Example of retry for operations that use EventEmitter and not Callback

[michaelkariv]

What is the right way of using node-retry for operations that use EventEmitter for 'error' events, rather than callback?

[tim-kos]

Hey Michal,

sorry for the long delay here, but I was on vacation.

Could you please provide some example code?

Best,
Tim

[tim-kos]

Hey @michaelkariv

Did you see my reply?

[jokesterfr]

@michaelkariv I think it's working the same way. Assuming you have a task object, which is an Event Listener emitting errors, and starting processing stuff after calling execute():

var operation = retry.operation();
var t = new Task();
t.on('error', function(err) {
 operation.retry(err);
});

operation.attempt(function (currentAttempt) {
    t.execute();
});

[tim-kos]

Closing this. Feel free to re-open if our comments did not help.

[AlexZeitler]

Based on @tim-kos answer here is a complete sample that checks for RabbitMQ + MongoDb connection using net and only continues code exection when both connections are available.

var net = require('net');
var retry = require('retry');
var async = require('async');


function tryConnect(HOST, PORT, cb) {
  var client = new net.Socket();
  var operation = retry.operation();
  var cbCalled = false;

  client.on('error', function(err) {
    console.log('error');
    operation.retry(err);
  });

  operation.attempt(function (currentAttempt) {
    client.connect(PORT, HOST, function(){
      console.log('CONNECTED TO: ' + HOST + ':' + PORT);
      if(!cbCalled) {      
        cb();
        cbCalled = true;
      }
    });
  });
}

async.parallel(
    [
    function(cb) {
      tryConnect('localhost', 5672, cb);
    },

    function(cb) {
      tryConnect('localhost', 27017, cb);
    }
    ], 
    function() { 
      console.log('both connected') 
    }
    )

[AlexZeitler]

@tim-kos Given the example above: How would I call the callback with an error if retry options are { retries : 2, factor: 1 } and the call eventually fails in the end?

[AlexZeitler]

Got it:

if(!operation.retry(err)) {
  cb(err, null)
}