Function Compute:Simple Message Queue (formerly MNS) queue triggers

Overview

Usage notes

• The Simple Message Queue (formerly MNS) queue that is used as the trigger source must reside in the same region as the Function Compute function.

• If the number of created event streams exceeds the upper limit, you can no longer create Simple Message Queue (formerly MNS) queue triggers.

For information about the limits on resources related to triggers in one region for each Alibaba Cloud account, see Limits.

Before you start

• EventBridge

  • Activate EventBridge and grant permissions to a RAM user

• Function Compute

  • Create an event function

• Simple Message Queue (formerly MNS)

  • Activate SMQ and authorize RAM users to access SMQ

  • Create a queue

Step 1: Create a trigger

After you create an Simple Message Queue (formerly MNS) queue, log on to the Function Compute console, click the desired function to go to the function details page, and then click the Configurations tab. Click Create Trigger on the Triggers page. Create a trigger and click OK. The following figure shows the details.

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

Step 2: (Optional) Configure input parameters

An Simple Message Queue (formerly MNS) source event is passed to the function as an input parameter in the form of event. You can use code to parse and process event. You can manually pass event to the function to simulate a trigger event to test whether the function code is correct.

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, click the Create New Test Event or Modify Existing Test Event tab, enter the event name and event content, and then click OK.

   Sample code of event:

   [
       {
       "id":"c2g71017-6f65-fhcf-a814-a396fc8d****",
       "source":"MNS-Function-mnstrigger",
       "specversion":"1.0",
       "type":"mns:Queue:SendMessage",
       "datacontenttype":"application/json; charset=utf-8",
       "subject":"acs:mns:cn-hangzhou:164901546557****:queues/zeus",
       "time":"2021-04-08T06:28:17.093Z",
       "aliyunaccountid":"164901546557****",
       "aliyunpublishtime":"2021-10-15T07:06:34.028Z",
       "aliyunoriginalaccountid":"164901546557****",
       "aliyuneventbusname":"MNS-Function-mnstrigger",
       "aliyunregionid":"cn-chengdu",
       "aliyunpublishaddr":"42.120.XX.XX",
       "data":{
           "requestId":"606EA3074344430D4C81****",
           "messageId":"C6DB60D1574661357FA227277445****",
           "messageBody":"TEST"
       }
       },
       {
       "id":"d2g71017-6f65-fhcf-a814-a396fc8d****",
       "source":"MNS-Function-mnstrigger",
       "specversion":"1.0",
       "type":"mns:Queue:SendMessage",
       "datacontenttype":"application/json; charset=utf-8",
       "subject":"acs:mns:cn-hangzhou:164901546557****:queues/zeus",
       "time":"2021-04-08T06:28:17.093Z",
       "aliyunaccountid":"164901546557****",
       "aliyunpublishtime":"2021-10-15T07:06:34.028Z",
       "aliyunoriginalaccountid":"164901546557****",
       "aliyuneventbusname":"MNS-Function-mnstrigger",
       "aliyunregionid":"cn-chengdu",
       "aliyunpublishaddr":"42.120.XX.XX",
       "data":{
           "requestId":"606EA3074344430D4C81****",
           "messageId":"C6DB60D1574661357FA227277445****",
           "messageBody":"TEST"
       }
       }
   ]

   The following table describes the parameters contained in data. For information about parameters that are defined in the CloudEvents specification, see Overview.

   Parameter	Type	Example	Description
   requestId	String	606EA3074344430D4C81****	The ID of the request. The ID of each request is unique.
   messageId	String	C6DB60D1574661357FA227277445****	The ID of the message. The ID of each message is unique.
   messageBody	String	TEST	The content of the message.

Step 3: Write function code and test the function

After you create the trigger, you can write function code and test the function to verify whether the code is correct. When events that are generated by Simple Message Queue (formerly MNS) are delivered to Function Compute by using EventBridge, the trigger automatically triggers the function.

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

   The following sample code provides an example of function code 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 and process event. 
     callback(null, 'return result');
   }

2. Test the function.

   Method 1: If you configure event to simulate an event source, click Test Function.

   Method 2: Log on to the Simple Message Queue (formerly MNS) console, select the queue that you created, and then click Send Message. The following figure shows an example.

   

3. After the execution is complete, view the result in Real-time Logs.

   

More information

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