Configuration File

This page describes the yaml configuration file used by Fluent Bit

One of the ways to configure Fluent Bit is using a YAML configuration file that works at a global scope.

The yaml configuration file supports the following sections:

• Env

• Service

• Pipeline

  • Inputs

  • Filters

  • Outputs

Env

The env section allows to configure variables that will be used later on this configuration file.

Example:

# setting up a local environment variable
env:
    flush_interval: 1

# service configuration
service:
    flush:       ${flush_interval}
    log_level:   info
    http_server: on

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
grace	Set the grace time in seconds as Integer value. The engine loop uses a Grace timeout to define wait time on exit	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
dns.mode	Set the primary transport layer protocol used by the asynchronous DNS resolver which can be overriden on a per plugin basis	UDP
log_file	Absolute path for an optional log file. By default all logs are redirected to the standard error interface (stderr).
log_level	Set the logging verbosity level. Allowed values are: off, error, warn, info, debug and trace. Values are accumulative, e.g: if 'debug' is set, it will include error, warning, 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. Multiple Parsers_File entries can be defined within the section.
plugins_file	Path for a plugins configuration file. A plugins configuration file allows to define paths for external plugins, for an example see here.
streams_file	Path for the Stream Processor configuration file. To learn more about Stream Processing configuration go here.
http_server	Enable built-in HTTP Server	Off
http_listen	Set listening interface for HTTP Server when it's enabled	0.0.0.0
http_port	Set TCP Port for the HTTP Server	2020
coro_stack_size	Set the coroutines stack size in bytes. The value must be greater than the page size of the running system. Don't set too small value (say 4096), or coroutine threads can overrun the stack buffer. Do not change the default value of this parameter unless you know what you are doing.	24576
scheduler.cap	Set a maximum retry time in second. The property is supported from v1.8.7.	2000
scheduler.base	Set a base of exponential backoff. The property is supported from v1.8.7.	5

The following is an example of a service section:

service:
    flush: 5
    daemon: off
    log_level: debug

Pipeline

A pipeline section will define a complete pipeline configuration, including inputs, filters and outputs subsections.

pipeline:
    inputs:
        ...
    filters:
        ...
    outputs:
        ...

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. Defined as subsection of the inputs section.
Tag	Tag name associated to all records coming 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 for the cpu plugin.

pipeline:
    inputs:
        - 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. Defined as a subsection of the filters section.
Match	A pattern to match against the tags of incoming records. It's case sensitive and support the star (*) character as a wildcard.
Match_Regex	A regular expression to match against the tags of incoming records. Use this option if you want to use the full regex syntax.

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 a filter section for the grep plugin:

pipeline:
    filters:
        - grep:
            match: *
            regex: log aa

Output

The outputs section specify a destination that certain records should follow after a Tag match. Currently, Fluent Bit can route up to 256 OUTPUT plugins. The configuration support the following keys:

Key	Description
Name	Name of the output plugin. Defined as a subsection of the outputs section.
Match	A pattern to match against the tags of incoming records. It's case sensitive and support the star (*) character as a wildcard.
Match_Regex	A regular expression to match against the tags of incoming records. Use this option if you want to use the full regex syntax.

Example

The following is an example of an output section:

pipeline:
    outputs:
        - 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

pipeline:
    inputs:
        - cpu:
            tag: my_cpu
    outputs:
        - stdout:
            match: my*cpu