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registry.go
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registry.go
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// 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.
// Copyright (c) 2013, The Prometheus Authors
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file.
package prometheus
import (
"bytes"
"compress/gzip"
"errors"
"fmt"
"io"
"net/http"
"net/url"
"sort"
"strings"
"sync"
"github.com/golang/protobuf/proto"
"github.com/prometheus/common/expfmt"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
// Handler returns an instrumented HTTP handler for the default Prometheus
// registry. It is already instrumented with InstrumentHandler (using
// "prometheus" as handler name). Usually the handler is used to handle the
// "/metrics" endpoint.
func Handler() http.Handler {
return promhttp.InstrumentHandler(
"prometheus",
promhttp.Handler(registry.Default),
)
}
// UninstrumentedHandler works in the same way as Handler, but the returned HTTP
// handler is not instrumented. This is useful if no instrumentation is desired
// (for whatever reason) or if the instrumentation has to happen with a
// different handler name (or with a different instrumentation approach
// altogether). See the InstrumentHandler example.
func UninstrumentedHandler() http.Handler {
return promhttp.Handler(registry.Default)
}
// Register registers a new Collector to be included in metrics collection with
// the default registry. It returns an error if the descriptors provided by the
// Collector are invalid or if they - in combination with descriptors of already
// registered Collectors - do not fulfill the consistency and uniqueness
// criteria described in the Desc documentation.
//
// Do not register the same Collector multiple times concurrently. (Registering
// the same Collector twice would result in an error anyway, but on top of that,
// it is not safe to do so concurrently.)
func Register(c Collector) error {
return registry.Default.Register(c)
}
// MustRegister works like Register but panics where Register would have
// returned an error.
func MustRegister(c Collector) {
registry.MustRegister(registry.Default, c)
}
// RegisterOrGet works like Register but does not return an error if a Collector
// is registered that equals a previously registered Collector. (Two Collectors
// are considered equal if their Describe method yields the same set of
// descriptors.) Instead, the previously registered Collector is returned (which
// is helpful if the new and previously registered Collectors are equal but not
// identical, i.e. not pointers to the same object).
//
// As for Register, it is still not safe to call RegisterOrGet with the same
// Collector multiple times concurrently.
func RegisterOrGet(c Collector) (Collector, error) {
return registry.RegisterOrGet(registry.Default, c)
}
// MustRegisterOrGet works like Register but panics where RegisterOrGet would
// have returned an error.
func MustRegisterOrGet(c Collector) Collector {
return registry.MustRegisterOrGet(registry.Default, c)
}
// Unregister unregisters the Collector that equals the Collector passed in as
// an argument. (Two Collectors are considered equal if their Describe method
// yields the same set of descriptors.) The function returns whether a Collector
// was unregistered.
func Unregister(c Collector) bool {
return registry.Default.Unregister(c)
}
// TODO: Move out from here.
// encoder is a function that writes a dto.MetricFamily to an io.Writer in a
// certain encoding. It returns the number of bytes written and any error
// encountered. Note that pbutil.WriteDelimited and pbutil.MetricFamilyToText
// are encoders.
type encoder func(io.Writer, *dto.MetricFamily) (int, error)
type registry struct {
mtx sync.RWMutex
collectorsByID map[uint64]Collector // ID is a hash of the descIDs.
descIDs map[uint64]struct{}
dimHashesByName map[string]uint64
bufPool chan *bytes.Buffer
metricFamilyPool chan *dto.MetricFamily
metricPool chan *dto.Metric
metricFamilyInjectionHook func() []*dto.MetricFamily
panicOnCollectError, collectChecksEnabled bool
}
func (r *registry) Register(c Collector) (Collector, error) {
descChan := make(chan *Desc, capDescChan)
go func() {
c.Describe(descChan)
close(descChan)
}()
newDescIDs := map[uint64]struct{}{}
newDimHashesByName := map[string]uint64{}
var collectorID uint64 // Just a sum of all desc IDs.
var duplicateDescErr error
r.mtx.Lock()
defer r.mtx.Unlock()
// Coduct various tests...
for desc := range descChan {
// Is the descriptor valid at all?
if desc.err != nil {
return c, fmt.Errorf("descriptor %s is invalid: %s", desc, desc.err)
}
// Is the descID unique?
