value is LATEST. To create a trigger for a different version or alias, first switch to it in the upper-right corner of the function details page. For more information, see Manage versions and Manage aliases.	LATEST
   Event Type	Select Custom Event Types or Select All Event Types. If you select Custom Event Types, you can select one or more event types for ECS.	Disk Retained
   Event Pattern Content	This parameter is read-only. The content is automatically populated after you select an event type. For more information about event patterns, see Event patterns.	{ "source": [ "acs.ecs" ], "type": [ "ecs:Disk:ConvertToPostpaidCompleted" ] }
   Invocation Method	Select the function invocation method. Valid values: Sync Invocation: This is the default method. After an event triggers a function invocation, Function Compute waits for the invocation to complete and then returns the result. For more information, see synchronous invocation. Async Invocation: This method is suitable for functions with long latencies. After an event triggers a function invocation, Function Compute immediately returns a response and ensures that the function executes successfully at least once but does not return the execution result. For more information, see asynchronous invocation.	Synchronous Invocation
   Trigger State	Specifies if the trigger is enabled upon creation. By default, Enable Trigger is selected.	Enable Trigger

   After the trigger is created, it is displayed on the Triggers tab. To modify or delete a trigger, see Trigger Management.

Step 2: Configure the input parameter

The function receives ECS events as the event input parameter. You can manually pass a sample event to the function to simulate a trigger.

1. On the Code tab of the function details page, click the icon next Test Function and select Configure Test Parameters from the drop-down list.

2. In the Configure Test Parameters panel, select Create New Test Event or Modify Existing Test Event, enter an event name and the event content, and click OK.

   The following code shows the format of the event parameter. For the event content of all official event sources, see Alibaba Cloud official event sources.

   {
       "datacontenttype": "application/json;charset=utf-8",
       "aliyunaccountid": "123456789098****",
       "data": {
           "result": "accomplished",
           "diskId": "d-bp11ba7acc69nkta****"
       },
       "subject": "acs:ecs:cn-hangzhou:123456789098****:disk/d-bp11ba7acc69nkta****",
       "source": "acs.ecs",
       "type": "ecs:Disk:ConvertToPostpaidCompleted",
       "aliyunpublishtime": "2021-01-18T03:58:31.762Z",
       "specversion": "1.0",
       "aliyuneventbusname": "default",
       "id": "70c0414c-b260-4923-b584-1d6e5646****",
       "time": "2021-01-18T11:58:31.125+08:00",
       "aliyunregionid": "cn-hangzhou",
       "aliyunpublishaddr": "172.25.XX.XX"
   }

   The following table describes the parameters in the event payload.

   Parameter	Type	Example	Description
   datacontenttype	String	application/json;charset=utf-8	Specifies the content format of the data parameter. The datacontenttype parameter supports only the application/json format.
   aliyunaccountid	String	123456789098****	The Alibaba Cloud account ID.
   data	Struct	{ "result": "accomplished", "diskId": "d-bp11ba7acc69nkta****" }	The event content. It is a JSON object whose content is determined by the service that initiated the event. CloudEvents may contain context from the event producer, which is encapsulated in the data field.
   subject	String	acs:ecs:cn-hangzhou:123456789098****:disk/d-bp11ba7acc69nkta****	The subject of the event.
   source	String	acs.ecs	The event source.
   type	String	ecs:Disk:ConvertToPostpaidCompleted	The type of the event.
   aliyunpublishtime	Timestamp	2021-01-18T03:58:31.762Z	The time when the event was received.
   specversion	String	1.0	The version of the CloudEvents specification.
   aliyuneventbusname	String	default	The name of the event bus that received the event.
   id	String	70c0414c-b260-4923-b584-1d6e5646****	The event ID.
   time	Timestamp	2021-01-18T11:58:31.125+08:00	The time when the event occurred.
   aliyunregionid	String	cn-hangzhou	The region where the event was received.
   aliyunpublishaddr	String	172.25.XX.XX	The IP address of the server that received the event.

Step 3: Write and test code

After creating the ECS trigger, you can write and test the function code to verify that it works as expected. In a real-world scenario, when an event from ECS is delivered to Function Compute through EventBridge, the trigger automatically invokes the function.

1. On the function details page, on the Code tab, write your code in the code editor and click Deploy.

   This topic uses Node.js code as an example.

   'use strict';
   /*
   To enable the initializer feature
   please implement the initializer function as below:
   exports.initializer = (context, callback) => {
     console.log('initializing');
     callback(null, '');
   };
   */
   exports.handler = (event, context, callback) => {
     console.log("event: %s", event);
     // Parse the event parameters and process the event. 
     callback(null, 'return result');
   }

2. Click Test Function.

More information

To modify or delete an existing trigger, see Manage triggers.