Trigger for Message Queue that sends messages to the Cloud Functions function
The trigger for Message Queue takes the load off the message queue. It picks up messages from the queue and forwards them to a Cloud Functions function for processing. Once the messages are successfully processed, the trigger deletes them from the queue, and if an error occurs, it places the messages back in the queue and sets a visibility timeout. If the queue does not have a Dead Letter Queue configured, a message will continue to be returned to a function until it is successfully processed or until its retention period expires.
Warning
- You can only create a trigger for a standard message queue.
- The trigger must be in the same cloud as the queue from which it reads messages.
- Only one trigger can be created for each message queue.
When the trigger is running, requests to the message queue are free of charge.
Message Queue triggers require service accounts to read messages from a message queue and call a function. You can use the same service account for both operations.
For more information about creating a trigger for Message Queue, see Create a trigger for Message Queue that sends messages to the Cloud Functions function.
Roles required for the proper operation of a trigger for Message Queue
- To create a trigger, you need:
viewerrole for a folder with a message queue the trigger reads messages from.viewerrole for the folder with the function that the trigger invokes.- Permission for the service account under which the trigger executes the operations. This permission comes with the iam.serviceAccounts.user and editor roles or higher.
- For the trigger to fire, service accounts need the following roles:
editorfor the folder with the message queue that the trigger reads messages from.functions.functionInvokerfor the folder with the function that the trigger invokes.
Read more about access management.
Message Queue trigger message format
After the trigger picks up a message from the queue, it sends it to the function in the following format:
{
"messages":[
{
"event_metadata":{
"event_id":"cce76685-5828-4304-a83d-9564********",
"event_type":"yandex.cloud.events.messagequeue.QueueMessage",
"created_at":"2019-09-24T00:54:28.980441Z",
"cloud_id":"b1gvlrnlh2sd********",
"folder_id":"b1g88tflh2sd********",
},
"details":{
"queue_id":"yrn:yc:ymq:ru-central1:21i6v06sqmsa********:event-queue",
"message":{
"message_id":"cce76685-5828-4304-a83d-9564********",
"md5_of_body":"d29343907090dff4cec4a9a0********",
"body":"message body",
"attributes":{
"SentTimestamp":"1569285804456"
},
"message_attributes":{
"messageAttributeKey":{
"data_type":"StringValue",
"string_value":"value"
}
},
"md5_of_message_attributes":"83eb2d0afefb150c1ffe69f6********"
}
}
},
{
"event_metadata":{
"event_id":"1f32fd25-11fc-4c08-88e7-d871********",
"event_type":"yandex.cloud.events.messagequeue.QueueMessage",
"created_at":"2019-09-24T00:54:28.980492Z",
"cloud_id":"b1gvlrnlh2sd********",
"folder_id":"b1g88tflh2sd********",
},
"details":{
"queue_id":"yrn:yc:ymq:ru-central1:21i6v06sqmsa********:event-queue",
"message":{
"message_id":"1f32fd25-11fc-4c08-88e7-d871********",
"md5_of_body":"d29343907090dff4cec4a9a0********",
"body":"message body",
"attributes":{
"SentTimestamp":"1569285806456"
},
"message_attributes":{
"messageAttributeKey":{
"data_type":"StringValue",
"string_value":"value"
}
},
"md5_of_message_attributes":"83eb2d0afefb150c1ffe69f6********"
}
}
}
]
}