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Remove warning about num_sync being too large in synchronous_standby_names.

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If we're not going to reject such setups entirely, throwing a WARNING in
check_synchronous_standby_names() is unhelpful, because it will cause the
warning to be logged again every time the postmaster receives SIGHUP.
Per discussion, just remove the warning.

In passing, improve the documentation for synchronous_commit, which had not
gotten the word that now there can be more than one synchronous standby.
This commit is contained in:
Tom Lane
2016-04-30 10:54:45 -04:00
parent 207d5a656e
commit 17d5db352c
2 changed files with 21 additions and 69 deletions
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45
src/backend/replication/syncrep.c
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@ -929,51 +929,6 @@ check_synchronous_standby_names(char **newval, void **extra, GucSource source)
return false;
}
/*
* Warn if num_sync exceeds the number of names of potential sync
* standbys. This setting doesn't make sense in most cases because it
* implies that enough number of sync standbys will not appear, which
* makes transaction commits wait for sync replication infinitely.
*
* If there are more than one standbys having the same name and
* priority, we can see enough sync standbys to complete transaction
* commits. However it's not recommended to run multiple standbys with
* the same priority because we cannot gain full control of the
* selection of sync standbys from them.
*
* OTOH, that setting is OK if we understand the above problem
* regarding the selection of sync standbys and intentionally specify *
* to match all the standbys.
*/
if (syncrep_parse_result->num_sync > syncrep_parse_result->nmembers)
{
const char *standby_name;
int i;
bool has_asterisk = false;
standby_name = syncrep_parse_result->member_names;
for (i = 1; i <= syncrep_parse_result->nmembers; i++)
{
if (strcmp(standby_name, "*") == 0)
{
has_asterisk = true;
break;
}
standby_name += strlen(standby_name) + 1;
}
/*
* Only the postmaster warns about this inappropriate setting to
* avoid cluttering the log.
*/
if (!has_asterisk && !IsUnderPostmaster)
ereport(WARNING,
(errmsg("configured number of synchronous standbys (%d) exceeds the number of names of potential synchronous ones (%d)",
syncrep_parse_result->num_sync,
syncrep_parse_result->nmembers),
errhint("Specify more names of potential synchronous standbys in synchronous_standby_names.")));
}
/* GUC extra value must be malloc'd, not palloc'd */
pconf = (SyncRepConfigData *)
malloc(syncrep_parse_result->config_size);