[pkg-go] Bug#918526: mtail: FTBFS randomly

[Santiago Vila]

Package: src:mtail
Version: 3.0.0~rc16-1
Severity: important
Tags: ftbfs

Dear maintainer:

I tried to build this package in buster but it failed:

--------------------------------------------------------------------------------
[...]
 debian/rules build-arch
dh build-arch --buildsystem=golang --with=golang --builddirectory=/<<PKGBUILDDIR>>/build
   dh_update_autotools_config -a -O--buildsystem=golang -O--builddirectory=/<<BUILDDIR>>/mtail-3.0.0\~rc16/build
   dh_autoreconf -a -O--buildsystem=golang -O--builddirectory=/<<BUILDDIR>>/mtail-3.0.0\~rc16/build
   dh_auto_configure -a -O--buildsystem=golang -O--builddirectory=/<<BUILDDIR>>/mtail-3.0.0\~rc16/build
   debian/rules override_dh_auto_build
make[1]: Entering directory '/<<PKGBUILDDIR>>'
dh_auto_build -- -ldflags " -X main.Version=3.0.0~rc16 -X main.Revision=3.0.0~rc16-1"
	cd build && go generate -v -ldflags " -X main.Version=3.0.0~rc16 -X main.Revision=3.0.0~rc16-1" github.com/google/mtail github.com/google/mtail/exporter github.com/google/mtail/logline github.com/google/mtail/metrics github.com/google/mtail/metrics/datum github.com/google/mtail/mtail github.com/google/mtail/tailer github.com/google/mtail/tailer/file github.com/google/mtail/testutil github.com/google/mtail/vm github.com/google/mtail/watcher
src/github.com/google/mtail/bench_test.go
src/github.com/google/mtail/ex_test.go
src/github.com/google/mtail/main.go
src/github.com/google/mtail/exporter/collectd.go
src/github.com/google/mtail/exporter/export.go

[... snipped ...]

    --- PASS: TestInstrs/cmp_ge (0.00s)
    --- PASS: TestInstrs/cmp_eq_string_string_true (0.00s)
    --- PASS: TestInstrs/cmp_eq_string_string_false (0.00s)
    --- PASS: TestInstrs/cmp_gt_int_float (0.00s)
    --- PASS: TestInstrs/cmp_gt_float_float (0.00s)
    --- PASS: TestInstrs/cmp_gt (0.00s)
    --- PASS: TestInstrs/cmp_gt_float_int (0.00s)
    --- PASS: TestInstrs/cmp_ne (0.00s)
    --- PASS: TestInstrs/cmp_le (0.00s)
    --- PASS: TestInstrs/cmp_eq (0.00s)
    --- PASS: TestInstrs/cmp_lt (0.00s)
=== RUN   TestDatumSetInstrs
--- PASS: TestDatumSetInstrs (0.00s)
=== RUN   TestStrptimeWithTimezone
--- PASS: TestStrptimeWithTimezone (0.00s)
=== RUN   TestStrptimeWithoutTimezone
--- PASS: TestStrptimeWithoutTimezone (0.00s)
=== RUN   TestDatumFetchInstrs
--- PASS: TestDatumFetchInstrs (0.00s)
=== RUN   TestWalkPanicsOnUnknown
--- PASS: TestWalkPanicsOnUnknown (0.00s)
PASS
ok  	github.com/google/mtail/vm	0.098s
=== RUN   TestFakeWatcher
--- PASS: TestFakeWatcher (0.00s)
=== RUN   TestFakeWatcherUnwatchedFiles
--- PASS: TestFakeWatcherUnwatchedFiles (0.00s)
=== RUN   TestNoSuchHandle
--- PASS: TestNoSuchHandle (0.00s)
=== RUN   TestLogWatcher
--- PASS: TestLogWatcher (0.00s)
=== RUN   TestNewLogWatcherError
--- PASS: TestNewLogWatcherError (0.00s)
=== RUN   TestLogWatcherAddError
--- PASS: TestLogWatcherAddError (0.00s)
=== RUN   TestLogWatcherAddWhilePermissionDenied
--- PASS: TestLogWatcherAddWhilePermissionDenied (0.00s)
=== RUN   TestWatcherErrors
E1208 18:50:34.156489   32599 log_watcher.go:85] fsnotify error: Injected error for test
--- PASS: TestWatcherErrors (0.00s)
PASS
ok  	github.com/google/mtail/watcher	0.013s
dh_auto_test: cd build && go test -vet=off -v -p 2 github.com/google/mtail github.com/google/mtail/exporter github.com/google/mtail/logline github.com/google/mtail/metrics github.com/google/mtail/metrics/datum github.com/google/mtail/mtail github.com/google/mtail/tailer github.com/google/mtail/tailer/file github.com/google/mtail/testutil github.com/google/mtail/vm github.com/google/mtail/watcher returned exit code 1
make[1]: *** [debian/rules:25: override_dh_auto_test] Error 1
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
make: *** [debian/rules:18: build-arch] Error 2
dpkg-buildpackage: error: debian/rules build-arch subprocess returned exit status 2
--------------------------------------------------------------------------------

This is just how the build ends and not necessarily the most relevant part,
so I've put a bunch of my build logs here:

https://people.debian.org/~sanvila/build-logs/mtail/

The test which usually fails for me is this one:

FAIL    github.com/google/mtail/tailer  0.018s

This does not seem to fail in reproducible-builds, but I found a build
failure here for mips64el, which is a release architecture:

https://buildd.debian.org/status/fetch.php?pkg=mtail&arch=mips64el&ver=3.0.0%7Erc16-1&stamp=1539028587&raw=0

The fact that I can reproduce this as well on amd64 suggests that this not arch-specific
but instead some sort of race condition.

If you need a test machine to reproduce this, please say so (contact me privately for details).

Thanks.