Introduce Satan

daemon.go

@@ -48,18 +48,18 @@ type BaseDaemon struct {
 	self         Daemon
 	name         string
 	stats        *statistics
-	enqueue      func(*task)
+	queue        chan<- *task
 	panicHandler func()
 	shutdown     chan struct{}
 }
 
 // Process creates a task and then adds it to processing queue.
 func (b *BaseDaemon) Process(a Actor) {
-	b.enqueue(&task{
+	b.queue <- &task{
 		daemon:    b.self,
 		actor:     a,
 		createdAt: time.Now(),
-	})
+	}
 }
 
 // HandlePanics sets up a panic handler function for the daemon.
@@ -89,10 +89,10 @@ func (b *BaseDaemon) String() string {
 
 // initialize saves a reference to the child daemon which is then used to print
 // the daemons' name. It also initializes other struct fields.
-func (b *BaseDaemon) initialize(self Daemon, enqueue func(*task)) {
+func (b *BaseDaemon) initialize(self Daemon, queue chan<- *task) {
 	b.self = self
 	b.stats = newStatistics()
-	b.enqueue = enqueue
+	b.queue = queue
 	b.shutdown = make(chan struct{})
 }
 

example/main.go

@@ -21,8 +21,8 @@ func main() {
 
 	s := satan.Summon()
 	s.AddDaemon(&daemons.NumberPrinter{})
-	s.Start()
-	defer s.Stop()
+	s.StartDaemons()
+	defer s.StopDaemons()
 
 	sig := make(chan os.Signal)
 	signal.Notify(sig, os.Interrupt)

satan.go

@@ -0,0 +1,92 @@
+package satan
+
+import (
+	"log"
+	"sync"
+	"time"
+)
+
+// Satan is the master daemon.
+type Satan struct {
+	daemons  []Daemon
+	queue    chan *task
+	wg       sync.WaitGroup
+	latency  *statistics
+	shutdown chan struct{}
+}
+
+type task struct {
+	daemon    Daemon
+	actor     Actor
+	createdAt time.Time
+}
+
+const (
+	defaultNumWorkers = 10
+)
+
+// Summon creates a new instance of Satan.
+func Summon() *Satan {
+	return &Satan{
+		queue:    make(chan *task),
+		latency:  newStatistics(),
+		shutdown: make(chan struct{}),
+	}
+}
+
+// AddDaemon adds a new daemon.
+func (s *Satan) AddDaemon(d Daemon) {
+	d.base().initialize(d, s.queue)
+	go d.Startup()
+
+	s.daemons = append(s.daemons, d)
+}
+
+// StartDaemons starts all registered daemons.
+func (s *Satan) StartDaemons() {
+	s.wg.Add(defaultNumWorkers)
+	for i := 0; i < defaultNumWorkers; i++ {
+		go func(i int) {
+			s.runWorker(i)
+			s.wg.Done()
+		}(i)
+	}
+}
+
+// StopDaemons stops all running daemons.
+func (s *Satan) StopDaemons() {
+	for _, d := range s.daemons {
+		close(d.base().shutdown)
+		d.Shutdown()
+
+		log.Printf("%s daemon performace statistics:\n%s\n",
+			d.base(), d.base().stats.snapshot())
+	}
+	close(s.queue)
+	s.wg.Wait()
+
+	log.Printf("Task processing latency statistics:\n%s\n", s.latency.snapshot())
+}
+
+func (s *Satan) runWorker(i int) {
+	log.Printf("Starting worker #%d", i+1)
+	defer log.Printf("Worker #%d has stopped", i+1)
+
+	for t := range s.queue {
+		dur := time.Now().UnixNano() - t.createdAt.UnixNano()
+		s.latency.add(time.Duration(dur))
+
+		log.Printf("Daemon #%d got some job to do!", i+1)
+		s.processTask(t)
+	}
+}
+
+func (s *Satan) processTask(t *task) {
+	defer t.daemon.base().handlePanic()
+	start := time.Now()
+
+	t.actor()
+
+	dur := time.Now().UnixNano() - start.UnixNano()
+	t.daemon.base().stats.add(time.Duration(dur))
+}