client_golang/prometheus/registry.go

650 lines
22 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 (
"errors"
"fmt"
"os"
"sort"
"sync"
"github.com/golang/protobuf/proto"
"github.com/hashicorp/go-multierror"
dto "github.com/prometheus/client_model/go"
)
const (
// Capacity for the channel to collect metrics and descriptors.
capMetricChan = 1000
capDescChan = 10
)
// DefaultRegistry is a Registry instance that has a ProcessCollector and a
// GoCollector pre-registered. DefaultRegisterer and DefaultDeliverer are both
// pointing to it. A number of convenience functions in this package act on
// them. This approach to keep a default instance as global state mirrors the
// approach of other packages in the Go standard library. Note that there are
// caveats. Change the variables with caution and only if you understand the
// consequences. Users who want to avoid global state altogether should not
// use the convenience function and act on custom instances instead.
var (
DefaultRegistry = NewRegistry()
DefaultRegisterer Registerer = DefaultRegistry
DefaultDeliverer Deliverer = DefaultRegistry
)
func init() {
MustRegister(NewProcessCollector(os.Getpid(), ""))
MustRegister(NewGoCollector())
}
// NewRegistry creates a new vanilla Registry without any Collectors
// pre-registered.
func NewRegistry() *Registry {
return &Registry{
collectorsByID: map[uint64]Collector{},
descIDs: map[uint64]struct{}{},
dimHashesByName: map[string]uint64{},
}
}
// NewPedanticRegistry returns a registry that checks during collection if each
// collected Metric is consistent with its reported Desc, and if the Desc has
// actually been registered with the registry.
//
// Usually, a Registry will be happy as long as the union of all collected
// Metrics is consistent and valid even if some metrics are not consistent with
// their own Desc or with one of the Descs provided by their
// Collector. Well-behaved Collectors and Metrics will only provide consistent
// Descs. This Registry is useful to test the implementation of Collectors and
// Metrics.
func NewPedanticRegistry() *Registry {
r := NewRegistry()
r.pedanticChecksEnabled = true
return r
}
// Registerer is the interface for the part of a registry in charge of
// registering and unregistering. Users of custom registries should use
// Registerer as type for registration purposes (rather then the Registry type
// directly). In that way, they are free to exchange the Registerer
// implementation (e.g. for testing purposes).
type Registerer interface {
// 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 documentation of metric.Desc.
//
// If the provided Collector is equal to a Collector already registered
// (which includes the case of re-registering the same Collector), the
// returned error is an instance of AlreadyRegisteredError, which
// contains the previously registered Collector.
//
// It is in general not safe to register the same Collector multiple
// times concurrently.
Register(Collector) error
// MustRegister works like Register but registers any number of
// Collectors and panics upon the first registration that causes an
// error.
MustRegister(...Collector)
// 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.
//
// Note that even after unregistering, it will not be possible to
// register a new Collector that is inconsistent with the unregistered
// Collector, e.g. a Collector collecting metrics with the same name but
// a different help string. The rationale here is that the same registry
// instance must only collect consistent metrics throughout its
// lifetime.
Unregister(Collector) bool
}
// Deliverer is the interface for the part of a registry in charge of delivering
// the collected metrics, wich the same general implication as described for the
// Registerer interface.
type Deliverer interface {
// Deliver collects metrics from registered Collectors and returns them
// as lexicographically sorted MetricFamily protobufs. Even if an error
// occurs, Deliver attempts to collect as many metrics as
// possible. Hence, if a non-nil error is returned, the returned
// MetricFamily slice could be nil (in case of a fatal error that
// prevented any meaningful metric collection) or contain a number of
// MetricFamily protobufs, some of which might be incomplete, and some
// might be missing altogether. The returned error (which might be a
// multierror.Error) explains the details. In any case, the MetricFamily
// protobufs are consistent and valid for Prometheus to ingest (e.g. no
// duplicate metrics, no invalid identifiers). In scenarios where
// complete collection is critical, the returned MetricFamily protobufs
// should be disregarded if the returned error is non-nil.
Deliver() ([]*dto.MetricFamily, error)
}
// Register registers the provided Collector with the DefaultRegisterer.