// (In other words: Is the fqName + constLabel combination unique?)
if _, exists := r.descIDs[desc.id]; exists {
duplicateDescErr = fmt.Errorf("descriptor %s already exists with the same fully-qualified name and const label values", desc)
}
// If it is not a duplicate desc in this collector, add it to
// the collectorID. (We allow duplicate descs within the same
// collector, but their existence must be a no-op.)
if _, exists := newDescIDs[desc.id]; !exists {
newDescIDs[desc.id] = struct{}{}
collectorID += desc.id
}
// Are all the label names and the help string consistent with
// previous descriptors of the same name?
// First check existing descriptors...
if dimHash, exists := r.dimHashesByName[desc.fqName]; exists {
if dimHash != desc.dimHash {
return nil, fmt.Errorf("a previously registered descriptor with the same fully-qualified name as %s has different label names or a different help string", desc)
}
} else {
// ...then check the new descriptors already seen.
if dimHash, exists := newDimHashesByName[desc.fqName]; exists {
if dimHash != desc.dimHash {
return nil, fmt.Errorf("descriptors reported by collector have inconsistent label names or help strings for the same fully-qualified name, offender is %s", desc)
}
} else {
newDimHashesByName[desc.fqName] = desc.dimHash
}
}
}
// Did anything happen at all?
if len(newDescIDs) == 0 {
return nil, errors.New("collector has no descriptors")
}
if existing, exists := r.collectorsByID[collectorID]; exists {
return existing, errAlreadyReg
}
// If the collectorID is new, but at least one of the descs existed
// before, we are in trouble.
if duplicateDescErr != nil {
return nil, duplicateDescErr
}
// Only after all tests have passed, actually register.
r.collectorsByID[collectorID] = c
for hash := range newDescIDs {
r.descIDs[hash] = struct{}{}
}
for name, dimHash := range newDimHashesByName {
r.dimHashesByName[name] = dimHash
}
return c, nil
}
func (r *registry) RegisterOrGet(m Collector) (Collector, error) {
existing, err := r.Register(m)
if err != nil && err != errAlreadyReg {
return nil, err
}
return existing, nil
}
func (r *registry) Unregister(c Collector) bool {
descChan := make(chan *Desc, capDescChan)
go func() {
c.Describe(descChan)
close(descChan)
}()
descIDs := map[uint64]struct{}{}
var collectorID uint64 // Just a sum of the desc IDs. TODO: should be fnv on its own
for desc := range descChan {
if _, exists := descIDs[desc.id]; !exists {
collectorID += desc.id
descIDs[desc.id] = struct{}{}
}
}
r.mtx.RLock()
if _, exists := r.collectorsByID[collectorID]; !exists {
r.mtx.RUnlock()
return false
}
r.mtx.RUnlock()
r.mtx.Lock()
defer r.mtx.Unlock()
delete(r.collectorsByID, collectorID)
for id := range descIDs {
delete(r.descIDs, id)
}
// dimHashesByName is left untouched as those must be consistent
// throughout the lifetime of a program.
