mirror of
https://github.com/prometheus-community/windows_exporter.git
synced 2026-10-21 12:09:03 +02:00
process, gpu, hyperv, netframework: reuse label pairs of unchanged series (#2685)
Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>
This commit is contained in:
Jan-Otto Kröpke
@@ -0,0 +1,212 @@
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// SPDX-License-Identifier: Apache-2.0
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//
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// Copyright 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 labelcache reuses the label pairs of const metrics between scrapes.
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//
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// prometheus.NewConstMetric builds and sorts the label pairs of a series on
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// every call. For series whose value changes on every scrape, such as process
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// counters, internal/metriccache can't reuse the metric, but the labels stay
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// the same as long as the series exists. A Scrape hands out metrics that share
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// the label pairs built for the same series in the previous scrape. Series that
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// aren't reported in a scrape are dropped when it commits.
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package labelcache
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import (
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"fmt"
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"sync"
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"github.com/prometheus/client_golang/prometheus"
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dto "github.com/prometheus/client_model/go"
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)
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// maxLabels is the largest number of label values a cached series can have.
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// Metrics with more labels are created without the cache.
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const maxLabels = 6
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// key identifies a series. It is a fixed-size array, so building and looking up
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// a key doesn't allocate.
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type key struct {
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desc *prometheus.Desc
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n int
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values [maxLabels]string
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}
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// Cache holds the label pairs of the last committed scrape. The zero value is
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// ready to use.
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type Cache struct {
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mu sync.Mutex
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entries map[key][]*dto.LabelPair
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// resets counts Reset calls, so that a scrape begun before a Reset doesn't
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// commit afterwards.
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resets uint64
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// active counts the scrapes between Begin and Commit. spare is a replaced
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// generation that no scrape reads anymore; the next scrape reuses it
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// instead of allocating a new map.
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active int
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spare map[key][]*dto.LabelPair
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}
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// Scrape creates the metrics of one scrape.
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type Scrape struct {
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cache *Cache
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resets uint64
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// prev is the last committed generation. It is never modified, so it is
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// read without holding mu.
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prev map[key][]*dto.LabelPair
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mu sync.Mutex
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// next collects the label pairs of this scrape. Commit hands it to the
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// cache and sets it to nil.
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next map[key][]*dto.LabelPair
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}
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// Begin starts a scrape. Call Commit when it is done.
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func (c *Cache) Begin() *Scrape {
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c.mu.Lock()
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prev, resets, next := c.entries, c.resets, c.spare
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c.spare = nil
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c.active++
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c.mu.Unlock()
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if next == nil {
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next = make(map[key][]*dto.LabelPair, len(prev))
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}
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return &Scrape{
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cache: c,
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resets: resets,
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prev: prev,
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next: next,
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}
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}
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// Reset drops all cached label pairs, for example when the collector closes.
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func (c *Cache) Reset() {
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c.mu.Lock()
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c.entries = nil
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c.spare = nil
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c.resets++
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c.mu.Unlock()
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}
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// Commit makes the series of this scrape the base of the next one. Series of
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// the previous scrape that this scrape didn't report are dropped.
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func (s *Scrape) Commit() {
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if s == nil {
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return
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}
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s.mu.Lock()
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next := s.next
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s.next = nil
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s.mu.Unlock()
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if next == nil {
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return
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}
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s.cache.mu.Lock()
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defer s.cache.mu.Unlock()
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s.cache.active--
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if s.cache.resets != s.resets {
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return
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}
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replaced := s.cache.entries
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s.cache.entries = next
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// Other scrapes may still read the replaced generation.
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if s.cache.active == 0 && replaced != nil {
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clear(replaced)
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s.cache.spare = replaced
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}
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}
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// MustNewConstMetric is prometheus.MustNewConstMetric, but it reuses the label
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// pairs of the series from the previous scrape. A nil Scrape creates the metric
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// without the cache.
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//
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//nolint:ireturn // Const metrics have no exported type.
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func (s *Scrape) MustNewConstMetric(desc *prometheus.Desc, valueType prometheus.ValueType, value float64, labelValues ...string) prometheus.Metric {
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if s == nil || len(labelValues) > maxLabels {
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return prometheus.MustNewConstMetric(desc, valueType, value, append([]string(nil), labelValues...)...)