//
// Register is a shortcut for DefaultRegisterer.Register(c). See there for more
// details.
func Register(c Collector) error {
return DefaultRegisterer.Register(c)
}
// MustRegister registers the provided Collectors with the DefaultRegisterer and
// panics if any error occurs.
//
// MustRegister is a shortcut for DefaultRegisterer.MustRegister(cs...). See
// there for more details.
func MustRegister(cs ...Collector) {
DefaultRegisterer.MustRegister(cs...)
}
// RegisterOrGet registers the provided Collector with the DefaultRegisterer and
// returns the Collector, unless an equal Collector was registered before, in
// which case that Collector is returned.
//
// Deprecated: RegisterOrGet is merely a convenience function for the
// implementation as described in the documentation for
// AlreadyRegisteredError. As the use case is relatively rare, this function
// will be removed in a future version of this package to clean up the
// namespace.
func RegisterOrGet(c Collector) (Collector, error) {
if err := Register(c); err != nil {
if are, ok := err.(AlreadyRegisteredError); ok {
return are.ExistingCollector, nil
}
return nil, err
}
return c, nil
}
// MustRegisterOrGet behaves like RegisterOrGet but panics instead of returning
// an error.
//
// Deprecated: This is deprecated for the same reason RegisterOrGet is. See
// there for details.
func MustRegisterOrGet(c Collector) Collector {
c, err := RegisterOrGet(c)
if err != nil {
panic(err)
}
return c
}
// Unregister removes the registration of the provided Collector from the
// DefaultRegisterer.
//
// Unregister is a shortcut for DefaultRegisterer.Unregister(c). See there for
// more details.
func Unregister(c Collector) bool {
return DefaultRegisterer.Unregister(c)
}
// SetMetricFamilyInjectionHook sets a MetricFamily injection hook on the
// DefaultRegistry.
//
// It's a shortcut for DefaultRegistry.SetInjectionHook(hook). See there for
// more details.
//
// Deprecated: In the rare cases this call is needed, users should simply call
// DefaultRegistry.SetInjectionHook directly.
func SetMetricFamilyInjectionHook(hook func() []*dto.MetricFamily) {
DefaultRegistry.SetInjectionHook(hook)
}
// AlreadyRegisteredError is returned by the Registerer.Register if the
// Collector to be registered has already been registered before, or a different
// Collector that collects the same metrics has been registered
// before. Registration fails in that case, but you can detect from the kind of
// error what has happened. The error contains fields for the existing Collector
// and the (rejected) new Collector that equals the existing one. This can be
// used to find out if an equal Collector has been registered before and switch
// over to using the old one, as demonstrated in the example.
type AlreadyRegisteredError struct {
ExistingCollector, NewCollector Collector
}
func (err AlreadyRegisteredError) Error() string {
return "duplicate metrics collector registration attempted"
}
// Registry registers Prometheus collectors, collects their metrics, and
// delivers them for exposition. It implements Registerer and Deliverer. The
// zero value is not usable. Use NewRegistry or NewPedanticRegistry to create
// instances.
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
metricFamilyInjectionHook func() []*dto.MetricFamily
pedanticChecksEnabled bool
}
// Register implements Registerer.
func (r *Registry) Register(c Collector) error {
var (
descChan = make(chan *Desc, capDescChan)
newDescIDs = map[uint64]struct{}{}
newDimHashesByName = map[string]uint64{}
collectorID uint64 // Just a sum of all desc IDs.
duplicateDescErr error
)
go func() {
c.Describe(descChan)
close(descChan)
}()
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 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 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 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 errors.New("collector has no descriptors")
}
if existing, exists := r.collectorsByID[collectorID]; exists {
return AlreadyRegisteredError{
ExistingCollector: existing,
NewCollector: c,
}
}
// If the collectorID is new, but at least one of the descs existed
// before, we are in trouble.
if duplicateDescErr != nil {
return 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 nil
}
// Unregister implements Registerer.
func (r *Registry) Unregister(c Collector) bool {
var (
descChan = make(chan *Desc, capDescChan)
descIDs = map[uint64]struct{}{}
collectorID uint64 // Just a sum of the desc IDs.
