I'm following through the workflow from primary to standby in our environment. However the one thing I can't seem to find is how WAL files are cleaned up from $PGDATA/pg_xlog once they are no longer needed on the standby.
The standby has archive_cleanup_command calling pg_archivecleanup to remove files from the incoming archive directory. My understanding is that files from there are restored to the pg_xlog directory via the restore_command, which jives with what I see in pg_xlog.
However something is cleaning up files from pg_xlog and I don't see any parameter command or cron job that does so. My documentation and list archive searching has come up empty so I thought I'd bug you guys yet again.
TL;DR: What cleans up restored WAL files from pg_xlog when they are no longer needed?