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synced 2024-12-25 05:34:05 -08:00
Make 2nd arg to delta optional. Add a deriv() function.
The 2nd isCounter argument to delta is ugly, make it optional as the first step of deprecating it. This will makes delta only ever applied to gauges. Add a deriv function to calculate the least squares slope of a gauge. This is more useful for prediction than delta, as it isn't as heavily influenced by outliers at the boundaries.
This commit is contained in:
Brian Brazil
parent
01f2bc4ee7
commit
a31730e88b
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@ -28,37 +28,44 @@ import (
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// Function represents a function of the expression language and is
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// used by function nodes.
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type Function struct {
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name string
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argTypes []ExprType
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returnType ExprType
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callFn func(timestamp clientmodel.Timestamp, args []Node) interface{}
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name string
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argTypes []ExprType
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optionalArgs int
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returnType ExprType
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callFn func(timestamp clientmodel.Timestamp, args []Node) interface{}
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}
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// CheckArgTypes returns a non-nil error if the number or types of
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// passed in arg nodes do not match the function's expectations.
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func (function *Function) CheckArgTypes(args []Node) error {
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if len(function.argTypes) != len(args) {
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if len(function.argTypes) < len(args) {
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return fmt.Errorf(
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"wrong number of arguments to function %v(): %v expected, %v given",
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"too many arguments to function %v(): %v expected at most, %v given",
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function.name, len(function.argTypes), len(args),
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)
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}
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for idx, argType := range function.argTypes {
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if len(function.argTypes) - function.optionalArgs > len(args) {
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return fmt.Errorf(
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"too few arguments to function %v(): %v expected at least, %v given",
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function.name, len(function.argTypes)-function.optionalArgs, len(args),
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)
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}
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for idx, arg := range args {
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invalidType := false
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var expectedType string
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if _, ok := args[idx].(ScalarNode); argType == ScalarType && !ok {
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if _, ok := arg.(ScalarNode); function.argTypes[idx] == ScalarType && !ok {
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invalidType = true
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expectedType = "scalar"
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}
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if _, ok := args[idx].(VectorNode); argType == VectorType && !ok {
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if _, ok := arg.(VectorNode); function.argTypes[idx] == VectorType && !ok {
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invalidType = true
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expectedType = "vector"
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}
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if _, ok := args[idx].(MatrixNode); argType == MatrixType && !ok {
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if _, ok := arg.(MatrixNode); function.argTypes[idx] == MatrixType && !ok {
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invalidType = true
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expectedType = "matrix"
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}
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if _, ok := args[idx].(StringNode); argType == StringType && !ok {
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if _, ok := arg.(StringNode); function.argTypes[idx] == StringType && !ok {
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invalidType = true
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expectedType = "string"
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}
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@ -78,10 +85,10 @@ func timeImpl(timestamp clientmodel.Timestamp, args []Node) interface{} {
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return clientmodel.SampleValue(timestamp.Unix())
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}
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// === delta(matrix MatrixNode, isCounter ScalarNode) Vector ===
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// === delta(matrix MatrixNode, isCounter=0 ScalarNode) Vector ===
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func deltaImpl(timestamp clientmodel.Timestamp, args []Node) interface{} {
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matrixNode := args[0].(MatrixNode)
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isCounter := args[1].(ScalarNode).Eval(timestamp) > 0
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isCounter := len(args) >= 2 && args[1].(ScalarNode).Eval(timestamp) > 0
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resultVector := Vector{}
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// If we treat these metrics as counters, we need to fetch all values
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@ -406,6 +413,49 @@ func absentImpl(timestamp clientmodel.Timestamp, args []Node) interface{} {
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}
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}
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// === deriv(node MatrixNode) Vector ===
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func derivImpl(timestamp clientmodel.Timestamp, args []Node) interface{} {
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matrixNode := args[0].(MatrixNode)
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resultVector := Vector{}
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matrixValue := matrixNode.Eval(timestamp)
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for _, samples := range matrixValue {
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// No sense in trying to compute a derivative without at least two points.
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// Drop this vector element.
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if len(samples.Values) < 2 {
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continue
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}
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// Least squares.
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n := clientmodel.SampleValue(0)
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sumY := clientmodel.SampleValue(0)
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sumX := clientmodel.SampleValue(0)
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sumXY := clientmodel.SampleValue(0)
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sumX2 := clientmodel.SampleValue(0)
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for _, sample := range samples.Values {
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x := clientmodel.SampleValue(sample.Timestamp.UnixNano() / 1e9)
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n += 1.0
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sumY += sample.Value
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sumX += x
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sumXY += x * sample.Value
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sumX2 += x * x
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}
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numerator := sumXY - sumX*sumY/n
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denominator := sumX2 - (sumX*sumX)/n
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resultValue := numerator / denominator
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resultSample := &Sample{
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Metric: samples.Metric,
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Value: resultValue,
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Timestamp: timestamp,
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}
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resultSample.Metric.Delete(clientmodel.MetricNameLabel)
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resultVector = append(resultVector, resultSample)
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}
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return resultVector
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}
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var functions = map[string]*Function{
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"abs": {
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name: "abs",
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@ -444,10 +494,11 @@ var functions = map[string]*Function{
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callFn: countScalarImpl,
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},
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"delta": {
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name: "delta",
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argTypes: []ExprType{MatrixType, ScalarType},
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returnType: VectorType,
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callFn: deltaImpl,
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name: "delta",
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argTypes: []ExprType{MatrixType, ScalarType},
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optionalArgs: 1, // The 2nd argument is deprecated.
