TTransportException Ignored On Service-to-Service Communication

[pawl]

Here's the scenario:

1. Client calls Service A
2. Service A calls Service B
3. Service A receives TTransportException while calling Service B (in my example this was because I returned an int instead of the expected string)

Currently you will see a TTransportException on the client that called Service A, but there is no indication in Service A that there was a problem communicating with Service B. This makes for some difficult debugging...

I made a gist illustrating the issue here: https://gist.github.com/pawl/5e1e71e6b9f410d4491fe68c24b9977a

This happens because TThreadedServer swallows the TTransportException here: https://github.com/eleme/thriftpy/blob/v0.3.9/thriftpy/server.py#L96-L97 If you remove that, then all calls will error out, because TTransportException seems to always occur at EOF.

For now, I'm resolving the issue by catching TTransportException where Service A calls Service B and re-raising a different error. However, I still think this is a major gotcha.

Do you think there's a way we can modify thriftpy to prevent this from happening?