The big picture

Testing and debugging monolithic applications is not simple, as every developer knows. However, there are a number of tools that make the task dramatically easier, including the pdb debugger, various profilers (notable mentions include cProfile and line_profile), linters, static code analysis tools, and a host of test frameworks, a number of which have been included in the standard library of Python 3.3 and higher.

The challenge with distributed applications is that most of the tools and packages that we can use for single-process applications lose much of their power when dealing with multiple processes, especially when these processes run on different computers.

Debugging and profiling distributed applications written in C, C++, and Fortran can be done with tools such as Intel VTune, Allinea MAP, and DDT. Unfortunately, Python developers are left with very few or no options for the time being.

Writing small- or medium-sized distributed systems is not terribly hard, as we saw...