我们可以使用 .net 代码从 Azure 服务总线中的死信队列中删除基于序列号的特定死信消息吗？

Question

I have created a program to read the message from deadletter queue based on the sequence number and copy the contents of dead letter message and sends it to active queue as a new message with the content of deadletter message along with the same messageId and other properties. And later I delete the same message from DLQ as well.

 public static async Task<string> GetDeadLetterMessagesAsync(string connectionString,
string queueName, long seqNum, int countDLQMessages)
    {
        //creating a service bus client
        var serviceBusClient = new ServiceBusClient(connectionString);
        Console.WriteLine("ServiceBusClient is created");
        //ReceiverOptions to access dead letter queue
        var receiverOptions = new ServiceBusReceiverOptions { SubQueue = SubQueue.DeadLetter };
        Console.WriteLine("receiverOption is created");
        //Create receiver to access the deadletter queue of main queue
        var receiver = serviceBusClient.CreateReceiver(queueName, receiverOptions);
        Console.WriteLine("receiver is created");
        // serviceBusSender used to send the message to service bus
        ServiceBusSender sender;
        sender= serviceBusClient.CreateSender(queueName);
        
        IList<ServiceBusReceivedMessage> receivedMessages = (IList<ServiceBusReceivedMessage>)await receiver.ReceiveMessagesAsync(countDLQMessages);
        Console.WriteLine("read all the messages in service bus DLQ");
        var totalMessageCount = receivedMessages.Count;
        if (totalMessageCount == 0)
        {
            return "No Message is available in DLQ";
        }
        // Binary search on deadletter messages in DLQ on sequence number
        Int32 lower = 0;
            Int32 upper = receivedMessages.Count - 1;
            Console.WriteLine("ReceivedMessage List");
            Console.WriteLine(receivedMessages[0].Body);
            int sequenceFlag = 0;
            while (lower <= upper)
            {
                Int32 middle = lower + (upper - lower) / 2;
                if (seqNum == receivedMessages[middle].SequenceNumber)
                {
                    var Body = receivedMessages[middle].Body;
                    var MessageId = receivedMessages[middle].MessageId;
                    var CorrelationId = receivedMessages[middle].CorrelationId;
                    var msg = new ServiceBusMessage
                    {
                        Body = Body,
                        MessageId = MessageId,
                        CorrelationId = CorrelationId
                    };
                    //Sending the dead letter message to active queue along with its other properties i.e MessageId, etc.
                    await sender.SendMessageAsync(msg);
                    Console.WriteLine($"Message has been published from dead letter to Active Queue.");
                    //complete the dead letter message which will remove the message from dead letter queue
                    await receiver.CompleteMessageAsync(receivedMessages[middle]);
                    //Changing the sequenceFlag value to 1, if requested sequence number exists in DLQ.
                    sequenceFlag = 1;
                    //clean up the service bus resources used by sender and receiver
                    await sender.DisposeAsync();
                    await receiver.DisposeAsync();
                    break;
                }
                else if (seqNum < receivedMessages[middle].SequenceNumber)
                    upper = middle - 1;
                else
                    lower = middle + 1;
            }
       
        if (sequenceFlag != 1)
        {
            return ($"Sequence number: {seqNum} doesn't exist in queue - {queueName}");
        }
        else
        {
            return "Data is moved to Active queue";
        }
        
    }

This code works if we have less than 100 of messages in DLQ, but when we have more than 100 or 1000 of messages in DLQ, it doesn't read the dead letter messages available in DLQ and throws an output as message is not available for sequence number 'xyz'. This issue happens due to the ReceiveMessagesAsync(MaxMessages) method, as it doesn't guarantee that it will return the exact same number of messages as requested in its parameter.

Do we have any other method from which we can extract n number of messages at once and can perform the further action on the same?

I have Also tried to peek the message based on sequence number and sends its content to active queue as a new message but I am not able to complete that specific message in DLQ.

Can we delete/complete the dead letter message based on sequence number?

Answer 1

Receiving N number of messages is not guaranteed when using the ReceiveMessageAsync method. If you need to receive N messages, you would need to loop until you've reached that amount, eg:

var remaining = numMessages;
var receivedMsgs = new List<ServiceBusReceivedMessage>();
while (remaining > 0)
{
    // loop in case we don't receive all messages in one attempt
    var received = await receiver.ReceiveMessagesAsync(remaining);
    receivedMsgs.AddRange(received);
    remaining -= received.Count;
}

Alternatively, if you are able to design your application in such a way that the messages can be deferred rather than deadlettered for this scenario, you can receive deferred messages directly based on the sequence number:

var deferredMessage = await receiver.ReceiveDeferredMessageAsync(seqNumber);