return true
}
func (r *registry) Push(job, instance, pushURL, method string) error {
if !strings.Contains(pushURL, "://") {
pushURL = "http://" + pushURL
}
if strings.HasSuffix(pushURL, "/") {
pushURL = pushURL[:len(pushURL)-1]
}
pushURL = fmt.Sprintf("%s/metrics/jobs/%s", pushURL, url.QueryEscape(job))
if instance != "" {
pushURL += "/instances/" + url.QueryEscape(instance)
}
buf := r.getBuf()
defer r.giveBuf(buf)
if err := r.writePB(expfmt.NewEncoder(buf, expfmt.FmtProtoDelim)); err != nil {
if r.panicOnCollectError {
panic(err)
}
return err
}
req, err := http.NewRequest(method, pushURL, buf)
if err != nil {
return err
}
req.Header.Set(contentTypeHeader, DelimitedTelemetryContentType)
resp, err := http.DefaultClient.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != 202 {
return fmt.Errorf("unexpected status code %d while pushing to %s", resp.StatusCode, pushURL)
}
return nil
}
func (r *registry) ServeHTTP(w http.ResponseWriter, req *http.Request) {
contentType := expfmt.Negotiate(req.Header)
buf := r.getBuf()
defer r.giveBuf(buf)
writer, encoding := decorateWriter(req, buf)
if err := r.writePB(expfmt.NewEncoder(writer, contentType)); err != nil {
if r.panicOnCollectError {
panic(err)
}
http.Error(w, "An error has occurred:\n\n"+err.Error(), http.StatusInternalServerError)
return
}
if closer, ok := writer.(io.Closer); ok {
closer.Close()
}
header := w.Header()
header.Set(contentTypeHeader, string(contentType))
header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
if encoding != "" {
header.Set(contentEncodingHeader, encoding)
}
w.Write(buf.Bytes())
}
func (r *registry) writePB(encoder expfmt.Encoder) error {
var metricHashes map[uint64]struct{}
if r.collectChecksEnabled {
metricHashes = make(map[uint64]struct{})
}
metricChan := make(chan Metric, capMetricChan)
wg := sync.WaitGroup{}
r.mtx.RLock()
metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName))
// Scatter.
// (Collectors could be complex and slow, so we call them all at once.)
wg.Add(len(r.collectorsByID))
go func() {
wg.Wait()
close(metricChan)
}()
for _, collector := range r.collectorsByID {
go func(collector Collector) {
defer wg.Done()
collector.Collect(metricChan)
}(collector)
}
r.mtx.RUnlock()
// Drain metricChan in case of premature return.
defer func() {
for _ = range metricChan {
}
}()
// Gather.
for metric := range metricChan {
// This could be done concurrently, too, but it required locking
// of metricFamiliesByName (and of metricHashes if checks are
// enabled). Most likely not worth it.
desc := metric.Desc()
metricFamily, ok := metricFamiliesByName[desc.fqName]
if !ok {
metricFamily = r.getMetricFamily()
defer r.giveMetricFamily(metricFamily)
metricFamily.Name = proto.String(desc.fqName)
metricFamily.Help = proto.String(desc.help)
metricFamiliesByName[desc.fqName] = metricFamily
}
dtoMetric := r.getMetric()
defer r.giveMetric(dtoMetric)
if err := metric.Write(dtoMetric); err != nil {
// TODO: Consider different means of error reporting so
// that a single erroneous metric could be skipped
// instead of blowing up the whole collection.
return fmt.Errorf("error collecting metric %v: %s", desc, err)
}
switch {
case metricFamily.Type != nil:
// Type already set. We are good.
case dtoMetric.Gauge != nil:
metricFamily.Type = dto.MetricType_GAUGE.Enum()
case dtoMetric.Counter != nil:
metricFamily.Type = dto.MetricType_COUNTER.Enum()
case dtoMetric.Summary != nil:
metricFamily.Type = dto.MetricType_SUMMARY.Enum()
case dtoMetric.Untyped != nil:
metricFamily.Type = dto.MetricType_UNTYPED.Enum()
case dtoMetric.Histogram != nil:
metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
default:
return fmt.Errorf("empty metric collected: %s", dtoMetric)
}
if r.collectChecksEnabled {
if err := r.checkConsistency(metricFamily, dtoMetric, desc, metricHashes); err != nil {
return err
}
}
metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
}
if r.metricFamilyInjectionHook != nil {
for _, mf := range r.metricFamilyInjectionHook() {
existingMF, exists := metricFamiliesByName[mf.GetName()]
if !exists {
metricFamiliesByName[mf.GetName()] = mf
if r.collectChecksEnabled {
for _, m := range mf.Metric {
if err := r.checkConsistency(mf, m, nil, metricHashes); err != nil {
return err
}
}
}
continue
}
for _, m := range mf.Metric {
if r.collectChecksEnabled {
if err := r.checkConsistency(existingMF, m, nil, metricHashes); err != nil {
return err
}
}
existingMF.Metric = append(existingMF.Metric, m)
}
}
}
// Now that MetricFamilies are all set, sort their Metrics
// lexicographically by their label values.
