Triggers for Message Queue

Roles required for the proper operation of a trigger for Message Queue
Trigger message format Message Queue

The trigger for Message Queue is used to process the message queue. It picks up messages from the queue and passes them to a function for processing. The trigger must be in the same cloud with the queue it reads messages from. Only one trigger can be created for each message queue.

The Message Queue trigger needs service accounts to read messages from a queue and call functions. You can use the same service account for both operations.

Roles required for the proper operation of a trigger for Message Queue

To create a trigger, you need the following roles:
- viewer for the folder with the message queue that the trigger reads messages from.
- viewer for the folder with the function that the trigger runs.
- Permission to the service account on whose behalf the trigger executes the operations. This permission is included in the roles iam.serviceAccounts.user, editor, and higher.
To run a trigger, service accounts need the following roles:
- editor for the folder with the message queue that the trigger reads messages from.
- serverless.functions.invoker for the folder with the function that the trigger runs.

Learn more about access management.

Trigger message format Message Queue

After the trigger picks up a message from the queue, it passes it to the function in the following format:

{
   "messages":[
      {
         "event_metadata":{
            "event_id":"cce76685-5828-4304-a83d-95643c0507a0",
            "event_type":"yandex.cloud.events.messagequeue.QueueMessage",
            "created_at":"2019-09-24T00:54:28.980441Z"
         },
         "details":{
            "queue_id": "yrn:yc:ymq:ru-central1:21i6v06sqmsaoeon7nus:event-queue",
            "message":{
               "message_id":"cce76685-5828-4304-a83d-95643c0507a0",
               "md5_of_body":"d29343907090dff4cec4a9a0efb80d20",
               "body":"message body",
               "attributes":{
                  "SentTimestamp":"1569285804456"
               },
               "message_attributes":{
                  "messageAttributeKey":{
                     "dataType":"StringValue",
                     "stringValue":"value"
                  }
               },
               "md5_of_message_attributes":"83eb2d0afefb150c1ffe69f66c3de068"
            }
         }
      },
      {
         "event_metadata":{
            "event_id":"1f32fd25-11fc-4c08-88e7-d871d6ffb91d",
            "event_type":"yandex.cloud.events.messagequeue.QueueMessage",
            "created_at":"2019-09-24T00:54:28.980492Z"
         },
         "details":{
            "queue_id": "yrn:yc:ymq:ru-central1:21i6v06sqmsaoeon7nus:event-queue",
            "message":{
               "message_id":"1f32fd25-11fc-4c08-88e7-d871d6ffb91d",
               "md5_of_body":"d29343907090dff4cec4a9a0efb80d20",
               "body":"message body",
               "attributes":{
                  "SentTimestamp":"1569285806456"
               },
               "message_attributes":{
                  "messageAttributeKey":{
                     "dataType":"StringValue",
                     "stringValue":"value"
                  }
               },
               "md5_of_message_attributes":"83eb2d0afefb150c1ffe69f66c3de068"
            }
         }
      }
   ]
}