debounce refresh requests with quietperiod

Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

pkg/compose/watch.go

@@ -18,9 +18,12 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"strings"
+	"time"
 
 	"github.com/compose-spec/compose-go/types"
 	"github.com/docker/compose/v2/pkg/api"
+	"github.com/docker/compose/v2/pkg/utils"
 	"github.com/fsnotify/fsnotify"
 	"github.com/mitchellh/mapstructure"
 	"github.com/pkg/errors"
@@ -30,10 +33,20 @@ import (
 type DevelopmentConfig struct {
 }
 
+const quietPeriod = 2 * time.Second
+
 func (s *composeService) Watch(ctx context.Context, project *types.Project, services []string, options api.WatchOptions) error {
 	fmt.Fprintln(s.stderr(), "not implemented yet")
 
 	eg, ctx := errgroup.WithContext(ctx)
+	needRefresh := make(chan string)
+	eg.Go(func() error {
+		debounce(ctx, newTimer(quietPeriod), needRefresh, func(services []string) {
+			fmt.Fprintf(s.stderr(), "Updating %s after changes were detected\n", strings.Join(services, ", "))
+		})
+		return nil
+	})
+
 	err := project.WithServices(services, func(service types.ServiceConfig) error {
 		var config DevelopmentConfig
 		if y, ok := service.Extensions["x-develop"]; ok {
@@ -64,6 +77,7 @@ func (s *composeService) Watch(ctx context.Context, project *types.Project, serv
 					return nil
 				case event := <-watcher.Events:
 					log.Println("fs event :", event.String())
+					needRefresh <- service.Name
 				case err := <-watcher.Errors:
 					return err
 				}
@@ -77,3 +91,52 @@ func (s *composeService) Watch(ctx context.Context, project *types.Project, serv
 
 	return eg.Wait()
 }
+
+func debounce(ctx context.Context, timer timer, input chan string, fn func(services []string)) {
+	services := utils.Set[string]{}
+	for {
+		select {
+		case service := <-input:
+			timer.reset()
+			services.Add(service)
+		case <-timer.time():
+			if len(services) > 0 {
+				refresh := services.Elements()
+				services.Clear()
+				fn(refresh)
+			}
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+// timer encapsulate the time.Timer API so we can control actual time in tests
+type timer interface {
+	reset()
+	time() <-chan time.Time
+}
+
+// timeTimer implements time interface using golang's time.Timer
+type timeTimer struct {
+	interval time.Duration
+	t        *time.Timer
+}
+
+func newTimer(interval time.Duration) *timeTimer {
+	return &timeTimer{
+		interval: interval,
+		t:        time.NewTimer(interval),
+	}
+}
+
+func (t *timeTimer) reset() {
+	if !t.t.Stop() {
+		<-t.t.C
+	}
+	t.t.Reset(t.interval)
+}
+
+func (t *timeTimer) time() <-chan time.Time {
+	return t.t.C
+}

pkg/compose/watch_test.go

@@ -0,0 +1,68 @@
+/*
+
+   Copyright 2020 Docker Compose CLI authors
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+       http://www.apache.org/licenses/LICENSE-2.0
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package compose
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"golang.org/x/sync/errgroup"
+	"gotest.tools/v3/assert"
+)
+
+// testTimer replaces a timer without requirement for controlled timing events
+type testTimer struct {
+	ch chan time.Time
+}
+
+func (t testTimer) reset() {
+	// noop
+}
+
+func (t testTimer) time() <-chan time.Time {
+	return t.ch
+}
+
+func Test_debounce(t *testing.T) {
+	ch := make(chan string)
+	var (
+		ran int
+		got []string
+	)
+	ctx, stop := context.WithTimeout(context.TODO(), 500*time.Millisecond)
+	defer stop()
+
+	timeC := make(chan time.Time)
+	timer := testTimer{ch: timeC}
+	eg, ctx := errgroup.WithContext(ctx)
+	eg.Go(func() error {
+		debounce(ctx, timer, ch, func(services []string) {
+			got = append(got, services...)
+			ran++
+			stop()
+		})
+		return nil
+	})
+	for i := 0; i < 100; i++ {
+		ch <- fmt.Sprintf("test-%d", i)
+	}
+	timeC <- time.Now()
+	err := eg.Wait()
+	assert.NilError(t, err)
+	assert.Equal(t, ran, 1)
+	assert.Equal(t, len(got), 100)
+}

pkg/utils/set.go

@@ -0,0 +1,39 @@
+/*
+
+   Copyright 2020 Docker Compose CLI authors
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+       http://www.apache.org/licenses/LICENSE-2.0
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package utils
+
+type Set[T comparable] map[T]struct{}
+
+func (s Set[T]) Add(v T) {
+	s[v] = struct{}{}
+}
+
+func (s Set[T]) Remove(v T) {
+	delete(s, v)
+}
+
+func (s Set[T]) Clear() {
+	for v := range s {
+		delete(s, v)
+	}
+}
+
+func (s Set[T]) Elements() []T {
+	elements := make([]T, 0, len(s))
+	for v := range s {
+		elements = append(elements, v)
+	}
+	return elements
+}