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For cascading replication, wake physical and logical walsenders separately

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Physical walsenders can't send data until it's been flushed; logical
walsenders can't decode and send data until it's been applied. On the
standby, the WAL is flushed first, which will only wake up physical
walsenders; and then applied, which will only wake up logical
walsenders.

Previously, all walsenders were awakened when the WAL was flushed. That
was fine for logical walsenders on the primary; but on the standby the
flushed WAL would have been not applied yet, so logical walsenders were
awakened too early.

Per idea from Jeff Davis and Amit Kapila.

Author: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>
Reviewed-By: Jeff Davis <pgsql@j-davis.com>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/CAA4eK1+zO5LUeisabX10c81LU-fWMKO4M9Wyg1cdkbW7Hqh6vQ@mail.gmail.com
This commit is contained in:
Andres Freund
2023-04-08 00:24:24 -07:00
parent 26669757b6
commit e101dfac3a
7 changed files with 84 additions and 29 deletions
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6
src/backend/access/transam/xlog.c
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@@ -2645,7 +2645,7 @@ XLogFlush(XLogRecPtr record)
END_CRIT_SECTION();
/* wake up walsenders now that we've released heavily contended locks */
WalSndWakeupProcessRequests();
WalSndWakeupProcessRequests(true, !RecoveryInProgress());
/*
* If we still haven't flushed to the request point then we have a
@@ -2816,7 +2816,7 @@ XLogBackgroundFlush(void)
END_CRIT_SECTION();
/* wake up walsenders now that we've released heavily contended locks */
WalSndWakeupProcessRequests();
WalSndWakeupProcessRequests(true, !RecoveryInProgress());
/*
* Great, done. To take some work off the critical path, try to initialize
@@ -5765,7 +5765,7 @@ StartupXLOG(void)
* If there were cascading standby servers connected to us, nudge any wal
* sender processes to notice that we've been promoted.
*/
WalSndWakeup();
WalSndWakeup(true, true);
/*
* If this was a promotion, request an (online) checkpoint now. This isn't