cmd: introduce control socket & subcommand

Move pprof debugging there.

cmd/config_job_control.go

@@ -0,0 +1,88 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"github.com/pkg/errors"
+	"github.com/zrepl/zrepl/util"
+	"net"
+	"net/http"
+	"net/http/pprof"
+)
+
+type ControlJob struct {
+	Name     string
+	sockaddr *net.UnixAddr
+}
+
+func NewControlJob(name, sockpath string) (j *ControlJob, err error) {
+	j = &ControlJob{Name: name}
+
+	j.sockaddr, err = net.ResolveUnixAddr("unix", sockpath)
+	if err != nil {
+		err = errors.Wrap(err, "cannot resolve unix address")
+		return
+	}
+
+	return
+}
+
+func (j *ControlJob) JobName() string {
+	return j.Name
+}
+
+const (
+	ControlJobEndpointProfile string = "/debug/pprof/profile"
+)
+
+func (j *ControlJob) JobStart(ctx context.Context) {
+
+	log := ctx.Value(contextKeyLog).(Logger)
+	defer log.Printf("control job finished")
+
+	l, err := ListenUnixPrivate(j.sockaddr)
+	if err != nil {
+		log.Printf("error listening: %s", err)
+		return
+	}
+
+	mux := http.NewServeMux()
+	mux.Handle(ControlJobEndpointProfile, requestLogger{log, pprof.Profile})
+	server := http.Server{Handler: mux}
+
+outer:
+	for {
+
+		served := make(chan error)
+		go func() {
+			served <- server.Serve(l)
+			close(served)
+		}()
+
+		select {
+		case <-ctx.Done():
+			log.Printf("context: %s", ctx.Err())
+			server.Shutdown(context.Background())
+			break outer
+		case err = <-served:
+			if err != nil {
+				log.Printf("error serving: %s", err)
+				break outer
+			}
+		}
+
+	}
+
+}
+
+type requestLogger struct {
+	log         Logger
+	handlerFunc func(w http.ResponseWriter, r *http.Request)
+}
+
+func (l requestLogger) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	log := util.NewPrefixLogger(l.log, fmt.Sprintf("%s %s", r.Method, r.URL))
+	log.Printf("start")
+	l.handlerFunc(w, r)
+	log.Printf("finish")
+}