Add healthchecker to check broker connection

internal/base/base.go

@@ -263,6 +263,7 @@ func (c *Cancelations) Get(id string) (fn context.CancelFunc, ok bool) {
 //
 // See rdb.RDB as a reference implementation.
 type Broker interface {
+	Ping() error
 	Enqueue(msg *TaskMessage) error
 	EnqueueUnique(msg *TaskMessage, ttl time.Duration) error
 	Dequeue(qnames ...string) (*TaskMessage, time.Time, error)

internal/rdb/rdb.go

@@ -45,6 +45,11 @@ func (r *RDB) Close() error {
 	return r.client.Close()
 }
 
+// Ping checks the connection with redis server.
+func (r *RDB) Ping() error {
+	return r.client.Ping().Err()
+}
+
 // KEYS[1] -> asynq:queues:<qname>
 // KEYS[2] -> asynq:queues
 // ARGV[1] -> task message data

internal/testbroker/testbroker.go

@@ -180,6 +180,15 @@ func (tb *TestBroker) PublishCancelation(id string) error {
 	return tb.real.PublishCancelation(id)
 }
 
+func (tb *TestBroker) Ping() error {
+	tb.mu.Lock()
+	defer tb.mu.Unlock()
+	if tb.sleeping {
+		return errRedisDown
+	}
+	return tb.real.Ping()
+}
+
 func (tb *TestBroker) Close() error {
 	tb.mu.Lock()
 	defer tb.mu.Unlock()