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ELK - Set up a Multi-Node Elasticsearch Cluster


Elasticsearch along with Logstash and Kibana is a great combination for aggregating and enriching log files, splitting them into different fields and visualizing them. For this setup, I will set up a 3 Node Cluster with every node operating every role.

The recommended Setup would be separating master-eligible nodes and data nodes, as well as ingest nodes (depending on your workload). 

Quick Note on the software components:

Elasticsearch:
Elasticsearch is a distributed search backend using the lucene engine for searching its shards and saved data. The Data indexed into this will be in the json-format.

Logstash:
Logstash takes your data, passes it through the grok filters you wrote, enriches them if you've configured to do so and indexes them into elasticsearch.

Kibana:
With Kibana you can control and manage your cluster as well as configure pipelines. Kibana will also give you a fancy frontend to search your data and build graphs.

Since I'm only going to go 3 Nodes, and my workload is rather small, I'll go with a "every node does everything" setup.

Each Node has the following specs:

4vCPUs
4GB RAM
80GB HDD
CentOS 7.6 with latest updates.
Elasticsearch 6.6.2
Logstash 6.6.2
Kibana 6.6.2

I'll skip the repository setup since I'm using foreman in my lab and imported the GPG Keys there, synced the repos and promoted the content view. Most of this can be automated, but I will still walk through the manual steps to get the cluster up and running. 

Now for the Setup:

This has to be done on every node:
 [archy@elk01 ~]$ sudo yum -y install openjdk-1.8.0 elasticsearch logstash kibana  
 [archy@elk02 ~]$ sudo yum -y install openjdk-1.8.0 elasticsearch logstash kibana  
 [archy@elk03 ~]$ sudo yum -y install openjdk-1.8.0 elasticsearch logstash kibana

First up, configure elasticsearch:

 [archy@elk01 ~]$ sudo vim /etc/elasticsearch/elasticsearch.yml  

 cluster.name: elk-homelab # your cluster name  
 node.name: elk01.archyslife.lan # your node name   
 node.master: true # node is master-eligible  
 node.data: true # node is a data node  
 node.attr.rack: r1 # attributes, come in handy when distributing it over mutlitple data centers / racks  
 path.data: /var/lib/elasticsearch # where your shards will be stored  
 path.logs: /var/log/elasticsearch # where your logs will be stored  
 network.host: _eth0:ipv4_ # this is a yaml-variable used to setting it to the ipv4 address of the interface eth0  
 http.port: 9200 # elasticsearch http-api listening port  
 transport.tcp.port: 9300 # inter-cluster communication port  
 discovery.zen.ping.unicast.hosts: ["elk01.archyslife.lan", "elk02.archyslife.lan", "elk03.archyslife.lan" ] # your nodes that will form the cluster  
 discovery.zen.minimum_master_nodes: 2 # sum of cluster nodes / 2 + 1  
 gateway.recover_after_nodes: 2 # sum of cluster nodes / 2 + 1  


 [archy@elk02 ~]$ sudo vim /etc/elasticsearch/elasticsearch.yml  

 cluster.name: elk-homelab # your cluster name  
 node.name: elk02.archyslife.lan # your node name   
 node.master: true # node is master-eligible  
 node.data: true # node is a data node  
 node.attr.rack: r1 # attributes, come in handy when distributing it over mutlitple data centers / racks  
 path.data: /var/lib/elasticsearch # where your shards will be stored  
 path.logs: /var/log/elasticsearch # where your logs will be stored  
 network.host: _eth0:ipv4_ # this is a yaml-variable used to setting it to the ipv4 address of the interface eth0  
 http.port: 9200 # elasticsearch http-api listening port  
 transport.tcp.port: 9300 # inter-cluster communication port  
 discovery.zen.ping.unicast.hosts: ["elk01.archyslife.lan", "elk02.archyslife.lan", "elk03.archyslife.lan" ] # your nodes that will form the cluster  
 discovery.zen.minimum_master_nodes: 2 # sum of cluster nodes / 2 + 1  
 gateway.recover_after_nodes: 2 # sum of cluster nodes / 2 + 1  


