31.10. Configuration Settings#
Logical replication requires several configuration options to be set. Most options are relevant only on one side of the replication. However,max_replication_slots is used on both the publisher and the subscriber, but it has a different meaning for each.
31.10.1. Publishers#
wal_level must be set tological.
max_replication_slots must be set to at least the number of subscriptions expected to connect, plus some reserve for table synchronization.
max_wal_senders should be set to at least the same asmax_replication_slots, plus the number of physical replicas that are connected at the same time.
Logical replication walsender is also affected bywal_sender_timeout.
31.10.2. Subscribers#
max_replication_slots must be set to at least the number of subscriptions that will be added to the subscriber, plus some reserve for table synchronization.
max_logical_replication_workers must be set to at least the number of subscriptions (for leader apply workers), plus some reserve for the table synchronization workers and parallel apply workers.
max_worker_processes may need to be adjusted to accommodate for replication workers, at least (max_logical_replication_workers +1). Note, some extensions and parallel queries also take worker slots frommax_worker_processes.
max_sync_workers_per_subscription controls the amount of parallelism of the initial data copy during the subscription initialization or when new tables are added.
max_parallel_apply_workers_per_subscription controls the amount of parallelism for streaming of in-progress transactions with subscription parameterstreaming = parallel.
Logical replication workers are also affected bywal_receiver_timeout,wal_receiver_status_interval andwal_retrieve_retry_interval.