Document the backup-timeout option to gitlab-ctl replicate-geo-database

doc/gitlab-geo/database.md

@@ -414,6 +414,10 @@ data before running `pg_basebackup`.
 
     If PostgreSQL is listening on a non-standard port, add `--port=` as well.
 
+    If your database is too large to be transferred in 30 minutes, you will need
+    to increase the timeout, e.g., `--backup-timeout=3600` if you expect the
+    initial replication to take under an hour.
+
     If you have to connect to a specific IP address, rather than the FQDN of the
     primary, to reach your PostgreSQL server, then you should pass
     `--sslmode=verify-ca` as well. This should **only** be the case if you have

doc/gitlab-geo/troubleshooting.md

@@ -91,6 +91,21 @@ This occurs when PostgreSQL does not have a replication slot for the
 secondary by that name. You may want to rerun the [replication
 process](database.md) on the secondary.
 
+#### How do I fix the message, "Command exceeded allowed execution time" when setting up replication?
+
+This may happen while [initiating the replication process](database.md#step-4-initiate-the-replication-process) on the Geo secondary, and indicates that your
+initial dataset is too large to be replicated in the default timeout (30 minutes).
+
+Re-run `gitlab-ctl replicate-geo-database`, but include a larger value for
+`--backup-timeout`:
+
+```bash
+sudo gitlab-ctl replicate-geo-database --host=primary.geo.example.com --slot-name=secondary_geo_example_com --backup-timeout=21600
+```
+
+This will give the initial replication up to six hours to complete, rather than
+the default thirty minutes. Adjust as required for your installation.
+
 #### How do I fix the message, "PANIC: could not write to file 'pg_xlog/xlogtemp.123': No space left on device"
 
 Determine if you have any unused replication slots in the primary database.  This can cause large amounts of log data to build up in `pg_xlog`.
@@ -136,3 +151,4 @@ sudo gitlab-ctl reconfigure
 
 This will increase the timeout to three hours (10800 seconds). Choose a time
 long enough to accomodate a full clone of your largest repositories.
+