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Ensure that num_sync is greater than zero in synchronous_standby_names.

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Previously num_sync could be set to zero and this setting caused
an assertion failure. This means that multiple synchronous standbys
code should assume that num_sync is greater than zero.
Also setting num_sync to zero is nonsense because it's basically
the configuration for synchronous replication. If users want not to
make transaction commits wait for any standbys,
synchronous_standby_names should be emptied to disable synchronous
replication instead of setting num_sync to zero.

This patch forbids users from setting num_sync to zero in
synchronous_standby_names. If zero is specified, an error will
happen during processing the parameter settings.

Back-patch to 9.6 where multiple synchronous standbys feature was added.

Patch by me. Reviewed by Tom Lane.
Discussion: <CAHGQGwHWB3izc6cXuFLh5kOcAbFXaRhhgwd-X5PeN9TEjxqXwg@mail.gmail.com>
This commit is contained in:
Fujii Masao 2016-12-17 02:20:59 +09:00
parent 6f734554c3
commit 6c75fb6b3d
1 changed files with 7 additions and 0 deletions
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7
src/backend/replication/syncrep.c
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@ -922,6 +922,13 @@ check_synchronous_standby_names(char **newval, void **extra, GucSource source)
return false;
}
if (syncrep_parse_result->num_sync <= 0)
{
GUC_check_errmsg("number of synchronous standbys (%d) must be greater than zero",
syncrep_parse_result->num_sync);
return false;
}
/* GUC extra value must be malloc'd, not palloc'd */
pconf = (SyncRepConfigData *)
malloc(syncrep_parse_result->config_size);