brewblox-ctl dynamic library (OBSOLETE)

With the 2021/10/29 release, brewblox-ctl and brewblox-ctl lib have been merged. All brewblox-ctl related code can be found in the https://github.com/BrewBlox/brewblox-ctl repository.

For more information, see https://brewblox.netlify.app/dev/decisions/20211101_unified_brewblox_ctl.html

brewblox-ctl is the CLI tool for installing and managing Brewblox. It is installed through Pip.

The problem is that Pip only ever has a single "latest" version, and Brewblox can have multiple: one for each release track. There can also be multiple Brewblox installations on the same host.

The chosen solution is to have a common core of functionality in the brewblox-ctl package, and import anything specific to the release or the install from a locally deployed python code directory.

This can satisfy use cases where:

• brewblox-one is using the edge release track, and brewblox-two is using develop
• brewblox-one is one or more releases ahead of brewblox-two

If we add the current directory to the search path, we can resolve an import of brewblox_ctl_lib at runtime.

Example file structure:

.
|-- brewblox-one/
|   |-- brewblox_ctl_lib/
|   |-- couchdb/
|   |-- influxdb/
|   |-- traefik/
|   |-- .env
|   `-- docker-compose.yml
|
`-- brewblox-two/
    |-- brewblox_ctl_lib/
    |-- couchdb/
    |-- influxdb/
    |-- traefik/
    |-- .env
    `-- docker-compose.yml

To avoid needlessly tight coupling between brewblox_ctl and brewblox_ctl_lib, the interface is defined as follows:

# brewblox_ctl_lib/loader.py

def cli_sources() -> List[click.Group]:
    ...

Deployment

Brewblox as a whole makes extensive use of Docker. This is not directly recommended as a versioning/deployment mechanism for raw files, but there is no reason why we shouldn't use it like that anyway.

We deploy the brewblox/brewblox-ctl-lib docker image, that inherits from scratch, and just contains the /brewblox_ctl_lib directory.

This way we keep our deployment mechanism consistent with the rest of the software, but avoid needless overhead in the image.

As it does not contain executable code, we don't need to build separate images for AMD and ARM architectures.

Development

./dev/ and ./brewblox/ are added to .gitignore. To create a dev environment, run the following commands:

brewblox-ctl install
cd brewblox
ln -s ../brewblox_ctl_lib brewblox_ctl_lib

# Optional
ln -s <BREWBLOX_CTL_REPO_DIR>/brewblox_ctl brewblox_ctl

Creating links to the source code of brewblox_ctl and brewblox_ctl_lib allows you to make changes, and use them in a brewblox install dir without having to go through any deployment steps.

The link to brewblox_ctl is only required if you're simultaneously making changes to brewblox_ctl and brewblox_ctl_lib.