Added "callback" metrics, e.g. GaugeFunc.
Change-Id: I449b558207963ce60572bd04c8102f1db684dd4c
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@ -147,3 +147,29 @@ func (m *CounterVec) WithLabelValues(lvs ...string) Counter {
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func (m *CounterVec) With(labels Labels) Counter {
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return m.MetricVec.With(labels).(Counter)
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}
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// CounterFunc is a Counter whose value is determined at collect time by calling a
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// provided function.
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//
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// To create CounterFunc instances, use NewCounterFunc.
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type CounterFunc interface {
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Metric
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Collector
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}
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// NewCounterFunc creates a new CounterFunc based on the provided
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// CounterOpts. The value reported is determined by calling the given function
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// from within the Write method. Take into account that metric collection may
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// happen concurrently. If that results in concurrent calls to Write, like in
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// the case where a CounterFunc is directly registered with Prometheus, the
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// provided function must be concurrency-safe. The function should also honor
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// the contract for a Counter (values only go up, not down), but compliance will
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// not be checked.
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func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc {
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return newValueFunc(NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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nil,
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opts.ConstLabels,
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), CounterValue, function)
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}
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@ -29,14 +29,15 @@ func NewCallbackMetric(desc *prometheus.Desc, callback func() float64) *Callback
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return result
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}
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// TODO: Come up with a better example.
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// CallbackMetric is an example for a user-defined Metric that exports the
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// result of a function call as a metric of type "untyped" without any
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// labels. It uses SelfCollector to turn the Metric into a Collector so that it
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// can be registered with Prometheus.
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//
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// Note that this is a pretty low-level approach. A more high-level approach is
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// to implement a Collector directly and not an individual Metric, see the
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// Collector examples.
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// Note that this example is pretty much academic as the prometheus package
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// already provides an UntypedFunc type.
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type CallbackMetric struct {
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prometheus.SelfCollector
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@ -18,6 +18,7 @@ import (
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"fmt"
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"math"
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"net/http"
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"runtime"
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"sort"
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dto "github.com/prometheus/client_model/go"
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@ -72,6 +73,24 @@ func ExampleGaugeVec() {
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opsQueued.With(prometheus.Labels{"type": "delete", "user": "alice"}).Inc()
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}
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func ExampleGaugeFunc() {
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if _, err := prometheus.Register(prometheus.NewGaugeFunc(
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prometheus.GaugeOpts{
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Subsystem: "runtime",
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Name: "goroutines_count",
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Help: "Number of goroutines that currently exist.",
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},
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func() float64 { return float64(runtime.NumGoroutine()) },
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)); err == nil {
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fmt.Println("GaugeFunc 'goroutines_count' registered.\n")
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}
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// Note that the count of goroutines is a gauge (and not a counter) as
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// it can go up and down.
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// Output:
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// GaugeFunc 'goroutines_count' registered.
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}
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func ExampleCounter() {
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pushCounter := prometheus.NewCounter(prometheus.CounterOpts{
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Name: "repository_pushes", // Note: No help string...
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@ -121,3 +121,27 @@ func (m *GaugeVec) WithLabelValues(lvs ...string) Gauge {
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func (m *GaugeVec) With(labels Labels) Gauge {
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return m.MetricVec.With(labels).(Gauge)
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}
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// GaugeFunc is a Gauge whose value is determined at collect time by calling a
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// provided function.
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//
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// To create GaugeFunc instances, use NewGaugeFunc.
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type GaugeFunc interface {
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Metric
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Collector
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}
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// NewGaugeFunc creates a new GaugeFunc based on the provided GaugeOpts. The
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// value reported is determined by calling the given function from within the
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// Write method. Take into account that metric collection may happen
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// concurrently. If that results in concurrent calls to Write, like in the case
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// where a GaugeFunc is directly registered with Prometheus, the provided
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// function must be concurrency-safe.
