qlog: defer creation of the qlog file in QLOGDIR until the first write #4310
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If the syscall to create the qlog file takes a non-negligible amount of time, this can block the connection's run loop, or, even worse, the server's run loop. By creating the qlog file on the first write, it will be created by a the qlogger's Go routine, and not be able to block the run loop. The qlogger uses a buffered channel (capacity: 50). The qlogger will therefore only block if more than 50 qlog events are queued before the syscall returns.
Codecov ReportAttention:
Additional details and impacted files@@ Coverage Diff @@
## master #4310 +/- ##
==========================================
- Coverage 84.13% 84.10% -0.03%
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Files 150 150
Lines 15368 15393 +25
==========================================
+ Hits 12929 12945 +16
- Misses 1940 1946 +6
- Partials 499 502 +3 ☔ View full report in Codecov by Sentry. |
birneee
reviewed
Feb 5, 2024
| log.Printf("Failed to create qlog file %s: %s", path, err.Error()) | ||
| return nil | ||
| } | ||
| return NewConnectionTracer(utils.NewBufferedWriteCloser(bufio.NewWriter(f), f), p, connID) |
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have you intentionally removed the buffered writer?
| // won't block the connection, since qlogs are serialized from a separate Go routine, | ||
| // that takes events from a buffered channel (size: eventChanSize). | ||
| type lazyWriteCloser struct { | ||
| createFile func() (*os.File, error) |
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Suggested change
| createFile func() (*os.File, error) | |
| createWriter func() (io.WriteCloser, error) |
| // This means that creating the qlog (there's no guarantee how long the syscalls will take) | ||
| // won't block the connection, since qlogs are serialized from a separate Go routine, | ||
| // that takes events from a buffered channel (size: eventChanSize). | ||
| type lazyWriteCloser struct { |
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should this util be exported just like utils.NewBufferedWriteCloser
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If the syscall to create the qlog file takes a non-negligible amount of time, this can block the connection's run loop, or, even worse, the server's run loop.
By creating the qlog file on the first write, it will be created by a the qlogger's Go routine, and not be able to block the run loop. The qlogger uses a buffered channel (capacity: 50). The qlogger will therefore only block if more than 50 qlog events are queued before the syscall returns.
@birneee Would you mind taking a look at this PR?