175 lines
6.4 KiB
Go
175 lines
6.4 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus
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import (
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"strings"
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"time"
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"github.com/golang/protobuf/proto"
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dto "github.com/prometheus/client_model/go"
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)
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const separatorByte byte = 255
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// A Metric models a single sample value with its meta data being exported to
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// Prometheus. Implementations of Metric in this package are Gauge, Counter,
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// Histogram, Summary, and Untyped.
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type Metric interface {
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// Desc returns the descriptor for the Metric. This method idempotently
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// returns the same descriptor throughout the lifetime of the
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// Metric. The returned descriptor is immutable by contract. A Metric
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// unable to describe itself must return an invalid descriptor (created
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// with NewInvalidDesc).
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Desc() *Desc
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// Write encodes the Metric into a "Metric" Protocol Buffer data
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// transmission object.
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//
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// Metric implementations must observe concurrency safety as reads of
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// this metric may occur at any time, and any blocking occurs at the
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// expense of total performance of rendering all registered
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// metrics. Ideally, Metric implementations should support concurrent
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// readers.
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//
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// While populating dto.Metric, it is the responsibility of the
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// implementation to ensure validity of the Metric protobuf (like valid
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// UTF-8 strings or syntactically valid metric and label names). It is
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// recommended to sort labels lexicographically. Callers of Write should
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// still make sure of sorting if they depend on it.
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Write(*dto.Metric) error
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// TODO(beorn7): The original rationale of passing in a pre-allocated
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// dto.Metric protobuf to save allocations has disappeared. The
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// signature of this method should be changed to "Write() (*dto.Metric,
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// error)".
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}
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// Opts bundles the options for creating most Metric types. Each metric
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// implementation XXX has its own XXXOpts type, but in most cases, it is just be
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// an alias of this type (which might change when the requirement arises.)
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//
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// It is mandatory to set Name to a non-empty string. All other fields are
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// optional and can safely be left at their zero value, although it is strongly
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// encouraged to set a Help string.
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type Opts struct {
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// Namespace, Subsystem, and Name are components of the fully-qualified
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// name of the Metric (created by joining these components with
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// "_"). Only Name is mandatory, the others merely help structuring the
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// name. Note that the fully-qualified name of the metric must be a
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// valid Prometheus metric name.
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Namespace string
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Subsystem string
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Name string
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// Help provides information about this metric.
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//
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// Metrics with the same fully-qualified name must have the same Help
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// string.
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Help string
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// ConstLabels are used to attach fixed labels to this metric. Metrics
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// with the same fully-qualified name must have the same label names in
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// their ConstLabels.
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//
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// ConstLabels are only used rarely. In particular, do not use them to
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// attach the same labels to all your metrics. Those use cases are
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// better covered by target labels set by the scraping Prometheus
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// server, or by one specific metric (e.g. a build_info or a
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// machine_role metric). See also
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// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels,-not-static-scraped-labels
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ConstLabels Labels
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}
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// BuildFQName joins the given three name components by "_". Empty name
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// components are ignored. If the name parameter itself is empty, an empty
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// string is returned, no matter what. Metric implementations included in this
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// library use this function internally to generate the fully-qualified metric
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// name from the name component in their Opts. Users of the library will only
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// need this function if they implement their own Metric or instantiate a Desc
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// (with NewDesc) directly.
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func BuildFQName(namespace, subsystem, name string) string {
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if name == "" {
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return ""
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}
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switch {
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case namespace != "" && subsystem != "":
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return strings.Join([]string{namespace, subsystem, name}, "_")
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case namespace != "":
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return strings.Join([]string{namespace, name}, "_")
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case subsystem != "":
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return strings.Join([]string{subsystem, name}, "_")
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}
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return name
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}
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// labelPairSorter implements sort.Interface. It is used to sort a slice of
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// dto.LabelPair pointers.
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type labelPairSorter []*dto.LabelPair
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func (s labelPairSorter) Len() int {
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return len(s)
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}
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func (s labelPairSorter) Swap(i, j int) {
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s[i], s[j] = s[j], s[i]
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}
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func (s labelPairSorter) Less(i, j int) bool {
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return s[i].GetName() < s[j].GetName()
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}
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type invalidMetric struct {
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desc *Desc
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err error
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}
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// NewInvalidMetric returns a metric whose Write method always returns the
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// provided error. It is useful if a Collector finds itself unable to collect
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// a metric and wishes to report an error to the registry.
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func NewInvalidMetric(desc *Desc, err error) Metric {
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return &invalidMetric{desc, err}
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}
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func (m *invalidMetric) Desc() *Desc { return m.desc }
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func (m *invalidMetric) Write(*dto.Metric) error { return m.err }
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type timestampedMetric struct {
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Metric
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t time.Time
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}
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func (m timestampedMetric) Write(pb *dto.Metric) error {
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e := m.Metric.Write(pb)
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pb.TimestampMs = proto.Int64(m.t.Unix()*1000 + int64(m.t.Nanosecond()/1000000))
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return e
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}
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// NewMetricWithTimestamp returns a new Metric wrapping the provided Metric in a
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// way that it has an explicit timestamp set to the provided Time. This is only
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// useful in rare cases as the timestamp of a Prometheus metric should usually
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// be set by the Prometheus server during scraping. Exceptions include mirroring
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// metrics with given timestamps from other metric
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// sources.
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//
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// NewMetricWithTimestamp works best with MustNewConstMetric,
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// MustNewConstHistogram, and MustNewConstSummary, see example.
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//
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// Currently, the exposition formats used by Prometheus are limited to
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// millisecond resolution. Thus, the provided time will be rounded down to the
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// next full millisecond value.
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func NewMetricWithTimestamp(t time.Time, m Metric) Metric {
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return timestampedMetric{Metric: m, t: t}
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}
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