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func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc {
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return newValueFunc(NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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nil,
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opts.ConstLabels,
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), GaugeValue, function)
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}
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@ -19,6 +19,8 @@ import (
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"sync"
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"testing"
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"testing/quick"
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dto "github.com/prometheus/client_model/go"
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)
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func listenGaugeStream(vals, result chan float64, done chan struct{}) {
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@ -156,3 +158,25 @@ func TestGaugeVecConcurrency(t *testing.T) {
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t.Fatal(err)
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}
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}
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func TestGaugeFunc(t *testing.T) {
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gf := NewGaugeFunc(
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GaugeOpts{
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Name: "test_name",
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Help: "test help",
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ConstLabels: Labels{"a": "1", "b": "2"},
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},
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func() float64 { return 3.1415 },
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)
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if expected, got := `Desc{fqName: "test_name", help: "test help", constLabels: {a="1",b="2"}, variableLabels: []}`, gf.Desc().String(); expected != got {
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t.Errorf("expected %q, got %q", expected, got)
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}
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m := &dto.Metric{}
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gf.Write(m)
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if expected, got := `label:<name:"a" value:"1" > label:<name:"b" value:"2" > gauge:<value:3.1415 > `, m.String(); expected != got {
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t.Errorf("expected %q, got %q", expected, got)
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}
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}
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@ -119,3 +119,27 @@ func (m *UntypedVec) WithLabelValues(lvs ...string) Untyped {
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func (m *UntypedVec) With(labels Labels) Untyped {
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return m.MetricVec.With(labels).(Untyped)
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}
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// UntypedFunc is an Untyped whose value is determined at collect time by
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// calling a provided function.
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//
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// To create UntypedFunc instances, use NewUntypedFunc.
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type UntypedFunc interface {
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Metric
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Collector
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}
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// NewUntypedFunc creates a new UntypedFunc based on the provided
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// UntypedOpts. The value reported is determined by calling the given function
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// from within the Write method. Take into account that metric collection may
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// happen concurrently. If that results in concurrent calls to Write, like in
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// the case where an UntypedFunc is directly registered with Prometheus, the
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// provided function must be concurrency-safe.
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func NewUntypedFunc(opts UntypedOpts, function func() float64) UntypedFunc {
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return newValueFunc(NewDesc(
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BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
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opts.Help,
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nil,
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opts.ConstLabels,
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), UntypedValue, function)
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}
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@ -51,7 +51,7 @@ type value struct {
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labelPairs []*dto.LabelPair
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}
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// newValue returns a newly allocated Value with the given Desc, ValueType,
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// newValue returns a newly allocated value with the given Desc, ValueType,
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// sample value and label values. It panics if the number of label
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// values is different from the number of variable labels in Desc.
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func newValue(desc *Desc, valueType ValueType, val float64, labelValues ...string) *value {
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@ -106,6 +106,45 @@ func (v *value) Write(out *dto.Metric) {
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populateMetric(v.valType, val, v.labelPairs, out)
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}
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// valueFunc is a generic metric for simple values retrieved on collect time
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// from a function. It implements Metric and Collector. Its effective type is
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// determined by ValueType. This is a low-level building block used by the
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// library to back the implementations of CounterFunc, GaugeFunc, and
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// UntypedFunc.
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type valueFunc struct {
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SelfCollector
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desc *Desc
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valType ValueType
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function func() float64
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labelPairs []*dto.LabelPair
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}
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// newValueFunc returns a newly allocated valueFunc with the given Desc and
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// ValueType. The value reported is determined by calling the given function
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// from within the Write method. Take into account that metric collection may
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// happen concurrently. If that results in concurrent calls to Write, like in
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// the case where a valueFunc is directly registered with Prometheus, the
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// provided function must be concurrency-safe.
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func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc {
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result := &valueFunc{
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desc: desc,
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valType: valueType,
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function: function,
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labelPairs: makeLabelPairs(desc, nil),
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}
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result.Init(result)
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return result
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}
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func (v *valueFunc) Desc() *Desc {
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return v.desc
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}
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func (v *valueFunc) Write(out *dto.Metric) {
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populateMetric(v.valType, v.function(), v.labelPairs, out)
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}
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// NewConstMetric returns a metric with one fixed value that cannot be
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// changed. Users of this package will not have much use for it in regular
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// operations. However, when implementing custom Collectors, it is useful as a
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