Elasticsearch is a platform for distributed search and analysis of data in real time. Its popularity is due to its ease of use, powerful features, and scalability.
Elasticsearch supports RESTful operations. This means that you can use HTTP methods (GET, POST, PUT, DELETE, etc.) in combination with an HTTP URI (/collection/entry) to manipulate your data. The intuitive RESTful approach is both developer and user friendly, which is one of the reasons for Elasticsearch’s popularity.
Elasticsearch is a free and open source software with a solid company behind it — Elastic. This combination makes it suitable for use in anywhere from personal testing to corporate integration.
This article will introduce you to Elasticsearch and show you how to install, configure, and start using it.
Before following this tutorial, please make sure you complete the following prerequisites:
- A Ubuntu 14.04 Droplet
- A non-root sudo user. Check out Initial Server Setup with Ubuntu 14.04 for details.
Except otherwise noted, all of the commands that require root privileges in this tutorial should be run as a non-root user with sudo privileges.
Step 1 — Installing Java
First, you will need a Java Runtime Environment (JRE) on your Droplet because Elasticsearch is written in the Java programming language. You can use the native Ubuntu OpenJDK native package for the JRE. This JRE is free, well-supported, and automatically managed through the Ubuntu APT installation manager.
Before installing OpenJDK with APT, update the list of available packages for installation on your Ubuntu Droplet by running the command:
$sudo apt-get update
After that, you can install OpenJDK with the command:
$sudo apt-get install openjdk-7-jre
To verify your JRE is installed and can be used, run the command:
Step 2 — Downloading and Installing Elasticsearch
Elasticsearch can be downloaded directly from elastic.co in zip, tar.gz, deb, or rpm packages. For Ubuntu, it’s best to use the deb (Debian) package which will install everything you need to run Elasticsearch.
At the time of this writing, the latest Elasticsearch version is 1.7.2. Download it in a directory of your choosing with the command:
Then install it in the usual Ubuntu way with the
dpkg command like this:
$sudo dpkg -i elasticsearch-1.7.2.deb
This results in Elasticsearch being installed in
/usr/share/elasticsearch/ with its configuration files placed in
/etc/elasticsearch and its init script added in
To make sure Elasticsearch starts and stops automatically with the Droplet, add its init script to the default runlevels with the command:
</pre> sudo update-rc.d elasticsearch defaults <pre>
Step 3 — Configuring Elastic
Now that Elasticsearch and its Java dependencies have been installed, it is time to configure Elasticsearch.
The Elasticsearch configuration files are in the
/etc/elasticsearch directory. There are two files:
elasticsearch.yml— Configures the Elasticsearch server settings. This is where all options, except those for logging, are stored, which is why we are mostly interested in this file.
logging.yml— Provides configuration for logging. In the beginning, you don’t have to edit this file. You can leave all default logging options. You can find the resulting logs in
The first variables to customize on any Elasticsearch server are
elasticsearch.yml. As their names suggest,
node.name specifies the name of the server (node) and the cluster to which the latter is associated.
If you don’t customize these variable, a
node.name will be assigned automatically in respect to the Droplet hostname. The
cluster.name will be automatically set to the name of the default cluster.
cluster.name value is used by the auto-discovery feature of Elasticsearch to automatically discover and associate Elasticsearch nodes to a cluster. Thus, if you don’t change the default value, you might have unwanted nodes, found on the same network, in your cluster.
To start editing the main
elasticsearch.yml configuration file:
</pre> $sudo nano /etc/elasticsearch/elasticsearch.yml <pre>
# character at the beginning of the lines for
cluster.name to uncomment them, and then change their values. Your first configuration changes in the
/etc/elasticsearch/elasticsearch.yml file should look like this:
Another important setting is the role of the server, which could be either “master” or “slave”. “Masters” are responsible for the cluster health and stability. In large deployments with a lot of cluster nodes, it’s recommended to have more than one dedicated “master.” Typically, a dedicated “master” will not store data or create indexes. Thus, there should be no chance of being overloaded, by which the cluster health could be endangered.
“Slaves” are used as “workhorses” which can be loaded with data tasks. Even if a “slave” node is overloaded, the cluster health shouldn’t be affected seriously, provided there are other nodes to take additional load.
The setting which determines the role of the server is called
node.master. If you have only one Elasticsearch node, you should leave this option commented out so that it keeps its default value of
true— i.e. the sole node should be also a master. Alternatively, if you wish to configure the node as a slave, remove the
# character at the beginning of the
node.master line, and change the value to
Another important configuration option is
node.data, which determines whether a node will store data or not. In most cases this option should be left to its default value (
true), but there are two cases in which you might wish not to store data on a node. One is when the node is a dedicated “master,” as we have already mentioned. The other is when a node is used only for fetching data from nodes and aggregating results. In the latter case the node will act up as a “search load balancer”.
Again, if you have only one Elasticsearch node, you should leave this setting commented out so that it keeps the default
true value. Otherwise, to disable storing data locally, uncomment the following line and change the value to
Two other important options are
index.number_of_replicas. The first determines into how many pieces (shards) the index will be split into. The second defines the number of replicas which will be distributed across the cluster. Having more shards improves the indexing performance, while having more replicas makes searching faster.
Assuming that you are still exploring and testing Elasticsearch on a single node, it’s better to start with only one shard and no replicas. Thus, their values should be set to the following (make sure to remove the
# at the beginning of the lines):
One final setting which you might be interested in changing is
path.data, which determines the path where data is stored. The default path is
/var/lib/elasticsearch. In a production environment it’s recommended that you use a dedicated partition and mount point for storing Elasticsearch data. In the best case, this dedicated partition will be a separate storage media which will provide better performance and data isolation. You can specify a different
path.data path by uncommenting the
path.data line and changing its value:
Once you make all the changes, please save and exit the file. Now you can start Elasticsearch for the first time with the command:
$sudo service elasticsearch start
Please allow at least 10 seconds for Elasticsearch to fully start before you are able to use it. Otherwise, you may get errors about not being able to connect.
Step 4 — Testing
By now, Elasticsearch should be running on port 9200. You can test it with curl, the command line client-side URL transfers tool and a simple GET request like this:
$curl -X GET 'http://localhost:9200'
You should see the following response:
If you see a response similar to the one above, Elasticsearch is working properly. If not, make sure that you have followed correctly the installation instructions and you have allowed some time for Elasticsearch to fully start.