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// Package health implements an HTTP handler that responds to health checks.
package health
import (
"context"
"io"
"net"
"net/http"
"net/url"
"time"
clog "github.com/coredns/coredns/plugin/pkg/log"
"github.com/coredns/coredns/plugin/pkg/reuseport"
)
var log = clog.NewWithPlugin("health")
// Health implements healthchecks by exporting a HTTP endpoint.
type health struct {
Addr string
lameduck time.Duration
healthURI *url.URL
ln net.Listener
nlSetup bool
mux *http.ServeMux
stop context.CancelFunc
}
func (h *health) OnStartup() error {
if h.Addr == "" {
h.Addr = ":8080"
}
var err error
h.healthURI, err = url.Parse("http://" + h.Addr)
if err != nil {
return err
}
h.healthURI.Path = "/health"
if h.healthURI.Host == "" {
// while we can listen on multiple network interfaces, we need to pick one to poll
h.healthURI.Host = "localhost"
}
ln, err := reuseport.Listen("tcp", h.Addr)
if err != nil {
return err
}
h.ln = ln
h.mux = http.NewServeMux()
h.nlSetup = true
h.mux.HandleFunc(h.healthURI.Path, func(w http.ResponseWriter, r *http.Request) {
// We're always healthy.
w.WriteHeader(http.StatusOK)
io.WriteString(w, http.StatusText(http.StatusOK))
})
ctx := context.Background()
ctx, h.stop = context.WithCancel(ctx)
go func() { http.Serve(h.ln, h.mux) }()
go func() { h.overloaded(ctx) }()
return nil
}
func (h *health) OnFinalShutdown() error {
if !h.nlSetup {
return nil
}
if h.lameduck > 0 {
log.Infof("Going into lameduck mode for %s", h.lameduck)
time.Sleep(h.lameduck)
}
h.stop()
h.ln.Close()
h.nlSetup = false
return nil
}
func (h *health) OnReload() error {
if !h.nlSetup {
return nil
}
h.stop()
h.ln.Close()
h.nlSetup = false
return nil
}
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