# CPU metrics

The *CPU* input plugin, measures the CPU usage of a process or the whole system by default (considering per CPU core). It reports values in percentage unit for every interval of time set. This plugin is available only for Linux.

The following tables describe the information generated by the plugin. The following keys represent the data used by the overall system, and all values associated to the keys are in a percentage unit (0 to 100%):

The CPU metrics plugin creates metrics that are log-based, such as JSON payload. For Prometheus-based metrics, see the *Node Exporter Metrics* input plugin.

| Key        | Description                                                                                                                                                                    |
| ---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `cpu_p`    | CPU usage of the overall system, this value is the summation of time spent on user and kernel space. The result takes in consideration the numbers of CPU cores in the system. |
| `user_p`   | CPU usage in User mode, for short it means the CPU usage by user space programs. The result of this value takes in consideration the numbers of CPU cores in the system.       |
| `system_p` | CPU usage in Kernel mode, for short it means the CPU usage by the Kernel. The result of this value takes in consideration the numbers of CPU cores in the system.              |
| `threaded` | Indicates whether to run this input in its own [thread](https://docs.fluentbit.io/manual/4.1/administration/multithreading#inputs). Default: `false`.                          |

In addition to the keys reported in the previous table, a similar content is created per CPU core. The cores are listed from `0` to `N` as the Kernel reports:

| Key             | Description                                                                  |
| --------------- | ---------------------------------------------------------------------------- |
| `cpuN.p_cpu`    | Represents the total CPU usage by core `N`.                                  |
| `cpuN.p_user`   | Total CPU spent in user mode or user space programs associated to this core. |
| `cpuN.p_system` | Total CPU spent in system or kernel mode associated to this core.            |

## Configuration parameters

The plugin supports the following configuration parameters:

| Key              | Description                                                                                                                                                                         | Default |
| ---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `Interval_Sec`   | Polling interval in seconds.                                                                                                                                                        | `1`     |
| \`Interval\_NSec | Polling interval in nanoseconds\`                                                                                                                                                   | `0`     |
| `PID`            | Specify the `ID` (`PID`) of a running process in the system. By default, the plugin monitors the whole system but if this option is set, it will only monitor the given process ID. | *none*  |

## Get started

In order to get the statistics of the CPU usage of your system, you can run the plugin from the command line or through the configuration file:

### Command line

You can run this filter from the command line using a command like the following:

```shell
build/bin/fluent-bit -i cpu -t my_cpu -o stdout -m '*'
```

The command returns results similar to the following:

```
...
[0] [1452185189, {"cpu_p"=>7.00, "user_p"=>5.00, "system_p"=>2.00, "cpu0.p_cpu"=>10.00, "cpu0.p_user"=>8.00, "cpu0.p_system"=>2.00, "cpu1.p_cpu"=>6.00, "cpu1.p_user"=>4.00, "cpu1.p_system"=>2.00}]
[1] [1452185190, {"cpu_p"=>6.50, "user_p"=>5.00, "system_p"=>1.50, "cpu0.p_cpu"=>6.00, "cpu0.p_user"=>5.00, "cpu0.p_system"=>1.00, "cpu1.p_cpu"=>7.00, "cpu1.p_user"=>5.00, "cpu1.p_system"=>2.00}]
[2] [1452185191, {"cpu_p"=>7.50, "user_p"=>5.00, "system_p"=>2.50, "cpu0.p_cpu"=>7.00, "cpu0.p_user"=>3.00, "cpu0.p_system"=>4.00, "cpu1.p_cpu"=>6.00, "cpu1.p_user"=>6.00, "cpu1.p_system"=>0.00}]
[3] [1452185192, {"cpu_p"=>4.50, "user_p"=>3.50, "system_p"=>1.00, "cpu0.p_cpu"=>6.00, "cpu0.p_user"=>5.00, "cpu0.p_system"=>1.00, "cpu1.p_cpu"=>5.00, "cpu1.p_user"=>3.00, "cpu1.p_system"=>2.00}]
...
```

As described previously, the CPU input plugin gathers the overall usage every one second and flushed the information to the output on the fifth second. This example uses the `stdout` plugin to demonstrate the output records. In a real use-case you might want to flush this information to some central aggregator such as [Fluentd](http://fluentd.org) or [Elasticsearch](http://elastic.co).

### Configuration file

In your main configuration file append the following:

{% tabs %}
{% tab title="fluent-bit.yaml" %}

```yaml

pipeline:
  inputs:
    - name: cpu
      tag: my_cpu

  outputs:
    - name: stdout
      match: '*'
```

{% endtab %}

{% tab title="fluent-bit.conf" %}

```shell
[INPUT]
  Name cpu
  Tag  my_cpu

[OUTPUT]
  Name  stdout
  Match *
```

{% endtab %}
{% endtabs %}