for _, mf := range metricFamiliesByName {
sort.Sort(metricSorter(mf.Metric))
}
// Write out MetricFamilies sorted by their name.
names := make([]string, 0, len(metricFamiliesByName))
for name := range metricFamiliesByName {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
if err := encoder.Encode(metricFamiliesByName[name]); err != nil {
return err
}
}
return nil
}
func (r *registry) checkConsistency(metricFamily *dto.MetricFamily, dtoMetric *dto.Metric, desc *Desc, metricHashes map[uint64]struct{}) error {
// Type consistency with metric family.
if metricFamily.GetType() == dto.MetricType_GAUGE && dtoMetric.Gauge == nil ||
metricFamily.GetType() == dto.MetricType_COUNTER && dtoMetric.Counter == nil ||
metricFamily.GetType() == dto.MetricType_SUMMARY && dtoMetric.Summary == nil ||
metricFamily.GetType() == dto.MetricType_HISTOGRAM && dtoMetric.Histogram == nil ||
metricFamily.GetType() == dto.MetricType_UNTYPED && dtoMetric.Untyped == nil {
return fmt.Errorf(
"collected metric %s %s is not a %s",
metricFamily.GetName(), dtoMetric, metricFamily.GetType(),
)
}
// Is the metric unique (i.e. no other metric with the same name and the same label values)?
h := hashNew()
h = hashAdd(h, metricFamily.GetName())
h = hashAddByte(h, separatorByte)
// Make sure label pairs are sorted. We depend on it for the consistency
// check. Label pairs must be sorted by contract. But the point of this
// method is to check for contract violations. So we better do the sort
// now.
sort.Sort(LabelPairSorter(dtoMetric.Label))
for _, lp := range dtoMetric.Label {
h = hashAdd(h, lp.GetValue())
h = hashAddByte(h, separatorByte)
}
if _, exists := metricHashes[h]; exists {
return fmt.Errorf(
"collected metric %s %s was collected before with the same name and label values",
metricFamily.GetName(), dtoMetric,
)
}
metricHashes[h] = struct{}{}
if desc == nil {
return nil // Nothing left to check if we have no desc.
}
// Desc consistency with metric family.
if metricFamily.GetName() != desc.fqName {
return fmt.Errorf(
"collected metric %s %s has name %q but should have %q",
metricFamily.GetName(), dtoMetric, metricFamily.GetName(), desc.fqName,
)
}
if metricFamily.GetHelp() != desc.help {
return fmt.Errorf(
"collected metric %s %s has help %q but should have %q",
metricFamily.GetName(), dtoMetric, metricFamily.GetHelp(), desc.help,
)
}
// Is the desc consistent with the content of the metric?
lpsFromDesc := make([]*dto.LabelPair, 0, len(dtoMetric.Label))
lpsFromDesc = append(lpsFromDesc, desc.constLabelPairs...)
