improve error messge in lib/dns

[MylesBorins]

Due to backwards compatibility dns.js is reporting UV_EAI_MEMORY, UV_EAI_NODATA, and UV_EAI_NONAME errors as ENOTFOUND

This is currently labelled FIXME --> https://github.com/nodejs/node/blob/master/lib/dns.js#L17-L23

ENOTFOUND is not even a proper POSIX error!
@bnoordhuis

The change breaks a few tests

• test-http-dns-error
• test-net-better-error-messages-port-hostname
• test-net-connect-immediate-finish
• test-net-dns-error

interestingly enough every testc ase we had was for EAI_NONAME, we have no tests for EAI_MEMORY or EAI_NODATA

If people are interested I'll get started on this change, including writing extra tests and smoke testing. This should be a great candidate for citgm

[MylesBorins]

/cc @jasnell @bnoordhuis @cjihrig

[cjihrig]

I'm all for removing these types of things from the codebase. My only reservation is that we don't know how much code would break for relatively little gain.

[jasnell]

I'm torn. Like @cjihrig I don't see a lot of value but eliminating technical debt is generally a good thing. Smoke testing this would be worthwhile.

[silverwind]

We discussed DNS errors in #1843, and ideally we'd like to return real DNS error codes (NXDOMAIN, SERVFAIL, REFUSED etc, see section 2.3 of https://tools.ietf.org/html/rfc2929) at some point. It'd be a huge breaking change of course, but if we're going to do it, I'd hold of from changing these now.

[MylesBorins]

@jasnell is this something I should try and get together for v6? Will it just create too much churn?

[jasnell]

We should likely hold off and do this post v6. It's still not yet clear how much this will impact.

[silverwind]

These are some exotic errors, I guess it would be pretty low impact, except maybe UV_EAI_NONAME. I'd say we should take the chance and fix this now.

[MylesBorins]

@jasnell with that in mind it makes sense to aim to get this in for v7, that way if it was a terrible idea we can back it out in v8 and not be stuck with it for 3 years!

[silverwind]

What's the supposed fix going to be, by the way? Remove the conditional and progagate libuv error codes the user?

[MylesBorins]

@silverwind indeed. It would be propogated proper error codes

[silverwind]

Hmm, I'm just worried about our E{SOMETHING} convention. Should UV_EAI_NONAME become ENONAME ?

[atomantic]

I've been wresting with an ENOTFOUND error (in Node.js 4.4.7) and I'd love to see deeper into why it's failing because it fails after 2,184 successful http.get calls:

redacteddomain.com error (had 2184 successes): { [Error: getaddrinfo ENOTFOUND redacteddomain.com redacteddomain.com:80]
  code: 'ENOTFOUND',
  errno: 'ENOTFOUND',
  syscall: 'getaddrinfo',
  hostname: 'redacteddomain.com',
  host: 'redacteddomain.com',
  port: 80 }

This happens within about 30 seconds after service startup.

Any idea how to get more info on what's really happening here?