Merge pull request #370 from prometheus/beorn7/performance
Create goroutines adaptively during metrics gathering
This commit is contained in:
Björn Rabenstein
GitHub
commit
f4fb1b73fb
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@ -18,6 +18,7 @@ import (
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"errors"
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"fmt"
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"os"
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"runtime"
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"sort"
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"sync"
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"unicode/utf8"
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@ -202,6 +203,13 @@ func (errs MultiError) Error() string {
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return buf.String()
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}
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// Append appends the provided error if it is not nil.
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func (errs *MultiError) Append(err error) {
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if err != nil {
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*errs = append(*errs, err)
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}
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}
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// MaybeUnwrap returns nil if len(errs) is 0. It returns the first and only
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// contained error as error if len(errs is 1). In all other cases, it returns
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// the MultiError directly. This is helpful for returning a MultiError in a way
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@ -368,22 +376,12 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
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)
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r.mtx.RLock()
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goroutineBudget := len(r.collectorsByID)
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metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName))
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// Scatter.
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// (Collectors could be complex and slow, so we call them all at once.)
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wg.Add(len(r.collectorsByID))
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go func() {
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wg.Wait()
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close(metricChan)
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}()
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collectors := make(chan Collector, len(r.collectorsByID))
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for _, collector := range r.collectorsByID {
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go func(collector Collector) {
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defer wg.Done()
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collector.Collect(metricChan)
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}(collector)
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collectors <- collector
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}
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// In case pedantic checks are enabled, we have to copy the map before
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// giving up the RLock.
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if r.pedanticChecksEnabled {
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@ -392,129 +390,176 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
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registeredDescIDs[id] = struct{}{}
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}
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}
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r.mtx.RUnlock()
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wg.Add(goroutineBudget)
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collectWorker := func() {
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for {
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select {
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case collector := <-collectors:
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collector.Collect(metricChan)
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wg.Done()
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default:
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return
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}
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}
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}
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// Start the first worker now to make sure at least one is running.
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go collectWorker()
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goroutineBudget--
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// Close the metricChan once all collectors are collected.
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go func() {
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wg.Wait()
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close(metricChan)
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}()
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// Drain metricChan in case of premature return.
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defer func() {
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for range metricChan {
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}
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}()
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// Gather.
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for metric := range metricChan {
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// This could be done concurrently, too, but it required locking
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// of metricFamiliesByName (and of metricHashes if checks are
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// enabled). Most likely not worth it.
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desc := metric.Desc()
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dtoMetric := &dto.Metric{}
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if err := metric.Write(dtoMetric); err != nil {
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errs = append(errs, fmt.Errorf(
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"error collecting metric %v: %s", desc, err,
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collectLoop:
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for {
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select {
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case metric, ok := <-metricChan:
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if !ok {
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// metricChan is closed, we are done.
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break collectLoop
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}
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errs.Append(processMetric(
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metric, metricFamiliesByName,
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metricHashes, dimHashes,
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registeredDescIDs,
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))
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continue
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default:
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if goroutineBudget <= 0 || len(collectors) == 0 {
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// All collectors are aleady being worked on or
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// we have already as many goroutines started as
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// there are collectors. Just process metrics
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// from now on.
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for metric := range metricChan {
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errs.Append(processMetric(
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metric, metricFamiliesByName,
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metricHashes, dimHashes,
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registeredDescIDs,
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))
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}
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break collectLoop
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}
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// Start more workers.
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go collectWorker()
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goroutineBudget--
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runtime.Gosched()
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}
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metricFamily, ok := metricFamiliesByName[desc.fqName]
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if ok {
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if metricFamily.GetHelp() != desc.help {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s has help %q but should have %q",
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desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
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))
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continue
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}
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// TODO(beorn7): Simplify switch once Desc has type.
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switch metricFamily.GetType() {
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case dto.MetricType_COUNTER:
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if dtoMetric.Counter == nil {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s should be a Counter",
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desc.fqName, dtoMetric,
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))
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continue
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}
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case dto.MetricType_GAUGE:
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if dtoMetric.Gauge == nil {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s should be a Gauge",
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desc.fqName, dtoMetric,
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))
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continue
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}
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case dto.MetricType_SUMMARY:
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if dtoMetric.Summary == nil {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s should be a Summary",
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desc.fqName, dtoMetric,
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))
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continue
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}
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case dto.MetricType_UNTYPED:
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if dtoMetric.Untyped == nil {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s should be Untyped",
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desc.fqName, dtoMetric,
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))
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continue
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}
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case dto.MetricType_HISTOGRAM:
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if dtoMetric.Histogram == nil {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s should be a Histogram",
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desc.fqName, dtoMetric,
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))
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continue
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}
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default:
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panic("encountered MetricFamily with invalid type")
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}
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} else {
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metricFamily = &dto.MetricFamily{}
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metricFamily.Name = proto.String(desc.fqName)
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metricFamily.Help = proto.String(desc.help)
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// TODO(beorn7): Simplify switch once Desc has type.
