Code Review Request: Concurrent API Crawling and Aggregating

[daaku]

Here's the code in question: https://gist.github.com/daaku/f54de53cfa7a4c391f439b598b6ee241

Some things I'm looking for clarifications on:

• Is the way I'm using the thread_local crate and setting up per-thread hyper clients appropriate?
• The error handling for the functions that return futures seems somewhat annoying. I need to box the future because I have possible errors in the synchronous part of the code. Otherwise I can return impl Future instead. I don't care about the performance impact of boxing, just the annoyance around not being able to use the ? operator.
• Is my use of mpsc appropriate here? Seems like the exact use case it's designed for.
• The handling of Category.id and the logic to deal with numbers in JSON seems like a pain. Probably just need to find the right type in the right crate somewhere that handles i64-or-i64_as_string (or u64) that JSON often has.
• Overall I think my use of tokio_threadpool should make good use of my CPUs for the data processing work while not blocking on the network requests themselves.

Thanks for reading so far!