CODEWITHSUNDEEP
node.jsrabbitmqmessage-queue
Tom Brock
Tom Brock

Reputation: 950

RabbitMQ subscriber sending message back onto RabbitMQ queue?

I would appreciate your thoughts on this.

I have a node app which subscribes to a RabbitMQ queue. When it receives a message, it checks it for something and then saves it to a database.

However, if the message is missing some information or some other criteria is not yet met, I would like the subscriber to publish the message back onto the RabbitMQ queue.

I understand logically this is just connecting to the queue and publishing the message, but is it really this simple or is this a bad practice or potentially dangerous?

Thanks for your help.

Upvotes: 1

Views: 1218

Answers (2)

theMayer
theMayer

Reputation: 16157

In your question, you describe two criterion for when a message may not be processed:

  1. if the message is missing some information or
  2. some other criteria is not yet met

The first of these appears to be an issue with the message, and it doesn't seem that it makes much sense to re-queue a message that has a problem. The appropriate action is to log an error and drop the message (or invoke whatever error-handling logic your application contains).

The second of these is rather vague, but for the purposes of this answer, we will assume that the problem is not with the message but with some other component in the system (e.g. perhaps a network connection issue). In this case, the consuming application can send a Nack (negative acknowldegement) which can optionally requeue the message.

Keep in mind that in the second case, it will be necessary to shut down the consumer until the error condition has resolved, or the message will be redelivered and erroneously processed ad infinitum until the system is back up, thus wasting resources on an unprocessable message.

Why use a nack instead of simply re-publishing?
This will set the "redelivered" flag on the message so that you know it was delivered once already. There are other options as well for handling bad messages.

Upvotes: 0

zangw
zangw

Reputation: 48356

As I point out in the comment, When you create connection with queue, and set autoAck = true, to enable message acknowledge. The message in the queue will be deleted until receive acknowledge.

When the received message meets requirement, then send ack message to this queue, and this message will be deleted from queue. Otherwise, no ack message is sent to queue, this message will stay in the queue.

As for you mentioned in comment, the valid process may take 5 minutes, just set the send ack message as callback function of validation function.

Upvotes: 1

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