Function Compute:Configure event triggers for Alibaba Cloud services

How it works

When you create an event trigger in the Function Compute console, Function Compute automatically creates a corresponding event rule on the default event bus in EventBridge. The rule is named {FunctionName}-{TriggerName}. When an event matching the rule is delivered to the event bus, the associated function is invoked.

Limits

• The default event bus supports a maximum of 10 event rules for Alibaba Cloud service event sources. Reaching this limit prevents you from creating additional event triggers for Alibaba Cloud services.

• Serverless Devs cannot be used to create event triggers for Alibaba Cloud services.

Prerequisites

Before you begin, make sure you have:

• Activated EventBridge and granted the required permissions. See Activate EventBridge and grant permissions.

• Created a function in Function Compute. See 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 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 following parameters and click OK.

After the trigger is created, it appears on the Triggers tab. To modify or delete it, see Manage triggers.

Step 2: Configure test parameters

ECS events are delivered to your function as the event input parameter. Before a real event fires, configure a test event to verify that your function handles the payload correctly.

1. On the Code tab of the function details page, click the icon next to 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 Edit existing test event, enter a name and the event content, then click OK.

The following is the structure of an ECS event payload:

{
    "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 event follows the CloudEvents specification. The top-level fields such as source, type, id, and time are consistent across all Alibaba Cloud service event sources. The data field is event-specific — its content is determined by the service that generates the event. When writing your function handler, focus on parsing the data field for business logic; the other fields can be used for routing or logging.

For event payloads from all supported Alibaba Cloud service sources, see Alibaba Cloud service event sources.

Step 3: Write and test the function code

After creating the trigger, write the function handler to process incoming events. Parse the data field for event-specific information; the other top-level fields are consistent across event types.

1. On the function details page, click the Code tab. Write the function code in the editor, then click Deploy code. The following example shows how to handle an ECS event in Node.js.

   '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 to run the function with the test event configured in Step 2.

What's next

• To modify or delete the trigger, see Manage triggers.