Add Close() method to Project to release resources

Problem Observed

Goroutine leaks because there is no way to "close" projects

Problem Detail

NewProject() creates a defaultListener in it.
The listener starts a new goroutine in NewDefaultListener().
We currently don't have a method to stop this goroutine.

Suggested Resolution

This comimt adds a new method Close() to release resources
tied to a Project.

Author: yudai

project/listener.go

@@ -39,13 +39,13 @@ type defaultListener struct {
 }
 
 // NewDefaultListener create a default listener for the specified project.
-func NewDefaultListener(p *Project) chan<- events.Event {
-	l := defaultListener{
+func NewDefaultListener(p *Project) *defaultListener {
+	l := &defaultListener{
 		listenChan: make(chan events.Event),
 		project:    p,
 	}
 	go l.start()
-	return l.listenChan
+	return l
 }
 
 func (d *defaultListener) start() {
@@ -79,3 +79,7 @@ func (d *defaultListener) start() {
 		}
 	}
 }
+
+func (d *defaultListener) close() {
+	close(d.listenChan)
+}

project/project.go

@@ -35,15 +35,16 @@ type Project struct {
 	ReloadCallback func() error
 	ParseOptions   *config.ParseOptions
 
-	runtime       RuntimeProject
-	networks      Networks
-	volumes       Volumes
-	configVersion string
-	context       *Context
-	reload        []string
-	upCount       int
-	listeners     []chan<- events.Event
-	hasListeners  bool
+	runtime         RuntimeProject
+	networks        Networks
+	volumes         Volumes
+	configVersion   string
+	context         *Context
+	reload          []string
+	upCount         int
+	listeners       []chan<- events.Event
+	hasListeners    bool
+	defaultListener *defaultListener
 }
 
 // NewProject creates a new project with the specified context.
@@ -93,11 +94,18 @@ func NewProject(context *Context, runtime RuntimeProject, parseOptions *config.P
 
 	context.Project = p
 
-	p.listeners = []chan<- events.Event{NewDefaultListener(p)}
+	p.defaultListener = NewDefaultListener(p)
+	p.listeners = []chan<- events.Event{p.defaultListener.listenChan}
 
 	return p
 }
 
+// Parse releases resources attached to the project
+func (p *Project) Close() error {
+	p.defaultListener.close()
+	return nil
+}
+
 // Parse populates project information based on its context. It sets up the name,
 // the composefile and the composebytes (the composefile content).
 func (p *Project) Parse() error {