Fix journald and logfile-powered (jsonfile, local) log readers
incorrectly filtering out messages with timestamps < Since which were
preceded by a message with a timestamp >= Since.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Marshalling log messages by json-file and local drivers involved
serializing the message into a shared buffer. This caused a regression
resulting in log corruption with recent changes where Log may be called
from multiple goroutines at the same time.
Solution is to use a sync.Pool to manage the buffers used for the
serialization. Also removed the MarshalFunc, which the driver had to
expose to the LogFile so that it can marshal the message. This is now
moved entirely to the driver.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
File watches have been a source of complexity and unreliability in the
LogFile follow implementation, especially when combined with file
rotation. File change events can be unreliably delivered, especially on
Windows, and the polling fallback adds latency. Following across
rotations has never worked reliably on Windows. Without synchronization
between the log writer and readers, race conditions abound: readers can
read from the file while a log entry is only partially written, leading
to decode errors and necessitating retries.
In addition to the complexities stemming from file watches, the LogFile
follow implementation had complexity from needing to handle file
truncations, and (due to a now-fixed bug in the polling file watcher
implementation) evictions to unlock the log file so it could be rotated.
Log files are now always rotated, never truncated, so these situations
no longer need to be handled by the follow code.
Rewrite the LogFile follow implementation in terms of waiting until
LogFile notifies it that a new message has been written to the log file.
The LogFile informs the follower of the file offset of the last complete
write so that the follower knows not to read past that, preventing it
from attempting to decode partial messages and making retries
unnecessary. Synchronization between LogFile and its followers is used
at critical points to prevent missed notifications of writes and races
between file rotations and the follower opening files for read.
Signed-off-by: Cory Snider <csnider@mirantis.com>
The LogFile follower would stop immediately upon the producer closing.
The close signal would race the file watcher; if a message were to be
logged and the logger immediately closed, the follower could miss that
last message if the close signal (formerly ProducerGone) was to win the
race. Add logic to perform one more round of reading when the producer
is closed to catch up on any final logs.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Whether or not the logger has been closed is a property of the logger,
and only of concern to its log reading implementation, not log watchers.
The loggers and their reader implementations can communicate as they see
fit. A single channel per logger which is closed when the logger is
closed is plenty sufficient to broadcast the state to log readers, with
no extra bookeeping or synchronization required.
Signed-off-by: Cory Snider <csnider@mirantis.com>
The asynchronous startup of the log-reading goroutine made the
follow-tail tests nondeterministic. The Log calls in the tests which
were supposed to happen after the reader started reading would sometimes
execute before the reader, throwing off the counts. Tweak the ReadLogs
implementation so that the order of operations is deterministic.
Signed-off-by: Cory Snider <csnider@mirantis.com>
The io/ioutil package has been deprecated in Go 1.16. This commit
replaces the existing io/ioutil functions with their new definitions in
io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
This fixes the case where log rotation fails on Windows while there are
clients reading container logs.
Evicts readers if there is an error during rotation and try rotation again.
This is needed for Windows with this scenario:
1. `docker logs -f` is called
2. Log rotation occurs (log.txt -> log.txt.1, truncate and re-open
log.txt)
3. Log rotation occurs again (rm log.txt.1, log.txt -> log.txt.1)
On step 3, before this change, the log rotation will fail with `Access
is denied`.
In this case, what we have is a reader holding a file handle to the
primary log file. The log file is then rotated, but the reader still has
a the handle open. `FILE_SHARE_DELETE` allows this to happen... but then
we try to do it again for the next rotation and it blows up.
So when it blows up we force all the readers to disconnect, close the
log file, and try rotation again, which will succeed based on the added
tests.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
The test was looking for the wrong file name.
Since compression happens asyncronously, sometimes the test would
succeed and sometimes fail.
This change makes sure to wait for the compressed version of the file
since we can't know when the compression is going to occur.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
This prevents getting into a situation where a container log cannot make
progress because we tried to rotate a file, got an error, and now the
file is closed. The next time we try to write a log entry it will try
and rotate again but error that the file is already closed.
I wonder if there is more we can do to beef up this rotation logic.
Found this issue while investigating missing logs with errors in the
docker daemon logs like:
```
Failed to log message for json-file: error closing file: close <file>:
file already closed
```
I'm not sure why the original rotation failed since the data was no
longer available.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Before this change, the log decoder function provided by the log driver
to logfile would not be able to re-use buffers, causing undeeded
allocations and memory bloat for dockerd.
