# Noise Processor Plugin

The _Noise_ processor is used to add noise to numerical field values. For each
field a noise is generated using a defined probability densitiy function and
added to the value. The function type can be configured as _Laplace_, _Gaussian_
or _Uniform_.  Depending on the function, various parameters need to be
configured:

## Configuration

```toml @sample.conf
# Adds noise to numerical fields
[[processors.noise]]
  ## Specified the type of the random distribution.
  ## Can be "laplacian", "gaussian" or "uniform".
  # type = "laplacian

  ## Center of the distribution.
  ## Only used for Laplacian and Gaussian distributions.
  # mu = 0.0

  ## Scale parameter for the Laplacian or Gaussian distribution
  # scale = 1.0

  ## Upper and lower bound of the Uniform distribution
  # min = -1.0
  # max = 1.0

  ## Apply the noise only to numeric fields matching the filter criteria below.
  ## Excludes takes precedence over includes.
  # include_fields = []
  # exclude_fields = []
```

Depending on the choice of the distribution function, the respective parameters
must be set. Default settings are `noise_type = "laplacian"` with `mu = 0.0` and
`scale = 1.0`:

Using the `include_fields` and `exclude_fields` options a filter can be
configured to apply noise only to numeric fields matching it.  The following
distribution functions are available.

### Laplacian

- `noise_type = laplacian`
- `scale`: also referred to as _diversity_ parameter, regulates the width & height of the function, a bigger `scale` value means a higher probability of larger noise, default set to 1.0
- `mu`: location of the curve, default set to 0.0

### Gaussian

- `noise_type = gaussian`
- `mu`: mean value, default set to 0.0
- `scale`: standard deviation, default set to 1.0

### Uniform

- `noise_type = uniform`
- `min`: minimal interval value, default set to -1.0
- `max`: maximal interval value, default set to 1.0

## Example

Add noise to each value the _inputs.cpu_ plugin generates, except for the
_usage\_steal_, _usage\_user_, _uptime\_format_, _usage\_idle_ field and all
fields of the metrics _swap_, _disk_ and _net_:

```toml
[[inputs.cpu]]
  percpu = true
  totalcpu = true
  collect_cpu_time = false
  report_active = false

[[processors.noise]]
  scale = 1.0
  mu = 0.0
  noise_type = "laplacian"
  include_fields = []
  exclude_fields = ["usage_steal", "usage_user", "uptime_format", "usage_idle" ]
  namedrop = ["swap", "disk", "net"]
```

Result of noise added to the _cpu_ metric:

```diff
- cpu map[cpu:cpu11 host:98d5b8dbad1c] map[usage_guest:0 usage_guest_nice:0 usage_idle:94.3999999994412 usage_iowait:0 usage_irq:0.1999999999998181 usage_nice:0 usage_softirq:0.20000000000209184 usage_steal:0 usage_system:1.2000000000080036 usage_user:4.000000000014552]
+ cpu map[cpu:cpu11 host:98d5b8dbad1c] map[usage_guest:1.0078071583066057 usage_guest_nice:0.523063861602435 usage_idle:95.53920223476884 usage_iowait:0.5162661526251292 usage_irq:0.7138529816101375 usage_nice:0.6119678488887954 usage_softirq:0.5573585443688622 usage_steal:0.2006120911289802 usage_system:1.2954475820198437 usage_user:6.885664792615023]
```