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}
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k := key{desc: desc, n: len(labelValues)}
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copy(k.values[:], labelValues)
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labels, ok := s.prev[k]
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s.mu.Lock()
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if !ok {
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labels, ok = s.next[k]
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}
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if ok && s.next != nil {
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s.next[k] = labels
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}
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s.mu.Unlock()
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if ok {
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return &constMetric{desc: desc, valueType: valueType, value: value, labels: labels}
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}
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// A new series: prometheus validates the label values and builds the
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// pairs, which the following scrapes share.
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metric := prometheus.MustNewConstMetric(desc, valueType, value, append([]string(nil), labelValues...)...)
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var out dto.Metric
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if err := metric.Write(&out); err == nil {
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s.mu.Lock()
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if s.next != nil {
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s.next[k] = out.GetLabel()
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}
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s.mu.Unlock()
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}
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return metric
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}
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// constMetric is a const metric with shared label pairs. Label pairs are
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// immutable once written, like those of prometheus.NewConstMetric.
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type constMetric struct {
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desc *prometheus.Desc
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labels []*dto.LabelPair
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value float64
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valueType prometheus.ValueType
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}
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func (m *constMetric) Desc() *prometheus.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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out.Label = m.labels
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switch m.valueType {
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case prometheus.CounterValue:
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out.Counter = &dto.Counter{Value: &m.value}
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case prometheus.GaugeValue:
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out.Gauge = &dto.Gauge{Value: &m.value}
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case prometheus.UntypedValue:
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out.Untyped = &dto.Untyped{Value: &m.value}
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default:
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return fmt.Errorf("encountered unknown type %v", m.valueType)
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}
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return nil
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}
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@@ -0,0 +1,214 @@
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// SPDX-License-Identifier: Apache-2.0
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//
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// Copyright 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 labelcache_test
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import (
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"strconv"
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"sync"
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"testing"
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"github.com/prometheus-community/windows_exporter/internal/labelcache"
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"github.com/prometheus/client_golang/prometheus"
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dto "github.com/prometheus/client_model/go"
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"github.com/stretchr/testify/require"
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"google.golang.org/protobuf/proto"
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)
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//nolint:gochecknoglobals
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var (
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counterDesc = prometheus.NewDesc("test_cpu_seconds_total", "test", []string{"process", "process_id", "mode"}, prometheus.Labels{"const": "x"})
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gaugeDesc = prometheus.NewDesc("test_handles", "test", []string{"process", "process_id"}, nil)
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untypedDesc = prometheus.NewDesc("test_untyped", "test", nil, nil)
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wideDesc = prometheus.NewDesc("test_info", "test", []string{"a", "b", "c", "d", "e", "f", "g"}, nil)
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)
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func write(t *testing.T, metric prometheus.Metric) *dto.Metric {
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t.Helper()
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var out dto.Metric
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require.NoError(t, metric.Write(&out))
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return &out
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}
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// Cached metrics must write exactly what prometheus.MustNewConstMetric writes,
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// in the first scrape (new series) and the following ones (shared labels).
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func TestMustNewConstMetric(t *testing.T) {
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t.Parallel()
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var cache labelcache.Cache
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cases := []struct {
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desc *prometheus.Desc
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valueType prometheus.ValueType
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values []string
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}{
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{counterDesc, prometheus.CounterValue, []string{"svchost", "1234", "user"}},
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{counterDesc, prometheus.CounterValue, []string{"svchost", "1234", "privileged"}},
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{gaugeDesc, prometheus.GaugeValue, []string{"svchost", "1234"}},
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{untypedDesc, prometheus.UntypedValue, nil},
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{wideDesc, prometheus.GaugeValue, []string{"1", "2", "3", "4", "5", "6", "7"}},
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}
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for scrapeNumber := range 3 {
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scrape := cache.Begin()
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for i, tc := range cases {
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value := float64(scrapeNumber*10 + i)
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got := scrape.MustNewConstMetric(tc.desc, tc.valueType, value, tc.values...)
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want := prometheus.MustNewConstMetric(tc.desc, tc.valueType, value, tc.values...)