for _, l := range desc.variableLabels {
lpsFromDesc = append(lpsFromDesc, &dto.LabelPair{
Name: proto.String(l),
})
}
if len(lpsFromDesc) != len(dtoMetric.Label) {
return fmt.Errorf(
"labels in collected metric %s %s are inconsistent with descriptor %s",
metricFamily.GetName(), dtoMetric, desc,
)
}
sort.Sort(LabelPairSorter(lpsFromDesc))
for i, lpFromDesc := range lpsFromDesc {
lpFromMetric := dtoMetric.Label[i]
if lpFromDesc.GetName() != lpFromMetric.GetName() ||
lpFromDesc.Value != nil && lpFromDesc.GetValue() != lpFromMetric.GetValue() {
return fmt.Errorf(
"labels in collected metric %s %s are inconsistent with descriptor %s",
metricFamily.GetName(), dtoMetric, desc,
)
}
}
r.mtx.RLock() // Remaining checks need the read lock.
defer r.mtx.RUnlock()
// Is the desc registered?
if _, exist := r.descIDs[desc.id]; !exist {
return fmt.Errorf(
"collected metric %s %s with unregistered descriptor %s",
metricFamily.GetName(), dtoMetric, desc,
)
}
return nil
}
func (r *registry) getBuf() *bytes.Buffer {
select {
case buf := <-r.bufPool:
return buf
default:
return &bytes.Buffer{}
}
}
func (r *registry) giveBuf(buf *bytes.Buffer) {
buf.Reset()
select {
case r.bufPool <- buf:
default:
}
}
func (r *registry) getMetricFamily() *dto.MetricFamily {
select {
case mf := <-r.metricFamilyPool:
return mf
default:
return &dto.MetricFamily{}
}
}
func (r *registry) giveMetricFamily(mf *dto.MetricFamily) {
mf.Reset()
select {
case r.metricFamilyPool <- mf:
default:
}
}
func (r *registry) getMetric() *dto.Metric {
select {
case m := <-r.metricPool:
return m
default:
return &dto.Metric{}
}
}
func (r *registry) giveMetric(m *dto.Metric) {
m.Reset()
select {
case r.metricPool <- m:
default:
}
}
func newRegistry() *registry {
return ®istry{
collectorsByID: map[uint64]Collector{},
descIDs: map[uint64]struct{}{},
dimHashesByName: map[string]uint64{},
bufPool: make(chan *bytes.Buffer, numBufs),
metricFamilyPool: make(chan *dto.MetricFamily, numMetricFamilies),
metricPool: make(chan *dto.Metric, numMetrics),
}
}
// decorateWriter wraps a writer to handle gzip compression if requested. It
// returns the decorated writer and the appropriate "Content-Encoding" header
// (which is empty if no compression is enabled).
func decorateWriter(request *http.Request, writer io.Writer) (io.Writer, string) {
header := request.Header.Get(acceptEncodingHeader)
parts := strings.Split(header, ",")
for _, part := range parts {
part := strings.TrimSpace(part)
if part == "gzip" || strings.HasPrefix(part, "gzip;") {
return gzip.NewWriter(writer), "gzip"
}
}
return writer, ""
}
type metricSorter []*dto.Metric
func (s metricSorter) Len() int {
return len(s)
}
func (s metricSorter) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
func (s metricSorter) Less(i, j int) bool {
if len(s[i].Label) != len(s[j].Label) {
// This should not happen. The metrics are
// inconsistent. However, we have to deal with the fact, as
// people might use custom collectors or metric family injection
// to create inconsistent metrics. So let's simply compare the
// number of labels in this case. That will still yield
// reproducible sorting.
return len(s[i].Label) < len(s[j].Label)
}
for n, lp := range s[i].Label {
vi := lp.GetValue()
vj := s[j].Label[n].GetValue()
if vi != vj {
return vi < vj
}
}
// We should never arrive here. Multiple metrics with the same
// label set in the same scrape will lead to undefined ingestion
// behavior. However, as above, we have to provide stable sorting
// here, even for inconsistent metrics. So sort equal metrics
// by their timestamp, with missing timestamps (implying "now")
// coming last.
if s[i].TimestampMs == nil {
return false
}
if s[j].TimestampMs == nil {
return true
}
return s[i].GetTimestampMs() < s[j].GetTimestampMs()
}