Extending Bravo

Bravo is designed to be highly extensible. This document is a short guide to the basics of writing extension code for Bravo.

Asynchronous Ideas

Bravo, being built on Twisted, has inherited most of the concepts of asynchronous control flow from Twisted, and uses them liberally. Nearly every plugin method is permitted to return a Deferred in place of their actual return value.

Exocet and You

Bravo uses a library called Exocet to help it with plugin discovery. Exocet is a remarkably powerful library which customizes the way imports are done. Instead of importing plugins by name, or package, Exocet can be asked to load a plugin, completely transforming its imports.

So, what does this mean for you, the plugin author? Well, there are a few things to keep in mind...


Exocet can blacklist imports, preventing them from actually happening and keeping your plugin from loading. Some of these blacklisted modules are chosen for security reasons, while others are chosen because they will cause slow or buggy behavior. If you think you absolutely need one of these modules, consider carefully whether the listed reason for it being on the blacklist is relevant and reasonable.

The following modules are blacklisted becuse they can be used to crash the server:

  • ctypes

The following modules are blacklisted because they can be used to examine the internals of the server or bypass Exocet’s protections:

  • gc
  • imp
  • inspect

The following modules are blacklisted because they conflict with, or are slow compared to, Twisted’s own systems:

  • asyncore
  • multiprocessing
  • socket
  • subprocess
  • thread
  • threading

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