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Configuration File

This page describes the main configuration file used by Fluent Bit

The main configuration file supports four types of sections:

  • Service

  • Input

  • Filter

  • Output

In addition, it's also possible to split the main configuration file in multiple files using the feature to include external files:

  • Include File

Service

The Service section defines global properties of the service, the keys available as of this version are described in the following table:

Key

Description

Default Value

Flush

Set the flush time in seconds.nanoseconds. The engine loop uses a Flush timeout to define when is required to flush the records ingested by input plugins through the defined output plugins.

5

Daemon

Boolean value to set if Fluent Bit should run as a Daemon (background) or not. Allowed values are: yes, no, on and off. note: If you are using a Systemd based unit as the one we provide in our packages, do not turn on this option.

Off

Log_File

Absolute path for an optional log file. By default all logs are redirected to the standard output interface (stdout).

The following is an example of a SERVICE section:

Input

An INPUT section defines a source (related to an input plugin), here we will describe the base configuration for each INPUT section. Note that each input plugin may add its own configuration keys:

The Name is mandatory and it let Fluent Bit know which input plugin should be loaded. The Tag is mandatory for all plugins except for the input forward plugin (as it provides dynamic tags).

Example

The following is an example of an INPUT section:

Filter

A FILTER section defines a filter (related to an filter plugin), here we will describe the base configuration for each FILTER section. Note that each filter plugin may add its own configuration keys:

The Name is mandatory and it let Fluent Bit know which filter plugin should be loaded. The Match or Match_Regex is mandatory for all plugins. If both are specified, Match_Regex takes precedence.

Example

The following is an example of an FILTER section:

Output

The OUTPUT section specify a destination that certain records should follow after a Tag match. The configuration support the following keys:

Example

The following is an example of an OUTPUT section:

Example: collecting CPU metrics

The following configuration file example demonstrates how to collect CPU metrics and flush the results every five seconds to the standard output:

Include File

To avoid complicated long configuration files is better to split specific parts in different files and call them (include) from one main file.

Starting from Fluent Bit 0.12 the new configuration command @INCLUDE has been added and can be used in the following way:

The configuration reader will try to open the path somefile.conf, if not found, it will assume it's a relative path based on the path of the base configuration file, e.g:

  • Main configuration file path: /tmp/main.conf

  • Included file: somefile.conf

  • Fluent Bit will try to open somefile.conf, if it fails it will try /tmp/somefile.conf.

The @INCLUDE command only works at top-left level of the configuration line, it cannot be used inside sections.

Wildcard character (*) is supported to include multiple files, e.g: