The short answer is to use domains to help you die gracefully, but an uncaughtException or a domain error REQUIRES a restart of the process.
The long answer is use trycatch, https://github.com/crabdude/trycatch. Because domains are not the equivalent of node.js' "On Error Resume Next" (See http://nodejs.org/docs/latest/api/all.html#all_warning_don_t_ignore_errors), there are certain obvious failure cases that resuming on error will place your code into a bad state (e.g., EventEmitter handler errors: https://github.com/joyent/node/issues/5114). trycatch resolves these by shimming EventEmitter and wrapping all handlers in try/catch, moving much closer to "On Error Resume Next". It also doesn't catch errors that have torn multiple layers of core stack (or to put it another way, only catches core errors that are TypeErrors occurring at the first layer of core logic). I'm currently wrapping up a comprehensive blog post on node.js error handling. I'll followup here with a link when it's posted. Cheers, Adam Crabtree On Mon, Jul 8, 2013 at 9:17 AM, Martin Cooper <mfncoo...@gmail.com> wrote: > > > > On Sun, Jul 7, 2013 at 10:01 PM, joel <orengo...@gmail.com> wrote: > >> I started working a project <https://github.com/oren/domains-examples>that >> demonstrate domains both on vanilla node and with express (it's based >> on the nodeconf session). >> take a look and feel free to send pull requests. >> >> from some reason the /database route does not get caught by the domain - >> https://github.com/oren/domains-examples/blob/master/express/server.js#L35 >> any idea what's missing there? > > > The problem is with Express. It wraps a try / catch around your request > handler function, such that any synchronous exception (e.g. from your > '/throw' handler) will be caught by that, and not handled by the domain. > The reason your '/database' handler works is that the exception is thrown > outside of the request handler itself, because of that setTimeout() call. > > -- > Martin Cooper > > > On Saturday, July 6, 2013 4:17:28 AM UTC-7, Tony Mobily wrote: >>> >>> Hi, >>> >>> I have been writing a bit of code with nodejs, and am sort of "going >>> back" to brush things up, checking that I am doing things the right way. >>> I recently read this: >>> >>> http://geoff.greer.fm/2012/06/**10/nodejs-dealing-with-errors/<http://geoff.greer.fm/2012/06/10/nodejs-dealing-with-errors/> >>> >>> After a bit of research, I got to this article: >>> >>> http://benno.id.au/blog/2011/**08/08/nodejs-exceptions<http://benno.id.au/blog/2011/08/08/nodejs-exceptions> >>> >>> And to this SO answer: >>> >>> http://stackoverflow.com/**questions/7310521/node-js-** >>> best-practice-exception-**handling<http://stackoverflow.com/questions/7310521/node-js-best-practice-exception-handling> >>> >>> At the moment, I am only ever throwing() if: >>> >>> 1) I am enclosing _async_ code with try/catch, like this: >>> >>> // Get the messages from Json, safely >>> try { >>> if( ! req.body.messages ) >>> throw( new Error("req.body.messages not there") ); >>> var messages = JSON.parse(req.body.messages); >>> } catch(e) { >>> var messages = []; >>> } >>> >>> 2) Something reeeeeeeeaaaaaaaalllllllyyyyyy**y bad happens in terms of >>> how my module was used. For example a class constructor is missing a >>> necessary parameter, etc. >>> >>> In any other case, I am using next( err ). If something really bad >>> happens, for example mongodb dies and calls to the db start failing, I >>> handle it with an error manager in express: >>> >>> app.use( function( err, req, res, next){ >>> // ... >>> }); >>> >>> But... does this mean that if my application uses a library that has a >>> random throw(), my app will effectively die? >>> What's the "current" state of affairs? >>> >>> Looking at existing code, well, I seem to have gotten it right: nodejs >>> libraries tend to only throw when things really aren't supposed to happen. >>> For example in qs/lib/querystring.js: >>> >>> function stringifyString(str, prefix) { >>> if (!prefix) throw new TypeError('stringify expects an object'); >>> return prefix + '=' + encodeURIComponent(str); >>> } >>> >>> But... am I missing something? >>> Would this be correct: >>> >>> * throw() when the program really deserves to die, and not for external >>> causes (see: the db server goes down, etc.) >>> * Always use next( err ) if anything goes wrong (business as usual) >>> * Figure out if some libraries emit events, and listen to them if >>> necessary >>> >>> Bye, >>> >>> Merc. >>> >> -- >> -- >> 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 nodejs@googlegroups.com >> To unsubscribe from this group, send email to >> nodejs+unsubscr...@googlegroups.com >> 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 nodejs+unsubscr...@googlegroups.com. >> 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 nodejs@googlegroups.com > To unsubscribe from this group, send email to > nodejs+unsubscr...@googlegroups.com > 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 nodejs+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- Better a little with righteousness than much gain with injustice. Proverbs 16:8 -- -- 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 nodejs@googlegroups.com To unsubscribe from this group, send email to nodejs+unsubscr...@googlegroups.com 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 nodejs+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
