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federate.go
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/
federate.go
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// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package web
import (
"fmt"
"net/http"
"sort"
"github.com/go-kit/kit/log/level"
"github.com/gogo/protobuf/proto"
"github.com/prometheus/client_golang/prometheus"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/pkg/timestamp"
"github.com/prometheus/prometheus/pkg/value"
"github.com/prometheus/prometheus/promql"
"github.com/prometheus/prometheus/storage"
)
var (
federationErrors = prometheus.NewCounter(prometheus.CounterOpts{
Name: "prometheus_web_federation_errors_total",
Help: "Total number of errors that occurred while sending federation responses.",
})
)
func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
h.mtx.RLock()
defer h.mtx.RUnlock()
if err := req.ParseForm(); err != nil {
http.Error(w, fmt.Sprintf("error parsing form values: %v", err), http.StatusBadRequest)
return
}
var matcherSets [][]*labels.Matcher
for _, s := range req.Form["match[]"] {
matchers, err := promql.ParseMetricSelector(s)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
matcherSets = append(matcherSets, matchers)
}
var (
mint = timestamp.FromTime(h.now().Time().Add(-promql.LookbackDelta))
maxt = timestamp.FromTime(h.now().Time())
format = expfmt.Negotiate(req.Header)
enc = expfmt.NewEncoder(w, format)
)
w.Header().Set("Content-Type", string(format))
q, err := h.storage.Querier(req.Context(), mint, maxt)
if err != nil {
federationErrors.Inc()
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
defer q.Close()
vec := make(promql.Vector, 0, 8000)
params := &storage.SelectParams{
Start: mint,
End: maxt,
}
var sets []storage.SeriesSet
for _, mset := range matcherSets {
s, err := q.Select(params, mset...)
if err != nil {
federationErrors.Inc()
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
sets = append(sets, s)
}
set := storage.NewMergeSeriesSet(sets)
it := storage.NewBuffer(int64(promql.LookbackDelta / 1e6))
for set.Next() {
s := set.At()
// TODO(fabxc): allow fast path for most recent sample either
// in the storage itself or caching layer in Prometheus.
it.Reset(s.Iterator())
var t int64
var v float64
ok := it.Seek(maxt)
if ok {
t, v = it.Values()
} else {
t, v, ok = it.PeekBack(1)
if !ok {
continue
}
}
// The exposition formats do not support stale markers, so drop them. This
// is good enough for staleness handling of federated data, as the
// interval-based limits on staleness will do the right thing for supported
// use cases (which is to say federating aggregated time series).
if value.IsStaleNaN(v) {
continue
}
vec = append(vec, promql.Sample{
Metric: s.Labels(),
Point: promql.Point{T: t, V: v},
})
}
if set.Err() != nil {
federationErrors.Inc()
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
sort.Sort(byName(vec))
externalLabels := h.config.GlobalConfig.ExternalLabels.Clone()
if _, ok := externalLabels[model.InstanceLabel]; !ok {
externalLabels[model.InstanceLabel] = ""
}
externalLabelNames := make(model.LabelNames, 0, len(externalLabels))
for ln := range externalLabels {
externalLabelNames = append(externalLabelNames, ln)
}
sort.Sort(externalLabelNames)
var (
lastMetricName string
protMetricFam *dto.MetricFamily
)
for _, s := range vec {
nameSeen := false
globalUsed := map[string]struct{}{}
protMetric := &dto.Metric{
Untyped: &dto.Untyped{},
}
for _, l := range s.Metric {
if l.Value == "" {
// No value means unset. Never consider those labels.
// This is also important to protect against nameless metrics.
continue
}
if l.Name == labels.MetricName {
nameSeen = true
if l.Value == lastMetricName {
// We already have the name in the current MetricFamily,
// and we ignore nameless metrics.
continue
}
// Need to start a new MetricFamily. Ship off the old one (if any) before
// creating the new one.
if protMetricFam != nil {
if err := enc.Encode(protMetricFam); err != nil {
federationErrors.Inc()
level.Error(h.logger).Log("msg", "federation failed", "err", err)
return
}
}
protMetricFam = &dto.MetricFamily{
Type: dto.MetricType_UNTYPED.Enum(),
Name: proto.String(l.Value),
}
lastMetricName = l.Value
continue
}
protMetric.Label = append(protMetric.Label, &dto.LabelPair{
Name: proto.String(l.Name),
Value: proto.String(l.Value),
})
if _, ok := externalLabels[model.LabelName(l.Name)]; ok {
globalUsed[l.Name] = struct{}{}
}
}
if !nameSeen {
level.Warn(h.logger).Log("msg", "Ignoring nameless metric during federation", "metric", s.Metric)
continue
}
// Attach global labels if they do not exist yet.
for _, ln := range externalLabelNames {
lv := externalLabels[ln]
if _, ok := globalUsed[string(ln)]; !ok {
protMetric.Label = append(protMetric.Label, &dto.LabelPair{
Name: proto.String(string(ln)),
Value: proto.String(string(lv)),
})
}
}
protMetric.TimestampMs = proto.Int64(s.T)
protMetric.Untyped.Value = proto.Float64(s.V)
protMetricFam.Metric = append(protMetricFam.Metric, protMetric)
}
// Still have to ship off the last MetricFamily, if any.
if protMetricFam != nil {
if err := enc.Encode(protMetricFam); err != nil {
federationErrors.Inc()
level.Error(h.logger).Log("msg", "federation failed", "err", err)
}
}
}
// byName makes a model.Vector sortable by metric name.
type byName promql.Vector
func (vec byName) Len() int { return len(vec) }
func (vec byName) Swap(i, j int) { vec[i], vec[j] = vec[j], vec[i] }
func (vec byName) Less(i, j int) bool {
ni := vec[i].Metric.Get(labels.MetricName)
nj := vec[j].Metric.Get(labels.MetricName)
return ni < nj
}