debugging_wordcount command

debugging_wordcount is an example that verifies word counts in Shakespeare and includes Beam best practices.

This example, debugging_wordcount, is the third in a series of four successively more detailed 'word count' examples. You may first want to take a look at minimal_wordcount and wordcount. After you've looked at this example, then see the windowed_wordcount pipeline, for introduction of additional concepts.

Basic concepts, also in the minimal_wordcount and wordcount examples: Reading text files; counting a PCollection; executing a Pipeline both locally and using a selected runner; defining DoFns.

New Concepts:

1. Using the richer struct DoFn form and accessing optional arguments.
2. Logging using the Beam log package, even in a distributed environment
3. Testing your Pipeline via passert

To change the runner, specify:

--runner=YOUR_SELECTED_RUNNER

The input file defaults to a public data set containing the text of King Lear, by William Shakespeare. You can override it and choose your own input with --input.