added StartStopper

Author: Mat Ryer

start/start.go

@@ -0,0 +1,72 @@
+package start
+
+import (
+	"sync"
+	"time"
+
+	"github.com/stretchr/pat/stop"
+)
+
+// StartStopper represents types that need starting and stopping.
+type StartStopper interface {
+	stop.Stopper
+	// Start is called to start the operations of the
+	// type, an error is returned if starting fails, otherwise
+	// nil.
+	Start() error
+}
+
+// All starts all StartStoppers and returns a map of any
+// errors that occurred keyed by the StartStopper object.
+// len(All(s...)) == 0 when everything started successfully.
+func All(startStoppers ...StartStopper) map[StartStopper]error {
+
+	var wg sync.WaitGroup
+	errs := make(map[StartStopper]error)
+	var errsL sync.Mutex
+	wg.Add(len(startStoppers))
+
+	// start everything
+	for _, s := range startStoppers {
+		go func(s StartStopper) {
+			if err := s.Start(); err != nil {
+				errsL.Lock()
+				errs[s] = err
+				errsL.Unlock()
+			}
+			wg.Done()
+		}(s)
+	}
+
+	// wait for all things to start
+	wg.Wait()
+
+	return errs
+}
+
+// MustAll starts all StartStoppers and if any one fails to start,
+// stops all of the others and returns a map of errors that occurred, keyed
+// by the StartStopper object.
+// len(All(s...)) == 0 when everything started successfully.
+// By the time MustAll returns, everything will have been given the chance to
+// start, and in the event of an error, everything will be properly stopped.
+func MustAll(stopGrace time.Duration, startStoppers ...StartStopper) map[StartStopper]error {
+	errs := All(startStoppers...)
+	if len(errs) > 0 {
+		// at least one thing failed to start - stop everything that
+		// started
+		var wg sync.WaitGroup
+		for _, s := range startStoppers {
+			if _, failed := errs[s]; failed == false {
+				s.Stop(stopGrace)
+				wg.Add(1)
+				go func() {
+					<-s.StopChan()
+					wg.Done()
+				}()
+			}
+		}
+		wg.Wait() // wait for everything to stop
+	}
+	return errs
+}

start/start_test.go

@@ -0,0 +1,95 @@
+package start_test
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/stretchr/pat/start"
+	"github.com/stretchr/pat/stop"
+	"github.com/stretchr/testify/require"
+)
+
+type TestStarter struct {
+	running bool
+}
+
+var _ start.StartStopper = (*TestStarter)(nil)
+
+func (t *TestStarter) Start() error {
+	time.Sleep(1 * time.Second)
+	t.running = true
+	return nil
+}
+func (t *TestStarter) Stop(time.Duration) {
+	t.running = false
+}
+func (t *TestStarter) StopChan() <-chan stop.Signal {
+	return stop.Stopped()
+}
+
+type ErrorStarter struct {
+	running bool
+}
+
+var _ start.StartStopper = (*ErrorStarter)(nil)
+
+func (t *ErrorStarter) Start() error {
+	time.Sleep(1 * time.Second)
+	return errors.New("something went wrong")
+}
+func (t *ErrorStarter) Stop(time.Duration) {
+	t.running = false
+}
+func (t *ErrorStarter) StopChan() <-chan stop.Signal {
+	return stop.Stopped()
+}
+
+func TestAll(t *testing.T) {
+
+	s1 := &TestStarter{}
+	s2 := &TestStarter{}
+	s3 := &TestStarter{}
+
+	errs := start.All(s1, s2, s3)
+	require.Equal(t, 0, len(errs))
+
+	require.True(t, s1.running)
+	require.True(t, s2.running)
+	require.True(t, s3.running)
+
+}
+
+func TestAllErr(t *testing.T) {
+
+	s1 := &TestStarter{}
+	s2 := &TestStarter{}
+	s3 := &ErrorStarter{}
+
+	errs := start.All(s1, s2, s3)
+	require.Equal(t, 1, len(errs))
+
+	require.Equal(t, errs[s3].Error(), "something went wrong")
+
+	require.True(t, s1.running)
+	require.True(t, s2.running)
+	require.False(t, s3.running)
+
+}
+
+func TestMustAll(t *testing.T) {
+
+	s1 := &TestStarter{}
+	s2 := &TestStarter{}
+	s3 := &ErrorStarter{}
+
+	errs := start.MustAll(500*time.Millisecond, s1, s2, s3)
+	require.Equal(t, 1, len(errs))
+
+	require.Equal(t, errs[s3].Error(), "something went wrong")
+
+	require.False(t, s1.running)
+	require.False(t, s2.running)
+	require.False(t, s3.running)
+
+}