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go_collector_go117.go
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/
go_collector_go117.go
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// Copyright 2021 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.
//go:build go1.17
// +build go1.17
package prometheus
import (
"math"
"runtime"
"runtime/metrics"
"sync"
//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
"github.com/golang/protobuf/proto"
"github.com/prometheus/client_golang/prometheus/internal"
dto "github.com/prometheus/client_model/go"
)
type goCollector struct {
base baseGoCollector
// rm... fields all pertain to the runtime/metrics package.
rmSampleBuf []metrics.Sample
rmSampleMap map[string]*metrics.Sample
rmMetrics []Metric
// With Go 1.17, the runtime/metrics package was introduced.
// From that point on, metric names produced by the runtime/metrics
// package could be generated from runtime/metrics names. However,
// these differ from the old names for the same values.
//
// This field exist to export the same values under the old names
// as well.
msMetrics memStatsMetrics
}
// NewGoCollector is the obsolete version of collectors.NewGoCollector.
// See there for documentation.
//
// Deprecated: Use collectors.NewGoCollector instead.
func NewGoCollector() Collector {
descriptions := metrics.All()
descMap := make(map[string]*metrics.Description)
for i := range descriptions {
descMap[descriptions[i].Name] = &descriptions[i]
}
// Generate a Desc and ValueType for each runtime/metrics metric.
metricSet := make([]Metric, 0, len(descriptions))
sampleBuf := make([]metrics.Sample, 0, len(descriptions))
sampleMap := make(map[string]*metrics.Sample, len(descriptions))
for i := range descriptions {
d := &descriptions[i]
namespace, subsystem, name, ok := internal.RuntimeMetricsToProm(d)
if !ok {
// Just ignore this metric; we can't do anything with it here.
// If a user decides to use the latest version of Go, we don't want
// to fail here. This condition is tested elsewhere.
continue
}
// Set up sample buffer for reading, and a map
// for quick lookup of sample values.
sampleBuf = append(sampleBuf, metrics.Sample{Name: d.Name})
sampleMap[d.Name] = &sampleBuf[len(sampleBuf)-1]
var m Metric
if d.Kind == metrics.KindFloat64Histogram {
_, hasSum := rmExactSumMap[d.Name]
m = newBatchHistogram(
NewDesc(
BuildFQName(namespace, subsystem, name),
d.Description,
nil,
nil,
),
hasSum,
)
} else if d.Cumulative {
m = NewCounter(CounterOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: name,
Help: d.Description,
})
} else {
m = NewGauge(GaugeOpts{
Namespace: namespace,
Subsystem: subsystem,
Name: name,
Help: d.Description,
})
}
metricSet = append(metricSet, m)
}
return &goCollector{
base: newBaseGoCollector(),
rmSampleBuf: sampleBuf,
rmSampleMap: sampleMap,
rmMetrics: metricSet,
msMetrics: goRuntimeMemStats(),
}
}
// Describe returns all descriptions of the collector.
func (c *goCollector) Describe(ch chan<- *Desc) {
c.base.Describe(ch)
for _, i := range c.msMetrics {
ch <- i.desc
}
for _, m := range c.rmMetrics {
ch <- m.Desc()
}
}
// Collect returns the current state of all metrics of the collector.
func (c *goCollector) Collect(ch chan<- Metric) {
// Collect base non-memory metrics.
c.base.Collect(ch)
// Populate runtime/metrics sample buffer.
metrics.Read(c.rmSampleBuf)
for i, sample := range c.rmSampleBuf {
// N.B. switch on concrete type because it's significantly more efficient
// than checking for the Counter and Gauge interface implementations. In
// this case, we control all the types here.
switch m := c.rmMetrics[i].(type) {
case *counter:
// Guard against decreases. This should never happen, but a failure
// to do so will result in a panic, which is a harsh consequence for
// a metrics collection bug.
