On Thu, Jun 3, 2010 at 12:11 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Greg Stark <gsst...@mit.edu> writes: >> I was assuming the walreceiver only requests more wal in relatively >> small chunks and only when replay has caught up and needs more data. I >> haven't actually read this code so if that assumption is wrong then >> I'm off-base. > > It is off-base. The receiver does not "request" data, the sender is > what determines how much WAL is sent when.
Hm, so what happens if the slave blocks, doesn't the sender block when the kernel buffers fill up? >> So I think this isn't necessarily such a blue moon event. As I >> understand it, all it would take is a single long-running report and a >> vacuum or HOT cleanup occurring on the master. > > I think this is mostly FUD too. How often do you see vacuum blocked for > an hour now? No, that's not comparable. On the master vacuum will just ignore tuples that are still visible to live transactions. On the slave it doesn't have a choice, it sees the cleanup record and must pause recovery until those transactions finish. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
