Stop processing more tasks from the queue once TSTP signal is received

background.go

@@ -80,9 +80,8 @@ func (bg *Background) Run(handler Handler) {
 	signal.Notify(sigs, syscall.SIGTERM, syscall.SIGINT, syscall.SIGTSTP)
 	for {
 		sig := <-sigs
-		fmt.Printf("[DEBUG] Got %v\n", sig) // TODO: Remove this
 		if sig == syscall.SIGTSTP {
-			fmt.Println("[DEBUG] Stop processing tasks")
+			bg.processor.stop()
 			continue
 		}
 		break

processor.go

@@ -5,6 +5,7 @@ import (
 	"log"
 	"math"
 	"math/rand"
+	"sync"
 	"time"
 
 	"github.com/hibiken/asynq/internal/rdb"
@@ -25,7 +26,9 @@ type processor struct {
 	sema chan struct{}
 
 	// channel to communicate back to the long running "processor" goroutine.
+	// once is used to send value to the channel only once.
 	done chan struct{}
+	once sync.Once
 
 	// quit channel communicates to the in-flight worker goroutines to stop.
 	quit chan struct{}
@@ -42,11 +45,20 @@ func newProcessor(r *rdb.RDB, numWorkers int, handler Handler) *processor {
 	}
 }
 
+// Note: stops only the "processor" goroutine, does not stop workers.
+// It's safe to call this method multiple times.
+func (p *processor) stop() {
+	p.once.Do(func() {
+		log.Println("[INFO] Processor shutting down...")
+		// Signal the processor goroutine to stop processing tasks
+		// from the queue.
+		p.done <- struct{}{}
+	})
+}
+
 // NOTE: once terminated, processor cannot be re-started.
 func (p *processor) terminate() {
-	log.Println("[INFO] Processor shutting down...")
+	p.stop()
-	// Signal the processor goroutine to stop processing tasks from the queue.
-	p.done <- struct{}{}
 
 	// TODO(hibiken): Allow user to customize this timeout value.
 	const timeout = 8 * time.Second