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Elastic Docs ›Elasticsearch Guide [7.1] ›Set up Elasticsearch ›Configuring Elasticsearch

Logging configuration

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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} 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.

######## Server JSON ############################
appender.rolling.type = RollingFile 
appender.rolling.name = rolling
appender.rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_server.json 
appender.rolling.layout.type = ESJsonLayout 
appender.rolling.layout.type_name = server 
appender.rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}-%i.json.gz 
appender.rolling.policies.type = Policies
appender.rolling.policies.time.type = TimeBasedTriggeringPolicy 
appender.rolling.policies.time.interval = 1 
appender.rolling.policies.time.modulate = true 
appender.rolling.policies.size.type = SizeBasedTriggeringPolicy 
appender.rolling.policies.size.size = 256MB 
appender.rolling.strategy.type = DefaultRolloverStrategy
appender.rolling.strategy.fileIndex = nomax
appender.rolling.strategy.action.type = Delete 
appender.rolling.strategy.action.basepath = ${sys:es.logs.base_path}
appender.rolling.strategy.action.condition.type = IfFileName 
appender.rolling.strategy.action.condition.glob = ${sys:es.logs.cluster_name}-* 
appender.rolling.strategy.action.condition.nested_condition.type = IfAccumulatedFileSize 
appender.rolling.strategy.action.condition.nested_condition.exceeds = 2GB 
################################################

Configure the RollingFile appender

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

Use JSON layout.

type_name is a flag populating the type field in a ESJsonLayout. It can be used to distinguish different types of logs more easily when parsing them.

Roll logs to /var/log/elasticsearch/production-yyyy-MM-dd-i.json; logs will be compressed on each roll and i will be incremented

Use 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)

Using a size-based roll policy

Roll logs after 256 MB

Use a delete action when rolling logs

Only delete logs matching a file pattern

The pattern is to only delete the main logs

Only delete if we have accumulated too many compressed logs

The size condition on the compressed logs is 2 GB

 
######## Server -  old style pattern ###########
appender.rolling_old.type = RollingFile
appender.rolling_old.name = rolling_old
appender.rolling_old.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_server.log 
appender.rolling_old.layout.type = PatternLayout
appender.rolling_old.layout.pattern = [%d{ISO8601}][%-5p][%-25c{1.}] [%node_name]%marker %m%n
appender.rolling_old.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}-%i.old_log.gz

The configuration for old style pattern appenders. These logs will be saved in *.log files and if archived will be in * .log.gz files. Note that these should be considered deprecated and will be removed in the future.

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.

Note than you can replace .gz by .zip in appender.rolling.filePattern to compress the rolled logs using the zip format. If you remove the .gz extension then logs will not 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 = IfFileName 
appender.rolling.strategy.action.condition.glob = ${sys:es.logs.cluster_name}-* 
appender.rolling.strategy.action.condition.nested_condition.type = IfLastModified 
appender.rolling.strategy.action.condition.nested_condition.age = 7D

Configure the DefaultRolloverStrategy

Configure the Delete action for handling rollovers

The base path to the Elasticsearch logs

The condition to apply when handling rollovers

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

A nested condition to apply to files matching the glob

Retain logs for seven days

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.discovery=debug). 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.discovery: debug). 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.discovery": "DEBUG"
  }
}

    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.discovery.name = org.elasticsearch.discovery
logger.discovery.level = debug

    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 like this:

logger.deprecation.name = org.elasticsearch.deprecation
logger.deprecation.level = error

JSON log format

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To make parsing Elasticsearch logs easier, logs are now printed in a JSON format. This is configured by a Log4J layout property appender.rolling.layout.type = ESJsonLayout. This layout requires a type_name attribute to be set which is used to distinguish logs streams when parsing.

appender.rolling.layout.type = ESJsonLayout
appender.rolling.layout.type_name = server

Each line contains a single JSON document with the properties configured in ESJsonLayout. See this class javadoc for more details. However if a JSON document contains an exception, it will be printed over multiple lines. The first line will contain regular properties and subsequent lines will contain the stacktrace formatted as a JSON array.

You can still use your own custom layout. To do that replace the line appender.rolling.layout.type with a different layout. See sample below:

appender.rolling.type = RollingFile
appender.rolling.name = rolling
appender.rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_server.log
appender.rolling.layout.type = PatternLayout
appender.rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c{1.}] [%node_name]%marker %.-10000m%n
appender.rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}-%i.log.gz
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