When I advised using an event emitter, I was referring to the exposed API, which looked like what Glenn was asking about.
That operation he mentioned can emit several different events throughout time, and the best fit would be, in my opinion, an event emitter. It's universally known to node programmers and makes the most sense, plus has error handling built-in that is pluggable with domains if the API user wishes to. When it comes to the *implementation* of the exposed API, sure, you can use async if you like it, or any control-flow API, or just roll out your own flow control thing, but that choice should never surface to the API user. -- Pedro On Monday, February 25, 2013 at 12:52 PM, Geerten van Meel wrote: > No need for event emitters, you can do this entirely functional. For this > sorts of asynchroneous tasks, the "async" module comes to the rescue. > > A possible implementation would use the "queue" function with a high value > for the concurrency of task procession. Whenever an error occurs, or you > retrieve your desired data, dump that in one (or two seperate) arrays. When > your queue is drained, your send both the errors and the results back. > > In regard to limiting the amount of errors, if your error array is too long, > you can just skip processing in the worker function. I,.e. a single line of > if (errors.length > 5) return callback(); at the beginning of your worker > function. > > Here's the documentation: https://github.com/caolan/async#queue > > Flow control, especially in the context of asynchroneous behaviour, is > something which you need to wrap your head around when working with node. > "async" is one of the most used packages that makes our lives easier for > tasks like this one. > > On Monday, February 25, 2013 10:57:52 AM UTC+1, Glenn Block wrote: > > Hello all > > > > Let's assume you have an API that results in a batch of HTTP calls which > > fire async and which are not sequential. A constraint of the API is that > > any errors that occur during the calls need to get returned to the user. > > > > How have you customarily designed this? > > > > One idea was something like the following > > > > function send(message, callback) { > > } > > > > where callback is function(error, results) { > > } > > > > In this case error if not null is a JSON object with a collection of child > > objects with the errors. > > > > An alternative idea I had was to have an additional completion callback per > > item. > > > > so: > > > > function send(message, completionCallback, itemCallback) { > > } > > > > This introduces a callback for each item that is processed. In this case > > the completion callback has a single error if ANY errors occur while the > > itemCallback has individual errors as they occur. > > > > This is useful for cases where you might want to stop further processing if > > the number of errors is very high. > > > > Thoughts / Experiences? > > Glenn > > > > > > > -- > -- > Job Board: http://jobs.nodejs.org/ > Posting guidelines: > https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines > You received this message because you are subscribed to the Google > Groups "nodejs" group. > To post to this group, send email to [email protected] > (mailto:[email protected]) > To unsubscribe from this group, send email to > [email protected] > (mailto:[email protected]) > For more options, visit this group at > http://groups.google.com/group/nodejs?hl=en?hl=en > > --- > You received this message because you are subscribed to the Google Groups > "nodejs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > (mailto:[email protected]). > For more options, visit https://groups.google.com/groups/opt_out. > > -- -- Job Board: http://jobs.nodejs.org/ Posting guidelines: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines You received this message because you are subscribed to the Google Groups "nodejs" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nodejs?hl=en?hl=en --- You received this message because you are subscribed to the Google Groups "nodejs" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
