[GSoC] Add missing IO instrumentation for Server Logging (Observer Effect)#15
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Documents the "Observer Effect" occurring during heavy logging scenarios where uninstrumented write() calls to stderr or the syslogger pipe cause backends to appear as consuming CPU (wait_event IS NULL). - Added section 1.5 to track this missing instrumentation in elog.c (write_console and write_pipe_chunks). - Marked as resolved, as a PoC patch introducing WaitEventIO:LogFileWrite has been developed and submitted to the mentors.
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🚀 Added & Resolved: Logging Observer Effect (Uninstrumented I/O)
Hi @NikolayS,
Following up on your suggestion to investigate the "Observer Effect" during heavy logging, I noticed this specific gap wasn't documented in the current
WAIT_EVENTS_ANALYSIS.md.What I did:
log_statement='all',logging_collector=on), backend processes hit significant I/O bottlenecks onwrite()system calls. Due to the lack of instrumentation, this appeared aswait_event IS NULLinpg_stat_activity, disguising I/O waits as active CPU time.WaitEventIO:LogFileWriteevent and instrumented thewrite_pipe_chunksandwrite_consolefunctions inelog.c.1.5 Server Logging Operationssection to your analysis and marked it as resolved.I will send the actual
.patchfile and the proof screenshot (showing the newly addedLogFileWriteevent in action) to thegsoc-mentorsmailing list so you and Kirk can review the code.