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switch {
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case dtoMetric.Gauge != nil:
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metricFamily.Type = dto.MetricType_GAUGE.Enum()
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case dtoMetric.Counter != nil:
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metricFamily.Type = dto.MetricType_COUNTER.Enum()
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case dtoMetric.Summary != nil:
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metricFamily.Type = dto.MetricType_SUMMARY.Enum()
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case dtoMetric.Untyped != nil:
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metricFamily.Type = dto.MetricType_UNTYPED.Enum()
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case dtoMetric.Histogram != nil:
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metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
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default:
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errs = append(errs, fmt.Errorf(
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"empty metric collected: %s", dtoMetric,
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))
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continue
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}
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metricFamiliesByName[desc.fqName] = metricFamily
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}
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if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes, dimHashes); err != nil {
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errs = append(errs, err)
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continue
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}
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if r.pedanticChecksEnabled {
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// Is the desc registered at all?
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if _, exist := registeredDescIDs[desc.id]; !exist {
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errs = append(errs, fmt.Errorf(
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"collected metric %s %s with unregistered descriptor %s",
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metricFamily.GetName(), dtoMetric, desc,
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))
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continue
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}
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if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
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errs = append(errs, err)
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continue
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}
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}
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metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
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}
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return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
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}
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// processMetric is an internal helper method only used by the Gather method.
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func processMetric(
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metric Metric,
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metricFamiliesByName map[string]*dto.MetricFamily,
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metricHashes map[uint64]struct{},
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dimHashes map[string]uint64,
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registeredDescIDs map[uint64]struct{},
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) error {
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desc := metric.Desc()
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dtoMetric := &dto.Metric{}
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if err := metric.Write(dtoMetric); err != nil {
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return fmt.Errorf("error collecting metric %v: %s", desc, err)
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}
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metricFamily, ok := metricFamiliesByName[desc.fqName]
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if ok {
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if metricFamily.GetHelp() != desc.help {
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return fmt.Errorf(
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"collected metric %s %s has help %q but should have %q",
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desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
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)
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}
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// TODO(beorn7): Simplify switch once Desc has type.
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switch metricFamily.GetType() {
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case dto.MetricType_COUNTER:
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if dtoMetric.Counter == nil {
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return fmt.Errorf(
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"collected metric %s %s should be a Counter",
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desc.fqName, dtoMetric,
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)
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}
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case dto.MetricType_GAUGE:
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if dtoMetric.Gauge == nil {
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return fmt.Errorf(
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"collected metric %s %s should be a Gauge",
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desc.fqName, dtoMetric,
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)
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}
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case dto.MetricType_SUMMARY:
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if dtoMetric.Summary == nil {
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return fmt.Errorf(
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"collected metric %s %s should be a Summary",
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desc.fqName, dtoMetric,
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)
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}
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case dto.MetricType_UNTYPED:
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if dtoMetric.Untyped == nil {
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return fmt.Errorf(
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"collected metric %s %s should be Untyped",
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desc.fqName, dtoMetric,
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)
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}
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case dto.MetricType_HISTOGRAM:
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if dtoMetric.Histogram == nil {
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return fmt.Errorf(
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"collected metric %s %s should be a Histogram",
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desc.fqName, dtoMetric,
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)
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}
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default:
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panic("encountered MetricFamily with invalid type")
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}
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} else {
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metricFamily = &dto.MetricFamily{}
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metricFamily.Name = proto.String(desc.fqName)
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metricFamily.Help = proto.String(desc.help)
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// TODO(beorn7): Simplify switch once Desc has type.
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switch {
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case dtoMetric.Gauge != nil:
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metricFamily.Type = dto.MetricType_GAUGE.Enum()
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case dtoMetric.Counter != nil:
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metricFamily.Type = dto.MetricType_COUNTER.Enum()
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case dtoMetric.Summary != nil:
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metricFamily.Type = dto.MetricType_SUMMARY.Enum()
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case dtoMetric.Untyped != nil:
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metricFamily.Type = dto.MetricType_UNTYPED.Enum()
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case dtoMetric.Histogram != nil:
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metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
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default:
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return fmt.Errorf("empty metric collected: %s", dtoMetric)
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}
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metricFamiliesByName[desc.fqName] = metricFamily
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}
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if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes, dimHashes); err != nil {
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return err
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}
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if registeredDescIDs != nil {
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// Is the desc registered at all?
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if _, exist := registeredDescIDs[desc.id]; !exist {
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return fmt.Errorf(
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"collected metric %s %s with unregistered descriptor %s",
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metricFamily.GetName(), dtoMetric, desc,
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)
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}
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if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
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return err
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}
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}
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metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
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return nil
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}
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// Gatherers is a slice of Gatherer instances that implements the Gatherer
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// interface itself. Its Gather method calls Gather on all Gatherers in the
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// slice in order and returns the merged results. Errors returned from the
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