v0, v1 := m.get(), unwrapScalarRMValue(sample.Value)
if v1 > v0 {
m.Add(unwrapScalarRMValue(sample.Value) - m.get())
}
m.Collect(ch)
case *gauge:
m.Set(unwrapScalarRMValue(sample.Value))
m.Collect(ch)
case *batchHistogram:
m.update(sample.Value.Float64Histogram(), c.exactSumFor(sample.Name))
m.Collect(ch)
default:
panic("unexpected metric type")
}
}
// ms is a dummy MemStats that we populate ourselves so that we can
// populate the old metrics from it.
var ms runtime.MemStats
memStatsFromRM(&ms, c.rmSampleMap)
for _, i := range c.msMetrics {
ch <- MustNewConstMetric(i.desc, i.valType, i.eval(&ms))
}
}
// unwrapScalarRMValue unwraps a runtime/metrics value that is assumed
// to be scalar and returns the equivalent float64 value. Panics if the
// value is not scalar.
func unwrapScalarRMValue(v metrics.Value) float64 {
switch v.Kind() {
case metrics.KindUint64:
return float64(v.Uint64())
case metrics.KindFloat64:
return v.Float64()
case metrics.KindBad:
// Unsupported metric.
//
// This should never happen because we always populate our metric
// set from the runtime/metrics package.
panic("unexpected unsupported metric")
default:
// Unsupported metric kind.
//
// This should never happen because we check for this during initialization
// and flag and filter metrics whose kinds we don't understand.
panic("unexpected unsupported metric kind")
}
}
var rmExactSumMap = map[string]string{
"/gc/heap/allocs-by-size:bytes": "/gc/heap/allocs:bytes",
"/gc/heap/frees-by-size:bytes": "/gc/heap/frees:bytes",
}
// exactSumFor takes a runtime/metrics metric name (that is assumed to
// be of kind KindFloat64Histogram) and returns its exact sum and whether
// its exact sum exists.
//
// The runtime/metrics API for histograms doesn't currently expose exact
// sums, but some of the other metrics are in fact exact sums of histograms.
func (c *goCollector) exactSumFor(rmName string) float64 {
sumName, ok := rmExactSumMap[rmName]
if !ok {
return 0
}
s, ok := c.rmSampleMap[sumName]
if !ok {
return 0
}
return unwrapScalarRMValue(s.Value)
}
func memStatsFromRM(ms *runtime.MemStats, rm map[string]*metrics.Sample) {
lookupOrZero := func(name string) uint64 {
if s, ok := rm[name]; ok {
return s.Value.Uint64()
}
return 0
}
// Currently, MemStats adds tiny alloc count to both Mallocs AND Frees.
// The reason for this is because MemStats couldn't be extended at the time
// but there was a desire to have Mallocs at least be a little more representative,
// while having Mallocs - Frees still represent a live object count.
// Unfortunately, MemStats doesn't actually export a large allocation count,
// so it's impossible to pull this number out directly.
tinyAllocs := lookupOrZero("/gc/heap/tiny/allocs:objects")
ms.Mallocs = lookupOrZero("/gc/heap/allocs:objects") + tinyAllocs
ms.Frees = lookupOrZero("/gc/heap/frees:objects") + tinyAllocs
ms.TotalAlloc = lookupOrZero("/gc/heap/allocs:bytes")
ms.Sys = lookupOrZero("/memory/classes/total:bytes")
ms.Lookups = 0 // Already always zero.