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returnType: VectorType,
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callFn: deltaImpl,
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},
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"drop_common_labels": {
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name: "drop_common_labels",
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@ -509,6 +560,12 @@ var functions = map[string]*Function{
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returnType: VectorType,
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callFn: topkImpl,
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},
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"deriv": {
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name: "deriv",
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argTypes: []ExprType{MatrixType},
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returnType: VectorType,
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callFn: derivImpl,
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},
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}
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// GetFunction returns a predefined Function object for the given
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@ -260,13 +260,27 @@ func TestExpressions(t *testing.T) {
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fullRanges: 0,
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intervalRanges: 2,
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}, {
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expr: `http_requests{job="api-server", group="canary"} + delta(http_requests{job="api-server"}[5m], 1)`,
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expr: `http_requests{job="api-server", group="canary"} + rate(http_requests{job="api-server"}[5m]) * 5 * 60`,
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output: []string{
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`{group="canary", instance="0", job="api-server"} => 330 @[%v]`,
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`{group="canary", instance="1", job="api-server"} => 440 @[%v]`,
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},
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fullRanges: 4,
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intervalRanges: 0,
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}, {
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expr: `rate(http_requests[25m]) * 25 * 60`,
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output: []string{
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`{group="canary", instance="0", job="api-server"} => 150 @[%v]`,
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`{group="canary", instance="0", job="app-server"} => 350 @[%v]`,
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`{group="canary", instance="1", job="api-server"} => 200 @[%v]`,
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`{group="canary", instance="1", job="app-server"} => 400 @[%v]`,
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`{group="production", instance="0", job="api-server"} => 50 @[%v]`,
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`{group="production", instance="0", job="app-server"} => 249.99999999999997 @[%v]`,
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`{group="production", instance="1", job="api-server"} => 100 @[%v]`,
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`{group="production", instance="1", job="app-server"} => 300 @[%v]`,
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},
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fullRanges: 8,
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intervalRanges: 0,
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}, {
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expr: `delta(http_requests[25m], 1)`,
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output: []string{
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@ -368,38 +382,44 @@ func TestExpressions(t *testing.T) {
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intervalRanges: 8,
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}, {
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// Deltas should be adjusted for target interval vs. samples under target interval.
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expr: `delta(http_requests{group="canary", instance="1", job="app-server"}[18m], 1)`,
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expr: `delta(http_requests{group="canary", instance="1", job="app-server"}[18m])`,
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output: []string{`{group="canary", instance="1", job="app-server"} => 288 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Rates should transform per-interval deltas to per-second rates.
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expr: `rate(http_requests{group="canary", instance="1", job="app-server"}[10m])`,
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// Deltas should perform the same operation when 2nd argument is 0.
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expr: `delta(http_requests{group="canary", instance="1", job="app-server"}[18m], 0)`,
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output: []string{`{group="canary", instance="1", job="app-server"} => 288 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Rates should calculate per-second rates.
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expr: `rate(http_requests{group="canary", instance="1", job="app-server"}[60m])`,
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output: []string{`{group="canary", instance="1", job="app-server"} => 0.26666666666666666 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Counter resets in middle of range are ignored by delta() if counter == 1.
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expr: `delta(testcounter_reset_middle[50m], 1)`,
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output: []string{`{} => 90 @[%v]`},
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// Deriv should return the same as rate in simple cases.
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expr: `deriv(http_requests{group="canary", instance="1", job="app-server"}[60m])`,
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output: []string{`{group="canary", instance="1", job="app-server"} => 0.26666666666666666 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Counter resets in middle of range are not ignored by delta() if counter == 0.
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expr: `delta(testcounter_reset_middle[50m], 0)`,
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output: []string{`{} => 50 @[%v]`},
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// Counter resets at in the middle of range are handled correctly by rate().
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expr: `rate(testcounter_reset_middle[60m])`,
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output: []string{`{} => 0.03 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Counter resets at end of range are ignored by delta() if counter == 1.
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expr: `delta(testcounter_reset_end[5m], 1)`,
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// Counter resets at end of range are ignored by rate().
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expr: `rate(testcounter_reset_end[5m])`,
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output: []string{`{} => 0 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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// Counter resets at end of range are not ignored by delta() if counter == 0.
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expr: `delta(testcounter_reset_end[5m], 0)`,
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output: []string{`{} => -90 @[%v]`},
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// Deriv should return correct result.
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expr: `deriv(testcounter_reset_middle[100m])`,
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output: []string{`{} => 0.010606060606060607 @[%v]`},
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fullRanges: 1,
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intervalRanges: 0,
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}, {
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