All, I'm trying to work on a OCF resource agent that uses postgresql streaming replication. I'm running into a few issues that I hope might be answered or at least some pointers given to steer me in the right direction.
1. A quick way of obtaining a list of "Online" nodes in the cluster that a
resource will be able to migrate to. I've accomplished it with some grep and
see but its not pretty or fast.
# time pcs status | grep Online | sed -e "s/.*\[\(.*\)\]/\1/" | sed 's/ //'
p1.example.net p2.example.net
real 0m2.797s
user 0m0.084s
sys 0m0.024s
Once I get a list of active/online nodes in the cluster my thinking was to use
PSQL to get the current xlog location and lag or each of the remaining nodes
and compare them. If the node has a greater log position and/or less lag it
will be given a greater master preference.
2. How to force a monitor/probe before a promote is run on ALL nodes to make
sure that the master preference is up to date before migrating/failing over the
resource.
- I was thinking that maybe during the promote call it could get the
log location and lag from each of the nodes via an psql call ( like above) and
then force the resource to a specific node. Is there a way to do this and does
it sound like a sane idea ?
The start of my RA is located here suggestions and comments 100% welcome
https://github.com/smbambling/pgsqlsr/blob/master/pgsqlsr
v/r
STEVE
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