- [x] Have you followed the guidelines for contributing? - [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? - [x] Have you successfully run `tox`? ----- The PID of the process that creates an instance is stored in the instance's LXD config and is used when launching an instance. The `is_valid()` check for base instances now ensures an instance is stopped and has been fully setup. If another process is busy launching and setting up the base instance, then `is_valid()` will wait (and eventually time out). If the process that launched the base instance is inactive, then the instance is auto-cleaned (deleted and recreated). This last statement has a slight behavioral change. Previously, craft-providers raised a generic error (`Instance setup failed. Check LXD logs for more details`) and required the user to delete the base instance manually. Now, the bad base instance will be auto-cleaned. I think this is OK because this aligns with the design of the rest of `launcher` module where errors and misconfigured instances are auto-cleaned. I recommend reviewing this per-commit. The base instance has a new config value (the pid), so this must be paired with #465. Fixes #448 Fixes #455 (CRAFT-2221)