wal receiver
also: walreceiver
A PostgreSQL background process that receives and applies write-ahead log (WAL) data from a primary server to a standby server during replication.
The WAL receiver is a critical component of PostgreSQL's streaming replication architecture. It runs on a standby (replica) database server and continuously connects to the primary server to fetch WAL segments—the sequential log records of all database changes.
When the primary server writes changes to disk, the WAL receiver on the standby pulls these logs in real-time and passes them to the WAL applier process, which replays the changes to keep the standby synchronized. This enables high-availability setups where the standby can quickly take over if the primary fails.
Example: In a PostgreSQL replication setup, the primary server at 10.0.0.1 continuously streams WAL data, and the standby server's WAL receiver process (visible as postgres: walreceiver in process listings) reads and buffers this data before the applier replays it.