Configure replication parameters

There are several replication settings that need to be added or edited in the postgresql.conf configuration file.

Configuring replication parameters

1. Set the synchronous_commit parameter to off.
2. Set the max_wal_senders parameter to the total number of concurrent connections from replicas or backup clients. As a minimum, this should equal the number of replicas you intend to have.
3. Set the wal_level parameter to the amount of information written to the Postgres write-ahead log (WAL). For replication to work, there needs to be enough data in the WAL to support archiving and replication. The default value is usually appropriate.
4. Set the max_replication_slots parameter to the total number of replication slots the primary database can support.
5. Set the listen_addresses parameter to the address of the primary database. Do not leave this parameter as the local loopback address, because the remote replicas must be able to connect to the primary to stream the WAL.
6. Restart Postgres to pick up the changes. This must be done before you create replication slots.

The most common streaming replication use case is asynchronous replication with one or more replicas. In this example, the WAL is streamed to the replica, but the primary server does not wait for confirmation that the WAL has been written to disk on either the primary or the replica. This is the most performant replication configuration, but it does carry the risk of a small amount of data loss in the event of a system failure. It also makes no guarantees that the replica is fully up to date with the primary, which could cause inconsistencies between read queries on the primary and the replica. The example configuration for this use case:

If you need stronger consistency on the replicas, or if your query load is heavy enough to cause significant lag between the primary and replica nodes in asynchronous mode, consider a synchronous replication configuration instead. For more information about the different replication modes, see the [replication modes section][replication-modes].