Extract signal handling to separate package

2 files changed, 121 insertions, 0 deletions

diff --git a/signal/signal.go b/signal/signal.go
new file mode 100644
index 0000000..96ef5f7
--- /dev/null
+++ b/signal/signal.go
@@ -0,0 +1,60 @@
+package signal
+
+import (
+	"io"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/mpolden/zdns/log"
+)
+
+// Reloader is the interface for types that need to act on a reload signal.
+type Reloader interface {
+	Reload()
+}
+
+// Handler represents a signal handler and holds references to types that should act on operating system signals.
+type Handler struct {
+	logger    *log.Logger
+	signal    chan os.Signal
+	reloaders []Reloader
+	closers   []io.Closer
+}
+
+// NewHandler creates a new handler for handling operating system signals.
+func NewHandler(c chan os.Signal, logger *log.Logger) *Handler {
+	h := &Handler{logger: logger, signal: c}
+	signal.Notify(h.signal)
+	go h.readSignal()
+	return h
+}
+
+// OnReload registers a reloader to call for the signal SIGHUP.
+func (s *Handler) OnReload(r Reloader) { s.reloaders = append(s.reloaders, r) }
+
+// OnClose registers a closer to call for signals SIGTERM and SIGINT.
+func (s *Handler) OnClose(c io.Closer) { s.closers = append(s.closers, c) }
+
+func (s *Handler) readSignal() {
+	for sig := range s.signal {
+		switch sig {
+		case syscall.SIGHUP:
+			s.logger.Printf("received signal %s: reloading", sig)
+			for _, r := range s.reloaders {
+				r.Reload()
+			}
+		case syscall.SIGTERM, syscall.SIGINT:
+			signal.Stop(s.signal)
+			s.logger.Printf("received signal %s: shutting down", sig)
+			for _, c := range s.closers {
+				if err := c.Close(); err != nil {
+					s.logger.Printf("close failed: %s", err)
+				}
+			}
+
+		default:
+			s.logger.Printf("received signal %s: ignoring", sig)
+		}
+	}
+}
diff --git a/signal/signal_test.go b/signal/signal_test.go
new file mode 100644
index 0000000..544b9a0
--- /dev/null
+++ b/signal/signal_test.go
@@ -0,0 +1,61 @@
+package signal
+
+import (
+	"io/ioutil"
+	"os"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/mpolden/zdns/log"
+)
+
+type reloaderCloser struct {
+	reloaded bool
+	closed   bool
+}
+
+func (rc *reloaderCloser) Reload() { rc.reloaded = true }
+func (rc *reloaderCloser) Close() error {
+	rc.closed = true
+	return nil
+}
+func (rc *reloaderCloser) isReloaded() bool { return rc.reloaded }
+func (rc *reloaderCloser) isClosed() bool   { return rc.closed }
+func (rc *reloaderCloser) reset() {
+	rc.reloaded = false
+	rc.closed = false
+}
+
+func TestHandler(t *testing.T) {
+	logger, err := log.New(ioutil.Discard, "", log.RecordOptions{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := NewHandler(make(chan os.Signal, 1), logger)
+
+	rc := &reloaderCloser{}
+	h.OnReload(rc)
+	h.OnClose(rc)
+
+	var tests = []struct {
+		signal syscall.Signal
+		value  func() bool
+	}{
+		{syscall.SIGHUP, rc.isReloaded},
+		{syscall.SIGTERM, rc.isClosed},
+		{syscall.SIGINT, rc.isClosed},
+	}
+
+	for _, tt := range tests {
+		rc.reset()
+		h.signal <- tt.signal
+		ts := time.Now()
+		for !tt.value() {
+			time.Sleep(10 * time.Millisecond)
+			if time.Since(ts) > 2*time.Second {
+				t.Fatalf("timed out waiting for handler of signal %s", tt.signal)
+			}
+		}
+	}
+}