Node.js async iteratee with timeout

Question

Bit new to node.js and javascript. Attempting to have my foreach call a function that in turn does a remote call. I'd like there to be a delay between each but can't seem to work out where to put the set timeout.

I know I have my setTimeout in the wrong place below but putting it in there as an example.

var likeRecommendation = function (recommendation, callback) {
    context.Client.like(recommendation._id, function (error, data) {
        recommendation['drupal_user_uid'] = context.message.uid;
        recommendation['drupal_user_uuid'] = context.message.uuid;
        if (error) return callback(new Error('Could not like recommendations'));
        context.broker.publish('saves_swipes_publication', recommendation, function (err, publication) {
            if (err) return callback(new Error('Could queue swipes to save'));
                publication.on('error', console.error);
            });
            console.log('Liked!');
            return callback()
        });
    }

    async.forEach(context.recommendations, likeRecommendation, function (error) {
        if (!error) return done(null);
        done(new Error('Could not like recommendations'));
    });
}

Neither return done(new Error('Could not like recommendations')); nor throw err will help you when actually you need to invoke callback — Bergi
– Bergi, Commented May 17, 2017 at 0:11
That's a good point I couldn't quite work out how to error out of the interatee function — Scott Hooker
– Scott Hooker, Commented May 17, 2017 at 0:49

Daphoque · Accepted Answer · 2017-05-17 08:58:05Z

See timeout, warning one of your callback was missing and one other was not well placed.

 var likeRecommendation = function (recommendation, callback) {
    context.Client.like(recommendation._id, function (error, data) {
        recommendation['drupal_user_uid'] = context.message.uid;
        recommendation['drupal_user_uuid'] = context.message.uuid;
        if (error)
            setTimeout(function(){return callback(new Error('Could not like recommendations'))}, 100);
        else {
            context.broker.publish('saves_swipes_publication', recommendation, function (err, publication) {
                if (err)
                    setTimeout(function(){return callback(new Error('Could queue swipes to save'))}, 100);
                else
                {
                    publication.on('error', console.error);
                    setTimeout(function(){ return callback();}, 100);
                }

            });
       }
    });
}

async.forEach(context.recommendations, likeRecommendation, function (error) {
    if (!error) return done(null);
    done(new Error('Could not like recommendations'));
});
}

Raj Nathani · Accepted Answer · 2017-05-17 00:30:00Z

0

The setTimeout will have to be placed at the end of the callback code.

Here is a possible solution (note that it doesn't use async.forEach)

var likeRecommendation = function (recommendation, callback) {
    context.Client.like(recommendation._id, function (error, data) {
      recommendation['drupal_user_uid'] = context.message.uid;
      recommendation['drupal_user_uuid'] = context.message.uuid;
      console.log(recommendation);
      if (error) return done(new Error('Could not like recommendations'));
      context.broker.publish('saves_swipes_publication', recommendation, function (err, publication) {
        if (err) throw err
        publication.on('error', console.error);
      });
      console.log('Liked!');
      return callback()
    });
}

function iterateWithTimeout(list, ctx, timeoutDuration) {
  var currentIndex = 0;
  (function invoke() {
    list[currentIndex](ctx, function(error) {
      if (!error) return done(null);
      done(new Error('Could not like recommendations'));
      setTimeout(function() {
        if (++currentIndex < list.length) {
          invoke();
        }
      }, timeoutDuration);
    });
  })();
}

// Interval is 1 second for now
iterateWithTimeout(context.recommendations, likeRecommendation, 1000);

edited May 17, 2017 at 0:30

answered May 16, 2017 at 23:23

Raj Nathani

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3 Comments

Scott Hooker Over a year ago

I can see what this is doing but I don't think it will quite work. e.g. ReferenceError: index is not defined at invoke (/Users/Scott/Sites/swiper/swipes_workflow/src/tasks/likeRecommendations.js:25:26)

Raj Nathani Over a year ago

@ScottHooker sorry, it looks I had an incorrect variable name. I just updated the code to fix that.

Scott Hooker Over a year ago

I need use async as this "task" needs to finish before the callback is called and the next step in my workflow can start.

Scott Hooker · Accepted Answer · 2017-05-17 08:51:58Z

0

So using "async.eachSeries" rather than "async.forEach" was the solution!

As always thanks for the help!

answered May 17, 2017 at 8:51

Scott Hooker

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