Slow delivery of messages between 8KB and 23KB

[rpack78]

I am bench marking ActiveMQ using Perl and Stomp+NIO.  I have setup 3 queues and 4 topics, and am sending messages of increasing size to see what the broker can handle.  The speed is really good up until 8KB, then it flatlines to 24 messages per second.  It stays that low until the message size reaches 23KB, then the message rate picks back up.  Take a look at the graph I have attached.  It's very strange but it happens each time I run the test.  Has anyone seen this before?

[rpack78]

Looks like the problem is with receipts.

I ran some additional tests without using receipts and was able to do about 4000 messages per second in these message size ranges.  As soon as I enable receiving of receipts, it goes back to 24 messages per second.  I'm using the Net::STOMP::Client module.  The documentation says this about receipts:

"By default, you do not get any confirmation that the message has indeed been received by the broker. If you want such a confirmation, you have to use receipts. The following code snippet sends two messages with a receipt header containing a pseudo-unique id and waits for matching RECEIPT frames coming from the broker. This is easy because the Net::STOMP::Client module keeps track of which receipts are expected and have not been received yet."

I am using the ack => 'client' parameter when subscribing to a queue.  Seems like sending an ack would be sufficient, but apparently I also need to send a receipt.