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require.Equal(t, want.Desc(), got.Desc())
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require.True(t, proto.Equal(write(t, want), write(t, got)), "scrape %d, case %d:\nwant %v\ngot %v", scrapeNumber, i, write(t, want), write(t, got))
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}
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scrape.Commit()
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}
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}
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// From the second scrape on, a series reuses the label pairs of the previous
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// one; series that a scrape didn't report get new pairs.
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func TestLabelReuse(t *testing.T) {
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t.Parallel()
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var cache labelcache.Cache
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labelsOf := func(scrape *labelcache.Scrape, pid string) []*dto.LabelPair {
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return write(t, scrape.MustNewConstMetric(gaugeDesc, prometheus.GaugeValue, 1, "p", pid)).GetLabel()
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}
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scrape := cache.Begin()
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first := labelsOf(scrape, "1")
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labelsOf(scrape, "2")
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scrape.Commit()
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scrape = cache.Begin()
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require.Same(t, first[0], labelsOf(scrape, "1")[0], "label pairs reused")
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scrape.Commit()
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// Process 2 wasn't reported in the second scrape, so its pairs were dropped.
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scrape = cache.Begin()
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second := labelsOf(scrape, "2")
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require.Equal(t, "2", second[1].GetValue())
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scrape.Commit()
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scrape = cache.Begin()
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require.Same(t, second[0], labelsOf(scrape, "2")[0])
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scrape.Commit()
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cache.Reset()
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scrape = cache.Begin()
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require.NotSame(t, second[0], labelsOf(scrape, "2")[0], "reset drops the cache")
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scrape.Commit()
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}
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// A scrape begun before Reset must not restore its generation afterwards.
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func TestResetDuringScrape(t *testing.T) {
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t.Parallel()
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var cache labelcache.Cache
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scrape := cache.Begin()
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pairs := write(t, scrape.MustNewConstMetric(gaugeDesc, prometheus.GaugeValue, 1, "p", "1")).GetLabel()
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cache.Reset()
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scrape.Commit()
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scrape = cache.Begin()
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require.NotSame(t, pairs[0], write(t, scrape.MustNewConstMetric(gaugeDesc, prometheus.GaugeValue, 1, "p", "1")).GetLabel()[0])
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scrape.Commit()
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scrape.Commit()
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}
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func TestInvalidLabelValues(t *testing.T) {
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t.Parallel()
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var cache labelcache.Cache
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scrape := cache.Begin()
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require.Panics(t, func() { scrape.MustNewConstMetric(gaugeDesc, prometheus.GaugeValue, 1, "only one") })
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require.Panics(t, func() { scrape.MustNewConstMetric(gaugeDesc, prometheus.GaugeValue, 1, "p", "\xff") })
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}
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func TestConcurrentScrapes(t *testing.T) {
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t.Parallel()
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var (
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cache labelcache.Cache
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wg sync.WaitGroup
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)
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for range 8 {
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wg.Go(func() {
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for range 20 {
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scrape := cache.Begin()
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var inner sync.WaitGroup
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for p := range 4 {
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inner.Go(func() {
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for pid := range 50 {
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m := scrape.MustNewConstMetric(counterDesc, prometheus.CounterValue, 1, "p"+strconv.Itoa(p), strconv.Itoa(pid), "user")
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if err := m.Write(&dto.Metric{}); err != nil {
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t.Error(err)
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}
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}
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})
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}
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inner.Wait()
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scrape.Commit()
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}
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})
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}
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wg.Wait()
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}
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func BenchmarkMustNewConstMetric(b *testing.B) {
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pids := make([]string, 500)
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for i := range pids {
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pids[i] = strconv.Itoa(1000 + i)
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}
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b.Run("prometheus", func(b *testing.B) {
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b.ReportAllocs()
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for b.Loop() {
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for _, pid := range pids {
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_ = prometheus.MustNewConstMetric(counterDesc, prometheus.CounterValue, 1, "svchost", pid, "user")
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}
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}
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})
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b.Run("labelcache", func(b *testing.B) {
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var cache labelcache.Cache
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b.ReportAllocs()
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for b.Loop() {
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scrape := cache.Begin()
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for _, pid := range pids {
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_ = scrape.MustNewConstMetric(counterDesc, prometheus.CounterValue, 1, "svchost", pid, "user")
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}
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scrape.Commit()
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}
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})
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}
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Reference in New Issue
Block a user