Hook before starting processing messages

[bbc]

Hook before starting processing messages

[robinjmurphy]

Could you provide a description of what is is you need to do before handling messages? Some example code where you use the consumer would be useful as well.

It may be that you can just call the initial consumer.start() inside a callback?

[lfreneda]

start is called once, right? at the beginning..

In my implementation I need to periodic train some classification algorithm (eg. https://github.com/NaturalNode/natural)

I would like to update/train it for each batch of received messages, so that is why beforeHandleMessages would be useful.

😢

[robinjmurphy]

If there's something you need to do before handling a message, you should be able to do it at the top of your handleMessage function. I'm not convinced that it's something that the library needs to do for you.

var app = Consumer.create({
  queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
  handleMessage: function (message, done) {
    // do some setup work
    // process message
    done();
  }
});

If your 'setup' task is asynchronous, you could use something like async:

var async = require('async');

function handleMessage(message, cb) {
  async.series([
    function doSomeSetup(done) {
      // setup
      done();
    },
    function processTheMessage(done) {
      // process
      done();
    }
  ], cb);
}

var app = Consumer.create({
  queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
  handleMessage: handleMessage
});

Admittedly there's not any way to run code before receiving a batch of messages, only an individual message. I'm not convinced of the use case for it though. If you need to run a periodic task, it could be run on a setInterval outside of the consumer function.

[lfreneda]

Ok, no problem <3