Horton

Re: About to add WAL write/fsync statistics to pg_stat_wal view

Masahiro Ikeda <ikedamsh@oss.nttdata.com>

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From: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Li Japin <japinli@hotmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, kuroda.hayato@fujitsu.com
Date: 2021-01-25T07:51:31Z
Lists: pgsql-hackers

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Hi, thanks for the reviews.

I updated the attached patch.
The summary of the changes is following.

1. fix document

I followed another view's comments.


2. refactor issue_xlog_fsync()

I removed "sync_called" variables, narrowed the "duration" scope and
change the switch statement to if statement.


3. make wal-receiver report WAL statistics

I add the code to collect the statistics for a written operation
in XLogWalRcvWrite() and to report stats in WalReceiverMain().

Since WalReceiverMain() can loop fast, to avoid loading stats collector,
I add "force" argument to the pgstat_send_wal function. If "force" is
false, it can skip reporting until at least 500 msec since it last 
reported. WalReceiverMain() almost calls pgstat_send_wal() with "force" 
as false.

Regards,
-- 
Masahiro Ikeda
NTT DATA CORPORATION

Commits

  1. Send statistics collected during shutdown checkpoint to the stats collector.

  2. Force to send remaining WAL stats to the stats collector at walwriter exit.

  3. Track total amounts of times spent writing and syncing WAL data to disk.

  4. Retry short writes when flushing WAL.