On 2014-03-12 12:23:01 -0700, Josh Berkus wrote: > On 03/12/2014 12:03 PM, Andres Freund wrote: > > Hi, > > > > On 2014-03-12 12:00:25 -0700, Josh Berkus wrote: > >> I was just reading Michael's explanation of replication slots > >> (http://michael.otacoo.com/postgresql-2/postgres-9-4-feature-highlight-replication-slots/) > >> and realized there was something which had completely escaped me in the > >> pre-commit discussion: > >> > >> select pg_drop_replication_slot('slot_1'); > >> ERROR: 55006: replication slot "slot_1" is already active > >> LOCATION: ReplicationSlotAcquire, slot.c:339 > >> > >> What defines an "active" slot? > > > > One with a connected walsender. > > In a world of network proxies, a walsender could be "connected" for > hours after the replica has ceased to exist. Fortunately, > wal_sender_timeout is changeable on a reload. We check for actual > standby feedback for the timeout, yes?
Yep. > >> It seems like there's no way for a DBA to drop slots from the master if > >> it's rapidly running out of disk WAL space without doing a restart, and > >> there's no way to drop the slot for a replica which the DBA knows is > >> permanently offline but was connected earlier. Am I missing something? > > > > It's sufficient to terminate the walsender and then drop the slot. That > > seems ok for now? > > We have no safe way to terminate the walsender that I know of; > pg_terminate_backend() doesn't include walsenders last I checked. SELECT pg_terminate_backend(pid) FROM pg_stat_replication; works. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
