Merge pull request #443 from prometheus/beorn7/timestamp
Add a wrapper to add a timestamp to a metric
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commit
29e6500a95
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@ -21,11 +21,12 @@ import (
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"runtime"
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"sort"
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"strings"
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dto "github.com/prometheus/client_model/go"
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"github.com/prometheus/common/expfmt"
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"time"
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"github.com/golang/protobuf/proto"
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"github.com/prometheus/common/expfmt"
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dto "github.com/prometheus/client_model/go"
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"github.com/prometheus/client_golang/prometheus"
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)
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@ -751,3 +752,36 @@ temperature_kelvin 4.5
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// temperature_kelvin{location="inside"} 298.44
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// temperature_kelvin{location="outside"} 273.14
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}
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func ExampleNewMetricWithTimestamp() {
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desc := prometheus.NewDesc(
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"temperature_kelvin",
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"Current temperature in Kelvin.",
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nil, nil,
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)
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// Create a constant gauge from values we got from an external
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// temperature reporting system. Those values are reported with a slight
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// delay, so we want to add the timestamp of the actual measurement.
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temperatureReportedByExternalSystem := 298.15
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timeReportedByExternalSystem := time.Date(2009, time.November, 10, 23, 0, 0, 12345678, time.UTC)
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s := prometheus.NewMetricWithTimestamp(
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timeReportedByExternalSystem,
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prometheus.MustNewConstMetric(
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desc, prometheus.GaugeValue, temperatureReportedByExternalSystem,
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),
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)
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// Just for demonstration, let's check the state of the gauge by
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// (ab)using its Write method (which is usually only used by Prometheus
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// internally).
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metric := &dto.Metric{}
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s.Write(metric)
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fmt.Println(proto.MarshalTextString(metric))
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// Output:
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// gauge: <
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// value: 298.15
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// >
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// timestamp_ms: 1257894000012
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}
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@ -15,6 +15,9 @@ package prometheus
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import (
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"strings"
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"time"
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"github.com/gogo/protobuf/proto"
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dto "github.com/prometheus/client_model/go"
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)
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@ -142,3 +145,31 @@ func NewInvalidMetric(desc *Desc, err error) Metric {
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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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