Oliver Davies
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This is a follow-up to commit 3be9031de8
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| permalink | title | pubDate |
|---|---|---|
| daily/2022/08/12/git-worktrees-docker-compose | Git Worktrees and Docker Compose | 2022-08-12 |
I've recently started trialing Git worktrees again as part of my development workflow.
If you are unfamiliar with Git worktrees, they allow you to have muliple branches of a repository checked out at the same time in different directories.
For example, this is what I see within my local checkout of my website repository:
.
├── config
├── HEAD
├── main
│ ├── ansible
│ ├── nginx
│ ├── README.md
│ └── website
├── new-post
│ ├── ansible
│ ├── nginx
│ ├── README.md
│ └── website
├── objects
│ ├── info
│ └── pack
├── packed-refs
├── refs
│ ├── heads
│ └── tags
└── worktrees
├── main
└── new-post
The first thing that you'll notice is, because it's a bare clone, it looks a little different to a what you usually see in a Git repository.
Each worktree has it's own directory, so my "main" branch inside the main directory.
If I need to work on a different branch, such as new-post, then I can create a new worktree, move into that directory and start working. I don't need to commit or stash any in-progress work and switch branches.
Complications with Docker Compose
I use Docker and Docker Compose for my projects, and this caused some issues for me the last time that I tried using worktrees.
By default, Docker Compose will use the name of the directory that the Compose file is in to name its containers. If the directory name is "oliverdavies-uk", then the containers will be oliverdavies-uk-web_1, oliverdavies-uk-db_1 etc.
This doesn't work so well if the directory is a worktree called "main" or "master" as you'll have containers called main_web_1 or master_db_1.
The way to solve this is to use the COMPOSE_PROJECT_NAME environment variable.
If you prefix Docker Compose commands with COMPOSE_PROJECT_NAME=your-project, or add it to an .env file (Docker Compose will load this automatically), then this will override the prefix in the container names to be your-project-{service}.
Container names per worktree
Whilst you could use the same Compose project name within all of your worktrees, I prefer to include the worktree name as a suffix - something like my-project-main or my-project-staging - and keep these stored in an .env file in each worktree's directory.
As each worktree now has unique container names, I can have multiple instances of a project running at the same time, and each worktree will have it's own separate data - meaning that I can make changes and test something in one worktree without affecting any others.
You can also use the COMPOSE_PROJECT_NAME variable inside Docker Compose files.
For example, if you use Traefik and needed to override the host URL for a service, the string will be interpolated and the project name would be injected as you'd expect.
labels:
- "traefik.http.routers.${COMPOSE_PROJECT_NAME}.rule=Host(
`${COMPOSE_PROJECT_NAME}.docker.localhost`,
`admin.${COMPOSE_PROJECT_NAME}.docker.localhost`
)"
This means that Traefik would continue to use a different URL for each worktree without you needing to make any changes to your Docker Compose file.