Azure Service Bus: Read messages with offset

Question

I'm reading messages from Azure Service Bus in my C# application. I'm reading them from Dead Letter Queue but I suppose it doesn't matter here. I need to read a block of messages of a given size, starting at a given offset (aka a page of messages).

I came up with the following, very inefficient, code:

SubscriptionClient client  = SubscriptionClient.CreateFromConnectionString(
  connectionString, 
  topic, 
  QueueClient.FormatDeadLetterPath(subscription));

var result = new List<string>();
for (var i = 0; i < offset + size; i++)
{
  var msg = await client.PeekAsync();
  if (msg == null)
  {
    return result;
  }

  if (i >= offset)
  {
    result.Add(msg);
  }
}

return result;

Is there a way I can write this "seek" in a more efficient way?

There's no concept of offset. It's a queue, you can receive or peek. https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-messaging-overview — Sean Feldman, Sep 25 '18 at 16:28

score 0 · Answer 1 · answered Sep 25 '18 at 12:51

0

The SubscriptionClient.ReceiveAsync method accepts an Int64 sequence number (offset):

for (var i = offset; i < offset + size; i++)
{
    var msg = await client.ReceiveAsync(i);
    result.Add(msg);
}

answered Sep 25 '18 at 12:51

mm8

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Is the sequence number supposed to increase by 1 per message? Unfortunatelly the `PeekAsync` with sequence number seems to be returning the same message although offset is increasing. – Dušan Rychnovský Sep 25 '18 at 14:23
The `offset` is not increasing. `i` is. – mm8 Sep 25 '18 at 14:32
That's what I meant. I updated the code to reflect your diff and it returns the first message `size` times. – Dušan Rychnovský Sep 25 '18 at 14:49
What SequenceNumber does the first returned message have? – mm8 Sep 25 '18 at 15:02
It's 18577348462903296. – Dušan Rychnovský Sep 26 '18 at 08:57

Azure Service Bus: Read messages with offset

1 Answers1