4. Elasticsearch Node Maintenance

4.1. Performing Updates

When updates are applied to the Analysis Cockpit, you also need to update all additional cluster nodes by running:

nextron@es-node1:~$ sudo apt update
nextron@es-node1:~$ sudo apt upgrade

It is recommended that you update one node at a time, in particular when a reboot is required. It is not necessary to remove the node from the cluster for the update.

4.2. Checking Elasticsearch status

You can check elasticsearch status and index distribution on any of the nodes:

nextron@es-node1:~$ curl http://127.0.0.1:9200/_cat/health
nextron@es-node1:~$ curl http://127.0.0.1:9200/_cat/nodes
nextron@es-node1:~$ curl http://127.0.0.1:9200/_cat/shards

4.3. Removing Elasticsearch nodes

Before temporarily or permanently removing a node, you should reconfigure the cluster to move away any shards from that node.

You can tell Elasticsearch to remove all indexes from a node (change the placeholder value of “node_to_remove” to the actual node name):

nextron@es-node1:~$ curl -XPUT “http://127.0.0.1:9200/_cluster/settings” -d '{"transient": {"cluster.routing.allocation.exclude._name": "node_to_remove"} }'

Then wait until the node has no shards left:

nextron@es-node1:~$ curl http://127.0.0.1:9200/_cat/shards

Once no shards are assigned to the node, it is safe to shut it down. When you have replicas of each index (number_of_replicas >= 1), the cluster should automatically cope with the removal of any single node. Refer to Elasticsearch documentation!

For obvious reasons, you must not remove the Analysis Cockpit node itself from the cluster but it is ok to shut it down or restart it for maintenance.