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| author | Michael Paquier <michael@paquier.xyz> | 2019-07-24 11:26:24 +0900 |
|---|---|---|
| committer | Michael Paquier <michael@paquier.xyz> | 2019-07-24 11:26:24 +0900 |
| commit | a15a40aaaedfa01f41471f74aa8ac44168603fb9 (patch) | |
| tree | 645a54c0e5fa45e136257c1c292bb59e2e7ab2cf | |
| parent | 0ceb28da06152cbf69c7e9a71c09e9de47783472 (diff) | |
| download | postgresql-a15a40aaaedfa01f41471f74aa8ac44168603fb9.tar.gz postgresql-a15a40aaaedfa01f41471f74aa8ac44168603fb9.zip | |
Doc: Clarify interactions of pg_receivewal with remote_apply
Using pg_receivewal with synchronous_commit = remote_apply set in the
backend is incompatible if pg_receivewal is a synchronous standby as it
never applies WAL, so document this problem and solutions to it.
Backpatch to 9.6, where remote_apply has been added.
Author: Robert Haas, Jesper Pedersen
Reviewed-by: Laurenz Albe, Álvaro Herrera, Michael Paquier
Discussion: https://postgr.es/m/1427a2d3-1e51-9335-1931-4f8853d90d5e@redhat.com
Backpatch-through: 9.6
| -rw-r--r-- | doc/src/sgml/ref/pg_receivewal.sgml | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/doc/src/sgml/ref/pg_receivewal.sgml b/doc/src/sgml/ref/pg_receivewal.sgml index 0506120c00b..177e9211c08 100644 --- a/doc/src/sgml/ref/pg_receivewal.sgml +++ b/doc/src/sgml/ref/pg_receivewal.sgml @@ -52,7 +52,17 @@ PostgreSQL documentation Unlike the WAL receiver of a PostgreSQL standby server, <application>pg_receivewal</application> by default flushes WAL data only when a WAL file is closed. The option <option>--synchronous</option> must be specified to flush WAL data - in real time. + in real time. Since <application>pg_receivewal</application> does not + apply WAL, you should not allow it to become a synchronous standby when + <xref linkend="guc-synchronous-commit"/> equals + <literal>remote_apply</literal>. If it does, it will appear to be a + standby that never catches up, and will cause transaction commits to + block. To avoid this, you should either configure an appropriate value + for <xref linkend="guc-synchronous-standby-names"/>, or specify + <varname>application_name</varname> for + <application>pg_receivewal</application> that does not match it, or + change the value of <varname>synchronous_commit</varname> to + something other than <literal>remote_apply</literal>. </para> <para> |