Zones – Robust error handling and flow control for Node.js

http://strongloop.com/strongblog/announcing-zones-for-node-js/

by piscisaureus • 12 years ago

30 19 12 years ago

bajtos• 12 years ago

We’re waiting eagerly for node v0.12 to be released. Unfortunately, the release may not happen soon since there are about 800 open bugs and about 180 pull requests waiting to be reviewed.

Is it a real problem? Seems that other popular projects like Ruby on Rails have a similar number of opened issues and it's not stopping them from releasing new versions.

Does the Node core team have any plans how to prevent this situation in the future?

james332• 12 years ago

That quote and those numbers are incredibly misleading, I'm not sure why they use that to prove Node 0.12 isn't coming soon. If you actually look at the issues on Github, only around 30 of those are marked as 0.12, with the rest being various other milestones including 0.13 and 1.0. It has also already been stated that there is only one more 0.11 release before 0.12.

octetcloud• 12 years ago

No one is trying to "prove" 0.12 isn't coming soon, we've put lots of work into it, and look forward to its release, and its got some great new features.

I'm not sure the tag states are always up to date, perhaps they are, but the fact remains that 0.12 has been "real soon now" for quite a while, so saying it might be a while still is a pretty safe statement.

The core team is working hard, but I think the PR queue is a good indication of how scarce a resource review time is.

stormbrew3• 12 years ago

I'm having a really hard time seeing how this is an actual improvement on the status quo. It just seems to build up a lot of complexity and create new and more confusing corner cases. I have a hard time following the demos, even with copious comments, and one of them even has a null exception catch and calls it a good thing (the http long stack demo).

piscisaureus6• 12 years ago

I'm having a really hard time seeing how this is an actual improvement on the status quo

What we're doing is make it unnecessary to add error handlers everywhere and still get caught by surprising failure modes. If the zone catches an error it cleans up (closes resources, cancel operations when that makes sense) and then routes the error to the zone's result callback so you can handle it in once place.

The 'status quo' is that node has domains, but zones should be conceptually cleaner and thus have less corner cases.

one of them even has a null exception catch

I'm not sure what you mean here. The http demo catches an exception and prints the stack trace. We can do that because the zone cleans up the socket so it's not necessary to exit and restart node.

stormbrew3• 12 years ago

https://github.com/strongloop/zone/blob/master/showcase/long... <- this is the line I was referring to.

I can see why it's doing it, actually, because the connection is presumably done at that point and an error after everything important is done is less important, but it's poorly explained at best (as being to prevent the 'zone from exploding').

stormbrew3• 12 years ago

So, looking at the examples again and going back to this:

What we're doing is make it unnecessary to add error handlers everywhere and still get caught by surprising failure modes. If the zone catches an error it cleans up (closes resources, cancel operations when that makes sense) and then routes the error to the zone's result callback so you can handle it in once place.

I'm really unclear on how the zone library is doing the magical interception of errors. In the curl example you don't put error handlers on things. But clearly something must be. Does a library (say, one that came from npm and not the core library) have to be zone-aware to function correctly with zones? What does using zones mixed with libraries that aren't zone-aware look like? How much complexity does it add to the library to make it zone aware?

munro• 12 years ago

The comparison page highlights that Zone.js is better than promises because of long stack traces [1], but most promise implementations already have that [2]. I'm confused, that seems to be the only comparison to promises.

Edit: Conceptually it seems the same as promises. The main difference seems to be that they've added hooks [3] into the pipeline, and they duck punch the core API to intercept errors. Bluebird has solved this without duck punching using `Promise.promisifyAll(require("fs"))` [4]. I would love to see a write up on Zone.js's forks, because the article could of trivially been rewriten to use promises.

[1] http://strongloop.com/strongblog/comparing-node-js-promises-... [2] https://github.com/kriskowal/q#long-stack-traces [3] https://github.com/btford/zone.js/#zonefork [4] https://github.com/petkaantonov/bluebird

orand• 12 years ago

I highly recommend listening to JavaScript Jabber's Zone.js interview [1] with Brian Ford that came out yesterday. He mentions collaborating with this NodeJS Zones project and the possibility of convergence.

I also recommend watching his ng-conf talk [2] on Zone.js to get a better understanding of what zones enable.

[1] http://javascriptjabber.com/110-jsj-zones-with-brian-ford/

[2] https://www.youtube.com/watch?v=3IqtmUscE_U

ypcx• 12 years ago

Any error handling that forces me to add extra lines into my code is one I see as too obstructing. First and foremost, asynchronous exception handling and propagation, and "long" stacktraces that go with it, should be a core part of the JavaScript language, and I'm personally waiting for that to happen at some point. In the meantime, the best solution I was able to come up with is "LAEH2". See it here: https://github.com/ypocat/laeh2

reissbaker3• 12 years ago

Looking through the Zone API documentation, this is a reimplementation of what most Promise libraries already provide (Zones even support "then" and "catch" methods, but don't follow the chaining standard). The only new feature is "Gates," which the documentation admits are awkward and need to be revisited — and many Promise libraries already provide simple mechanisms for sharing resources similar to what Gates allow, but with more-consistent APIs. Zones also don't work several important Node-core libraries (cluster, fs, zlib, and more), whereas Promise libraries solved interop long ago.

Promises/A+ is already standardized and is shipping in browsers. Yes, Promises/A+ is more complicated than it needs to be, and I wish a simpler, more monadic approach had won out. But this is an unnecessary flow-control fork, and it's not even a particularly good one by comparison. If Zones were built on top of the ES6 standard, all ES6-compatible promise libraries would immediately work with it (and there are many mature ones that already exist). No existing libraries work with Zones, and the existing ones will need to be amended to add Zone-specific interop.

God knows nobody needs a zone-to-promise converter; there are enough ways to do asynchronous flow control as it stands. This blog post seems to hope that Zones will some day make it into Node core; I sincerely hope they don't in their current state.

piscisaureus6• 12 years ago

I'm sorry if it wasn't clear enough from the blog, but the attempt here is not to write a flow control library that solves the callback hell problem like promises does.

You should think of it more as an asynchronous try-catch block, where resources created in the "try" block are automaticially cleaned up.

I believe that flow control in the future will be done with generators; check out https://github.com/visionmedia/co for example.

reissbaker3• 12 years ago

Okay. But Promises already provide asynchronous try/catch blocks, and you could have used those as the basis of your API (and as first-class objects that get returned), rather than inventing a new API and set of objects.

I believe that flow control in the future will be done with generators; check out https://github.com/visionmedia/co for example.

Generators and promises are both types of flow control that will be used in the future: they're both in the ES6 standard. In fact, visionmedia/co already supports promises.

Zones – Robust error handling and flow control for Node.js

Related Stories