When it takes hours or days to run your computation, it can take a long time before you notice something has gone wrong. This means your feedback loop for fixes can be very slow. If you want to solve problems quickly—whether it's inconsistent results, crashes, or slowness—you need to understand what was going on in your process as it was running: you need logging.

In this talk you'll learn how logging in general, and the Eliot logging library in particular, can help you:

• Debug problems that may have occurred far along within your computation.
• Identify and localize performance problems: which parts of your computation were slow, and (unlike profilers) what arguments were involved.

You'll also learn how Eliot's causal tracing makes understanding the flow of logic in your program much easier than traditional logging, and of course how to integrate Eliot with your Dask application.