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journald logs: drain 1 more time at container exit

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In the journald log driver, attempt to drain the journal 1 more time
after being told to stop following the log. Due to a possible race
condition, sometimes data is written to the journal at almost the same
time the log watch is closed, and depending on the order of operations,
sometimes you miss the last journal entry.

Signed-off-by: Andy Goldstein <agoldste@redhat.com>
This commit is contained in:
Andy Goldstein 2016-12-21 09:17:12 -05:00
parent e9c0de0de6
commit 76f58d7294
1 changed files with 20 additions and 11 deletions
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31
daemon/logger/journald/read.go
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@ -245,20 +245,28 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
s.readers.mu.Lock() s.readers.mu.Lock()
s.readers.readers[logWatcher] = logWatcher s.readers.readers[logWatcher] = logWatcher
s.readers.mu.Unlock() s.readers.mu.Unlock()
go func() { go func() {
// Keep copying journal data out until we're notified to stop for {
// or we hit an error. // Keep copying journal data out until we're notified to stop
status := C.wait_for_data_cancelable(j, pfd[0]) // or we hit an error.
for status == 1 { status := C.wait_for_data_cancelable(j, pfd[0])
if status < 0 {
cerrstr := C.strerror(C.int(-status))
errstr := C.GoString(cerrstr)
fmtstr := "error %q while attempting to follow journal for container %q"
logrus.Errorf(fmtstr, errstr, s.vars["CONTAINER_ID_FULL"])
break
}
cursor = s.drainJournal(logWatcher, config, j, cursor) cursor = s.drainJournal(logWatcher, config, j, cursor)
status = C.wait_for_data_cancelable(j, pfd[0])
} if status != 1 {
if status < 0 { // We were notified to stop
cerrstr := C.strerror(C.int(-status)) break
errstr := C.GoString(cerrstr) }
fmtstr := "error %q while attempting to follow journal for container %q"
logrus.Errorf(fmtstr, errstr, s.vars["CONTAINER_ID_FULL"])
} }
// Clean up. // Clean up.
C.close(pfd[0]) C.close(pfd[0])
s.readers.mu.Lock() s.readers.mu.Lock()
@ -267,6 +275,7 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
C.sd_journal_close(j) C.sd_journal_close(j)
close(logWatcher.Msg) close(logWatcher.Msg)
}() }()
// Wait until we're told to stop. // Wait until we're told to stop.
select { select {
case <-logWatcher.WatchClose(): case <-logWatcher.WatchClose():