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? -- Guillaume http://www.postgresql.fr http://dalibo.com _______________________________________________ Pgpool-hackers mailing list [email protected] http://pgfoundry.org/mailman/listinfo/pgpool-hackers
