Elasticsearch is a highly scalable open-source full-text search and analytics engine based on Lucene. This post focus on how to setup an Elasticsearch cluster.
I have three Linux servers to build an Elasticsearch cluster. I referred to many materials on the web to get a clear configuration on how to setup an Elasticsearch cluster but many articles were too old with a lot of outdated parameters. The best reference is documentation on official website of Elasticsearch. Here I will get you a concise and informative reference. Following these steps the cluster will be easily setup.
Table of Contents
Elasticsearch here is based on version 6.2.4.
Install Java and Elasticsearch
Create a user for Elasticsearch
Elasticsearch is not allowed to run by root user. Elasticsearch will execute scripts input by users so for the sake of system security starting Elasticsearch by root is banned. Create a user elastic for Elasticsearch within group elastic. A directory is also created in /opt where Elasticsearch will be installed.
groupadd elastic
useradd elastic -g elastic
mkdir /opt/elastic
chown -R elastic:elastic /opt/elastic
Update the Installation packages
It is required to install Java before Elasticsearch. A supported LTS version of Java version 1.8.0_131 or a later version in the Java 8 release series is preferred. Before continuing, download Java and Elasticsearch and Kibana. Upload three file onto every server you want them installed. Suppose you have the following three file:
- elasticsearch-6.2.4.tar.gz
- jdk-8u171-linux-x64.tar.gz
- kibana-6.2.4-linux-x86_64.tar.gz
I used to put files on the user home directory here for user elastic is /home/elastic
Install Java
Check if Java is already installed in bash mode:
which java
If nothing replied go on the installation or you must examine the Java version can satisfy the requirement. If not, I suggest to reinstall Java. It is better to install Java in /usr and Elasticsearch in /opt.
mkdir /usr/java/
tar -zxvf /home/elastic/jdk-8u171-linux-x64.tar.gz -C /usr/java/
Modify PATH
vi /etc/profile
Append the following four lines in the end of profile.
export JAVA_HOME=/usr/java/jdk1.8.0_171
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH
Save the file and exit edit. Make the setting effective by command:
source /etc/profile
Install Elasticsearch
First give a password for elastic for the next login (optional since you can switch to elastic from root) and unpack the file in /opt/elastic.
passwd elastic
su elastic
cd /home/elastic
tar -zxvf elasticsearch-6.2.4.tar.gz -C /opt/elastic/
Configure Elasticsearch
elasticsearch.yml
The first part is trivial. To make a reliable cluster for Elasticsearch some parameters should be taken carefully. Come back to root user and create directories data and logs for Elasticsearch which are usually put on the directories away from the installation directory of Elasticsearch.
exit
mkdir -p /var/elasticsearch/data
mkdir -p /var/elasticsearch/logs
chown -R elastic:elastic /var/elasticsearch
su elastic
cd /opt/elastic/elasticsearch-6.2.4/
vi config/elasticsearch.yml
The most important part is Elasticsearch configuration file config/elasticsearch.yml. Replace 192.168.0.1, 192.168.0.2 and 192.168.0.3 by your three server IPs and each node.name set to be ES1, ES2 and ES3 or any strings you like.
#======================== Elasticsearch Configuration =========================
#
# NOTE: Elasticsearch comes with reasonable defaults for most settings.
# Before you set out to tweak and tune the configuration, make sure you
# understand what are you trying to accomplish and the consequences.
#
# The primary way of configuring a node is via this file. This template lists
# the most important settings you may want to configure for a production cluster.
#
# Please consult the documentation for further information on configuration options:
# https://www.elastic.co/guide/en/elasticsearch/reference/index.html
#
# ————————————————— Cluster —————————————————
#
# Use a descriptive name for your cluster:
#
cluster.name: ES_Cluster
node.master: true
node.data: true
#
# —————————————————— Node ——————————————————
#
# Use a descriptive name for the node:
#
node.name: “ES1”
