Message Queue for RabbitMQ triggers - Function Compute - Alibaba Cloud Documentation Center

Overview

After you submit a request to create a trigger in the Function Compute console, Function Compute creates EventBridge resources based on the trigger configurations. Two message push models are available: Event Model and Event Stream Model. The following resources are created for each model:

Event Model
Event Stream Model
- Event streams

After the 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 enqueued in the source Message Queue for RabbitMQ instance, the function in Function Compute is triggered. The parameters vary with different message push models.

Event model: Each message is passed into a function as an event parameter. The event follows the specifications for CloudEvents. For information about the relationship between message content and CloudEvents, see the details of parameters.
Event stream model: One or more messages are passed into a function in batches based on your batch configurations. This model is suitable for scenarios in which end-to-end streaming data is processed.

Usage notes

The Message Queue 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 model.
When the number of created event streams reaches the upper limit, you cannot create a Message Queue for RabbitMQ trigger of the event stream model.

The following table describes the limits on the number of resources that can be created by using an Alibaba Cloud account in each region.


Item	Upper limit
Number of custom event buses	10
Number of event rules created in each custom event bus	10
Number of event streams	30

Before you begin

EventBridge
- Activate EventBridge and grant permissions to a RAM user
Function Compute
- Create a service
- Create a function
Message Queue for RabbitMQ
- Activate Message Queue for RabbitMQ
- Create an instance, a vhost, and a queue

Step 1: Create a trigger

Log on to the Function Compute console. In the left-side navigation pane, click Services & Functions.
In the top navigation bar, select a region. On the Services page, click the desired service.
On the Functions page, click the function that you want to manage.
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.

In the Create Trigger panel, specify related parameters. After you specify the parameters, click OK.

For more information about advanced settings, see Advanced features of EventBridge triggers.


Category	Parameter	Description	Example
Basic settings	Trigger Type	Select Message Queue for RabbitMQ from the drop-down list.	Message Queue for RabbitMQ
	Name	Enter a trigger name.	rabbitmq-trigger
	Version or Alias	The 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 information about versions and aliases of a service, see Manage versions and Manage aliases.	LATEST
	RabbitMQ Instance	Select a Message Queue for RabbitMQ instance from the drop-down list.	amqp-cn-i7m2l6m2****
	vhost	Select a vhost of a Message Queue for RabbitMQ instance from the drop-down list.	myhost-1
	Queue	Select a queue of a Message Queue for RabbitMQ instance from the drop-down list.	myqueue-1
Advanced settings	Invocation Method	Select a method to invoke the function. Valid values: Synchronous Invocation: After an event triggers a function, Function Compute returns the execution result when the execution is complete. This is the default value. For more information about synchronous invocation, see Synchronous invocations. Asynchronous Invocation: After an event triggers a function, Function Compute immediately returns a response and ensures that the function is executed at least once. However, the detailed execution result is not returned. This invocation method is suitable for functions that have higher scheduling latency. For more information about asynchronous invocation, see Overview.	Synchronous Invocation
	Message Push Model	The underlying application model when message data is pushed to Function Compute. Valid values: Event Model: Each message is passed into a function as an event parameter. The event follows the specifications for CloudEvents. For information about the relationship between message content and CloudEvents, see Parameters. Event Stream Model: One or more messages are passed into a function in batches based on your batch configuration. This model is suitable for scenarios in which end-to-end streaming data is processed.	Event Model
	Batch Push	This parameter is available only if you select Event Stream Model as the message push model. Batch push helps you aggregate multiple events. Batch push is triggered when the conditions of either Batch Push Messages or Batch Push Interval are met. For example, if you set Batch Push Messages to 100 and Batch Push Interval to 15 seconds, the batch push is triggered immediately when the number of messages reaches 100 in less than 15 seconds.	Enable
	Batch Push Messages	The maximum number of messages that are sent by each function invocation in a batch. Requests are sent when the number of backlog messages reaches the specified value. Valid values: [1, 500].	1
	Batch Push Interval	The interval for function invocation. The system sends the aggregated messages to Function Compute at the specified interval. Valid values: [0, 15] (unit: seconds). A value of 0 specifies that the system sends the messages to Function Compute in real time.	1
	Retry Policy	This parameter is available only if you select Event Stream Model as the message push model. The retry policy to be used when a message fails to be pushed. Valid values: Backoff Retry: A message push request can be retried for up to three times at random intervals in the range of 10 to 20 seconds. Exponential Decay Retry: A message push request can be retried for up to 176 times, and the retry lasts for a maximum of one day. The interval between each retry is increased by a factor of 2 up to a maximum of 512 seconds: 1, 2, 4, 8, ... 512 seconds.	Backoff Retry
	Fault Tolerance Policy	This parameter is available only if you select Event Stream Model as the message push model. The method to handle errors. Valid values: Fault Tolerance Allowed: Fault tolerance is allowed. Event processing is not blocked when an error occurs. The messages that fail after they are retried based on the retry policy are delivered to dead-letter queues or discarded based on your configurations. Fault Tolerance Prohibited: Fault tolerance is prohibited. If an error occurs and the message fails after it is retried based on the retry policy, event processing is blocked.	Fault Tolerance Allowed
	Dead-letter Queue	This parameter is available only if you select Event Stream Model as the message push model. The message queue to which events that are not processed or have exceeded the number of retries are sent. If you disable this feature, messages that have exceeded the number of retries specified by the retry policy are discarded.	Enable Dead-letter Queue
	Queue Type	The type of the dead-letter queue. Valid values: MNS Message Queue for Apache RocketMQ	MNS
	Queue Name	The name of the dead-letter queue.	test-queue

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

Step 2: Configure the input parameters of the function

The Message Queue 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.

On the function details page, click the Code tab and click the icon. From the drop-down list that appears, select Configure Test Parameters.

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 for the event of the event model:

  {
    "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 for the event of the event stream model:

[
      {
    "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 Message Queue for RabbitMQ events are delivered to Function Compute by using EventBridge, the trigger triggers function execution.

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');
}

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 Manage triggers.