diff options
| author | Michael Paquier <michael@paquier.xyz> | 2019-07-24 11:26:33 +0900 |
|---|---|---|
| committer | Michael Paquier <michael@paquier.xyz> | 2019-07-24 11:26:33 +0900 |
| commit | 1c423463e4b91ec784b935895d77b6ceb3301141 (patch) | |
| tree | 9f488ce4e636fc15d1a0b3ece6e04db4f0d4cbd5 | |
| parent | 46fb7ff65ec29f7aab2e479ab43a180d67a267ed (diff) | |
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 a17082bb11c..cd4f4917791 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</> by default flushes WAL data only when a WAL file is closed. The option <option>--synchronous</> 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> |