Elastic Search restart

Elastic Stack Elasticsearch
1

Hello Folks,

I have 3 elastic(5.1.2) nodes (01,02,03), of which 01,02 are in Datacenter1 and 03 is in Datacenter2. the elasticsearch.yml on all 3 has the below settings

  1. Cluster name is same across all - it is cluster01
  2. host and node names specific to the Linux server , like node01 ,node02 and node03.
  3. discovery.zen.ping.unicast.hosts: ["node01", "node02" , "node03"]
  4. We have kibana pointing to node01.

I have few questions here

  1. In the above scenario is there a Master ? and slave ?
  2. what is the best way to stop/start ES ? 1 node at a time , we tried to stop/start 3,2,1 , the nodes threw errors like no master etc
    path: /_bulk, params: {}org.elasticsearch.cluster.block.ClusterBlockException: blocked by: [SERVICE_UNAVAILABLE/2/no master];
  3. is it recommended to switch to master/slave mode ? Currently this set up of ours is running fine,wanted to make sure the stop/start of nodes to minimize errors.

Any feedback/recommendations will be helpful

2
  1. Check _cat/master
  2. What settings have you applied to the cluster?
  3. There is no such thing as a slave, only master and master-eligible.
3

I checked the _cat/master , on all 3 nodes , it returns node01. So that means node01 is master and other 2 master-eligible ?

4

Yep :slight_smile:

5

That helps , thanks a lot

so for any maintenance or anything we need to start/stop node1 first before proceeding to others. is that a correct statement in my scenario

6

No, you should be able to restart any single node in that cluster and not lose access to the cluster.

What settings have you set in your config?

7

I have below settings and was wondering why did that error message came like no master ( meaning it was refering to my node01) and no data was being lost ?

cluster.name: cluster01
node.name: node01
path.data: /opt/data/elasticsearch-5.1.2
path.logs: /opt/logs/elasticsearch-5.1.2
bootstrap.memory_lock: true
network.host: node01
http.port: 9200
discovery.zen.ping.unicast.hosts: ["node01", "node02" , "node03"]
discovery.zen.minimum_master_nodes: 3
http.cors.enabled: true
http.cors.allow-origin: "*"

8

That is why. Change that to 2.

10

After going through the documentation , it says below.

This setting must be set to a quorum of your master eligible nodes. It is recommended to avoid having only two master eligible nodes, since a quorum of two is two. Therefore, a loss of either master eligible node will result in an inoperable cluster

Any thoughts ? And also how did you come up with 2 ?

11

The docs also say (number master eligible nodes / 2) + 1.
So (3 / 2) + 1 = 2, when you round up.

12

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