thermograph/observability/alloy/docker-compose.agent.yml

# The Alloy log-collector agent. Runs on EACH node (prod, beta, LAN dev) — one
# per node — reading that node's Docker containers, Caddy logs, and the app's
# JSON logs, and shipping them to the central Loki on beta over the mesh.
#
# Per-node config comes from the environment (an .env file next to this, or
# exported before `up`):
#   ALLOY_NODE   this node's label:  prod | beta | dev
#   LOKI_URL     push endpoint. All nodes push over the mesh:
#                http://10.10.0.2:3100/loki/api/v1/push
#
# Deploy on a node:
#   ALLOY_NODE=prod LOKI_URL=http://10.10.0.2:3100/loki/api/v1/push \
#     docker compose -f docker-compose.agent.yml up -d
#
# The app's JSON logs are read from its `applogs` Docker volume, named
# `<project>_applogs`. prod and beta run the app under the compose project
# `thermograph`, so the external volume below is `thermograph_applogs`. The LAN
# dev stack uses the project `thermograph-dev` — on that node, change the two
# `thermograph_applogs` references below to `thermograph-dev_applogs`.

services:
  alloy:
    image: grafana/alloy:v1.9.1
    command:
      - run
      - /etc/alloy/config.alloy
      - --storage.path=/var/lib/alloy/data
      - --server.http.listen-addr=0.0.0.0:12345
    environment:
      ALLOY_NODE: ${ALLOY_NODE:?set ALLOY_NODE (prod|beta|dev)}
      LOKI_URL: ${LOKI_URL:?set LOKI_URL}
    volumes:
      - ./config.alloy:/etc/alloy/config.alloy:ro
      # Read-only Docker socket: discover + tail every container's stdout/stderr.
      - /var/run/docker.sock:/var/run/docker.sock:ro
      # Caddy's host access logs (runs on the host, not a container).
      - /var/log/caddy:/var/log/caddy:ro
      # The app's structured JSON logs, straight off its named volume.
      - thermograph_applogs:/applogs:ro
      - alloy_data:/var/lib/alloy/data
    restart: unless-stopped

volumes:
  # The app's existing log volume (created by the app's own stack). external:true
  # means compose references it, never creates or deletes it.
  thermograph_applogs:
    external: true
  alloy_data: {}