)
go func() {
c.Describe(descChan)
close(descChan)
}()
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
}
// MustRegister implements Registerer.
func (r *Registry) MustRegister(cs ...Collector) {
for _, c := range cs {
if err := r.Register(c); err != nil {
panic(err)
}
}
}
// Deliver implements Deliverer.
func (r *Registry) Deliver() ([]*dto.MetricFamily, error) {
var (
metricChan = make(chan Metric, capMetricChan)
metricHashes = map[uint64]struct{}{}
wg sync.WaitGroup
errs error // The collected errors to return in the end.
registeredDescIDs map[uint64]struct{} // Only used for pedantic checks
)
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)
}
// In case pedantic checks are enabled, we have to copy the map before
// giving up the RLock.
if r.pedanticChecksEnabled {
registeredDescIDs = make(map[uint64]struct{}, len(r.descIDs))
for id := range r.descIDs {
registeredDescIDs[id] = struct{}{}
}
}
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 = &dto.MetricFamily{}
metricFamily.Name = proto.String(desc.fqName)
metricFamily.Help = proto.String(desc.help)
metricFamiliesByName[desc.fqName] = metricFamily
}
dtoMetric := &dto.Metric{}
if err := metric.Write(dtoMetric); err != nil {
errs = multierror.Append(errs, fmt.Errorf(
"error collecting metric %v: %s", desc, err,
))
continue
}
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:
errs = multierror.Append(errs, fmt.Errorf(
"empty metric collected: %s", dtoMetric,
))
continue
}
if err := r.checkConsistency(metricFamily, dtoMetric, desc, metricHashes, registeredDescIDs); err != nil {
errs = multierror.Append(errs, err)
continue
}
metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
}
r.mtx.RLock()
if r.metricFamilyInjectionHook != nil {
for _, mf := range r.metricFamilyInjectionHook() {
existingMF, exists := metricFamiliesByName[mf.GetName()]
if !exists {
existingMF = &dto.MetricFamily{}
existingMF.Name = mf.Name
existingMF.Help = mf.Help
existingMF.Type = mf.Type
metricFamiliesByName[mf.GetName()] = existingMF
}
for _, m := range mf.Metric {
if err := r.checkConsistency(existingMF, m, nil, metricHashes, nil); err != nil {
errs = multierror.Append(errs, err)
continue
}
existingMF.Metric = append(existingMF.Metric, m)
}
}
}
r.mtx.RUnlock()
// 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, skipping those without
// metrics.
names := make([]string, 0, len(metricFamiliesByName))
for name, mf := range metricFamiliesByName {
if len(mf.Metric) > 0 {
names = append(names, name)
}
}
sort.Strings(names)
result := make([]*dto.MetricFamily, 0, len(names))
for _, name := range names {
result = append(result, metricFamiliesByName[name])
}
return result, errs
}
func (r *Registry) checkConsistency(
metricFamily *dto.MetricFamily,
dtoMetric *dto.Metric,
desc *Desc,
metricHashes map[uint64]struct{},
registeredDescIDs 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.
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 || !r.pedanticChecksEnabled {
return nil // Nothing left to check if we have no desc.
}
// Desc help consistency with metric family help.
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,
)
}
}
// Is the desc registered?
if _, exist := registeredDescIDs[desc.id]; !exist {
return fmt.Errorf(
"collected metric %s %s with unregistered descriptor %s",
metricFamily.GetName(), dtoMetric, desc,
)
}
return nil
}
// SetInjectionHook sets the provided hook to inject MetricFamilies. The hook is
// a function that is called whenever metrics are collected. The MetricFamily
// protobufs returned by the hook function are merged with the metrics collected
// in the usual way.
//
// This is a way to directly inject MetricFamily protobufs managed and owned by
// the caller. The caller has full responsibility. As no registration of the
// injected metrics has happened, there was no check at registration time. If
// the injection results in inconsistent metrics, the Collect call will return
// an error. Some problems may even go undetected, like invalid label names in
// the injected protobufs.
//
// The hook function must be callable at any time and concurrently.
func (r *Registry) SetInjectionHook(hook func() []*dto.MetricFamily) {
r.mtx.Lock()
defer r.mtx.Unlock()
r.metricFamilyInjectionHook = hook
}
// metricSorter is a sortable slice of *dto.Metric.
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()
}