The thing I struggled with the most was adapting the provided docker-compose.yml for my Caddy setup.

I am using caddy-docker-proxy, which I absolutely love but their documentation is not the greatest for matchers.

If anyone else wants a super basic Lemmy instance running on Caddy with their domain on Cloudflare here is a docker-compose.yml

Please make sure you update your lemmy.hjson hostname field to match the domain you used in the docker-compose.yml for the caddy labels

If you’re not using Cloudflare you can replace build: . (and not use the Dockerfile I provided below) in the caddy service with image: lucaslorentz/caddy-docker-proxy:ci-alpine (and remove the caddy.acme_dns label) and I believe it will fall back to Let’sEncrypt

version: "3.9"

services:
  caddy:
    container_name: caddy
    build: .
    depends_on:
      - lemmy-ui
      - pictrs
    ports:
      - 80:80
      - 443:443
    environment:
      CADDY_INGRESS_NETWORKS: caddy
    networks:
      - caddy
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /opt/docker/caddy/data:/data
      - /opt/docker/caddy/config:/config
    labels:
      caddy.log.format: console
      caddy.acme_dns: cloudflare YOUR_CLOUDFLARE_API_TOKEN
    restart: unless-stopped
  lemmy:
    container_name: lemmy
    image: dessalines/lemmy:0.17.3
    depends_on:
      - postgres
      - pictrs
    environment:
      RUST_LOG: "warn,lemmy_server=info,lemmy_api=info,lemmy_api_common=info,lemmy_api_crud=info,lemmy_apub=info,lemmy_db_schema=info,lemmy_db_views=info,lemmy_db_views_actor=info,lemmy_db_views_moderator=info,lemmy_routes=info,lemmy_utils=info,lemmy_websocket=info"
    networks:
      - caddy
    volumes:
      - /opt/docker/lemmy/lemmy.hjson:/config/config.hjson:ro
    labels:
      caddy: "your.domain.com"
      caddy.@lemmy: path_regexp ^/(api|pictrs|feeds|nodeinfo|\.well-known)/.*$
      caddy.@post: method POST
      caddy.@accept: header Accept application/*
      caddy.reverse_proxy_1: "@lemmy {{upstreams 8536}}"
      caddy.reverse_proxy_2: "@post {{upstreams 8536}}"
      caddy.reverse_proxy_3: "@accept {{upstreams 8536}}"
    restart: unless-stopped
  lemmy-ui:
    container_name: lemmy-ui
    image: dessalines/lemmy-ui:0.17.3
    depends_on:
      - lemmy
    environment:
      LEMMY_UI_LEMMY_INTERNAL_HOST: lemmy:8536
      LEMMY_UI_LEMMY_EXTERNAL_HOST: localhost:1234
      LEMMY_HTTPS: true
    networks:
      - caddy
    labels:
      caddy: "your.domain.com"
      caddy.reverse_proxy: "{{upstreams 1234}}"
    restart: unless-stopped
  pictrs:
    container_name: pictrs
    image: asonix/pictrs:0.3.1
    environment:
      PICTRS__API_KEY: API_KEY
    user: 991:991
    volumes:
      - /opt/docker/pictrs:/mnt
    networks:
      - caddy
  postgres:
    container_name: postgres
    image: postgres:15-alpine
    environment:
      POSTGRES_DB: lemmy
      POSTGRES_USER: lemmy
      POSTGRES_PASSWORD: password
    volumes:
      - /opt/docker/postgres:/var/lib/postgresql/data
    networks:
      - caddy
    restart: unless-stopped

networks:
  caddy:
    external: true

Here is the Dockerfile used for the caddy container:

ARG CADDY_VERSION=2.6.4

FROM caddy:${CADDY_VERSION}-builder AS builder

RUN xcaddy build \
    --with github.com/lucaslorentz/caddy-docker-proxy/v2@v2.8.4 \
    --with github.com/caddy-dns/cloudflare

FROM caddy:${CADDY_VERSION}-alpine

RUN apk add --no-cache tzdata

COPY --from=builder /usr/bin/caddy /usr/bin/caddy

CMD ["caddy", "docker-proxy"]