On 4/11/12, Fujii Masao <masao.fujii@xxxxxxxxx> wrote: > On Wed, Apr 11, 2012 at 3:31 PM, 乔志强 <qiaozhiqiang@xxxxxxxxxxxxxxxx> wrote: >> So in sync streaming replication, if master delete WAL before sent to the >> only standby, all transaction will fail forever, >> "the master tries to avoid a PANIC error rather than termination of >> replication." but in sync replication, termination of replication is THE >> bigger PANIC error. > > I see your point. When there are backends waiting for replication, the WAL > files > which the standby might not have received yet must not be removed. If they > are > removed, replication keeps failing forever because required WAL files don't > exist in the master, and then waiting backends will never be released unless > replication mode is changed to async. This should be avoided. > > To fix this issue, we should prevent the master from deleting the WAL files > including the minimum waiting LSN or bigger ones. I'll think more and > implement > the patch. With asynchonous replication, does the master even know if a slave fails because of a WAL problem? And does/should it care? Isn't there a separate issue with synchronous replication? If it fails, what's the appropriate action to take on the master? PANICing it seems to be a bad idea, but having transactions never complete because they never hear back from the synchronous slave (for whatever reason) seems bad too. -- Mike Nolan -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
