Anyone still using PostgreSQL 9.4 should re-examine their life choices
at this point, but as it is not yet de-supported by repmgr, consolidate
the references to it whenever pg_rewind is mentioned to a single
section.
Specifically, don't attempt to disable walsenders if "standby_disconnect_on_failover"
is "true", but the repmgr user is not a superuser.
This restriction can be lifted from PostgreSQL 15.
Core commit 4f2400cb3f adds shmem_request_hook, meaning the
memory initialization previously carried out in _PG_init() needs
to be handled in that hook.
Information about using repmgr with a non-superuser was spread
throughout individual documentation systems; this commit creates
an overview of requirements and potential issues.
Previously, if the witness node's PostgreSQL was unreachable, it would
be marked as "inactive" on the primary, and under some circumstances
would not be corrected to "active" once the witness node's PostgreSQL
came back.
PR #754; some modifications by Ian Barwick.
The cluster size check is purely informative, and is not in any way
essential for the standby clone operation. As it's possible the query
may fail if the repmgr user does not have sufficient privileges to
query all databases in the cluster, we can simply ignore any failure.
Note that the code comment indicated the query also served to sanity-
check that queries can actually be executed. While this was the case
historically, the preceding server version check now serves the same
purpose and will not have the same risk of failure due to missing
permissions.
A number of C functions were added in releases 4.2 to 4.4; however
these were renamed in 5.3 to prevent naming clashes with other
extensions.
This does however mean that when upgrading from one of the above
versions, the intermediate upgrade steps will attempt to create
SQL functions referencing C functions which no longer exist in
repmgr.so, and hence cause the upgrade to fail.
We can work around this by providing empty upgrade scripts
from these versions to 4.4, which skip the problematic CREATE
FUNCTION commands. The functions will be correctly created in
the 5.2--5.3 upgrade script.
