Trigger for Message Queue that sends messages to WebSocket connections
A trigger for Message Queue speeds up the processing of messages in a queue. It picks up messages from the queue and forwards them to WebSocket connections.
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.
- You can create only one trigger for each message queue.
When the trigger is running, requests to the message queue are free of charge.
A trigger for Message Queue requires service accounts to read messages from a queue and send them to WebSocket connections. You can use the same service account for both operations.
For more information about creating a trigger for Message Queue, see Creating a trigger for Message Queue that sends messages to WebSocket connections.
Message batching
The batching settings allow sending several messages to WebSocket connections at a time. They set a top limit on a message batch size and its accumulation time. For example, if the message batch size is 3, WebSocket connections can receive batches containing from 1 to 3 messages.
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 a folder containing the API gateway whose WebSocket connections the trigger sends messages to.- Permission for the service account under which the trigger runs 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 a message queue the trigger reads messages from.api-gateway.websocketBroadcasterfor the folder containing the API gateway.
Read more about access management.
Message Queue trigger message format
After the trigger picks up a message from the queue, it will send it to WebSocket connections 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********"
}
}
}
]
}