Investigate flaky test-dns

[Trott]

Example failure:

• pi2-raspbian-wheezy

[Trott]

Another failure:

• pi2-raspbian-wheezy

[Trott]

And another:

• pi2-raspbian-wheezy

[Trott]

It appears that this test is flaky due to timing out when the callback never fires on one of the two test cases:

assert.doesNotThrow(function() {
  dns.lookup('www.google.com', {}, noop);
});

assert.doesNotThrow(function() {
  dns.lookup('www.google.com', {
    family: 4,
    hints: 0
  }, noop);
});

I'm not sure what can be done (from within Node) to make sure those dns.lookup() calls always return. dns.getServers() returns an empty array so I'd imagine that these tests don't try to actually do the lookup. But run locally, if I replace noop with something that logs the found address, it is in fact finding the address. (Maybe c-ares is looking at my machine's DNS cache or something?)

Anyway, if anyone has ideas how to make those tests more robust, I'd love to hear it. /cc @nodejs/testing @nodejs/build

[Trott]

Oh, I see now that I had it backwards in my mind: dns.lookup() always tries to resolve. So dns.getServers() is irrelevant. (It's relevant for dns.resolve(). I thought it was the other way around.)

OK, so I'm thinking there's might be no foolproof way around this problem and maybe these test cases should be moved from parallel to internet. But I'd welcome a more informed opinion on this.

[Trott]

Maybe we can move those two tests into their own test file and find a way to replace cares.getaddrinfo() in lib/dns.js with a test double?

[Trott]

Another one: https://ci.nodejs.org/job/node-test-binary-arm/1489/RUN_SUBSET=0,nodes=pi2-raspbian-wheezy/console

[Trott]

Still happening: https://ci.nodejs.org/job/node-test-binary-arm/1540/RUN_SUBSET=1,nodes=pi2-raspbian-wheezy/console

Any ideas, anyone? Pretty thin roster using git shortlog but maybe @bnoordhuis or @evanlucas might have some ideas what's going wrong here?

[Trott]

Specific part of the test that's being problematic was added in 43067864. /cc @cjihrig although I'm really just kind of throwing darts at a wall to pick out names to cc at this point...

[cjihrig]

Do those requests come back, given enough time? I don't think 4306786 would cause the flakey behavior.