What does Falling behind by : X ms in the load generation mean?

[rith-iqlect]

When the core.clj starts the data generation process, I see these messages
"Falling behind by" : 102ms etc. What does this mean? And does this effect the numbers in anyway?
Thanks!

[knusbaum]

"Falling behing by X" is a message that gets output by the producer when it is unable to produce messages as quickly as it needs to in order to keep up with the specified throughput.

As long as this number doesn't get very large, it is not a huge deal.