Horton

Re: Use standard SIGHUP and SIGTERM handlers in autoprewarm module

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: bharath.rupireddyforpostgres@gmail.com
Cc: masao.fujii@oss.nttdata.com, pgsql-hackers@postgresql.org
Date: 2020-11-10T07:17:40Z
Lists: pgsql-hackers 
At Sat, 7 Nov 2020 19:31:21 +0530, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote in 
> The main reason for having SetLatch() in
> SignalHandlerForConfigReload() is to wake up the calling process if
> waiting in WaitLatchOrSocket() or WaitLatch() and reload the new
> config file and use the reloaded config variables. Maybe we should
> give a thought on the scenarios in which the walreceiver process
> waits, and what happens in case the latch is set when SIGHUP is
> received.

The difference is whether the config file is processed at the next
wakeup (by force-reply-request or SIGTERM) of walreceiver or
immediately. If server-reload happened frequently, say, several times
per second(?), we should consider to reduce the useless reloading, but
actually that's not the case.

> And also, I think it's worth having a look at the commit 40f908bdcdc7
> that introduced WalRcvSigHupHandler() and 597a87ccc that replaced
> custom latch with procLatch.

At the time of the first patch, PostgreSQL processes used arbitrarily
implemented SIGHUP handlers for their own so it is natural that
walreceiver used its own one.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Revert "Get rid of the dedicated latch for signaling the startup process".

  2. Improve log message about termination of background workers.

  3. Use standard SIGTERM signal handler die() in test_shm_mq worker.

  4. Use standard SIGHUP and SIGTERM signal handlers in worker_spi.

  5. Use standard SIGHUP and SIGTERM handlers in walreceiver.

  6. pg_prewarm: make autoprewarm leader use standard SIGHUP and SIGTERM handlers.

  7. Get rid of the dedicated latch for signaling the startup process.

  8. Use standard SIGHUP handler in syslogger.

  9. Use PostgresSigHupHandler in more places.

  10. Fix race condition with unprotected use of a latch pointer variable.

  11. Remove remnants of ImmediateInterruptOK handling.

  12. Introduce Streaming Replication.