How to set up ES cluster? - elasticsearch

Question

Assuming I have 5 machines I want to run an elasticsearch cluster on, and they are all connected to a shared drive. I put a single copy of elasticsearch onto that shared drive so all three can see it. Do I just start the elasticsearch on that shared drive on eall of my machines and the clustering would automatically work its magic? Or would I have to configure specific settings to get the elasticsearch to realize that its running on 5 machines? If so, what are the relevant settings? Should I worry about configuring for replicas or is it handled automatically?

Answer 1

its super easy.
You'll need each machine to have it's own copy of ElasticSearch (simply copy the one you have now) -- the reason is that each machine / node whatever is going to keep it's own files that are sharded accross the cluster.
The only thing you really need to do is edit the config file to include the name of the cluster.
If all machines have the same cluster name elasticsearch will do the rest automatically (as long as the machines are all on the same network)
Read here to get you started:
https://www.elastic.co/guide/en/elasticsearch/guide/current/deploy.html
When you create indexes (where the data goes) you define at that time how many replicas you want (they'll be distributed around the cluster)

Answer 2

It is usually handled automatically.
If autodiscovery doesn't work. Edit the elastic search config file, by enabling unicast discovery
Node 1:
cluster.name: mycluster
node.name: "node1"
node.master: true
node.data: true
discovery.zen.ping.multicast.enabled: false
discovery.zen.ping.unicast.hosts: ["node1.example.com"]
Node 2:
cluster.name: mycluster
node.name: "node2"
node.master: false
node.data: true
discovery.zen.ping.multicast.enabled: false
discovery.zen.ping.unicast.hosts: ["node1.example.com"]
and so on for node 3,4,5. Make node 1 master, and the rest only as data nodes.
Edit: Please note that by ES rule, if you have N nodes, then by convention, N/2+1 nodes should be masters for fail-over mechanisms They may or may not be data nodes, though.
Also, in case auto-discovery doesn't work, most probable reason is because the network doesn't allow it (and therefore disabled). If too many auto-discovery pings take place across multiple servers, the resources to manage those pings will prevent other services from running correctly.
For ex, think of a 10,000 node cluster and all 10,000 nodes doing the auto-pings.

Answer 3

Elastic Search 7 changed the configurations for cluster initialisation.
What is important to note is the ES instances communicate internally using the Transport layer(TCP) and not the HTTP protocol which is normally used to perform ops on the indices. Below is sample config for 2 machines cluster.
cluster.name: cluster-new
node.name: node-1
node.master: true
node.data: true
bootstrap.memory_lock: true
network.host: 0.0.0.0
http.port: 9200
transport.host: 102.123.322.211
transport.tcp.port: 9300
discovery.seed_hosts: [“102.123.322.211:9300”,"102.123.322.212:9300”]
cluster.initial_master_nodes:
- "node-1"
- "node-2”
Machine 2 config:-
cluster.name: cluster-new
node.name: node-2
node.master: true
node.data: true
bootstrap.memory_lock: true
network.host: 0.0.0.0
http.port: 9200
transport.host: 102.123.322.212
transport.tcp.port: 9300
discovery.seed_hosts: [“102.123.322.211:9300”,"102.123.322.212:9300”]
cluster.initial_master_nodes:
- "node-1"
- "node-2”
cluster.name: This has be same across all the machines that are going to be part of a cluster.
node.name : Identifier for the ES instance. Defaults to machine name if not given.
node.master: specifies whether this ES instance is going to be master or not
node.data: specifies whether this ES instance is going to be data node or not(hold data)
bootsrap.memory_lock: disable swapping.You can start the cluster without setting this flag. But its recommended to set the lock.More info: https://www.elastic.co/guide/en/elasticsearch/reference/master/setup-configuration-memory.html
network.host: 0.0.0.0 if you want to expose the ES instance over network. 0.0.0.0 is different from 127.0.0.1( aka localhost or loopback address).
It means all IPv4 addresses on the machine. If machine has multiple ip addresses with a server listening on 0.0.0.0, the client can reach the machine from any of the IPv4 addresses.
http.port: port on which this ES instance will listen to for HTTP requests
transport.host: The IPv4 address of the host(this will be used to communicate with other ES instances running on different machines). More info: https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-transport.html
transport.tcp.port: 9300 (the port where the machine will accept the tcp connections)
discovery.seed_hosts: This was changed in recent versions. Initialise all the IPv4 addresses with TCP port(important) of ES instances that are going to be part of this cluster. This is going to be same across all ES instances that are part of this cluster.
cluster.initial_master_nodes: node names(node.name) of the ES machines that are going to participate in master election.(Quorum based decision making :- https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-discovery-quorums.html#modules-discovery-quorums)

Answer 4

I tried the steps that #KannarKK suggested on ES 2.0.2, however, I could not bring the cluster up and running. Evidently, I figured out something, as I had set tcp port number on Master, on the Slave configuration discovery.zen.ping.unicast.hosts needs Master's port number along with IP address ( tcp port number ) for discovery. So when I try following configuration it works for me.
Node 1
cluster.name: mycluster
node.name: "node1"
node.master: true
node.data: true
http.port : 9200
tcp.port : 9300
discovery.zen.ping.multicast.enabled: false
# I think unicast.host on master is redundant.
discovery.zen.ping.unicast.hosts: ["node1.example.com"]
Node 2
cluster.name: mycluster
node.name: "node2"
node.master: false
node.data: true
http.port : 9201
tcp.port : 9301
discovery.zen.ping.multicast.enabled: false
# The port number of Node 1
discovery.zen.ping.unicast.hosts: ["node1.example.com:9300"]