feat: Add noise plugin

docs/LICENSE_OF_DEPENDENCIES.md

@@ -246,6 +246,7 @@ following works:
 - go.uber.org/atomic [MIT License](https://pkg.go.dev/go.uber.org/atomic?tab=licenses)
 - go.uber.org/multierr [MIT License](https://pkg.go.dev/go.uber.org/multierr?tab=licenses)
 - golang.org/x/crypto [BSD 3-Clause Clear License](https://github.com/golang/crypto/blob/master/LICENSE)
+- golang.org/x/exp [BSD 3-Clause Clear License](https://github.com/golang/exp/blob/master/LICENSE)
 - golang.org/x/net [BSD 3-Clause Clear License](https://github.com/golang/net/blob/master/LICENSE)
 - golang.org/x/oauth2 [BSD 3-Clause "New" or "Revised" License](https://github.com/golang/oauth2/blob/master/LICENSE)
 - golang.org/x/sync [BSD 3-Clause "New" or "Revised" License](https://github.com/golang/sync/blob/master/LICENSE)
@@ -256,6 +257,7 @@ following works:
 - golang.org/x/xerrors [BSD 3-Clause Clear License](https://github.com/golang/xerrors/blob/master/LICENSE)
 - golang.zx2c4.com/wireguard [MIT License](https://github.com/WireGuard/wgctrl-go/blob/master/LICENSE.md)
 - golang.zx2c4.com/wireguard/wgctrl [MIT License](https://github.com/WireGuard/wgctrl-go/blob/master/LICENSE.md)
+- gonum.org/v1/gonum [BSD 3-Clause "New" or "Revised" License](https://github.com/gonum/gonum/blob/master/LICENSE)
 - google.golang.org/api [BSD 3-Clause "New" or "Revised" License](https://github.com/googleapis/google-api-go-client/blob/master/LICENSE)
 - google.golang.org/genproto [Apache License 2.0](https://github.com/google/go-genproto/blob/master/LICENSE)
 - google.golang.org/grpc [Apache License 2.0](https://github.com/grpc/grpc-go/blob/master/LICENSE)

go.mod

@@ -351,8 +351,11 @@ require (
 	go.opentelemetry.io/otel/sdk/export/metric v0.24.0 // indirect
 	go.opentelemetry.io/otel/trace v1.0.1 // indirect
 	go.opentelemetry.io/proto/otlp v0.9.0 // indirect
+	gonum.org/v1/gonum v0.9.3
 )
 
+require golang.org/x/exp v0.0.0-20200513190911-00229845015e // indirect
+
 // replaced due to https://github.com/satori/go.uuid/issues/73
 replace github.com/satori/go.uuid => github.com/gofrs/uuid v3.2.0+incompatible
 

go.sum

@@ -2709,6 +2709,7 @@ gonum.org/v1/gonum v0.8.2/go.mod h1:oe/vMfY3deqTw+1EZJhuvEW2iwGF1bW9wwu7XCu0+v0=
 gonum.org/v1/gonum v0.9.3 h1:DnoIG+QAMaF5NvxnGe/oKsgKcAc6PcUyl8q0VetfQ8s=
 gonum.org/v1/gonum v0.9.3/go.mod h1:TZumC3NeyVQskjXqmyWt4S3bINhy7B4eYwW69EbyX+0=
 gonum.org/v1/netlib v0.0.0-20181029234149-ec6d1f5cefe6/go.mod h1:wa6Ws7BG/ESfp6dHfk7C6KdzKA7wR7u/rKwOGE66zvw=
+gonum.org/v1/netlib v0.0.0-20190313105609-8cb42192e0e0 h1:OE9mWmgKkjJyEmDAAtGMPjXu+YNeGvK9VTSHY6+Qihc=
 gonum.org/v1/netlib v0.0.0-20190313105609-8cb42192e0e0/go.mod h1:wa6Ws7BG/ESfp6dHfk7C6KdzKA7wR7u/rKwOGE66zvw=
 gonum.org/v1/plot v0.0.0-20190515093506-e2840ee46a6b/go.mod h1:Wt8AAjI+ypCyYX3nZBvf6cAIx93T+c/OS2HFAYskSZc=
 gonum.org/v1/plot v0.9.0/go.mod h1:3Pcqqmp6RHvJI72kgb8fThyUnav364FOsdDo2aGW5lY=

plugins/processors/all/all.go

@@ -12,6 +12,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/processors/execd"
 	_ "github.com/influxdata/telegraf/plugins/processors/filepath"
 	_ "github.com/influxdata/telegraf/plugins/processors/ifname"
+	_ "github.com/influxdata/telegraf/plugins/processors/noise"
 	_ "github.com/influxdata/telegraf/plugins/processors/override"
 	_ "github.com/influxdata/telegraf/plugins/processors/parser"
 	_ "github.com/influxdata/telegraf/plugins/processors/pivot"

