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http/net: fix catching immediate connect errors

Rodrigo Muino Tomonari requested to merge github/fork/m0ppers/net-create-connection-error-handling into master

When creating a standard http client request the agent is calling net.createConnection. The agent will then defer installing error handling to nextTick(). If there is any immediate error in createConnection iojs will bail with an uncaught error. There is already one error situation which is handled in a special way (i.e. throwing error is deferred so the standard error handler may catch it). However there are more situations where this may happen: Namely in the connect() function.

Due to a locally changed ip address I was getting the following error and the iojs bailed out (which should not happen as error management was in place):

events.js:141
      throw er; // Unhandled 'error' event
            ^
Error: connect EHOSTDOWN 192.168.1.11:80 - Local (192.168.1.10:54125)
    at Object.exports._errnoException (util.js:846:11)
    at exports._exceptionWithHostPort (util.js:869:20)
    at connect (net.js:840:14)
    at lookupAndConnect (net.js:933:5)
    at Socket.connect (net.js:902:5)
    at Agent.exports.connect.exports.createConnection (net.js:61:35)
    at Agent.createSocket (_http_agent.js:177:16)
    at Agent.addRequest (_http_agent.js:147:23)
    at new ClientRequest (_http_client.js:132:16)
    at Object.exports.request (http.js:30:10)

I am still unsure why I am the only one facing this problem and maybe the pull request is entirely bogus. The error situation seems pretty common to me (and that's why I am surprised): My dhcp assigned my dev machine a new address and connecting to the old, hardcoded ip address is now failing with an ETIMEOUT (as expected). However another, slightly (few seconds) deferred request (while the first one is still working) will trigger an immediate EHOSTDOWN/EHOSTUNREACH error for me which cannot be caught using request.on("error", fn).

I can 100% reproduce this with iojs 2.1 and master using the following gist:

https://gist.github.com/m0ppers/3709f7d87b73be9aca7b

I am on osx yosemite.

The wrapped nextTick, nextTick thing is of course totally evil. However I cannot seem to fix it otherwise. The root cause IMHO is the deferred error management in the http client. I don't know the reason for it and left it untouched but IMHO this should be the real fix.

It has been introduced with this commit (which makes me even more unsure as this is years ago):

https://github.com/joyent/node/commit/7c87e092fb97ab293e19b21a8b07f622c80c68b3

Can somebody reproduce the problem? Am missing something? Does somebody have a better fix (nextTick(nextTick()))? :S

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