Le 20/01/2011 21:37, Guillaume Lelarge a écrit : > Le 20/01/2011 20:15, Gilles Darold a écrit : >> Hi, >> >> PgPool is a very cool project, when I start to use it this was in plan >> of PostgreSQL high availability and scalability using Pg 9.0 streaming >> replication. The objective is to have one PostgreSQL master with 10 or >> more slaves where I can load balance huge read only queries. >> >> Everything works well until a failover happens. When the PostgreSQL >> master is down for some reason, PgPool force a failover to the next node >> in the replication line. The problem is not with PgPool but with >> PostgreSQL as there's no cascading replication yet. When the failover >> occurs, the next node is promoted as master by PgPool but all other >> slaves are still trying to connect/replicate to the old master. That >> mean that all these nodes have to be reconstructed from the new master >> again. >> >> The other point is that PgPool always takes the next backend declared in >> his configuration file but maybe an other slave node has less >> replication lags and should be promoted instead of the next one. >> >> All this make me do some work on PgPool source code as I think it may >> handle that easily. The patch do the following: >> >> Add a PCP command to promote any node in the pgpool line as the new >> master : pcp_promote_node >> Add a follow master configuration option to call an external command >> when the failover is over. >> >> So that if I run : >> >> pcp_promote_node 10 192.168.1.11 9898 postgres postgres 3 >> >> Node 3 is promoted as master and all other nodes are degenerated. >> >> When the failover is ended PgPool fork a child to execute the command >> given in the follow_master_command successively for each node >> degenerated. The follow master command is simply a call to the >> pcp_recovery_node. >> >> I've played some time with that patch and it works pretty well for me. >> >> Well before going further I need to know if this is something useful >> that can be applied to PgPool? I also need help for testing under other >> modes than streaming replication. >> > Am I wrong or you forgot to send the patch
I've not attached the patch as I want to have community advices before. It also still need some sanity check that I will do today. Regards, -- Gilles Darold http://dalibo.com - http://dalibo.org _______________________________________________ Pgpool-hackers mailing list [email protected] http://pgfoundry.org/mailman/listinfo/pgpool-hackers
