Hi, On Tue, Dec 16, 2008 at 7:21 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > > On Tue, 2008-12-16 at 12:36 +0900, Fujii Masao wrote: > >> > So from my previous list >> > >> > 1. We sent the message to standby (A) >> > 2. We received the message on standby >> > 3. We wrote the WAL to the WAL file (B) >> > 4. We fsync'd the WAL file (C) >> > 5. We CRC checked the WAL commit record >> > 6. We applied the WAL commit record >> > >> > Please could you also add an option #4, i.e. add the *option* to fsync >> > the WAL to disk at commit time also. That requires us to add a third >> > option to synchronous_replication parameter. >> >> The above option should be configured on the primary? or standby? >> The primary is suitable to vary it from transaction to transaction. On >> the other hand, it should be configured on the standby in order to >> choose it for every standby (in the future). >> >> I prefer the latter, and thought that it should be added into recovery.conf. >> I mean, synchronous_replication identifies only whether commit waits for >> replication (if the name is confusing, I would rename it). The above >> options (#1-#6) are chosen in recovery.conf. What is your opion? > > No, we've been through that loop already a few months back: > Transaction-controlled robustness. > > It should be up to the client on the primary to decide how much waiting > they would like to perform in order to provide a guarantee. A change of > setting on the standby should not be allowed to alter the performance or > durability on the primary.
OK. I will extend synchronous_replication, make walsender send XLOG with synchronization mode flag and make walreceiver perform according to the flag. > > My perspective is that synchronous_replication specifies how long to > wait. Current settings are "off" (don't wait) or "on" (meaning wait > until point #3). So I think we should change this to a list of options > to allow people to more carefully select how much waiting is required. In the latest patch, "off" keeps us waiting for replication in some cases, e.g. forceSyncCommit = true. This is analogous to the way synchronous_commit works. When "off" keeps us waiting for replication, which option (#1-#6) should we choose? Should it be user-configurable (though the parameter values are doubled)? hardcode #3? "off" always should not keep us waiting for replication? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
