Extract manager to its own type

manager.go

@@ -0,0 +1,101 @@
+package asynq
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/go-redis/redis/v7"
+)
+
+type manager struct {
+	rdb *redis.Client
+
+	handler TaskHandler
+
+	// sema is a counting semaphore to ensure the number of active workers
+	// does not exceed the limit
+	sema chan struct{}
+
+	done chan struct{}
+}
+
+func newManager(rdb *redis.Client, numWorkers int, handler TaskHandler) *manager {
+	return &manager{
+		rdb:     rdb,
+		handler: handler,
+		sema:    make(chan struct{}, numWorkers),
+		done:    make(chan struct{}),
+	}
+}
+
+func (m *manager) terminate() {
+	m.done <- struct{}{}
+}
+
+func (m *manager) start() {
+	go func() {
+		for {
+			select {
+			case <-m.done:
+				m.shutdown()
+			default:
+				m.processTasks()
+			}
+		}
+	}()
+}
+
+func (m *manager) processTasks() {
+	// pull message out of the queue and process it
+	// TODO(hibiken): sort the list of queues in order of priority
+	res, err := m.rdb.BLPop(5*time.Second, listQueues(m.rdb)...).Result() // NOTE: BLPOP needs to time out because if case a new queue is added.
+	if err != nil {
+		if err != redis.Nil {
+			log.Printf("BLPOP command failed: %v\n", err)
+		}
+		return
+	}
+
+	q, data := res[0], res[1]
+	fmt.Printf("perform task %v from %s\n", data, q)
+	var msg taskMessage
+	err = json.Unmarshal([]byte(data), &msg)
+	if err != nil {
+		log.Printf("[Servere Error] could not parse json encoded message %s: %v", data, err)
+		return
+	}
+	t := &Task{Type: msg.Type, Payload: msg.Payload}
+	m.sema <- struct{}{} // acquire token
+	go func(task *Task) {
+		defer func() { <-m.sema }() // release token
+		err := m.handler(task)
+		if err != nil {
+			if msg.Retried >= msg.Retry {
+				fmt.Println("Retry exhausted!!!")
+				if err := kill(m.rdb, &msg); err != nil {
+					log.Printf("[SERVER ERROR] could not add task %+v to 'dead' set\n", err)
+				}
+				return
+			}
+			fmt.Println("RETRY!!!")
+			retryAt := time.Now().Add(delaySeconds((msg.Retried)))
+			fmt.Printf("[DEBUG] retying the task in %v\n", retryAt.Sub(time.Now()))
+			msg.Retried++
+			msg.ErrorMsg = err.Error()
+			if err := zadd(m.rdb, retry, float64(retryAt.Unix()), &msg); err != nil {
+				// TODO(hibiken): Not sure how to handle this error
+				log.Printf("[SEVERE ERROR] could not add msg %+v to 'retry' set: %v\n", msg, err)
+				return
+			}
+		}
+	}(t)
+}
+
+func (m *manager) shutdown() {
+	// TODO(hibiken): implement this. Gracefully shutdown all active goroutines.
+	fmt.Println("-------------[Manager]---------------")
+	fmt.Println("Manager shutting down...")
+	fmt.Println("------------------------------------")
+}