DirectScale Emissary is a framework that allows you to run and debug code from your Extension logic locally. The goal is to minimize the need for git pushes and code deploys to a DirectScale environment just to test some new code.
You can read the documentation here: DirectScale Emissary Walkthrough.
The preceding document walks you through the basics to get set up, followed by a more detailed example of how to use Emissary effectively. Finally, the documentation shows how to use all of Emissary’s features with additional troubleshooting notes.
Disclaimer: Emissary is very early in development. If you run into issues with using it, please let your DirectScale contact know so it can get fixed ASAP.