ms.HeapAlloc = lookupOrZero("/memory/classes/heap/objects:bytes")
ms.Alloc = ms.HeapAlloc
ms.HeapInuse = ms.HeapAlloc + lookupOrZero("/memory/classes/heap/unused:bytes")
ms.HeapReleased = lookupOrZero("/memory/classes/heap/released:bytes")
ms.HeapIdle = ms.HeapReleased + lookupOrZero("/memory/classes/heap/free:bytes")
ms.HeapSys = ms.HeapInuse + ms.HeapIdle
ms.HeapObjects = lookupOrZero("/gc/heap/objects:objects")
ms.StackInuse = lookupOrZero("/memory/classes/heap/stacks:bytes")
ms.StackSys = ms.StackInuse + lookupOrZero("/memory/classes/os-stacks:bytes")
ms.MSpanInuse = lookupOrZero("/memory/classes/metadata/mspan/inuse:bytes")
ms.MSpanSys = ms.MSpanInuse + lookupOrZero("/memory/classes/metadata/mspan/free:bytes")
ms.MCacheInuse = lookupOrZero("/memory/classes/metadata/mcache/inuse:bytes")
ms.MCacheSys = ms.MCacheInuse + lookupOrZero("/memory/classes/metadata/mcache/free:bytes")
ms.BuckHashSys = lookupOrZero("/memory/classes/profiling/buckets:bytes")
ms.GCSys = lookupOrZero("/memory/classes/metadata/other:bytes")
ms.OtherSys = lookupOrZero("/memory/classes/other:bytes")
ms.NextGC = lookupOrZero("/gc/heap/goal:bytes")
// N.B. LastGC is omitted because runtime.GCStats already has this.
// See https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034
// for more details.
ms.LastGC = 0
// N.B. GCCPUFraction is intentionally omitted. This metric is not useful,
// and often misleading due to the fact that it's an average over the lifetime
// of the process.
// See https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034
// for more details.
ms.GCCPUFraction = 0
}
// batchHistogram is a mutable histogram that is updated
// in batches.
type batchHistogram struct {
selfCollector
// Static fields updated only once.
desc *Desc
hasSum bool
// Because this histogram operates in batches, it just uses a
// single mutex for everything. updates are always serialized
// but Write calls may operate concurrently with updates.
// Contention between these two sources should be rare.
mu sync.Mutex
buckets []float64 // Inclusive lower bounds.
counts []uint64
sum float64 // Used if hasSum is true.
}
func newBatchHistogram(desc *Desc, hasSum bool) *batchHistogram {
h := &batchHistogram{desc: desc, hasSum: hasSum}
h.init(h)
return h
}
// update updates the batchHistogram from a runtime/metrics histogram.
//
// sum must be provided if the batchHistogram was created to have an exact sum.
func (h *batchHistogram) update(his *metrics.Float64Histogram, sum float64) {
counts, buckets := his.Counts, his.Buckets
// Skip a -Inf bucket altogether. It's not clear how to represent that.
if math.IsInf(buckets[0], -1) {
buckets = buckets[1:]
counts = counts[1:]
}
h.mu.Lock()
defer h.mu.Unlock()
// Check if we're initialized.
if h.buckets == nil {
// Make copies of counts and buckets. It's really important
// that we don't retain his.Counts or his.Buckets anywhere since
// it's going to get reused.
h.buckets = make([]float64, len(buckets))
copy(h.buckets, buckets)
h.counts = make([]uint64, len(counts))
}
copy(h.counts, counts)
if h.hasSum {
h.sum = sum
}
}
func (h *batchHistogram) Desc() *Desc {
return h.desc
}
func (h *batchHistogram) Write(out *dto.Metric) error {
h.mu.Lock()
defer h.mu.Unlock()
sum := float64(0)
if h.hasSum {
sum = h.sum
}
dtoBuckets := make([]*dto.Bucket, 0, len(h.counts))
totalCount := uint64(0)
for i, count := range h.counts {
totalCount += count
if !h.hasSum {
// N.B. This computed sum is an underestimate.
sum += h.buckets[i] * float64(count)
}
// Skip the +Inf bucket, but only for the bucket list.
// It must still count for sum and totalCount.
if math.IsInf(h.buckets[i+1], 1) {
break
}
// Float64Histogram's upper bound is exclusive, so make it inclusive
// by obtaining the next float64 value down, in order.
upperBound := math.Nextafter(h.buckets[i+1], h.buckets[i])
dtoBuckets = append(dtoBuckets, &dto.Bucket{
CumulativeCount: proto.Uint64(totalCount),
UpperBound: proto.Float64(upperBound),
})
}
out.Histogram = &dto.Histogram{
Bucket: dtoBuckets,
SampleCount: proto.Uint64(totalCount),
SampleSum: proto.Float64(sum),
}
return nil
}