client_golang/prometheus/vec.go

362 lines
10 KiB
Go

// Copyright 2014 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package prometheus
import (
"fmt"
"sync"
"github.com/prometheus/common/model"
)
// metricVec is a Collector to bundle metrics of the same name that differ in
// their label values. metricVec is not used directly (and therefore
// unexported). It is used as a building block for implementations of vectors of
// a given metric type, like GaugeVec, CounterVec, SummaryVec, HistogramVec, and
// UntypedVec.
type metricVec struct {
mtx sync.RWMutex // Protects the children.
children map[uint64][]metricWithLabelValues
desc *Desc
newMetric func(labelValues ...string) Metric
hashAdd func(h uint64, s string) uint64 // replace hash function for testing collision handling
hashAddByte func(h uint64, b byte) uint64
}
// newMetricVec returns an initialized metricVec.
func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec {
return &metricVec{
children: map[uint64][]metricWithLabelValues{},
desc: desc,
newMetric: newMetric,
hashAdd: hashAdd,
hashAddByte: hashAddByte,
}
}
// metricWithLabelValues provides the metric and its label values for
// disambiguation on hash collision.
type metricWithLabelValues struct {
values []string
metric Metric
}
// Describe implements Collector. The length of the returned slice
// is always one.
func (m *metricVec) Describe(ch chan<- *Desc) {
ch <- m.desc
}
// Collect implements Collector.
func (m *metricVec) Collect(ch chan<- Metric) {
m.mtx.RLock()
defer m.mtx.RUnlock()
for _, metrics := range m.children {
for _, metric := range metrics {
ch <- metric.metric
}
}
}
func (m *metricVec) getMetricWithLabelValues(lvs ...string) (Metric, error) {
h, err := m.hashLabelValues(lvs)
if err != nil {
return nil, err
}
return m.getOrCreateMetricWithLabelValues(h, lvs), nil
}
func (m *metricVec) getMetricWith(labels Labels) (Metric, error) {
h, err := m.hashLabels(labels)
if err != nil {
return nil, err
}
return m.getOrCreateMetricWithLabels(h, labels), nil
}
func (m *metricVec) withLabelValues(lvs ...string) Metric {
metric, err := m.getMetricWithLabelValues(lvs...)
if err != nil {
panic(err)
}
return metric
}
func (m *metricVec) with(labels Labels) Metric {
metric, err := m.getMetricWith(labels)
if err != nil {
panic(err)
}
return metric
}
// DeleteLabelValues removes the metric where the variable labels are the same
// as those passed in as labels (same order as the VariableLabels in Desc). It
// returns true if a metric was deleted.
//
// It is not an error if the number of label values is not the same as the
// number of VariableLabels in Desc. However, such inconsistent label count can
// never match an actual metric, so the method will always return false in that
// case.
//
// Note that for more than one label value, this method is prone to mistakes
// caused by an incorrect order of arguments. Consider Delete(Labels) as an
// alternative to avoid that type of mistake. For higher label numbers, the
// latter has a much more readable (albeit more verbose) syntax, but it comes
// with a performance overhead (for creating and processing the Labels map).
// See also the CounterVec example.
func (m *metricVec) DeleteLabelValues(lvs ...string) bool {
m.mtx.Lock()
defer m.mtx.Unlock()
h, err := m.hashLabelValues(lvs)
if err != nil {
return false
}
return m.deleteByHashWithLabelValues(h, lvs)
}
// Delete deletes the metric where the variable labels are the same as those
// passed in as labels. It returns true if a metric was deleted.
//
// It is not an error if the number and names of the Labels are inconsistent
// with those of the VariableLabels in Desc. However, such inconsistent Labels
// can never match an actual metric, so the method will always return false in
// that case.
//
// This method is used for the same purpose as DeleteLabelValues(...string). See
// there for pros and cons of the two methods.
func (m *metricVec) Delete(labels Labels) bool {
m.mtx.Lock()
defer m.mtx.Unlock()
h, err := m.hashLabels(labels)
if err != nil {
return false
}
return m.deleteByHashWithLabels(h, labels)
}
// deleteByHashWithLabelValues removes the metric from the hash bucket h. If
// there are multiple matches in the bucket, use lvs to select a metric and
// remove only that metric.
func (m *metricVec) deleteByHashWithLabelValues(h uint64, lvs []string) bool {
metrics, ok := m.children[h]
if !ok {
return false
}
i := m.findMetricWithLabelValues(metrics, lvs)
if i >= len(metrics) {
return false
}
if len(metrics) > 1 {
m.children[h] = append(metrics[:i], metrics[i+1:]...)
