[pgpool-general: 2830] backend_flag for streaming replication
bruce.mcalister at blueface.com
Thu May 15 22:10:25 JST 2014
We are currently testing a postgresql cluster and pgpool cluster. I
would just like to clarify the backend_flag parameter suitable for this
The postgresql cluster is managed as a pacemaker cluster resource using
pgsql resource agent, this manages the startup/shutdown/failover of the
postgresql master instace and synchronous slaves. The postgresql version
is 9.3.4 and is configured in streaming replication mode.
The pgpool cluster is setup using the pgpool-ii-ha resource agent (v2.2)
which is also magaed by pacemaker.
I have been reading the pgpool doc's and it appears that the
'DISALLOW_TO_FAILOVER' parameter is the recommended setting for
backend_flag for a host definition. I presume that this is because
pgpool will not need to perform any sort of recovery operations in case
a postgresql node failed.
If I set the DISALLOW_TO_FAILOVER parameter, will pgpool continue to
probe for the new master if there was a failure. For example, if db node
0 was master and db node 1 & 2 were slaves, then postgresql fails on the
master node, the cluster promotes db node 1 as the new master, will
pgpool reconnect the sessions and active db node 1 as the new write master.
Currently with the testing we have done thus far, pgpool is doing this
correctly, but I have just noticed that my backen_flag setting is
'ALLOW_TO_FAILOVER' so pgpool is firing it's recovery steps.
Additionally, in this mode, I need to pcp_attach_node once the failed db
node is recovered.
How does pgpool handle this scenario when DISALLOW_TO_FAILOVER is the
parameter in use? Do I also need to run pcp_attach_node in this mode if
the system failes over a db node?
Your thoughts and comments are appreciated :)
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