Merge branch...

Merge branch '231252-geo-document-patroni-failover-for-postgres-ha-primary-single-node-secondary' into 'master'

Geo: Document Patroni failover for single-node secondary

See merge request gitlab-org/gitlab!51614

doc/administration/postgresql/replication_and_failover.md

@@ -714,28 +714,6 @@ consul['configuration'] = {
 
 The manual steps for this configuration are the same as for the [example recommended setup](#example-recommended-setup-manual-steps).
 
-### Manual failover procedure for Patroni
-
-While Patroni supports automatic failover, you also have the ability to perform
-a manual one, where you have two slightly different options:
-
-- **Failover**: allows you to perform a manual failover when there are no healthy nodes.
-  You can perform this action in any PostgreSQL node:
-
-  ```shell
-  sudo gitlab-ctl patroni failover
-  ```
-
-- **Switchover**: only works when the cluster is healthy and allows you to schedule a switchover (it can happen immediately).
-  You can perform this action in any PostgreSQL node:
-
-  ```shell
-  sudo gitlab-ctl patroni switchover
-  ```
-
-For further details on this subject, see the
-[Patroni documentation](https://patroni.readthedocs.io/en/latest/rest_api.html#switchover-and-failover-endpoints).
-
 ## Patroni
 
 NOTE:
@@ -828,6 +806,38 @@ want to signal Patroni to reload its configuration or restart PostgreSQL process
 must use the `reload` or `restart` sub-commands of `gitlab-ctl patroni` instead. These two sub-commands are wrappers of
 the same `patronictl` commands.
 
+### Manual failover procedure for Patroni
+
+While Patroni supports automatic failover, you also have the ability to perform
+a manual one, where you have two slightly different options:
+
+- **Failover**: allows you to perform a manual failover when there are no healthy nodes.
+  You can perform this action in any PostgreSQL node:
+
+  ```shell
+  sudo gitlab-ctl patroni failover
+  ```
+
+- **Switchover**: only works when the cluster is healthy and allows you to schedule a switchover (it can happen immediately).
+  You can perform this action in any PostgreSQL node:
+
+  ```shell
+  sudo gitlab-ctl patroni switchover
+  ```
+
+For further details on this subject, see the
+[Patroni documentation](https://patroni.readthedocs.io/en/latest/rest_api.html#switchover-and-failover-endpoints).
+
+#### Geo secondary site considerations
+
+Similar to `repmgr`, when a Geo secondary site is replicating from a primary site that uses `Patroni` and `PgBouncer`, [replicating through PgBouncer is not supported](https://github.com/pgbouncer/pgbouncer/issues/382#issuecomment-517911529) and the secondary must replicate directly from the leader node in the `Patroni` cluster. Therefore, when there is an automatic or manual failover in the `Patroni` cluster, you will need to manually re-point your secondary site to replicate from the new leader with:
+
+```shell
+sudo gitlab-ctl replicate-geo-database --host=<new_leader_ip> --replication-slot=<slot_name>
+```
+
+Otherwise, the replication will not happen anymore, even if the original node gets re-added as a follower node. This will re-sync your secondary site database and may take a long time depending on the amount of data to sync. You may also need to run `gitlab-ctl reconfigure` if replication is still not working after re-syncing.
+
 ### Recovering the Patroni cluster
 
 To recover the old primary and rejoin it to the cluster as a replica, you can simply start Patroni with:
@@ -1222,7 +1232,7 @@ When a Geo secondary site is replicating from a primary site that uses `repmgr`
 sudo gitlab-ctl replicate-geo-database --host=<new_leader_ip> --replication-slot=<slot_name>
 ```
 
-Otherwise, the replication will not happen anymore, even if the original node gets re-added as a follower node. This will re-sync your secondary site database and may take a long time depending on the amount of data to sync.
+Otherwise, the replication will not happen anymore, even if the original node gets re-added as a follower node. This will re-sync your secondary site database and may take a long time depending on the amount of data to sync. You may also need to run `gitlab-ctl reconfigure` if replication is still not working after re-syncing.
 
 ### Repmgr Restore procedure