plugins/processors/noise/README.md

@@ -0,0 +1,58 @@
+# Noise Processor
+
+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:
+
+### 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
+
+### Configuration
+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`:
+
+```toml
+[[processors.noise]]
+  scale = 1.0
+  mu = 0.0
+  noise_type = "laplacian"
+```
+
+Using the `include_fields` and `exclude_fields` options a filter can be configured to apply noise only to numeric fields matching it.
+
+### 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]
+```

plugins/processors/noise/noise.go

@@ -0,0 +1,157 @@
+package noise
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/filter"
+	"github.com/influxdata/telegraf/plugins/processors"
+	"gonum.org/v1/gonum/stat/distuv"
+)
+
+const (
+	defaultScale     = 1.0
+	defaultMin       = -1.0
+	defaultMax       = 1.0
+	defaultMu        = 0.0
+	defaultNoiseType = "laplacian"
+)
+
+const sampleConfig = `
+  [[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 = []
+`
+
+type Noise struct {
+	Scale         float64         `toml:"scale"`
+	Min           float64         `toml:"min"`
+	Max           float64         `toml:"max"`
+	Mu            float64         `toml:"mu"`
+	IncludeFields []string        `toml:"include_fields"`
+	ExcludeFields []string        `toml:"exclude_fields"`
+	NoiseType     string          `toml:"type"`
+	Log           telegraf.Logger `toml:"-"`
+	generator     distuv.Rander
+	fieldFilter   filter.Filter
+}
+
+func (p *Noise) SampleConfig() string {
+	return sampleConfig
+}
+
+func (p *Noise) Description() string {
+	return "Adds noise to numerical fields"
+}
+
+// generates a random noise value depending on the defined probability density
+// function and adds that to the original value. If any integer overflows
+// happen during the calculation, the result is set to MaxInt or 0 (for uint)
+func (p *Noise) addNoise(value interface{}) interface{} {
+	n := p.generator.Rand()
+	switch v := value.(type) {
+	case int:
+	case int8:
+	case int16:
+	case int32:
+	case int64:
+		if v > 0 && (n > math.Nextafter(float64(math.MaxInt64), 0) || int64(n) > math.MaxInt64-v) {
+			p.Log.Debug("Int64 overflow, setting value to MaxInt64")
+			return int64(math.MaxInt64)
+		}
+		if v < 0 && (n < math.Nextafter(float64(math.MinInt64), 0) || int64(n) < math.MinInt64-v) {
+			p.Log.Debug("Int64 (negative) overflow, setting value to MinInt64")
+			return int64(math.MinInt64)
+		}
+		return v + int64(n)
+	case uint:
+	case uint8:
+	case uint16:
+	case uint32:
+	case uint64:
+		if n < 0 {
+			if uint64(-n) > v {
+				p.Log.Debug("Uint64 (negative) overflow, setting value to 0")
+				return uint64(0)
+			}
+			return v - uint64(-n)
+		}
+		if n > math.Nextafter(float64(math.MaxUint64), 0) || uint64(n) > math.MaxUint64-v {
+			p.Log.Debug("Uint64 overflow, setting value to MaxUint64")
+			return uint64(math.MaxUint64)
+		}
+		return v + uint64(n)
+	case float32:
+	case float64:
+		return v + n
+	default:
+		p.Log.Debugf("Value (%v) type invalid: [%v] is not an int, uint or float", v, reflect.TypeOf(value))
+	}
+	return value
+}
+
+// Creates a filter for Include and Exclude fields and sets the desired noise
+// distribution
+func (p *Noise) Init() error {
+	fieldFilter, err := filter.NewIncludeExcludeFilter(p.IncludeFields, p.ExcludeFields)
+	if err != nil {
+		return fmt.Errorf("creating fieldFilter failed: %v", err)
+	}
+	p.fieldFilter = fieldFilter
+
+	switch p.NoiseType {
+	case "", "laplacian":
+		p.generator = &distuv.Laplace{Mu: p.Mu, Scale: p.Scale}
+	case "uniform":
+		p.generator = &distuv.Uniform{Min: p.Min, Max: p.Max}
+	case "gaussian":
+		p.generator = &distuv.Normal{Mu: p.Mu, Sigma: p.Scale}
+	default:
+		return fmt.Errorf("unknown distribution type %q", p.NoiseType)
+	}
+	return nil
+}
+
+func (p *Noise) Apply(metrics ...telegraf.Metric) []telegraf.Metric {
+	for _, metric := range metrics {
+		p.Log.Debugf("Adding noise to [%s]", metric.Name())
+		for _, field := range metric.FieldList() {
+			if !p.fieldFilter.Match(field.Key) {
+				continue
+			}
+			field.Value = p.addNoise(field.Value)
+		}
+	}
+	return metrics
+}
+
+func init() {
+	processors.Add("noise", func() telegraf.Processor {
+		return &Noise{
+			NoiseType: defaultNoiseType,
+			Mu:        defaultMu,
+			Scale:     defaultScale,
+			Min:       defaultMin,
+			Max:       defaultMax,
+		}
+	})
+}