Pull request 2100: v0.107.42-rc

Squashed commit of the following:

commit 284190f748345c7556e60b67f051ec5f6f080948
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Dec 6 19:36:00 2023 +0300

    all: sync with master; upd chlog

internal/next/cmd/signal.go

@@ -0,0 +1,167 @@
+package cmd
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
+	"github.com/AdguardTeam/AdGuardHome/internal/next/configmgr"
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/google/renameio/v2/maybe"
+)
+
+// signalHandler processes incoming signals and shuts services down.
+type signalHandler struct {
+	// confMgrConf contains the configuration parameters for the configuration
+	// manager.
+	confMgrConf *configmgr.Config
+
+	// signal is the channel to which OS signals are sent.
+	signal chan os.Signal
+
+	// pidFile is the path to the file where to store the PID, if any.
+	pidFile string
+
+	// services are the services that are shut down before application exiting.
+	services []agh.Service
+}
+
+// handle processes OS signals.
+func (h *signalHandler) handle() {
+	defer log.OnPanic("signalHandler.handle")
+
+	h.writePID()
+
+	for sig := range h.signal {
+		log.Info("sighdlr: received signal %q", sig)
+
+		if aghos.IsReconfigureSignal(sig) {
+			h.reconfigure()
+		} else if aghos.IsShutdownSignal(sig) {
+			status := h.shutdown()
+			h.removePID()
+
+			log.Info("sighdlr: exiting with status %d", status)
+
+			os.Exit(status)
+		}
+	}
+}
+
+// reconfigure rereads the configuration file and updates and restarts services.
+func (h *signalHandler) reconfigure() {
+	log.Info("sighdlr: reconfiguring adguard home")
+
+	status := h.shutdown()
+	if status != statusSuccess {
+		log.Info("sighdlr: reconfiguring: exiting with status %d", status)
+
+		os.Exit(status)
+	}
+
+	// TODO(a.garipov): This is a very rough way to do it.  Some services can be
+	// reconfigured without the full shutdown, and the error handling is
+	// currently not the best.
+
+	confMgr, err := newConfigMgr(h.confMgrConf)
+	check(err)
+
+	web := confMgr.Web()
+	err = web.Start()
+	check(err)
+
+	dns := confMgr.DNS()
+	err = dns.Start()
+	check(err)
+
+	h.services = []agh.Service{
+		dns,
+		web,
+	}
+
+	log.Info("sighdlr: successfully reconfigured adguard home")
+}
+
+// Exit status constants.
+const (
+	statusSuccess       = 0
+	statusError         = 1
+	statusArgumentError = 2
+)
+
+// shutdown gracefully shuts down all services.
+func (h *signalHandler) shutdown() (status int) {
+	ctx, cancel := ctxWithDefaultTimeout()
+	defer cancel()
+
+	status = statusSuccess
+
+	log.Info("sighdlr: shutting down services")
+	for i, service := range h.services {
+		err := service.Shutdown(ctx)
+		if err != nil {
+			log.Error("sighdlr: shutting down service at index %d: %s", i, err)
+			status = statusError
+		}
+	}
+
+	return status
+}
+
+// newSignalHandler returns a new signalHandler that shuts down svcs.
+func newSignalHandler(
+	confMgrConf *configmgr.Config,
+	pidFile string,
+	svcs ...agh.Service,
+) (h *signalHandler) {
+	h = &signalHandler{
+		confMgrConf: confMgrConf,
+		signal:      make(chan os.Signal, 1),
+		pidFile:     pidFile,
+		services:    svcs,
+	}
+
+	aghos.NotifyShutdownSignal(h.signal)
+	aghos.NotifyReconfigureSignal(h.signal)
+
+	return h
+}
+
+// writePID writes the PID to the file, if needed.  Any errors are reported to
+// log.
+func (h *signalHandler) writePID() {
+	if h.pidFile == "" {
+		return
+	}
+
+	// Use 8, since most PIDs will fit.
+	data := make([]byte, 0, 8)
+	data = strconv.AppendInt(data, int64(os.Getpid()), 10)
+	data = append(data, '\n')
+
+	err := maybe.WriteFile(h.pidFile, data, 0o644)
+	if err != nil {
+		log.Error("sighdlr: writing pidfile: %s", err)
+
+		return
+	}
+
+	log.Debug("sighdlr: wrote pid to %q", h.pidFile)
+}
+
+// removePID removes the PID file, if any.
+func (h *signalHandler) removePID() {
+	if h.pidFile == "" {
+		return
+	}
+
+	err := os.Remove(h.pidFile)
+	if err != nil {
+		log.Error("sighdlr: removing pidfile: %s", err)
+
+		return
+	}
+
+	log.Debug("sighdlr: removed pid at %q", h.pidFile)
+}