client_golang/prometheus/registry.go

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// Copyright 2014 Prometheus Team
// 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, Prometheus Team
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file.
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package prometheus
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import (
"bytes"
"errors"
"fmt"
"hash/fnv"
"io"
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"net/http"
"net/url"
"sort"
"strings"
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"sync"
dto "github.com/prometheus/client_model/go"
"code.google.com/p/goprotobuf/proto"
"compress/gzip"
"github.com/prometheus/client_golang/_vendor/goautoneg"
"github.com/prometheus/client_golang/model"
"github.com/prometheus/client_golang/text"
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)
var (
defRegistry = newRegistry()
errAlreadyReg = errors.New("duplicate metrics collector registration attempted")
)
// Constants relevant to the HTTP interface.
const (
// APIVersion is the version of the format of the exported data. This
// will match this library's version, which subscribes to the Semantic
// Versioning scheme.
APIVersion = "0.0.4"
// DelimitedTelemetryContentType is the content type set on telemetry
// data responses in delimited protobuf format.
DelimitedTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited`
// TextTelemetryContentType is the content type set on telemetry data
// responses in text format.
TextTelemetryContentType = `text/plain; version=` + APIVersion
// ProtoTextTelemetryContentType is the content type set on telemetry
// data responses in protobuf text format. (Only used for debugging.)
ProtoTextTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=text`
// ProtoCompactTextTelemetryContentType is the content type set on
// telemetry data responses in protobuf compact text format. (Only used
// for debugging.)
ProtoCompactTextTelemetryContentType = `application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=compact-text`
// Constants for object pools.
numBufs = 4
numMetricFamilies = 1000
numMetrics = 10000
// Capacity for the channel to collect metrics and descriptors.
capMetricChan = 1000
capDescChan = 10
contentTypeHeader = "Content-Type"
contentLengthHeader = "Content-Length"
contentEncodingHeader = "Content-Encoding"
acceptEncodingHeader = "Accept-Encoding"
acceptHeader = "Accept"
)
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// Handler returns the HTTP handler for the global 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 InstrumentHandler("prometheus", defRegistry)
}
// 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 defRegistry
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}
// Register registers a new Collector to be included in metrics collection. 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. If the registration is successful, the registered Collector
// is returned.
//
// 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(m Collector) (Collector, error) {
return defRegistry.Register(m)
}
// MustRegister works like Register but panics where Register would have
// returned an error.
func MustRegister(m Collector) Collector {
m, err := Register(m)
if err != nil {
panic(err)
}
return m
}
// 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(m Collector) (Collector, error) {
return defRegistry.RegisterOrGet(m)
}
// MustRegisterOrGet works like Register but panics where RegisterOrGet would
// have returned an error.
func MustRegisterOrGet(m Collector) Collector {
existing, err := RegisterOrGet(m)
if err != nil {
panic(err)
}
return existing
}
// 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 defRegistry.Unregister(c)
}
// SetMetricFamilyInjectionHook sets a function that is called whenever metrics
// are collected. The hook function must be set before metrics collection begins
// (i.e. call SetMetricFamilyInjectionHook before setting the HTTP handler.) The
// MetricFamily protobufs returned by the hook function are added to the
// delivered metrics. Each returned MetricFamily must have a unique name (also
// taking into account the MetricFamilies created in the regular way).
//
// This is a way to directly inject MetricFamily protobufs managed and owned by
// the caller. The caller has full responsibility. No sanity checks are
// performed on the returned protobufs (besides the name checks described
// above). The function must be callable at any time and concurrently.
func SetMetricFamilyInjectionHook(hook func() []*dto.MetricFamily) {
defRegistry.metricFamilyInjectionHook = hook
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}
// PanicOnCollectError sets the behavior whether a panic is caused upon an error
// while metrics are collected and served to the http endpoint. By default, an
// internal server error (status code 500) is served with an error message.
func PanicOnCollectError(b bool) {
defRegistry.panicOnCollectError = b
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}
// EnableCollectChecks enables (or disables) additional consistency checks
// during metrics collection. These additional checks are not enabled by default
// because they inflict a performance penalty and the errors they check for can
// only happen if the used Metric and Collector types have internal programming
// errors. It can be helpful to enable these checks while working with custom
// Collectors or Metrics whose correctness is not well established yet.
func EnableCollectChecks(b bool) {
defRegistry.collectChecksEnabled = b
}
// Push triggers a metric collection and pushes all collected metrics to the
// Pushgateway specified by addr. See the Pushgateway documentation for detailed
// implications of the job and instance parameter. instance can be left
// empty. The Pushgateway will then use the client's IP number instead. Use just
// host:port or ip:port ass addr. (Don't add 'http://' or any path.)
//
// Note that all previously pushed metrics with the same job and instance will
// be replaced with the metrics pushed by this call. (It uses HTTP method 'PUT'
// to push to the Pushgateway.)
func Push(job, instance, addr string) error {
return defRegistry.Push(job, instance, addr, "PUT")
}
// PushAdd works like Push, but only previously pushed metrics with the same
// name (and the same job and instance) will be replaced. (It uses HTTP method
// 'POST' to push to the Pushgateway.)
func PushAdd(job, instance, addr string) error {
return defRegistry.Push(job, instance, addr, "POST")
}
// 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 ext.WriteDelimited and text.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.