#
# Add custom attributes to the node:
#
#node.attr.rack: r1
#
# ————————————————— Paths ——————————————————
#
# Path to directory where to store the data (separate multiple locations by comma):
#
path.data: /var/elasticsearch/data
#
# Path to log files:
#
path.logs: /var/elasticsearch/logs
#
# ————————————————— Memory —————————————————
#
# Lock the memory on startup:
#
bootstrap.memory_lock: false
bootstrap.system_call_filter: false
#
# Make sure that the heap size is set to about half the memory available
# on the system and that the owner of the process is allowed to use this
# limit.
#
# Elasticsearch performs poorly when the system is swapping the memory.
#
# ————————————————— Network —————————————————
#
# Set the bind address to a specific IP (IPv4 or IPv6):
#
network.host: 192.168.0.1
#
# Set a custom port for HTTP:
#
http.port: 9200
#
# For more information, consult the network module documentation.
#
# ———————————————— Discovery —————————————————
#
# Pass an initial list of hosts to perform discovery when new node is started:
# The default list of hosts is [“127.0.0.1”, “[::1]”]
#
discovery.zen.ping.unicast.hosts: [“192.168.0.1”, “192.168.0.2”, “192.168.0.3”]
#
# Prevent the “split brain” by configuring the majority of nodes (total number of master-eligible nodes / 2 + 1):
#
discovery.zen.minimum_master_nodes: 2
#
# For more information, consult the zen discovery module documentation.
#
# ————————————————— Gateway —————————————————
#
# Block initial recovery after a full cluster restart until N nodes are started:
#
#gateway.recover_after_nodes: 3
#
# For more information, consult the gateway module documentation.
#
# ————————————————— Various —————————————————
#
# Require explicit names when deleting indices:
#
#action.destructive_requires_name: true
Note: Prevent the “split brain” by configuring the majority of nodes (total number of master-eligible nodes / 2 + 1). In this case it is 2.
jvm.options
By default, Elasticsearch tells the JVM to use a heap with a minimum and maximum size of 1 GB. When moving to production, it is important to configure heap size to ensure that Elasticsearch has enough heap available. See: setting heap size. To make things easier, let’s skip this step.
Important system configuration
Switch to root.
vi /etc/security/limits.conf
Add these lines:
* soft nofile 65536
* hard nofile 131072
* soft nproc 4096
* hard nproc 4096
* soft memlock unlimited
* hard memlock unlimited
Save and edit /etc/security/limits.d/90-nproc.conf
cp /etc/security/limits.d/90-nproc.conf /etc/security/limits.d/90-nproc.conf_bak
vi /etc/security/limits.d/90-nproc.conf
Add the same content:
* soft nofile 65536
* hard nofile 131072
* soft nproc 4096
* hard nproc 4096
* soft memlock unlimited
* hard memlock unlimited
Logout and relogon as root. Edit /etc/sysctl.conf and append vm.max_map_count=262144.
vi /etc/sysctl.conf
vm.max_map_count=262144
Make setting effective:
sudo sysctl -p /etc/sysctl.conf
Do the above settings the same to the other servers except network.host. After all those done all you need is to start Elasticsearch one by one.
Start Elasticsearch
Change user to elastic:
cd /opt/elastic/elasticsearch-6.2.4/bin
./elasticsearch -d
Open browser on your desktop and refer to the address http://192.168.0.1:9200 to check whether it works.
One more thing: Kibana
Kibana is an open source analytics and visualization platform designed to work with Elasticsearch. You use Kibana to search, view, and interact with data stored in Elasticsearch indices.
Logon as user elastic and change directory to /home/elastic.
tar –zxvf kibana-6.2.4-linux-x86_64.tar.gz -C /opt/elastic/
In the kibana configuration file /opt/elastic/kibana-6.2.4-linux-x86_64/config/kibana.yml three parameters should be replaced:
server.port:5601
server.host:192.168.0.1
elasticsearch.url:192.168.0.1:9200
Now you can start kibana on the background.
nohup ./kibana &
Open kibana by input http://192.168.0.1:5601 in the browser.
Read Elastic documentation for further reference or watch Getting Started video.