doc: Improve description of wal_receiver_status_interval

This parameter description was previously confusing, telling that a
value of 0 disabled completely status updates.  This is not true as
there are cases where an update is sent while ignoring this parameter
value.  The documentation is improved to outline the difference of
treatment for scheduled status messages and when these are forced.

Reported-by: Dmitriy Kuzmin
Author: Michael Paquier
Reviewed-by: Euler Taveira
Discussion: https://postgr.es/m/161346024420.3455.1345266601055047937@wrigleys.postgresql.org
This commit is contained in:
Michael Paquier 2021-02-24 11:15:58 +09:00
parent 5a65eacfdc
commit c82d59d64e

View File

@ -4503,15 +4503,16 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
view. The standby will report view. The standby will report
the last write-ahead log location it has written, the last position it the last write-ahead log location it has written, the last position it
has flushed to disk, and the last position it has applied. has flushed to disk, and the last position it has applied.
This parameter's This parameter's value is the maximum amount of time between reports.
value is the maximum amount of time between reports. Updates are Updates are sent each time the write or flush positions change, or as
sent each time the write or flush positions change, or at least as often as specified by this parameter if set to a non-zero value.
often as specified by this parameter. Thus, the apply position may There are additional cases where updates are sent while ignoring this
lag slightly behind the true position. parameter; for example, when processing of the existing WAL completes
or when <varname>synchronous_commit</varname> is set to
<literal>remote_apply</literal>.
Thus, the apply position may lag slightly behind the true position.
If this value is specified without units, it is taken as seconds. If this value is specified without units, it is taken as seconds.
The default value is 10 seconds. The default value is 10 seconds. This parameter can only be set in
Setting this parameter to zero disables status updates completely.
This parameter can only be set in
the <filename>postgresql.conf</filename> file or on the server the <filename>postgresql.conf</filename> file or on the server
command line. command line.
</para> </para>