After the ApsaraMQ for RabbitMQ event source is integrated with Function Compute by using EventBridge, the ApsaraMQ for RabbitMQ trigger (RabbitMQ trigger) can trigger associated functions. The functions can be used to perform custom operations on the messages that are published to ApsaraMQ for RabbitMQ. This topic describes how to create a RabbitMQ trigger, configure function input parameters, and write and test code in the Function Compute console.

Overview

After you specify to create a trigger in the Function Compute console, Function Compute creates EventBridge resources based on the trigger configurations. Function Compute provides the event mode and the event stream mode to push messages. The following items describe the resources that you can create in each model:
After a trigger is created, you can view the trigger information in the Function Compute console. You can also view the information about the created resources in the EventBridge console. When a message is sent to a ApsaraMQ for RabbitMQ instance that is used as a trigger source, function execution is triggered. Different push models support different parameters. For more information, see Step 2: Configure the input parameters of the function.
  • Event mode: A single message is passed to the function as an event parameter. The event follows the CloudEvents specification. For information about the relationship between the message content and CloudEvents, see Step 2: Configure the input parameters of the function.
  • Event stream mode: One or more messages are pushed to Function Compute for batch processing based on your batch configurations. This model is suitable for scenarios in which end-to-end streaming data is processed.

Usage notes

  • The ApsaraMQ for RabbitMQ instance that is the trigger source must be in the same region as the function in Function Compute.
  • When the number of created custom event buses and the number of created event rules reach the upper limits, you cannot create a Message Queue for RabbitMQ trigger of the event mode.
  • When the number of created event streams reaches the upper limit, you cannot create a Message Queue for RabbitMQ trigger of the event stream mode.

For information about the limits on the number of resources that can be created by using an Alibaba Cloud account in each region, see Limits.

Before you begin

Step 1: Create a trigger

  1. Log on to the Function Compute console. In the left-side navigation pane, click Services & Functions.
  2. In the top navigation bar, select a region. On the Services page, click the desired service.
  3. On the Functions page, click the function that you want to manage.
  4. On the function details page, click the Triggers tab, select the version or alias from the Version or Alias drop-down list, and then click Create Trigger.
  5. In the Create Trigger panel, specify related parameters. After you specify the parameters, click OK.
    The following table describes the basic parameters.
    ParameterDescriptionExample
    Trigger TypeSelect Message Queue for RabbitMQ from the drop-down list. Message Queue for RabbitMQ
    NameEnter a custom trigger name. rabbitmq-trigger
    Version or AliasThe default value is LATEST. If you want to create a trigger for another version or alias, switch to the specified version or alias in the upper-right corner of the function details page. For more information about versions and aliases of a service, see Manage versions and Manage aliases. LATEST
    RabbitMQ InstanceSelect a ApsaraMQ for RabbitMQ instance. amqp-cn-i7m2l6m2****
    VhostSelect a vhost of a ApsaraMQ for RabbitMQ instance from the drop-down list. myhost-1
    QueueSelect a queue of a ApsaraMQ for RabbitMQ instance from the drop-down list. myqueue-1
    Invocation MethodSelect a function invocation mode.
    Valid values:
    • Sync Invocation: This mode is suitable for sequential invocations. When a single event or a batch of events trigger the function, Function Compute runs the function and waits for a response before it processes the next event or batch of events. The upper limit of the payload for a synchronous invocation request is 32 MB. For more information, see Synchronous invocations.
    • Async Invocation: This mode allows you to quickly consume events. When a single event or a batch of events trigger the function, Function Compute immediately returns a response and continue to process the next event or batch of events During this process, the function is run in asynchronous mode. The upper limit of the payload for an asynchronous invocation request is 128 KB. For more information, see Overview.
    Sync Invocation
    Message Push ModeThe underlying application mode that is used for pushing message data to Function Compute.
    Valid values:
    • Event Mode: A single message is passed to the function as an event parameter. The event follows the CloudEvents specification. For information about the relationship between message content and CloudEvents, see Parameters.
    • Event Stream Mode: One or more messages are pushed to Function Compute for batch processing based on your batch configurations. This model is suitable for scenarios in which end-to-end streaming data is processed.
    Event Mode
    Trigger StateSpecifies whether to enable the trigger immediately after it is created. By default, Enable Trigger is selected and the trigger is enabled after it is created. N/A

    For more information about advanced configurations such as message pushing, retry, and dead letter configurations, see Advanced features of triggers.

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

Step 2: Configure the input parameters of the function

The ApsaraMQ for RabbitMQ event source is passed to the function in the form of event, which acts as the input parameter. You can also manually pass event to the function to trigger the function and test whether the code of the function is correct.

