1

I have Service A that publishes an event to RabbitMQ. I have two instances of Service B that will use the event to write to its database. I have two instances of Service C that will send the event data back to a client via websockets.

Only one instance of Service B should handle the event so data isn't written to the database twice.

All instances of Service C should receive the event as any one of them could have the websocket connection that needs to get the data.

How do I have some services handle events round-robin and some instances handle events as broadcast, do I need to publish the same event to two different exchange types?

Improve this question
3
  • 1
    have a fan out exchange. B creates a single work queue and all Bs subscribe to that queue. C creates a new queue per instance. Commented Jul 9, 2023 at 14:19
  • Thanks, that was the answer I needed to get me on the right track 👍 Commented Jul 10, 2023 at 20:12
  • let me type it up as an answer Commented Jul 11, 2023 at 7:46

1 Answer 1

Reset to default
1

With Rabbit MQ you send messages to exchanges and route them to queues defined by the consumers.

So in your case you can publish your messages to a "fan out" exchange, which will send a copy of the message to all attached queues.

Your consumers then connect, defining their queue. So B can define a single queue which all Bs share and will pick up messages from round robin and C can use a random name to define a new queue for each instance of the service. Because the exchange is "fan out" all of these new queues, and hence each instance of C will get a copy of the message.

Improve this answer

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.