Star Caller makes use of the Amazon Cloud, so I wanted to know just how FIFO the Amazon Simple Queue Service is. Amazon says that the SQS is not FIFO. So I (with hobbs from #catalyst) wrote a script to test the SQS's Spearman's rank correlation coefficient between set order and get order.

The results for 1000 gets/sets to the queue usually look something like this:

SAD: 42.04
Spearman: 0.9835

The data is plotted for 1000 inserts/gets, with a 0 second delay between the finish of get/set here:

So far, a delay between the sets and gets seems to have no effect on FIFO-ness, but the rate of sets may.

The results? Its pretty FIFO. Not completely ordered, but its in a distributed cloud so that would be quite hard.

How much did the tests cost me?

29,021 Requests: $0.03
0.000035 GB In: $0.01
0.000023 GB Out: $0.01
----------------------
Total Cost: $0.05

How FIFO is Amazon's SQS? - Pretty FIFO