Detecting GCE sometimes takes forever.

[craigcitro]

on some networks (@dhermes has one at home), doing a lookup on a bogus URL takes ~20-30s. this means that the default way of discovering the current environment (say for fetching the application default credential) can be insanely slow.

[craigcitro]

this was originally misdiagnosed in #92

[dhermes]

Now running gcloud auth and other commands I realize it has always stalled for a really long time on my machines. It seems this could be the cause there as well.

[craigcitro]

we definitely need to fix this, but there's no clear answer; deferring to @anthmgoogle to decide how to do this consistently for usable auth libraries.

[dhermes]

FYI this didn't actually fix the issue, I think the slowdown is something other than timeout (DNS related).

#100 will be fine I guess?

[craigcitro]

😢 #100 won't help you when you still need to fall through to 3LO, i.e. all the time.

just for kicks, can you try installing requests and doing the same thing? does it have the smarts to avoid this? (i'm guessing "no", but want to confirm.)

[craigcitro]

or urllib for that matter.

[dhermes]

In [3]: %paste
start = time.time()
try:
    requests.get('http://github.com/', timeout=0.001)
except:
    pass
print time.time() - start
## -- End pasted text --
0.0234730243683

In [4]: %paste
start = time.time()
try:
    requests.get('http://metadata.google.internal/', timeout=0.001)
except:
    pass
print time.time() - start
## -- End pasted text --
20.0183758736

I'm trying to read about ways to avoid this but not having much luck.

Seemed promising, but meh: http://askubuntu.com/questions/272358/extrememly-slow-dns-lookup

[craigcitro]

yeah, there's no way around doing some refactoring and just doing this check at the veeeery last minute. that's also what the AWS SDK does, it seems.

in the short term, here's a tweak to fix it for now ... thoughts?