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Elastic Docs ›Elasticsearch Reference [5.5] ›Set up Elasticsearch

Configuring Elasticsearch

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Configuring Elasticsearch

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Elasticsearch ships with good defaults and requires very little configuration. Most settings can be changed on a running cluster using the Cluster Update Settings API.

The configuration files should contain settings which are node-specific (such as node.name and paths), or settings which a node requires in order to be able to join a cluster, such as cluster.name and network.host.

Config file location

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Elasticsearch has two configuration files:

  • elasticsearch.yml for configuring Elasticsearch, and
  • log4j2.properties for configuring Elasticsearch logging.

These files are located in the config directory, whose location defaults to $ES_HOME/config/. The Debian and RPM packages set the config directory location to /etc/elasticsearch/.

The location of the config directory can be changed with the path.conf setting, as follows:

./bin/elasticsearch -Epath.conf=/path/to/my/config/

Config file format

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The configuration format is YAML. Here is an example of changing the path of the data and logs directories:

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

Settings can also be flattened as follows:

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

Environment variable substitution

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Environment variables referenced with the ${...} notation within the configuration file will be replaced with the value of the environment variable, for instance:

node.name:    ${HOSTNAME}
network.host: ${ES_NETWORK_HOST}

Prompting for settings

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For settings that you do not wish to store in the configuration file, you can use the value ${prompt.text} or ${prompt.secret} and start Elasticsearch in the foreground. ${prompt.secret} has echoing disabled so that the value entered will not be shown in your terminal; ${prompt.text} will allow you to see the value as you type it in. For example:

node:
  name: ${prompt.text}

When starting Elasticsearch, you will be prompted to enter the actual value like so:

Enter value for [node.name]:

Elasticsearch will not start if ${prompt.text} or ${prompt.secret} is used in the settings and the process is run as a service or in the background.

Logging configuration

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Elasticsearch uses Log4j 2 for logging. Log4j 2 can be configured using the log4j2.properties file. Elasticsearch exposes three properties, ${sys:es.logs.base_path}, ${sys:es.logs.cluster_name}, and ${sys:es.logs.node_name} (if the node name is explicitly set via node.name) that can be referenced in the configuration file to determine the location of the log files. The property ${sys:es.logs.base_path} will resolve to the log directory, ${sys:es.logs.cluster_name} will resolve to the cluster name (used as the prefix of log filenames in the default configuration), and ${sys:es.logs.node_name} will resolve to the node name (if the node name is explicitly set).

For example, if your log directory (path.logs) is /var/log/elasticsearch and your cluster is named production then ${sys:es.logs.base_path} will resolve to /var/log/elasticsearch and ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}.log will resolve to /var/log/elasticsearch/production.log.

appender.rolling.type = RollingFile 
appender.rolling.name = rolling
appender.rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}.log 
appender.rolling.layout.type = PatternLayout
appender.rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] %.10000m%n
appender.rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}.log 
appender.rolling.policies.type = Policies
appender.rolling.policies.time.type = TimeBasedTriggeringPolicy 
appender.rolling.policies.time.interval = 1 
appender.rolling.policies.time.modulate = true

Configure the RollingFile appender

Log to /var/log/elasticsearch/production.log

Roll logs to /var/log/elasticsearch/production-yyyy-MM-dd.log

Using a time-based roll policy

Roll logs on a daily basis

Align rolls on the day boundary (as opposed to rolling every twenty-four hours)

Log4j’s configuration parsing gets confused by any extraneous whitespace; if you copy and paste any Log4j settings on this page, or enter any Log4j configuration in general, be sure to trim any leading and trailing whitespace.

If you append .gz or .zip to appender.rolling.filePattern, then the logs will be compressed as they are rolled.

If you want to retain log files for a specified period of time, you can use a rollover strategy with a delete action.

appender.rolling.strategy.type = DefaultRolloverStrategy 
appender.rolling.strategy.action.type = Delete 
appender.rolling.strategy.action.basepath = ${sys:es.logs.base_path} 
appender.rolling.strategy.action.condition.type = IfLastModified 
appender.rolling.strategy.action.condition.age = 7D 
appender.rolling.strategy.action.PathConditions.type = IfFileName 
appender.rolling.strategy.action.PathConditions.glob = ${sys:es.logs.cluster_name}-*

Configure the DefaultRolloverStrategy

Configure the Delete action for handling rollovers

The base path to the Elasticsearch logs

The condition to apply when handling rollovers

Retain logs for seven days

Only delete files older than seven days if they match the specified glob

Delete files from the base path matching the glob ${sys:es.logs.cluster_name}-*; this is the glob that log files are rolled to; this is needed to only delete the rolled Elasticsearch logs but not also delete the deprecation and slow logs

Multiple configuration files can be loaded (in which case they will get merged) as long as they are named log4j2.properties and have the Elasticsearch config directory as an ancestor; this is useful for plugins that expose additional loggers. The logger section contains the java packages and their corresponding log level. The appender section contains the destinations for the logs. Extensive information on how to customize logging and all the supported appenders can be found on the Log4j documentation.

Configuring logging levels

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There are four ways to configuring logging levels, each having situations in which they are appropriate to use.

  1. Via the command-line: -E <name of logging hierarchy>=<level> (e.g., -E logger.org.elasticsearch.transport=trace). This is most appropriate when you are temporarily debugging a problem on a single node (for example, a problem with startup, or during development).
  2. Via elasticsearch.yml: <name of logging hierarchy>: <level> (e.g., logger.org.elasticsearch.transport: trace). This is most appropriate when you are temporarily debugging a problem but are not starting Elasticsearch via the command-line (e.g., via a service) or you want a logging level adjusted on a more permanent basis.

  3. Via cluster settings:

    PUT /_cluster/settings
{
  "transient": {
    "<name of logging hierarchy>": "<level>"
  }
}

    For example:

    PUT /_cluster/settings
{
  "transient": {
    "logger.org.elasticsearch.transport": "trace"
  }
}

    This is most appropriate when you need to dynamically need to adjust a logging level on an actively-running cluster.

  4. Via the log4j2.properties:

    logger.<unique_identifier>.name = <name of logging hierarchy>
logger.<unique_identifier>.level = <level>

    For example:

    logger.transport.name = org.elasticsearch.transport
logger.transport.level = trace

    This is most appropriate when you need fine-grained control over the logger (for example, you want to send the logger to another file, or manage the logger differently; this is a rare use-case).

Deprecation logging

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In addition to regular logging, Elasticsearch allows you to enable logging of deprecated actions. For example this allows you to determine early, if you need to migrate certain functionality in the future. By default, deprecation logging is enabled at the WARN level, the level at which all deprecation log messages will be emitted.

logger.deprecation.level = warn

This will create a daily rolling deprecation log file in your log directory. Check this file regularly, especially when you intend to upgrade to a new major version.

The default logging configuration has set the roll policy for the deprecation logs to roll and compress after 1 GB, and to preserve a maximum of five log files (four rolled logs, and the active log).

You can disable it in the config/log4j2.properties file by setting the deprecation log level to error.

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