logger: fix follow logs for max-file=1#39969
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cpuguy83 merged 1 commit intomoby:masterfrom Sep 23, 2019
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In case jsonlogfile is used with max-file=1 and max-size set, the log rotation is not perfomed; instead, the log file is closed and re-open with O_TRUNC. This situation is not handled by the log reader in follow mode, leading to an issue of log reader being stuck forever. This situation (file close/reopen) could be handled in waitRead(), but fsnotify library chose to not listen to or deliver this event (IN_CLOSE_WRITE in inotify lingo). So, we have to handle this by checking the file size upon receiving io.EOF from the log reader, and comparing the size with the one received earlier. In case the new size is less than the old one, the file was truncated and we need to seek to its beginning. Fixes moby#39235. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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Update: the above was mistakenly done using journald log driver :) Using |
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thaJeztah
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Sep 21, 2019
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thaJeztah
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SGTM
should we have a test for this?
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ah, I see your comment above; guess that means we can't add a test? |
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@cpuguy83 ptal |
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I think a test that's actually testing the problem would be rather difficult. |
This was referenced Sep 23, 2019
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In case jsonlogfile is used with
max-file=1andmax-sizeset,the log rotation is not performed; instead, the log file is closed
and re-opened with
O_TRUNC.This situation is not handled by the log reader in follow mode,
leading to an issue of log reader being stuck forever.
This situation (file close/reopen) could be handled in
waitRead(),but fsnotify library chose to not listen to or deliver this event
(
IN_CLOSE_WRITEin inotify lingo) as it's not portable,see fsnotify/fsnotify#252.
So, we have to handle this by checking the file size upon receiving
io.EOFfrom the log reader, and comparing the size with the one receivedearlier. In case the new size is less than the old one, the file was
truncated and we need to seek to its beginning.
Fixes #39235. See the steps to verify in that issue.
Description for the changelog
jsonfile logger: Fix lollow logs stuck when max-size is set and max-file=1