Logging
editLogging
editLogstash emits internal logs during its operation, which are placed in LS_HOME/logs
(or /var/log/logstash
for
DEB/RPM). The default logging level is INFO
. Logstash’s logging framework is based on
Log4j 2 framework, and much of its functionality is exposed directly to users.
You can configure logging for a particular subsystem, module, or plugin.
When you need to debug problems, particularly problems with plugins, consider
increasing the logging level to DEBUG
to get more verbose messages. For
example, if you are debugging issues with Elasticsearch Output, you can increase
log levels just for that component. This approach reduces noise from
excessive logging and helps you focus on the problem area.
You can configure logging using the log4j2.properties
file or the Logstash API.
-
log4j2.properties
file. Changes made through thelog4j2.properties
file require you to restart Logstash for the changes to take effect. Changes persist through subsequent restarts. - Logging API. Changes made through the Logging API are effective immediately without a restart. The changes do not persist after Logstash is restarted.
Log4j2 configuration
editLogstash ships with a log4j2.properties
file with out-of-the-box settings. You
can modify this file to change the rotation policy, type, and other
log4j2
configuration.
You must restart Logstash to apply any changes that you make to
this file.
Changes to log4j2.properties
persist after Logstash is restarted.
Here’s an example using outputs.elasticsearch
:
logger.elasticsearchoutput.name = logstash.outputs.elasticsearch logger.elasticsearchoutput.level = debug
Logging APIs
editFor temporary logging changes, modifying the log4j2.properties
file and restarting Logstash leads to unnecessary
downtime. Instead, you can dynamically update logging levels through the logging API. These settings are effective
immediately and do not need a restart.
By default, the logging API attempts to bind to tcp:9600
. If this port is already in use by another Logstash
instance, you need to launch Logstash with the --http.port
flag specified to bind to a different port. See
Command-Line Flags for more information.
Retrieve list of logging configurations
editTo retrieve a list of logging subsystems available at runtime, you can do a GET
request to _node/logging
curl -XGET 'localhost:9600/_node/logging?pretty'
Example response:
{ ... "loggers" : { "logstash.agent" : "INFO", "logstash.api.service" : "INFO", "logstash.basepipeline" : "INFO", "logstash.codecs.plain" : "INFO", "logstash.codecs.rubydebug" : "INFO", "logstash.filters.grok" : "INFO", "logstash.inputs.beats" : "INFO", "logstash.instrument.periodicpoller.jvm" : "INFO", "logstash.instrument.periodicpoller.os" : "INFO", "logstash.instrument.periodicpoller.persistentqueue" : "INFO", "logstash.outputs.stdout" : "INFO", "logstash.pipeline" : "INFO", "logstash.plugins.registry" : "INFO", "logstash.runner" : "INFO", "logstash.shutdownwatcher" : "INFO", "org.logstash.Event" : "INFO", "slowlog.logstash.codecs.plain" : "TRACE", "slowlog.logstash.codecs.rubydebug" : "TRACE", "slowlog.logstash.filters.grok" : "TRACE", "slowlog.logstash.inputs.beats" : "TRACE", "slowlog.logstash.outputs.stdout" : "TRACE" } }
Update logging levels
editPrepend the name of the subsystem, module, or plugin with logger.
.
Here is an example using outputs.elasticsearch
:
curl -XPUT 'localhost:9600/_node/logging?pretty' -H 'Content-Type: application/json' -d' { "logger.logstash.outputs.elasticsearch" : "DEBUG" } '
While this setting is in effect, Logstash emits DEBUG-level logs for all the Elasticsearch outputs specified in your configuration. Please note this new setting is transient and will not survive a restart.
If you want logging changes to persist after a restart, add them to log4j2.properties
instead.
Reset dynamic logging levels
editTo reset any logging levels that may have been dynamically changed via the logging API, send a PUT
request to
_node/logging/reset
. All logging levels will revert to the values specified in the log4j2.properties
file.
curl -XPUT 'localhost:9600/_node/logging/reset?pretty'
Log file location
editYou can specify the log file location using --path.logs
setting.
Slowlog
editSlowlog for Logstash adds the ability to log when a specific event takes an abnormal amount of time to make its way
through the pipeline. Just like the normal application log, you can find slowlogs in your --path.logs
directory.
Slowlog is configured in the logstash.yml
settings file with the following options:
slowlog.threshold.warn (default: -1) slowlog.threshold.info (default: -1) slowlog.threshold.debug (default: -1) slowlog.threshold.trace (default: -1)
Slowlog is disabled by default. The default threshold values are set to
-1nanos
to represent an infinite threshold. No slowlog will be invoked.
Enable slowlog
editThe slowlog.threshold
fields use a time-value format which enables a wide
range of trigger intervals. You can specify ranges using the following time
units: nanos
(nanoseconds), micros
(microseconds), ms
(milliseconds), s
(second), m
(minute), h
(hour), d
(day).
Slowlog becomes more sensitive and logs more events as you raise the log level.
Example:
slowlog.threshold.warn: 2s slowlog.threshold.info: 1s slowlog.threshold.debug: 500ms slowlog.threshold.trace: 100ms
In this example:
-
If the log level is set to
warn
, the log shows events that took longer than 2 seconds to process. -
If the log level is set to
info
, the log shows events that took longer than 1s to process. -
If the log level is set to
trace
, the log shows events that took longer than 100ms to process. -
If the log level is set to
debug
, the log shows events that took longer than 500ms to process.
The logs include the full event and filter configuration that are responsible for the slowness.