Configuration

Within the scripts, ElasticSearch comes with built in JAVA_OPTS passed to the JVM started. The most important setting for that is the -Xmx to control the maximum allowed memory for the process, and -Xms to control the minimum allocated memory for the process (in general, the more memory allocated to the process, the better).

Most times it is better to leave the default JAVA_OPTS as they are, and use the ES_JAVA_OPTS environment variable in order to set / change JVM settings or arguments.

The ES_HEAP_SIZE environment variable allows to set the heap memory that will be allocated to elasticsearch java process. It will allocate the same value to both min and max values, though those can be set explicitly (not recommended) by setting ES_MIN_MEM (defaults to 256m), and ES_MAX_MEM (defaults to 1gb).

It is recommended to set the min and max memory to the same value, and enable mlockall.

Make sure to increase the number of open files descriptors on the machine (or for the user running elasticsearch). Setting it to 32k or even 64k is recommended.

In order to test how many open files the process can open, start it with -Des.max-open-files set to true. This will print the number of open files the process can open on startup.

Alternatively, you can retrieve the max_file_descriptors for each node using the Nodes Info API, with:

curl localhost:9200/_nodes/process?pretty

There is an option to use mlockall to try to lock the process address space so it won’t be swapped. For this to work, the bootstrap.mlockall should be set to true and it is recommended to set both the min and max memory allocation to be the same. Note: This option is only available on Linux/Unix operating systems.

In order to see if this works or not, set the common.jna logging to DEBUG level. A solution to "Unknown mlockall error 0" can be to set ulimit -l unlimited.

Note, mlockall might cause the JVM or shell session to exit if it fails to allocate the memory (because not enough memory is available on the machine).

elasticsearch configuration files can be found under ES_HOME/config folder. The folder comes with two files, the elasticsearch.yml for configuring ElasticSearch different modules, and logging.yml for configuring the ElasticSearch logging.

The configuration format is YAML. Here is an example of changing the address all network based modules will use to bind and publish to:

network :
    host : 10.0.0.4

In production use, you will almost certainly want to change paths for data and log files:

path:
  logs: /var/log/elasticsearch
  data: /var/data/elasticsearch

Also, don’t forget to give your production cluster a name, which is used to discover and auto-join other nodes:

cluster:
  name: <NAME OF YOUR CLUSTER>

You may also want to change the default node name for each node to something like the display hostname. By default ElasticSearch will randomly pick a Marvel character name from a list of around 3000 names when your node starts up.

node:
  name: <NAME OF YOUR NODE>

Internally, all settings are collapsed into "namespaced" settings. For example, the above gets collapsed into node.name. This means that its easy to support other configuration formats, for example, JSON. If JSON is a preferred configuration format, simply rename the elasticsearch.yml file to elasticsearch.json and add:

{
    "network" : {
        "host" : "10.0.0.4"
    }
}

It also means that its easy to provide the settings externally either using the ES_JAVA_OPTS or as parameters to the elasticsearch command, for example:

$ elasticsearch -f -Des.network.host=10.0.0.4

Another option is to set es.default. prefix instead of es. prefix, which means the default setting will be used only if not explicitly set in the configuration file.

Another option is to use the ${...} notation within the configuration file which will resolve to an environment setting, for example:

{
    "network" : {
        "host" : "${ES_NET_HOST}"
    }
}

The location of the configuration file can be set externally using a system property:

$ elasticsearch -f -Des.config=/path/to/config/file

Indices created within the cluster can provide their own settings. For example, the following creates an index with memory based storage instead of the default file system based one (the format can be either YAML or JSON):

$ curl -XPUT http://localhost:9200/kimchy/ -d \
'
index :
    store:
        type: memory
'

Index level settings can be set on the node level as well, for example, within the elasticsearch.yml file, the following can be set:

index :
    store:
        type: memory

This means that every index that gets created on the specific node started with the mentioned configuration will store the index in memory unless the index explicitly sets it. In other words, any index level settings override what is set in the node configuration. Of course, the above can also be set as a "collapsed" setting, for example:

$ elasticsearch -f -Des.index.store.type=memory

All of the index level configuration can be found within each index module.

ElasticSearch uses an internal logging abstraction and comes, out of the box, with log4j. It tries to simplify log4j configuration by using YAML to configure it, and the logging configuration file is config/logging.yml file.