239 lines
6.7 KiB
Go
239 lines
6.7 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus
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import (
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"errors"
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"fmt"
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"math"
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"sort"
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"sync/atomic"
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"time"
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dto "github.com/prometheus/client_model/go"
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"github.com/golang/protobuf/proto"
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)
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// ValueType is an enumeration of metric types that represent a simple value.
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type ValueType int
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// Possible values for the ValueType enum.
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const (
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_ ValueType = iota
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CounterValue
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GaugeValue
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UntypedValue
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)
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var errInconsistentCardinality = errors.New("inconsistent label cardinality")
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// value is a generic metric for simple values. It implements Metric, Collector,
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// Counter, Gauge, and Untyped. Its effective type is determined by
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// ValueType. This is a low-level building block used by the library to back the
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// implementations of Counter, Gauge, and Untyped.
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type value struct {
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// valBits contains the bits of the represented float64 value. It has
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// to go first in the struct to guarantee alignment for atomic
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// operations. http://golang.org/pkg/sync/atomic/#pkg-note-BUG
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valBits uint64
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selfCollector
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desc *Desc
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valType ValueType
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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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// 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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if len(labelValues) != len(desc.variableLabels) {
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panic(errInconsistentCardinality)
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}
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result := &value{
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desc: desc,
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valType: valueType,
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valBits: math.Float64bits(val),
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labelPairs: makeLabelPairs(desc, labelValues),
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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 *value) Desc() *Desc {
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return v.desc
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}
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func (v *value) Set(val float64) {
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atomic.StoreUint64(&v.valBits, math.Float64bits(val))
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}
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func (v *value) SetToCurrentTime() {
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v.Set(float64(time.Now().UnixNano()) / 1e9)
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}
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func (v *value) Inc() {
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v.Add(1)
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}
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func (v *value) Dec() {
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v.Add(-1)
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}
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func (v *value) Add(val float64) {
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for {
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oldBits := atomic.LoadUint64(&v.valBits)
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newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
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if atomic.CompareAndSwapUint64(&v.valBits, oldBits, newBits) {
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return
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}
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}
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}
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func (v *value) Sub(val float64) {
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v.Add(val * -1)
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}
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func (v *value) Write(out *dto.Metric) error {
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val := math.Float64frombits(atomic.LoadUint64(&v.valBits))
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return 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) error {
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return 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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// throw-away metric that is generated on the fly to send it to Prometheus in
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// the Collect method. NewConstMetric returns an error if the length of
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// labelValues is not consistent with the variable labels in Desc.
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func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error) {
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if len(desc.variableLabels) != len(labelValues) {
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return nil, errInconsistentCardinality
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}
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return &constMetric{
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desc: desc,
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valType: valueType,
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val: value,
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labelPairs: makeLabelPairs(desc, labelValues),
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}, nil
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}
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// MustNewConstMetric is a version of NewConstMetric that panics where
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// NewConstMetric would have returned an error.
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func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric {
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m, err := NewConstMetric(desc, valueType, value, labelValues...)
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if err != nil {
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panic(err)
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}
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return m
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}
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type constMetric struct {
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desc *Desc
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valType ValueType
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val float64
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labelPairs []*dto.LabelPair
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}
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func (m *constMetric) Desc() *Desc {
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return m.desc
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}
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func (m *constMetric) Write(out *dto.Metric) error {
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return populateMetric(m.valType, m.val, m.labelPairs, out)
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}
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func populateMetric(
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t ValueType,
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v float64,
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labelPairs []*dto.LabelPair,
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m *dto.Metric,
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) error {
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m.Label = labelPairs
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switch t {
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case CounterValue:
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m.Counter = &dto.Counter{Value: proto.Float64(v)}
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case GaugeValue:
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m.Gauge = &dto.Gauge{Value: proto.Float64(v)}
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case UntypedValue:
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m.Untyped = &dto.Untyped{Value: proto.Float64(v)}
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default:
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return fmt.Errorf("encountered unknown type %v", t)
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}
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return nil
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}
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func makeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
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totalLen := len(desc.variableLabels) + len(desc.constLabelPairs)
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if totalLen == 0 {
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// Super fast path.
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return nil
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}
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if len(desc.variableLabels) == 0 {
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// Moderately fast path.
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return desc.constLabelPairs
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}
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labelPairs := make([]*dto.LabelPair, 0, totalLen)
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for i, n := range desc.variableLabels {
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labelPairs = append(labelPairs, &dto.LabelPair{
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Name: proto.String(n),
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Value: proto.String(labelValues[i]),
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})
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}
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for _, lp := range desc.constLabelPairs {
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labelPairs = append(labelPairs, lp)
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}
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sort.Sort(LabelPairSorter(labelPairs))
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return labelPairs
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}
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