  1. On the function details page, click the Code tab and click the xialatubiao icon. From the drop-down list that appears, select Configure Test Parameters.
  2. In the Configure Test Parameters panel, click the Create New Test Event or Modify Existing Test Event tab, and specify Event Name and the event content. After you specify the parameters, click OK.
    Sample code of event in the event mode:
      {
        "id":"bj694332-4cj1-389e-9d8c-b137h30b****",
        "source":"RabbitMQ-Function-rabbitmq-trigger",
        "specversion":"1.0",
        "type":"amqp:Queue:SendMessage",
        "datacontenttype":"application/json;charset=utf-8",
        "subject":"acs:amqp:cn-hangzhou:164901546557****:/instances/amqp-cn-tl32e756****/vhosts/eb-connect/queues/housekeeping",
        "time":"2021-08-12T06:56:40.709Z",
        "aliyunaccountid":"164901546557****",
        "aliyunpublishtime":"2021-10-15T08:58:55.140Z",
        "aliyunoriginalaccountid":"164901546557****",
        "aliyuneventbusname":"RabbitMQ-Function-rabbitmq-trigger",
        "aliyunregionid":"cn-chengdu",
        "aliyunpublishaddr":"42.120.XX.XX",
        "data":{
            "envelope":{
                "deliveryTag":98,
                "exchange":"",
                "redeliver":false,
                "routingKey":"housekeeping"
            },
            "body":{
                "Hello":"RabbitMQ"
            },
            "props":{
                "contentEncoding":"UTF-8",
                "messageId":"f7622d51-e198-41de-a072-77c1ead7****"
            }
        }
    }
    Sample code of event in the event stream mode:
    [
          {
        "id":"bj694332-4cj1-389e-9d8c-b137h30b****",
        "source":"RabbitMQ-Function-rabbitmq-trigger",
        "specversion":"1.0",
        "type":"amqp:Queue:SendMessage",
        "datacontenttype":"application/json;charset=utf-8",
        "subject":"acs:amqp:cn-hangzhou:164901546557****:/instances/amqp-cn-tl32e756****/vhosts/eb-connect/queues/housekeeping",
        "time":"2021-08-12T06:56:40.709Z",
        "aliyunaccountid":"164901546557****",
        "aliyunpublishtime":"2021-10-15T08:58:55.140Z",
        "aliyunoriginalaccountid":"164901546557****",
        "aliyuneventbusname":"RabbitMQ-Function-rabbitmq-trigger",
        "aliyunregionid":"cn-chengdu",
        "aliyunpublishaddr":"42.120.XX.XX",
        "data":{
            "envelope":{
                "deliveryTag":98,
                "exchange":"",
                "redeliver":false,
                "routingKey":"housekeeping"
            },
            "body":{
                "Hello":"RabbitMQ"
            },
            "props":{
                "contentEncoding":"UTF-8",
                "messageId":"f7622d51-e198-41de-a072-77c1ead7****"
            }
        }
        },
        {
        "id":"bj694332-4cj1-389e-9d8c-b137h30b****",
        "source":"RabbitMQ-Function-rabbitmq-trigger",
        "specversion":"1.0",
        "type":"amqp:Queue:SendMessage",
        "datacontenttype":"application/json;charset=utf-8",
        "subject":"acs:amqp:cn-hangzhou:164901546557****:/instances/amqp-cn-tl32e756****/vhosts/eb-connect/queues/housekeeping",
        "time":"2021-08-12T06:56:40.709Z",
        "aliyunaccountid":"164901546557****",
        "aliyunpublishtime":"2021-10-15T08:58:55.140Z",
        "aliyunoriginalaccountid":"164901546557****",
        "aliyuneventbusname":"RabbitMQ-Function-rabbitmq-trigger",
        "aliyunregionid":"cn-chengdu",
        "aliyunpublishaddr":"42.120.XX.XX",
        "data":{
            "envelope":{
                "deliveryTag":98,
                "exchange":"",
                "redeliver":false,
                "routingKey":"housekeeping"
            },
            "body":{
                "Hello":"RabbitMQ"
            },
            "props":{
                "contentEncoding":"UTF-8",
                "messageId":"f7622d51-e198-41de-a072-77c1ead7****"
            }
        }
        }
    ]
    The following table describes the parameters in data. For information about the parameters that are defined in the CloudEvents specification, see Overview.
    Parameter Type Example Description
    body Map The content of the message.
    Hello String EventBridge The user data.
    props Map The properties of the message.
    contentEncoding String utf-8 The format in which the content of the message is encoded.
    messageId String f7622d51-e198-41de-a072-77c1ead7**** The ID of the message. The ID of each message is unique.
    envelope Map The envelope information about the message.
    deliveryTag Int 98 The tag of the message.
    exchange String N/A The name of the exchange that sent the message.
    redeliver Boolean false Indicates whether the message can be resent. Valid values:
    • true: The message can be resent.
    • false: The message cannot be resent.
    routingKey String housekeeping The routing rule of the message.

Step 3: Write and test the function

After you create the trigger, you can write function code and test the function to verify that the code is correct. When ApsaraMQ for RabbitMQ events are delivered to Function Compute by using EventBridge, the trigger triggers function execution.

  1. On the function details page, click the Code tab, edit the function code in the code editor, and then click Deploy.
    This topic uses the Node.js function 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 the Code tab and click Test Function.
    After the function is executed, you can view the result on the Code tab.

References

To modify or delete an existing trigger, see Trigger management.