Merge branch 'add-docs-for-srv-handling' into 'master'

CE port: Document SRV handling for DB load balancing

See merge request gitlab-org/gitlab-ce!32539

doc/administration/database_load_balancing.md

@@ -146,7 +146,11 @@ The following options can be set:
 | `use_tcp`            | Lookup DNS resources using TCP instead of UDP                                                     | false     |
 If `record_type` is set to `SRV`, GitLab will continue to use a round-robin algorithm
-and will ignore the `weight` and `priority` in the record.
+and will ignore the `weight` and `priority` in the record. Since SRV records usually
+return hostnames instead of IPs, GitLab will look for the IPs of returned hostnames
+in the additional section of the SRV response. If no IP is found for a hostname, Gitlab
+will query the configured `nameserver` for ANY record for each such hostname looking for A or AAAA records, eventually
+dropping this hostname from rotation if it can't resolve its IP.
 The `interval` value specifies the _minimum_ time between checks. If the A
 record has a TTL greater than this value, then service discovery will honor said