feat: Add FastAPI s6 sidecar PoC

- Sidecar DragonflyDB as Redis replacement
- Run pytheus in multiprocessing mode with Redis backend

.gitignore

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+*.venv
+.python-version
+*__pycache__

Dockerfile

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+FROM public.ecr.aws/docker/library/python:3.11-slim-bookworm
+ARG S6_OVERLAY_VERSION=3.1.5.0
+
+RUN apt-get update && apt-get upgrade -y && apt-get install -y xz-utils libssl-dev libxml2-dev && rm -rf /var/cache/apt/archives /var/lib/apt/lists
+
+# Add s6-overlay
+ADD https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz /tmp
+RUN tar -C / -Jxpf /tmp/s6-overlay-noarch.tar.xz
+ADD https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-x86_64.tar.xz /tmp
+RUN tar -C / -Jxpf /tmp/s6-overlay-x86_64.tar.xz
+
+# Add FastAPI s6 config
+RUN mkdir -p /etc/s6-overlay/s6-rc.d/fastapi/dependencies.d/
+RUN echo "longrun" >> /etc/s6-overlay/s6-rc.d/fastapi/type
+COPY s6/run_fastapi /etc/s6-overlay/s6-rc.d/fastapi/run
+RUN touch /etc/s6-overlay/s6-rc.d/user/contents.d/fastapi && touch /etc/s6-overlay/s6-rc.d/fastapi/dependencies.d/base && touch /etc/s6-overlay/s6-rc.d/fastapi/dependencies.d/dragonfly
+
+# Install DragonflyDB
+ADD https://github.com/dragonflydb/dragonfly/releases/download/v1.7.1/dragonfly_amd64.deb /tmp
+RUN dpkg -i /tmp/dragonfly_amd64.deb
+
+# Cleanup /tmp
+RUN rm -rf /tmp/*
+
+# Add DragonflyDB s6 config
+RUN mkdir -p /etc/s6-overlay/s6-rc.d/dragonfly/dependencies.d/
+RUN echo "longrun" >> /etc/s6-overlay/s6-rc.d/dragonfly/type
+COPY s6/run_dragonfly /etc/s6-overlay/s6-rc.d/dragonfly/run
+RUN touch /etc/s6-overlay/s6-rc.d/user/contents.d/dragonfly && touch /etc/s6-overlay/s6-rc.d/dragonfly/dependencies.d/base
+
+# Add FastAPI code + dependencies
+WORKDIR /code
+COPY ./requirements.txt /code/requirements.txt
+RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt
+COPY ./app /code/app
+
+# Execute s6 overlay entrypoint
+ENTRYPOINT ["/init"]

README.md

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+# FastAPI - s6-overlay - sidecar PoC
+
+### How-To:
+
+    docker build -t fastapi-s6-sidecar-poc
+    docker run --rm -p 8080:80 fastapi-s6-sidecar-poc
+    curl http://localhost:8080/metrics
+
+### Sources:
+- [s6-overlay for docker](https://github.com/just-containers/s6-overlay)
+- [FastAPI](https://fastapi.tiangolo.com)
+- [Pytheus FastAPI Prometheus Middleware](https://github.com/Llandy3d/pytheus)
+- [DragonflyDB - Redis drop-in replacement](https://github.com/dragonflydb/dragonfly)

app/main.py

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+from fastapi import FastAPI
+from fastapi.responses import PlainTextResponse
+from pytheus.exposition import generate_metrics
+from pytheus.middleware import PytheusMiddlewareASGI
+
+from pytheus.backends import load_backend
+from pytheus.backends.redis import MultiProcessRedisBackend
+
+load_backend(
+    backend_class=MultiProcessRedisBackend,
+    backend_config={"host": "127.0.0.1", "port": 6379},
+)
+
+app = FastAPI()
+app.add_middleware(PytheusMiddlewareASGI)
+
+
+@app.get("/metrics", response_class=PlainTextResponse)
+async def pytheus_metrics():
+    return generate_metrics()

requirements.txt

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+annotated-types==0.5.0
+anyio==3.7.1
+black==23.7.0
+click==8.1.6
+fastapi==0.101.0
+flake8==6.1.0
+gunicorn==21.2.0
+h11==0.14.0
+httptools==0.6.0
+idna==3.4
+mccabe==0.7.0
+mypy-extensions==1.0.0
+packaging==23.1
+pathspec==0.11.2
+platformdirs==3.10.0
+pycodestyle==2.11.0
+pydantic==2.1.1
+pydantic_core==2.4.0
+pyflakes==3.1.0
+pytheus==0.2.0
+python-dotenv==1.0.0
+PyYAML==6.0.1
+redis==4.6.0
+sniffio==1.3.0
+starlette==0.27.0
+typing_extensions==4.7.1
+uvicorn==0.23.2
+uvloop==0.17.0
+watchfiles==0.19.0
+websockets==11.0.3

s6/run_dragonfly

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+#!/command/execlineb -P
+dragonfly --logtostderr --bind localhost --port 6379
+

s6/run_fastapi

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+#!/command/execlineb -P
+ /bin/sh -c "cd /code && gunicorn app.main:app --workers 2 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:80"
+