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Kir Kolyshkin
9928ca93a8
TL;DR: simplify the code, fix --follow hanging indefinitely
Do the following to simplify the followJournal() code:
1. Use Go-native select instead of C-native polling.
2. Use Watch{Producer,Consumer}Gone(), eliminating the need
to have journald.closed variable, and an extra goroutine.
3. Use sd_journal_wait(). In the words of its own man page:
> A synchronous alternative for using sd_journal_get_fd(),
> sd_journal_get_events(), sd_journal_get_timeout() and
> sd_journal_process() is sd_journal_wait().
Unfortunately, the logic is still not as simple as it
could be; the reason being, once the container has exited,
journald might still be writing some logs from its internal
buffers onto journal file(s), and there is no way to
figure out whether it's done so we are guaranteed to
read all of it back. This bug can be reproduced with
something like
> $ ID=$(docker run -d busybox seq 1 150000); docker logs --follow $ID
> ...
> 128123
> $
(The last expected output line should be `150000`).
To avoid exiting from followJournal() early, add the
following logic: once the container is gone, keep trying
to drain the journal until there's no new data for at
least `waitTimeout` time period.
Should fix https://github.com/docker/for-linux/issues/575
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit f091febc942859ffbc881f3a3aa327366603ae65)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Upstream-commit: be568f93432ed1399a0aacca5fbd2c1046ccbc85
Component: engine