# Configuration File ![](https://static.scarf.sh/a.png?x-pxid=5e67142e-3887-4b56-b940-18494bcc23a7) One of the ways to configure Fluent Bit is using a main configuration file. Fluent Bit allows the use one configuration file that works at a global scope and uses the defined [Format and Schema](https://docs.fluentbit.io/manual/3.2/administration/configuring-fluent-bit/classic-mode/format-schema). The main configuration file supports four sections: * Service * Input * Filter * Output It's also possible to split the main configuration file into multiple files using the Include File feature to include external files. ## Service The `Service` section defines global properties of the service. The following keys are: | Key | Description | Default Value | | ---------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------- | | `flush` | Set the flush time in `seconds.nanoseconds`. The engine loop uses a Flush timeout to define when it's required to flush the records ingested by input plugins through the defined output plugins. | `1` | | `grace` | Set the grace time in `seconds` as an integer value. The engine loop uses a grace timeout to define wait time on exit. | `5` | | daemon | Boolean. Determines whether Fluent Bit should run as a Daemon (background). Allowed values are: `yes`, `no`, `on`, and `off`. Don't enable when using a Systemd based unit, such as the one provided in Fluent Bit packages. | `Off` | | `dns.mode` | Set the primary transport layer protocol used by the asynchronous DNS resolver. 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). | *none* | | `log_level` | Set the logging verbosity level. Allowed values are: `off`, `error`, `warn`, `info`, `debug`, and `trace`. Values are cumulative. If `debug` is set, it will include `error`, `warning`, `info`, and `debug`. 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. | *none* | | `plugins_file` | Path for a `plugins` configuration file. A `plugins` configuration file defines paths for external plugins. [See an example](https://github.com/fluent/fluent-bit/blob/master/conf/plugins.conf). | *none* | | `streams_file` | Path for the Stream Processor configuration file. [Learn more about Stream Processing configuration](https://docs.fluentbit.io/manual/3.2/stream-processing/introduction). | *none* | | `http_server` | Enable the 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. Setting the value too small (`4096`) can cause coroutine threads to overrun the stack buffer. The default value of this parameter shouldn't be changed. | `24576` | | `scheduler.cap` | Set a maximum retry time in seconds. Supported in v1.8.7 and greater. | `2000` | | `scheduler.base` | Set a base of exponential backoff. Supported in v1.8.7 and greater. | `5` | | `json.convert_nan_to_null` | If enabled, `NaN` converts 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: ```python [SERVICE] Flush 5 Daemon off Log_Level debug ``` For scheduler and retry details, see [scheduling and retries](https://docs.fluentbit.io/manual/3.2/scheduling-and-retries#Scheduling-and-Retries). ## Config input The `INPUT` section defines a source (related to an input plugin). Each [input plugin](https://docs.fluentbit.io/manual/pipeline/inputs) can add its 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`. | `Name` is mandatory and tells Fluent Bit which input plugin to load. `Tag` is mandatory for all plugins except for the `input forward` plugin, which provides dynamic tags. ### Example The following is an example of an `INPUT` section: ```python [INPUT] Name cpu Tag my_cpu ``` ## Config filter The `FILTER` section defines a filter (related to an filter plugin). Each filter plugin can add it own configuration keys. The base configuration for each `FILTER` section contains: | Key | Description | | ------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `Name` | Name of the filter plugin. | | `Match` | A pattern to match against the tags of incoming records. Case sensitive, supports asterisk (`*`) 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 regular expression 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`. | `Name` is mandatory and lets Fluent Bit know which filter plugin should be loaded. `Match` or `Match_Regex` is mandatory for all plugins. If both are specified, `Match_Regex` takes precedence. ### Filter example The following is an example of a `FILTER` section: ```python [FILTER] Name grep Match * Regex log aa ``` ## Config output The `OUTPUT` section specifies a destination that certain records should go to after a `Tag` match. Fluent Bit can route up to 256 `OUTPUT` plugins. The configuration supports the following keys: | Key | Description | | ------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `Name` | Name of the output plugin. | | `Match` | A pattern to match against the tags of incoming records. Case sensitive and supports the asterisk (`*`) 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 regular expression 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`. | ### Output example The following is an example of an `OUTPUT` section: ```python [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: ```python [SERVICE] Flush 5 Daemon off Log_Level debug [INPUT] Name cpu Tag my_cpu [OUTPUT] Name stdout Match my*cpu ``` ## Config 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. The `@INCLUDE` can be used in the following way: ``` @INCLUDE somefile.conf ``` The configuration reader will try to open the path `somefile.conf`. If not found, the reader assumes the file is on a relative path based on the path of the base configuration file: * Main configuration 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, and can't be used inside sections. Wildcard character (`*`) supports including multiple files. For example: ``` @INCLUDE input_*.conf ``` Files matching the wildcard character are included unsorted. If plugin ordering between files needs to be preserved, the files should be included explicitly.