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, addr, method string) error {
u := fmt.Sprintf("http://%s/metrics/jobs/%s", addr, url.QueryEscape(job))
if instance != "" {
u += "/instances/" + url.QueryEscape(instance)
}
buf := r.getBuf()
defer r.giveBuf(buf)
if _, err := r.writePB(buf, text.WriteProtoDelimited); err != nil {
if r.panicOnCollectError {
panic(err)
}
return err
}
req, err := http.NewRequest(method, u, 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, u)
}
return nil
}
func (r *registry) ServeHTTP(w http.ResponseWriter, req *http.Request) {
enc, contentType := chooseEncoder(req)
buf := r.getBuf()
defer r.giveBuf(buf)
writer, encoding := decorateWriter(req, buf)
if _, err := r.writePB(writer, enc); 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, contentType)
header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
if encoding != "" {
header.Set(contentEncodingHeader, encoding)
}
w.Write(buf.Bytes())
}
func (r *registry) writePB(w io.Writer, writeEncoded encoder) (int, error) {
metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName))
var metricHashes map[uint64]struct{}
if r.collectChecksEnabled {
metricHashes = make(map[uint64]struct{})
}
metricChan := make(chan Metric, capMetricChan)
wg := sync.WaitGroup{}
// Scatter.
// (Collectors could be complex and slow, so we call them all at once.)
r.mtx.RLock()
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)
metric.Write(dtoMetric)
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()
default:
return 0, fmt.Errorf("empty metric collected: %s", dtoMetric)
}
if r.collectChecksEnabled {
if err := r.checkConsistency(metricFamily, dtoMetric, desc, metricHashes); err != nil {
return 0, err
}
}
metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
}
if r.metricFamilyInjectionHook != nil {
for _, mf := range r.metricFamilyInjectionHook() {
if _, exists := metricFamiliesByName[mf.GetName()]; exists {
return 0, fmt.Errorf("metric family with duplicate name injected: %s", mf)
}
metricFamiliesByName[mf.GetName()] = mf
}
}
// 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)
var written int
for _, name := range names {
w, err := writeEncoded(w, metricFamiliesByName[name])
written += w
if err != nil {
return written, err
}
}
return written, nil
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}
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_UNTYPED && dtoMetric.Untyped == nil {
return fmt.Errorf(
"collected metric %q is not a %s",
dtoMetric, metricFamily.Type,
)
}
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// Desc consistency with metric family.
if metricFamily.GetHelp() != desc.help {
return fmt.Errorf(
"collected metric %q has help %q but should have %q",
dtoMetric, desc.help, metricFamily.GetHelp(),
)
}
// 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 %q are inconsistent with descriptor %s",
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 %q are inconsistent with descriptor %s",
dtoMetric, desc,
)
}
}
// Is the metric unique (i.e. no other metric with the same name and the same label values)?
h := fnv.New64a()
var buf bytes.Buffer
buf.WriteString(desc.fqName)
buf.WriteByte(model.SeparatorByte)
h.Write(buf.Bytes())
for _, lp := range dtoMetric.Label {
buf.Reset()
buf.WriteString(lp.GetValue())
buf.WriteByte(model.SeparatorByte)
h.Write(buf.Bytes())
}
metricHash := h.Sum64()
if _, exists := metricHashes[metricHash]; exists {
return fmt.Errorf(
"collected metric %q was collected before with the same name and label values",
dtoMetric,
)
}
metricHashes[metricHash] = struct{}{}
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 %q with unregistered descriptor %s", dtoMetric, desc)
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}
return nil
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}
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 &registry{
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),
}
}
func chooseEncoder(req *http.Request) (encoder, string) {
accepts := goautoneg.ParseAccept(req.Header.Get(acceptHeader))
for _, accept := range accepts {
switch {
case accept.Type == "application" &&
accept.SubType == "vnd.google.protobuf" &&
accept.Params["proto"] == "io.prometheus.client.MetricFamily":
switch accept.Params["encoding"] {
case "delimited":
return text.WriteProtoDelimited, DelimitedTelemetryContentType
case "text":
return text.WriteProtoText, ProtoTextTelemetryContentType
case "compact-text":
return text.WriteProtoCompactText, ProtoCompactTextTelemetryContentType
default:
continue
}
case accept.Type == "text" &&
accept.SubType == "plain" &&
(accept.Params["version"] == "0.0.4" || accept.Params["version"] == ""):
return text.MetricFamilyToText, TextTelemetryContentType
default:
continue
}
}
return text.MetricFamilyToText, TextTelemetryContentType
}
// 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 {
for n, lp := range s[i].Label {
vi := lp.GetValue()
vj := s[j].Label[n].GetValue()
if vi != vj {
return vi < vj
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}
}
return true
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}