﻿---
title: Elasticsearch log4j configuration
description: 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},...
url: https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5253/deploy-manage/monitor/logging-configuration/elasticsearch-log4j-configuration-self-managed
products:
  - Elasticsearch
applies_to:
  - Self-managed Elastic deployments: Generally available
---

# Elasticsearch log4j configuration
<important>
  Elastic strongly recommends using the Log4j 2 configuration that is shipped by default.
</important>

Elasticsearch uses [Log4j 2](https://logging.apache.org/log4j/2.x/) 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`.
<tip>
  To learn how to configure logging levels, refer to [Update Elasticsearch logging levels](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5253/deploy-manage/monitor/logging-configuration/update-elasticsearch-logging-levels).
</tip>

```properties
####### 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 = ECSJsonLayout 
appender.rolling.layout.dataset = elasticsearch.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 
################################################
```

```properties
####### 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
```

<note>
  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>

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.
```properties
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 
```

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](https://logging.apache.org/log4j/2.x/manual/configuration.html).

## JSON log format

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 = ECSJsonLayout`. This layout requires a `dataset` attribute to be set which is used to distinguish logs streams when parsing.
```properties
appender.rolling.layout.type = ECSJsonLayout
appender.rolling.layout.dataset = elasticsearch.server
```

Each line contains a single JSON document with the properties configured in `ECSJsonLayout`. See this class [javadoc](https://artifacts.elastic.co/javadoc/org/elasticsearch/elasticsearch/8.17.3/org.elasticsearch.server/org/elasticsearch/common/logging/ESJsonLayout.html) for more details.
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.
<note>
  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:
</note>

```properties
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
```