Jev Kuznetsov
50 lines
1.2 KiB
Markdown
50 lines
1.2 KiB
Markdown
# Containerization
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Package your app and its environment together so it runs identically on every machine — dev, CI, and production.
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## Tools
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**Docker** is the standard. Everything else (Podman, containerd) is compatible with Docker images.
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## Key Concepts
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- **Image** — a snapshot of your app + OS + dependencies
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- **Container** — a running instance of an image
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- **Dockerfile** — the recipe for building an image
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- **Local CI pattern** — run your test suite inside a container before pushing; catches environment drift before it reaches remote CI
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## Minimal Dockerfile (Python)
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```dockerfile
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FROM python:3.12-slim
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WORKDIR /app
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COPY pyproject.toml .
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RUN pip install uv && uv pip install --system -e ".[dev]"
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COPY . .
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CMD ["python", "-m", "mypackage"]
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```
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## Quickstart
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```bash
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# build
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docker build -t myapp .
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# run
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docker run --rm myapp
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# local CI — run tests inside the container
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docker run --rm myapp pytest
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# interactive shell for debugging
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docker run --rm -it myapp bash
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```
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## Tips
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- Use `.dockerignore` to exclude `__pycache__`, `.git`, `.venv`, `*.pyc`
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- Pin the base image tag (`python:3.12-slim`, not `python:latest`)
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- Layer ordering matters: copy dependency files before source so the install layer is cached
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