`mock-resolver.c` is a mock implementation of `GResolver` used in the
`network-address` tests. It returns resolver results, and implements
timeouts, as directed by the test calling it.
In particular, it allows the IPv4 and IPv6 resolver results to be
returned using independent delays. This allows code paths which deal
with IPv4 and IPv6 results being returned at different times to be
tested, as the ‘Happy Eyeballs’ spec mandates various hard-coded
timeouts for returning the best results it can in a reasonable
timeframe.
Previously, `mock-resolver.c` implemented the timeouts by handling
`lookup_by_name()` in a `GTask` worker thread, and calling `g_usleep()`
for the timeout. This seemed to cause occasional CI failures, such as
https://gitlab.gnome.org/GNOME/glib/-/jobs/1843454, where a resolver
error would be returned rather than the expected results:
```
ok 52 /network-address/happy-eyeballs/ipv4-error-ipv6-first
\# GLib-GIO-DEBUG: IPv4 DNS error: IPv4 Broken
(/var/tmp/gitlab_runner/builds/Ff4WDDRj/0/GNOME/glib/_build/gio/tests/network-address:18428): GLib-GIO-DEBUG: 09:03:08.587: IPv4 DNS error: IPv4 Broken
Bail out! GLib-GIO:ERROR:../gio/tests/network-address.c:586:got_addr: assertion failed (error == NULL): IPv4 Broken (g-io-error-quark, 24)
stderr:
**
GLib-GIO:ERROR:../gio/tests/network-address.c:586:got_addr: assertion failed (error == NULL): IPv4 Broken (g-io-error-quark, 24)
```
While I’ve been unable to reproduce these failures locally, I suspect
they might be down to thread spawning occasionally taking long enough on
a CI runner to change the ordering of the timeouts, such that the ‘Happy
Eyeballs’ algorithm returns a different set of results from what the
test expects.
So, this commit rewrites part of `mock-resolver.c` to implement timeouts
in the main thread, rather than in a worker thread. That should
eliminate the delays in spawning threads, and should mean that the
timeout sources in `mock-resolver.c` are attached to the same
`GMainContext` as those from the ‘Happy Eyeballs’ algorithm which are
monitoring them, so a total order over the timeouts can be guaranteed.
Of course, I might be completely wrong since this is just a guess and I
can’t properly test it since I can’t reproduce the failure. Worth a try.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
As RFC 8305 recommends we can start multiple DNS queries in parallel
to more quickly make an initial response, especially when one is
particularly slow/broken.
