Configuration File
This page describes the main configuration file used by Fluent Bit
One of the ways to configure Fluent Bit is using a main configuration file. Fluent Bit allows to use one configuration file which works at a global scope and uses the Format and Schema defined previously.
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 | 1 |
grace | Set the grace time in | 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 overridden 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 | |
plugins_file | Path for a | |
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 |
json.convert_nan_to_null | If enabled, NaN is converted to null when fluent-bit converts msgpack to json. | false |
sp.convert_from_str_to_num | If enabled, Stream processor converts from number string to number type. | true |
The following is an example of a SERVICE section:
For scheduler and retry details, please check there: scheduling and retries
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 coming from this plugin. |
Log_Level | Set the plugin's logging verbosity level. Allowed values are: off, error, warn, info, debug and trace. Defaults to the SERVICE section's Log_Level. |
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 it own configuration keys:
Key | Description |
---|---|
Name | Name of the filter plugin. |
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. |
Log_Level | Set the plugin's logging verbosity level. Allowed values are: off, error, warn, info, debug and trace. Defaults to the SERVICE section's Log_Level. |
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. Currently, Fluent Bit can route up to 256 OUTPUT plugins. The configuration support the following keys:
Key | Description |
---|---|
Name | Name of the output plugin. |
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. |
Log_Level | Set the plugin's logging verbosity level. Allowed values are: off, error, warn, info, debug and trace. Defaults to the SERVICE section's Log_Level. |
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:
Visualize
You can also visualize Fluent Bit INPUT, FILTER, and OUTPUT configuration via Calyptia
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:
Note files matching the wildcard character are included unsorted. If plugins ordering between files need to be preserved, the files should be included explicitly.
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