} else {
delete(m.children, h)
}
return true
}
// deleteByHashWithLabels removes the metric from the hash bucket h. If there
// are multiple matches in the bucket, use lvs to select a metric and remove
// only that metric.
func (m *metricVec) deleteByHashWithLabels(h uint64, labels Labels) bool {
metrics, ok := m.children[h]
if !ok {
return false
}
i := m.findMetricWithLabels(metrics, labels)
if i >= len(metrics) {
return false
}
if len(metrics) > 1 {
m.children[h] = append(metrics[:i], metrics[i+1:]...)
} else {
delete(m.children, h)
}
return true
}
// Reset deletes all metrics in this vector.
func (m *metricVec) Reset() {
m.mtx.Lock()
defer m.mtx.Unlock()
for h := range m.children {
delete(m.children, h)
}
}
func (m *metricVec) hashLabelValues(vals []string) (uint64, error) {
if len(vals) != len(m.desc.variableLabels) {
return 0, errInconsistentCardinality
}
h := hashNew()
for _, val := range vals {
h = m.hashAdd(h, val)
h = m.hashAddByte(h, model.SeparatorByte)
}
return h, nil
}
func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
if len(labels) != len(m.desc.variableLabels) {
return 0, errInconsistentCardinality
}
h := hashNew()
for _, label := range m.desc.variableLabels {
val, ok := labels[label]
if !ok {
return 0, fmt.Errorf("label name %q missing in label map", label)
}
h = m.hashAdd(h, val)
h = m.hashAddByte(h, model.SeparatorByte)
}
return h, nil
}
// getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
// or creates it and returns the new one.
//
// This function holds the mutex.
func (m *metricVec) getOrCreateMetricWithLabelValues(hash uint64, lvs []string) Metric {
m.mtx.RLock()
metric, ok := m.getMetricWithHashAndLabelValues(hash, lvs)
m.mtx.RUnlock()
if ok {
return metric
}
m.mtx.Lock()
defer m.mtx.Unlock()
metric, ok = m.getMetricWithHashAndLabelValues(hash, lvs)
if !ok {
// Copy to avoid allocation in case wo don't go down this code path.
copiedLVs := make([]string, len(lvs))
copy(copiedLVs, lvs)
metric = m.newMetric(copiedLVs...)
m.children[hash] = append(m.children[hash], metricWithLabelValues{values: copiedLVs, metric: metric})
}
return metric
}
// getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
// or creates it and returns the new one.
//
// This function holds the mutex.
func (m *metricVec) getOrCreateMetricWithLabels(hash uint64, labels Labels) Metric {
m.mtx.RLock()
metric, ok := m.getMetricWithHashAndLabels(hash, labels)
m.mtx.RUnlock()
if ok {
return metric
}
m.mtx.Lock()
defer m.mtx.Unlock()
metric, ok = m.getMetricWithHashAndLabels(hash, labels)
if !ok {
lvs := m.extractLabelValues(labels)
metric = m.newMetric(lvs...)
m.children[hash] = append(m.children[hash], metricWithLabelValues{values: lvs, metric: metric})
}
return metric
}
// getMetricWithHashAndLabelValues gets a metric while handling possible
// collisions in the hash space. Must be called while holding the read mutex.
func (m *metricVec) getMetricWithHashAndLabelValues(h uint64, lvs []string) (Metric, bool) {
metrics, ok := m.children[h]
if ok {
if i := m.findMetricWithLabelValues(metrics, lvs); i < len(metrics) {
return metrics[i].metric, true
}
}
return nil, false
}
// getMetricWithHashAndLabels gets a metric while handling possible collisions in
// the hash space. Must be called while holding read mutex.
func (m *metricVec) getMetricWithHashAndLabels(h uint64, labels Labels) (Metric, bool) {
metrics, ok := m.children[h]
if ok {
if i := m.findMetricWithLabels(metrics, labels); i < len(metrics) {
return metrics[i].metric, true
}
}
return nil, false
}
// findMetricWithLabelValues returns the index of the matching metric or
// len(metrics) if not found.
func (m *metricVec) findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string) int {
for i, metric := range metrics {
if m.matchLabelValues(metric.values, lvs) {
return i
}
}
return len(metrics)
}
// findMetricWithLabels returns the index of the matching metric or len(metrics)
// if not found.
func (m *metricVec) findMetricWithLabels(metrics []metricWithLabelValues, labels Labels) int {
for i, metric := range metrics {
if m.matchLabels(metric.values, labels) {
return i
}
}
return len(metrics)
}
func (m *metricVec) matchLabelValues(values []string, lvs []string) bool {
if len(values) != len(lvs) {
return false
}
for i, v := range values {
if v != lvs[i] {
return false
}
}
return true
}
func (m *metricVec) matchLabels(values []string, labels Labels) bool {
if len(labels) != len(values) {
return false
}
for i, k := range m.desc.variableLabels {
if values[i] != labels[k] {
return false
}
}
return true
}
func (m *metricVec) extractLabelValues(labels Labels) []string {
labelValues := make([]string, len(labels))
for i, k := range m.desc.variableLabels {
labelValues[i] = labels[k]
}
return labelValues
}