Change internal representation of task data written to redis

asynq.go

@@ -17,7 +17,6 @@ import (
 	"time"
 
 	"github.com/go-redis/redis/v7"
-	"github.com/google/uuid"
 )
 
 // Redis keys
@@ -27,6 +26,9 @@ const (
 	scheduled   = "asynq:scheduled"
 )
 
+// Max retry count by default
+const defaultMaxRetry = 25
+
 // Client is an interface for scheduling tasks.
 type Client struct {
 	rdb *redis.Client
@@ -42,10 +44,25 @@ type Task struct {
 	Payload map[string]interface{}
 }
 
-type delayedTask struct {
-	ID    string
+// taskMessage is an internal representation of a task with additional metadata fields.
+// This data gets written in redis.
+type taskMessage struct {
+	// fields from type Task
+	Type    string
+	Payload map[string]interface{}
+
+	//------- metadata fields ----------
+	// queue name this message should be enqueued to
 	Queue string
-	Task  *Task
+
+	// remainig retry count
+	Retry int
+
+	// number of times we've retried so far
+	Retried int
+
+	// error message from the last failure
+	ErrorMsg string
 }
 
 // RedisOpt specifies redis options.
@@ -67,15 +84,16 @@ func (c *Client) Process(task *Task, executeAt time.Time) error {
 
 // enqueue pushes a given task to the specified queue.
 func (c *Client) enqueue(queue string, task *Task, executeAt time.Time) error {
-	if time.Now().After(executeAt) {
-		return push(c.rdb, queue, task)
-	}
-	dt := &delayedTask{
-		ID:    uuid.New().String(),
+	msg := &taskMessage{
+		Type:    task.Type,
+		Payload: task.Payload,
 		Queue:   queue,
-		Task:  task,
+		Retry:   defaultMaxRetry,
 	}
-	bytes, err := json.Marshal(dt)
+	if time.Now().After(executeAt) {
+		return push(c.rdb, msg)
+	}
+	bytes, err := json.Marshal(msg)
 	if err != nil {
 		return err
 	}
@@ -120,19 +138,25 @@ func (w *Workers) Run(handler TaskHandler) {
 			continue
 		}
 
-		q, msg := res[0], res[1]
-		fmt.Printf("perform task %v from %s\n", msg, q)
-		var task Task
-		err = json.Unmarshal([]byte(msg), &task)
+		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", msg, err)
+			log.Printf("[Servere Error] could not parse json encoded message %s: %v", data, err)
 			continue
 		}
 		w.poolTokens <- struct{}{} // acquire a token
+		t := &Task{Type: msg.Type, Payload: msg.Payload}
 		go func(task *Task) {
-			handler(task)
-			<-w.poolTokens
-		}(&task)
+			err := handler(task)
+			if err != nil {
+				fmt.Println("RETRY!!!")
+				//timeout := 10 * time.Second // TODO(hibiken): Implement exponential backoff.
+				// TODO(hibiken): Enqueue the task to "retry" ZSET with some timeout
+			}
+			<-w.poolTokens // release the token
+		}(t)
 	}
 }
 
@@ -156,17 +180,17 @@ func (w *Workers) pollScheduledTasks() {
 		}
 
 		for _, j := range jobs {
-			var job delayedTask
-			err = json.Unmarshal([]byte(j), &job)
+			var msg taskMessage
+			err = json.Unmarshal([]byte(j), &msg)
 			if err != nil {
 				fmt.Println("unmarshal failed")
 				continue
 			}
 
 			if w.rdb.ZRem(scheduled, j).Val() > 0 {
-				err = push(w.rdb, job.Queue, job.Task)
+				err = push(w.rdb, &msg)
 				if err != nil {
-					log.Printf("could not push task to queue %q: %v", job.Queue, err)
+					log.Printf("could not push task to queue %q: %v", msg.Queue, err)
 					// TODO(hibiken): Handle this error properly. Add back to scheduled ZSET?
 					continue
 				}
@@ -176,12 +200,12 @@ func (w *Workers) pollScheduledTasks() {
 }
 
 // push pushes the task to the specified queue to get picked up by a worker.
-func push(rdb *redis.Client, queue string, t *Task) error {
-	bytes, err := json.Marshal(t)
+func push(rdb *redis.Client, msg *taskMessage) error {
+	bytes, err := json.Marshal(msg)
 	if err != nil {
 		return fmt.Errorf("could not encode task into JSON: %v", err)
 	}
-	qname := queuePrefix + queue
+	qname := queuePrefix + msg.Queue
 	err = rdb.SAdd(allQueues, qname).Err()
 	if err != nil {
 		return fmt.Errorf("could not execute command SADD %q %q: %v",