[[reloading-config]]
=== Reloading the Config File

Starting with Logstash 2.3, you can set Logstash to detect and reload configuration
changes automatically.

To enable automatic config reloading, start Logstash with the `--config.reload.automatic` (or `-r`)
command-line option specified. For example:

[source,shell]
----------------------------------
bin/logstash –f apache.config --config.reload.automatic
----------------------------------

NOTE: The `--config.reload.automatic` option is not available when you specify the `-e` flag to pass
in  configuration settings from the command-line.

By default, Logstash checks for configuration changes every 3 seconds. To change this interval,
use the `--config.reload.interval <interval>` option,  where `interval` specifies how often Logstash
checks the config files for changes. 

If Logstash is already running without auto-reload enabled, you can force Logstash to
reload the config file and restart the pipeline by sending a SIGHUP (signal hangup) to the
process running Logstash. For example:

[source,shell]
----------------------------------
kill -SIGHUP 14175
----------------------------------

Where 14175 is the ID of the process running Logstash.

==== How Automatic Config Reloading Works

When Logstash detects a change in a config file, it stops the current pipeline by stopping
all inputs, and it attempts to create a new pipeline that uses the updated configuration.
After validating the syntax of the new configuration, Logstash verifies that all inputs
and outputs can be initialized (for example, that all required ports are open). If the checks
are successful, Logstash swaps the existing pipeline with the new pipeline. If the checks
fail, the old pipeline continues to function, and the errors are propagated to the console.

During automatic config reloading, the JVM is not restarted. The creating and swapping of
pipelines all happens within the same process. 

Changes to <<plugins-filters-grok,grok>> pattern files are also reloaded, but only when
a change in the config file triggers a reload (or the pipeline is restarted).  