This change introduces an interface that allows the log driver to manage
it's memory usge more effectively.
This only affects json-file and local log drivers.
`json-file` still is not great just because of how the json decoder in the
stdlib works.
`local` is significantly improved.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
This should test that
- all the messages produced are delivered (i.e. not lost)
- followLogs() exits
Loosely based on the test having the same name by Brian Goff, see
https://gist.github.com/cpuguy83/e538793de18c762608358ee0eaddc197
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When daemon.ContainerLogs() is called with options.follow=true
(as in "docker logs --follow"), the "loggerutils.followLogs()"
function never returns (even then the logs consumer is gone).
As a result, all the resources associated with it (including
an opened file descriptor for the log file being read, two FDs
for a pipe, and two FDs for inotify watch) are never released.
If this is repeated (such as by running "docker logs --follow"
and pressing Ctrl-C a few times), this results in DoS caused by
either hitting the limit of inotify watches, or the limit of
opened files. The only cure is daemon restart.
Apparently, what happens is:
1. logs producer (a container) is gone, calling (*LogWatcher).Close()
for all its readers (daemon/logger/jsonfilelog/jsonfilelog.go:175).
2. WatchClose() is properly handled by a dedicated goroutine in
followLogs(), cancelling the context.
3. Upon receiving the ctx.Done(), the code in followLogs()
(daemon/logger/loggerutils/logfile.go#L626-L638) keeps to
send messages _synchronously_ (which is OK for now).
4. Logs consumer is gone (Ctrl-C is pressed on a terminal running
"docker logs --follow"). Method (*LogWatcher).Close() is properly
called (see daemon/logs.go:114). Since it was called before and
due to to once.Do(), nothing happens (which is kinda good, as
otherwise it will panic on closing a closed channel).
5. A goroutine (see item 3 above) keeps sending log messages
synchronously to the logWatcher.Msg channel. Since the
channel reader is gone, the channel send operation blocks forever,
and resource cleanup set up in defer statements at the beginning
of followLogs() never happens.
Alas, the fix is somewhat complicated:
1. Distinguish between close from logs producer and logs consumer.
To that effect,
- yet another channel is added to LogWatcher();
- {Watch,}Close() are renamed to {Watch,}ProducerGone();
- {Watch,}ConsumerGone() are added;
*NOTE* that ProducerGone()/WatchProducerGone() pair is ONLY needed
in order to stop ConsumerLogs(follow=true) when a container is stopped;
otherwise we're not interested in it. In other words, we're only
using it in followLogs().
2. Code that was doing (logWatcher*).Close() is modified to either call
ProducerGone() or ConsumerGone(), depending on the context.
3. Code that was waiting for WatchClose() is modified to wait for
either ConsumerGone() or ProducerGone(), or both, depending on the
context.
4. followLogs() are modified accordingly:
- context cancellation is happening on WatchProducerGone(),
and once it's received the FileWatcher is closed and waitRead()
returns errDone on EOF (i.e. log rotation handling logic is disabled);
- due to this, code that was writing synchronously to logWatcher.Msg
can be and is removed as the code above it handles this case;
- function returns once ConsumerGone is received, freeing all the
resources -- this is the bugfix itself.
While at it,
1. Let's also remove the ctx usage to simplify the code a bit.
It was introduced by commit a69a59ffc7 ("Decouple removing the
fileWatcher from reading") in order to fix a bug. The bug was actually
a deadlock in fsnotify, and the fix was just a workaround. Since then
the fsnofify bug has been fixed, and a new fsnotify was vendored in.
For more details, please see
https://github.com/moby/moby/pull/27782#issuecomment-416794490
2. Since `(*filePoller).Close()` is fixed to remove all the files
being watched, there is no need to explicitly call
fileWatcher.Remove(name) anymore, so get rid of the extra code.
Should fix https://github.com/moby/moby/issues/37391
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This test case checks that followLogs() exits once the reader is gone.
Currently it does not (i.e. this test is supposed to fail) due to #37391.
[kolyshkin@: test case Brian Goff, changelog and all bugs are by me]
Source: https://gist.github.com/cpuguy83/e538793de18c762608358ee0eaddc197
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This makes it so consumers of `LogFile` should pass in how to get an
io.Reader to the requested number of lines to tail.
This is also much more efficient when tailing a large number of lines.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
