Content Comparison

action.auto_create_index: "+csmeter*,+*_nfsconnector,.watches,
.triggered_watches,.watcher-history-*"

Needed to disable automatic index creation, csmeter indices, and Swarm NFS connectors. (v10.1)

cluster.name: <ES_cluster_name>

Provide the Elasticsearch cluster a unique name, which is unrelated to the Swarm cluster name. Do not use periods in the name.

node.name: <ES_node_name>

Optional: Elasticsearch supplies a node name if one is not set. Do not use periods in the name.

network.host: _site_

Assign a specific hostname or IP address, which requires clients to access the ES server using that address. Update /etc/hosts if using a hostname. Defaults to the special value, _site_.

cluster.initial_master_nodes

(ES 7+) For first-time bootstrapping of a production ES cluster. Set to an array or comma-delimited list of the hostnames of the master-eligible ES nodes whose votes should be counted in the very first election.

discovery.zen.
minimum_master_nodes: 3

(ES 6 only)  Set to (number of master-eligible nodes / 2, rounded down) + 1. Prevents split-brain scenarios by setting the minimum number of ES nodes online before deciding on electing a new master.

discovery.seed_hosts

(ES 7+) Enables auto-clustering of ES nodes across hosts. Set to an array or comma-delimited list of the addresses of all master-eligible nodes in the cluster. 

discovery.zen.ping.unicast.hosts: ["es0", "es1"]

(ES 6 only) Set to the list of node names/IPs in the cluster, verifying all ES servers are included. Multicast is disabled by default.

gateway.expected_nodes: 4

Add and set to the number of nodes in the ES cluster. Recovery of local shards starts as soon as this number of nodes have joined the cluster. It falls back to the recover_after_nodes value after 5 minutes. This example is for a 4-node cluster.

gateway.recover_after_nodes: 2

Set to the minimum number of ES nodes started before going into operation status:

• Set to 1 if total nodes is 1 or 2.

• Set to 2 if total nodes is 3 or 4.

• Set to the number – 2 if total nodes is 5 to 7.

• Set to the number – 3 if total nodes 8 or more.

bootstrap.memory_lock: true

Set to lock the memory on startup to verify Elasticsearch does not swap (swapping leads to poor performance). Verify enough system memory resources are available for all processes running on the server.

The RPM installer makes these edits to/etc/security/limits.d/10-caringo-elasticsearch.conf to allow the elasticsearch user to disable swapping and to increase the number of open file descriptors: 

# Custom for Caringo Swarm
elasticsearch soft nofile 65536
elasticsearch hard nofile 65536
elasticsearch soft nproc 4096
elasticsearch hard nproc 4096
# allow user 'elasticsearch' memlock
elasticsearch soft memlock unlimited
elasticsearch hard memlock unlimited

path.data: <path_to_data_directory>

path.data goes to /var/lib/elasticsearch with the needed ownership by default. Choose a separate, dedicated partition of ample size, and make the elasticsearch user the owner of that directory to move the Elasticsearch data directory:

chown -R elasticsearch:elasticsearch <path_to_data_directory>

thread_pool.write.queue_size

The size of the queue used for bulk indexing.

This variable was called threadpool.bulk.queue_size in earlier Elasticsearch versions.

node.attr.rack

Optional: A setting for Elasticsearch that tells to not assign the replica shard to a node running in the same “rack” where the primary shard lives. This allows for example a 6-node cluster running with 2 nodes on each of 3 ESXi hosts to survive one of the ESXi hosts being down. The state is yellow, not red.

Set to a rack name or ESXi host identifier like esxi3 on the Elasticsearch node(s) running on the third virtual machine host. This also requires setting cluster.routing.allocation.awareness.attributes=rack on all ES nodes. Both settings should already be in your Elasticsearch.yml but commented out.

Ideally, this is set right after initial configuration when first starting Elasticsearch. To add to an existing deployment, all nodes must be restarted before shards are reallocated. To do this without downtime, first turn off shard allocation, then restart each node one by one waiting for it to show in GET /_cat/nodes before moving to the next node. When done, reenable shard allocation. Health is yellow during this time. As an example, this process takes an hour for a 9 node cluster (20 x 30GB shards) to go green.
Monitor shard allocation with GET _cluster/allocation/explain, also see:
https://www.elastic.co/guide/en/elasticsearch/reference/7.5/allocation-awareness.html
Rolling Restart of Elasticsearch