# Configuration File
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:
```yaml
# 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](https://github.com/fluent/fluent-bit/blob/master/conf/plugins.conf). | |
| streams\_file | Path for the Stream Processor configuration file. To learn more about Stream Processing configuration go [here](https://docs.fluentbit.io/manual/1.9/stream-processing/introduction). | |
| 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:
```yaml
service:
flush: 5
daemon: off
log_level: debug
```
## Pipeline
A *pipeline* section will define a complete pipeline configuration, including *inputs*, *filters* and *outputs* subsections.
```yaml
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.
```yaml
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:
```yaml
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:
```yaml
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:
```yaml
service:
flush: 5
daemon: off
log_level: debug
pipeline:
inputs:
- cpu:
tag: my_cpu
outputs:
- stdout:
match: my*cpu
```