Nagios Support Forum

Since I have a 4 node cluster, and have the potential of having any of the 4 become the 'master'

Does this make sense? An even number of systems allows for the 'split brain' problem.

Should I designate 3 as potential masters and have the 4th just be a data node?

Another question from inside the elasticsearch.yml file

I see the following line:
discovery.zen.ping.unicast.hosts: ["localhost"]

Should that instead be:
discovery.zen.ping.unicast.hosts: ["node1", "node2", "node3"]

Please advise. It works as is, but you know...

Thanks

Steve B

SteveBeauchemin wrote:Since I have a 4 node cluster, and have the potential of having any of the 4 become the 'master'

Does this make sense? An even number of systems allows for the 'split brain' problem.

Should I designate 3 as potential masters and have the 4th just be a data node?

If you did this in theory you could still get a split brain problem as any of the 3 that are designated master capable could become master leaving the potential for 2 of them to be designated as master..

In practice we haven't seen this materialize but the only real way around it would be to designate several nodes as master and make the data node NOT able to be master (with no data).

For licensing, the nodes you pay to license are the data nodes, so actually, you could leave 4 data nodes and have several other nodes used as designated masters.

SteveBeauchemin wrote:I see the following line:
discovery.zen.ping.unicast.hosts: ["localhost"]

Should that instead be:
discovery.zen.ping.unicast.hosts: ["node1", "node2", "node3"]

Please advise. It works as is, but you know...

This actually gets overridden when you start the service, from the included
/etc/sysconfig/elasticsearch

the bottom of that script sets ES_JAVA_OPTS after running this gets the list of nodes from /usr/local/nagioslogserver/var/cluster_hosts which is constantly updated

Thank you for the info Scott. It's good stuff.

You can close this.

Steve B

Locking.