change sqs receiveMessage func to pass in a callback operation for th…

…e calling func to do something when the process is waiting on an empty queue for a long time

aws/sqs/sqs.go

@@ -27,6 +27,11 @@ type SQS struct {
 	client *sqs.Client
 }
 
+// define a func to callback when no message received from the sqs and the process continues
+// to receive for a long time, for the calling func to do sth in the middle,
+// e.g. send a heartbeat
+type CallBackOperation func()
+
 // New returns an SQS struct which wraps an SQS client using the default AWS credentials chain.
 // This consults (in order) environment vars, config files, EC2 and ECS roles.
 // It is an error if the AWS_REGION environment variable is not set.
@@ -111,20 +116,26 @@ func (s *SQS) ReceiveWithAttributes(queueURL string, visibilityTimeout int32, at
 // to receive system stop signal, register the context with signal.NotifyContext before passing in this function,
 // when system stop signal is received, an error with message '... context canceled' will be returned
 // which can be used to safely stop the system
-func (s *SQS) ReceiveWithContextAttributes(ctx context.Context, queueURL string, visibilityTimeout int32, attrs []types.QueueAttributeName) (Raw, error) {
+func (s *SQS) ReceiveWithContextAttributesCallback(ctx context.Context, queueURL string, visibilityTimeout int32,
+	attrs []types.QueueAttributeName, callback CallBackOperation) (Raw, error) {
 	input := sqs.ReceiveMessageInput{
 		QueueUrl:            aws.String(queueURL),
 		MaxNumberOfMessages: 1,
 		VisibilityTimeout:   visibilityTimeout,
 		WaitTimeSeconds:     20,
 		AttributeNames:      attrs,
 	}
-	return s.receiveMessage(ctx, &input)
+	return s.receiveMessage(ctx, &input, callback)
+}
+
+func (s *SQS) ReceiveWithContextAttributes(ctx context.Context, queueURL string, visibilityTimeout int32,
+	attrs []types.QueueAttributeName) (Raw, error) {
+	return s.ReceiveWithContextAttributesCallback(ctx, queueURL, visibilityTimeout, attrs, nil)
 }
 
 // receiveMessage is the common code used internally to receive an SQS message based
 // on the provided input.
-func (s *SQS) receiveMessage(ctx context.Context, input *sqs.ReceiveMessageInput) (Raw, error) {
+func (s *SQS) receiveMessage(ctx context.Context, input *sqs.ReceiveMessageInput, callBack CallBackOperation) (Raw, error) {
 
 	for {
 		r, err := s.client.ReceiveMessage(ctx, input)
@@ -135,6 +146,9 @@ func (s *SQS) receiveMessage(ctx context.Context, input *sqs.ReceiveMessageInput
 		switch {
 		case r == nil || len(r.Messages) == 0:
 			// no message received
+			if callBack != nil { //do something in the middle
+				callBack()
+			}
 			continue
 		case len(r.Messages) == 1:
 			raw := r.Messages[0]
@@ -155,14 +169,18 @@ func (s *SQS) receiveMessage(ctx context.Context, input *sqs.ReceiveMessageInput
 // to receive system stop signal, register the context with signal.NotifyContext before passing in this function,
 // when system stop signal is received, an error with message '... context canceled' will be returned
 // which can be used to safely stop the system
-func (s *SQS) ReceiveWithContext(ctx context.Context, queueURL string, visibilityTimeout int32) (Raw, error) {
+func (s *SQS) ReceiveWithContextCallback(ctx context.Context, queueURL string, visibilityTimeout int32, callback CallBackOperation) (Raw, error) {
 	input := sqs.ReceiveMessageInput{
 		QueueUrl:            aws.String(queueURL),
 		MaxNumberOfMessages: 1,
 		VisibilityTimeout:   visibilityTimeout,
 		WaitTimeSeconds:     20,
 	}
-	return s.receiveMessage(ctx, &input)
+	return s.receiveMessage(ctx, &input, callback)
+}
+
+func (s *SQS) ReceiveWithContext(ctx context.Context, queueURL string, visibilityTimeout int32) (Raw, error) {
+	return s.ReceiveWithContextCallback(ctx, queueURL, visibilityTimeout, nil)
 }
 
 // Delete deletes the message referred to by receiptHandle from the queue.