On Thu, 2008-09-11 at 15:42 +0300, Heikki Linnakangas wrote: > Gregory Stark wrote: > > b) vacuum on the server which cleans up a tuple the slave has in scope has > > to > > block WAL reply on the slave (which I suppose defeats the purpose of > > having > > a live standby for users concerned more with fail-over latency). > > One problem with this, BTW, is that if there's a continuous stream of > medium-length transaction in the slave, each new snapshot taken will > prevent progress in the WAL replay, so the WAL replay will advance in > "baby steps", and can fall behind indefinitely. As soon as there's a > moment that there's no active snapshot, it can catch up, but if the > slave is seriously busy, that might never happen.
It should be possible to do mixed mode. Stall WAL apply for up to X seconds, then cancel queries. Some people may want X=0 or low, others might find X = very high acceptable (Merlin et al). -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
