Node.js Async Loop to Query Database

Question

I'm new to node.js.

I'm building a loop to query a database with chat messages every 3 seconds to then send required new messages to required users.

This is the loop I have - but currently it only loops once:

  // New Database Chat Messages Send
  var newDBMessagesInterval = 3000;     // 3 Seconds
  (function newDBMessagesSchedule() {
    setTimeout(function() {
      async(function() {
        console.log('async is done!');
        newDBMessagesSchedule();
      });
    }, newDBMessagesInterval)
  })();





function async() {
  console.log('in async function....');
}

Do I need to return something from the async function for the loop to continue?

Also is this a good/bad way to do a loop - my intention is to put a DB SELECT into the async function and don't what the DB calls to overlap.

Also is this non-blocking?

thx

I don't know what your situation is, but I think you might be going about your problem the wrong way. This sounds like you should be really using socketIO socket.io It will remove the necessity to query the database for new messages, and will be in real time. — EmptyArsenal
– EmptyArsenal, Commented Dec 11, 2013 at 0:26
I am using socket.io... but my connetions are spread across a few servers so I need to query DB and respond to required sockets... (eg: they don't all terminate on the same server... — Adam
– Adam, Commented Dec 11, 2013 at 0:28

Aaron Dufour · Accepted Answer · 2013-12-11 00:34:28Z

4

There is nothing magical about aynchronous functions. You have to call the callback to an asynchronous function at some point. For testing purposes you should change async to:

function async(callback) {
  callback();
}

Yes, this is non-blocking.

However, from your comment, I see that you're doing this to send messages to sockets. This isn't a great way to do that. You should look into getting a "pub/sub" system, and having each server subscribe and publish their own messages. Redis is a good choice for this.

edited Dec 11, 2013 at 0:34

answered Dec 11, 2013 at 0:27

Aaron Dufour

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2 Comments

Adam Over a year ago

thx - that works - my knowledge is slowly growing... appreciated.

Aaron Dufour Over a year ago

@Adam Pleases see my edits. I think you'll have an easier time with the pub/sub system I suggested.

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