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// Package metrics implement a handler and plugin that provides Prometheus metrics.
package metrics
import (
"log"
"net"
"net/http"
"os"
"runtime"
"sync"
"github.com/coredns/coredns/coremain"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metrics/vars"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
// Metrics holds the prometheus configuration. The metrics' path is fixed to be /metrics
type Metrics struct {
Next plugin.Handler
Addr string
Reg *prometheus.Registry
ln net.Listener
mux *http.ServeMux
zoneNames []string
zoneMap map[string]bool
zoneMu sync.RWMutex
}
// New returns a new instance of Metrics with the given address
func New(addr string) *Metrics {
met := &Metrics{
Addr: addr,
Reg: prometheus.NewRegistry(),
zoneMap: make(map[string]bool),
}
// Add the default collectors
met.MustRegister(prometheus.NewGoCollector())
met.MustRegister(prometheus.NewProcessCollector(os.Getpid(), ""))
// Add all of our collectors
met.MustRegister(buildInfo)
met.MustRegister(vars.RequestCount)
met.MustRegister(vars.RequestDuration)
met.MustRegister(vars.RequestSize)
met.MustRegister(vars.RequestDo)
met.MustRegister(vars.RequestType)
met.MustRegister(vars.ResponseSize)
met.MustRegister(vars.ResponseRcode)
// Initialize metrics.
buildInfo.WithLabelValues(coremain.CoreVersion, coremain.GitCommit, runtime.Version()).Set(1)
return met
}
// MustRegister wraps m.Reg.MustRegister.
func (m *Metrics) MustRegister(c prometheus.Collector) { m.Reg.MustRegister(c) }
// AddZone adds zone z to m.
func (m *Metrics) AddZone(z string) {
m.zoneMu.Lock()
m.zoneMap[z] = true
m.zoneNames = keys(m.zoneMap)
m.zoneMu.Unlock()
}
// RemoveZone remove zone z from m.
func (m *Metrics) RemoveZone(z string) {
m.zoneMu.Lock()
delete(m.zoneMap, z)
m.zoneNames = keys(m.zoneMap)
m.zoneMu.Unlock()
}
// ZoneNames returns the zones of m.
func (m *Metrics) ZoneNames() []string {
m.zoneMu.RLock()
s := m.zoneNames
m.zoneMu.RUnlock()
return s
}
// OnStartup sets up the metrics on startup.
func (m *Metrics) OnStartup() error {
ln, err := net.Listen("tcp", m.Addr)
if err != nil {
log.Printf("[ERROR] Failed to start metrics handler: %s", err)
return err
}
m.ln = ln
ListenAddr = m.ln.Addr().String()
m.mux = http.NewServeMux()
m.mux.Handle("/metrics", promhttp.HandlerFor(m.Reg, promhttp.HandlerOpts{}))
go func() {
http.Serve(m.ln, m.mux)
}()
return nil
}
// OnShutdown tears down the metrics listener on shutdown and restart.
func (m *Metrics) OnShutdown() error {
// We allow prometheus statements in multiple Server Blocks, but only the first
// will open the listener, for the rest they are all nil; guard against that.
if m.ln != nil {
return m.ln.Close()
}
return nil
}
func keys(m map[string]bool) []string {
sx := []string{}
for k := range m {
sx = append(sx, k)
}
return sx
}
// ListenAddr is assigned the address of the prometheus listener. Its use is mainly in tests where
// we listen on "localhost:0" and need to retrieve the actual address.
var ListenAddr string
var (
buildInfo = prometheus.NewGaugeVec(prometheus.GaugeOpts{
Namespace: plugin.Namespace,
Name: "build_info",
Help: "A metric with a constant '1' value labeled by version, revision, and goversion from which CoreDNS was built.",
}, []string{"version", "revision", "goversion"})
)
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