Configuration File

There are some cases where using the command line to start Fluent Bit is not ideal for some escenarios, when running it as a service a configuration file it's times better.

Fluent Bit allows to use one configuration file which works at a global scope and uses the schema defined previously.

The configuration file supports four types of sections:

  • Service
  • Input
  • Filter
  • Output

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. Everytime it timeouts, the engine will flush the records to the output plugin. 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. Off
Log_File Absolute path for an optional log file.
Log_Level Set the logging verbosity level. Allowed values are: error, info, debug and trace. Values are accumulative, e.g: if 'debug' is set, it will include error, info and debug. Note that trace mode is only available if Fluent Bit was built with the WITH_TRACE option enabled. info
Parsers_File Path for a parsers configuration file.

Example

The following is an example of a SERVICE section:

[SERVICE]
    Flush           5
    Daemon          off
    Log_Level       debug

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 it own configuration keys:

Key Description
Name Name of the input plugin.
Tag Tag name associated to all records comming from this plugin.

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:

[INPUT]
    Name cpu
    Tag  my_cpu

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 it own configuration keys:

Key Description
Name Name of the filter plugin.
Match It sets a pattern to match certain records Tag. It's case sensitive and support the start (*) character as a wildcard.

The Name is mandatory and it let Fluent Bit know which filter plugin should be loaded. The Match is mandatory for all plugins.

Example

The following is an example of an FILTER section:

[FILTER]
    Name  stdout
    Match *

Output

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

Key Description
Name Name of the output plugin.
Match It sets a pattern to match certain records Tag. It's case sensitive and support the start (*) character as a wildcard.

Example

The following is an example of an OUTPUT section:

[OUTPUT]
    Name  stdout
    Match my*cpu

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:

[SERVICE]
    Flush     5
    Daemon    off
    Log_Level debug

[INPUT]
    Name  cpu
    Tag   my_cpu

[OUTPUT]
    Name  stdout
    Match my*cpu

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