Add a wrapper to add a timestamp to a metric

Signed-off-by: beorn7 <beorn@soundcloud.com>
This commit is contained in:
beorn7 2018-08-18 15:56:08 +02:00
parent 5b23715fac
commit 5240f7e8f5
2 changed files with 64 additions and 0 deletions

View File

@ -21,6 +21,7 @@ import (
"runtime"
"sort"
"strings"
"time"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
@ -751,3 +752,36 @@ temperature_kelvin 4.5
// temperature_kelvin{location="inside"} 298.44
// temperature_kelvin{location="outside"} 273.14
}
func ExampleNewMetricWithTimestamp() {
desc := prometheus.NewDesc(
"temperature_kelvin",
"Current temperature in Kelvin.",
nil, nil,
)
// Create a constant gauge from values we got from an external
// temperature reporting system. Those values are reported with a slight
// delay, so we want to add the timestamp of the actual measurement.
temperatureReportedByExternalSystem := 298.15
timeReportedByExternalSystem := time.Date(2009, time.November, 10, 23, 0, 0, 12345678, time.UTC)
s := prometheus.NewMetricWithTimestamp(
timeReportedByExternalSystem,
prometheus.MustNewConstMetric(
desc, prometheus.GaugeValue, temperatureReportedByExternalSystem,
),
)
// Just for demonstration, let's check the state of the gauge by
// (ab)using its Write method (which is usually only used by Prometheus
// internally).
metric := &dto.Metric{}
s.Write(metric)
fmt.Println(proto.MarshalTextString(metric))
// Output:
// gauge: <
// value: 298.15
// >
// timestamp_ms: 1257894000012
}

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@ -15,7 +15,9 @@ package prometheus
import (
"strings"
"time"
"github.com/gogo/protobuf/proto"
dto "github.com/prometheus/client_model/go"
)
@ -142,3 +144,31 @@ func NewInvalidMetric(desc *Desc, err error) Metric {
func (m *invalidMetric) Desc() *Desc { return m.desc }
func (m *invalidMetric) Write(*dto.Metric) error { return m.err }
type timestampedMetric struct {
Metric
t time.Time
}
func (m timestampedMetric) Write(pb *dto.Metric) error {
e := m.Metric.Write(pb)
pb.TimestampMs = proto.Int64(m.t.Unix()*1000 + int64(m.t.Nanosecond()/1000000))
return e
}
// NewMetricWithTimestamp returns a new Metric wrapping the provided Metric in a
// way that it has an explicit timestamp set to the provided Time. This is only
// useful in rare cases as the timestamp of a Prometheus metric should usually
// be set by the Prometheus server during scraping. Exceptions include mirroring
// metrics with given timestamps from other metric
// sources.
//
// NewMetricWithTimestamp works best with MustNewConstMetric,
// MustNewConstHistogram, and MustNewConstSummary, see example.
//
// Currently, the exposition formats used by Prometheus are limited to
// millisecond resolution. Thus, the provided time will be rounded down to the
// next full millisecond value.
func NewMetricWithTimestamp(t time.Time, m Metric) Metric {
return timestampedMetric{Metric: m, t: t}
}