postgrespro.git / summary / log / commit / refs

commit    fd7d387e0548fd371c06a91d75bc4632541ccfdd
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Wed Jul 24 02:25:43 2019 +0000

    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


 doc/src/sgml/ref/pg_receivewal.sgml | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/ref/pg_receivewal.sgml b/doc/src/sgml/ref/pg_receivewal.sgml
index 0506120c00..177e9211c0 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>


[parent: 7d81bdc8c0ce]