 [archy@elk03 ~]$ sudo vim /etc/elasticsearch/elasticsearch.yml  

 cluster.name: elk-homelab # your cluster name  
 node.name: elk03.archyslife.lan # your node name   
 node.master: true # node is master-eligible  
 node.data: true # node is a data node  
 node.attr.rack: r1 # attributes, come in handy when distributing it over mutlitple data centers / racks  
 path.data: /var/lib/elasticsearch # where your shards will be stored  
 path.logs: /var/log/elasticsearch # where your logs will be stored  
 network.host: _eth0:ipv4_ # this is a yaml-variable used to setting it to the ipv4 address of the interface eth0  
 http.port: 9200 # elasticsearch http-api listening port  
 transport.tcp.port: 9300 # inter-cluster communication port  
 discovery.zen.ping.unicast.hosts: ["elk01.archyslife.lan", "elk02.archyslife.lan", "elk03.archyslife.lan" ] # your nodes that will form the cluster  
 discovery.zen.minimum_master_nodes: 2 # sum of cluster nodes / 2 + 1  
 gateway.recover_after_nodes: 2 # sum of cluster nodes / 2 + 1

Start up and enable elasticsearch:
 [archy@elk01 ~]$ sudo systemctl enable elasticsearch.service  
 [archy@elk01 ~]$ sudo systemctl start elasticsearch.service  

 [archy@elk02 ~]$ sudo systemctl enable elasticsearch.service  
 [archy@elk02 ~]$ sudo systemctl start elasticsearch.service  

 [archy@elk03 ~]$ sudo systemctl enable elasticsearch.service  
 [archy@elk03 ~]$ sudo systemctl start elasticsearch.service

If everything is started as expected, you should now be having the elasticsearch cluster itself. Check by using curl against the elasticsearch-api:
 [archy@elk01 ~]$ curl -XGET 'https://elk03.archyslife.lan:9200/_cat/nodes?v'  

 ip     heap.percent ram.percent cpu load_1m load_5m load_15m node.role master name  
 172.31.0.12      31     95  1  0.01  0.12   0.14 mdi    -   elk01.archyslife.lan  
 172.31.0.13      47     95  2  0.05  0.12   0.16 mdi    *   elk02.archyslife.lan  
 172.31.0.14      30     95  3  0.10  0.11   0.16 mdi    -   elk03.archyslife.lan

Next step, logstash.

 [archy@elk01 ~]$ sudo vim /etc/logstash/logstash.yml  

 path.data: /var/lib/logstash  
 config.reload.automatic: true  
 path.logs: /var/log/logstash  

 [archy@elk02 ~]$ sudo vim /etc/logstash/logstash.yml  

 path.data: /var/lib/logstash  
 config.reload.automatic: true  
 path.logs: /var/log/logstash  

 [archy@elk03 ~]$ sudo vim /etc/logstash/logstash.yml  

 path.data: /var/lib/logstash  
 config.reload.automatic: true  
 path.logs: /var/log/logstash

Start up and enable logstash:
 [archy@elk01 ~]$ sudo systemctl enable logstash.service  
 [archy@elk01 ~]$ sudo systemctl start logstash.service  

 [archy@elk02 ~]$ sudo systemctl enable logstash.service  
 [archy@elk02 ~]$ sudo systemctl start logstash.service  

 [archy@elk03 ~]$ sudo systemctl enable logstash.service  
 [archy@elk03 ~]$ sudo systemctl start logstash.service

Last step, kibana:
 [archy@elk01 ~]$ sudo vim /etc/kibana/kibana.yml  

 server.port: 5601  
 server.host: "0.0.0.0"  
 elasticsearch.hosts: ["http://elk01.archyslife.lan:9200"]  

 [archy@elk02 ~]$ sudo vim /etc/kibana/kibana.yml  

 server.port: 5601  
 server.host: "0.0.0.0"  
 elasticsearch.hosts: ["http://elk02.archyslife.lan:9200"]  

 [archy@elk03 ~]$ sudo vim /etc/kibana/kibana.yml  

 server.port: 5601  
 server.host: "0.0.0.0"  
 elasticsearch.hosts: ["http://elk03.archyslife.lan:9200"]

Start up and enable kibana:
 [archy@elk01 ~]$ sudo systemctl enable kibana.service  
 [archy@elk01 ~]$ sudo systemctl start kibana.service  

 [archy@elk02 ~]$ sudo systemctl enable kibana.service  
 [archy@elk02 ~]$ sudo systemctl start kibana.service  

 [archy@elk03 ~]$ sudo systemctl enable kibana.service  
 [archy@elk03 ~]$ sudo systemctl start kibana.service

You can now log in to your cluster on any node with port 5601 using your browser.
If you have a license, you can also enable xpack with central monitoring and orchestration of the pipelines in logstash, as well as https and users. This makes the setup much more secure since in the current state, everyone that can access the interface, can access the complete cluster.

The simplest fix would be using nginx as a reverse proxy and make nginx do the authentication. However, this is not part of this tutorial.

Feel free to comment and / or suggest a topic.
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