prometheus/web/federate.go

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package web
import (
"io"
"net/http"
"bitbucket.org/ww/goautoneg"
"github.com/golang/protobuf/proto"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/text"
"github.com/prometheus/prometheus/promql"
"github.com/prometheus/prometheus/storage/local"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/model"
)
type Federation struct {
Storage local.Storage
}
func (fed *Federation) ServeHTTP(w http.ResponseWriter, req *http.Request) {
req.ParseForm()
metrics := map[model.Fingerprint]model.COWMetric{}
for _, s := range req.Form["match[]"] {
matchers, err := promql.ParseMetricSelector(s)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
for fp, met := range fed.Storage.MetricsForLabelMatchers(matchers...) {
metrics[fp] = met
}
}
enc, contentType := chooseEncoder(req)
w.Header().Set("Content-Type", contentType)
protMetric := &dto.Metric{
Label: []*dto.LabelPair{},
Untyped: &dto.Untyped{},
}
protMetricFam := &dto.MetricFamily{
Metric: []*dto.Metric{protMetric},
Type: dto.MetricType_UNTYPED.Enum(),
}
for fp, met := range metrics {
sp := fed.Storage.LastSamplePairForFingerprint(fp)
if sp == nil {
continue
}
// Reset label slice.
protMetric.Label = protMetric.Label[:0]
for ln, lv := range met.Metric {
if ln == model.MetricNameLabel {
protMetricFam.Name = proto.String(string(lv))
continue
}
protMetric.Label = append(protMetric.Label, &dto.LabelPair{
Name: proto.String(string(ln)),
Value: proto.String(string(lv)),
})
}
protMetric.TimestampMs = (*int64)(&sp.Timestamp)
protMetric.Untyped.Value = (*float64)(&sp.Value)
if _, err := enc(w, protMetricFam); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
}
}
type encoder func(w io.Writer, p *dto.MetricFamily) (int, error)
func chooseEncoder(req *http.Request) (encoder, string) {
accepts := goautoneg.ParseAccept(req.Header.Get("Accept"))
for _, accept := range accepts {
switch {
case accept.Type == "application" &&
accept.SubType == "vnd.google.protobuf" &&
accept.Params["proto"] == "io.prometheus.client.MetricFamily":
switch accept.Params["encoding"] {
case "delimited":
return text.WriteProtoDelimited, prometheus.DelimitedTelemetryContentType
case "text":
return text.WriteProtoText, prometheus.ProtoTextTelemetryContentType
case "compact-text":
return text.WriteProtoCompactText, prometheus.ProtoCompactTextTelemetryContentType
default:
continue
}
case accept.Type == "text" &&
accept.SubType == "plain" &&
(accept.Params["version"] == "0.0.4" || accept.Params["version"] == ""):
return text.MetricFamilyToText, prometheus.TextTelemetryContentType
default:
continue
}
}
return text.MetricFamilyToText, prometheus.TextTelemetryContentType
}