7f7f324eb5
This commit adds two improvements related to the monitoring of WAL
writes for the WAL receiver.
First, write counts and timings are now counted in pg_stat_io for the
WAL receiver. These have been discarded from pg_stat_wal in
ff99918c62 due to performance concerns, related to the fact that we
still relied on an on-disk file for the stats back then, even with
track_wal_io_timing to avoid the overhead of the timestamp calculations.
This implementation is simpler than the original proposal as it is
possible to rely on the APIs of pgstat_io.c to do the job. Like the
fsync and read data, track_wal_io_timing needs to be enabled to track
the timings.
Second, a wait event is added around the pg_pwrite() call in charge of
the writes, using the exiting WAIT_EVENT_WAL_WRITE. This is useful as
the WAL receiver data is tracked in pg_stat_activity.
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/Z8gFnH4o3jBm5BRz@ip-10-97-1-34.eu-west-3.compute.internal
PostgreSQL Database Management System
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