🚧 WIP

broker-control/Dockerfile

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+# broker-control — internal control sidecar (spec §29)
+#
+# Runs in the mosquitto container's PID namespace (compose `pid: "service:mosquitto"`)
+# so it can signal the broker process (PID 1) without docker.sock access.
+# The backend calls its HTTP API over the backend-net network.
+#
+# Responsibilities (deliberately minimal, spec §29):
+#   - validate staged configuration (mosquitto -c <staged> --test-config)
+#   - activate a configuration revision (atomic rename into place)
+#   - signal config reload (mosquitto_signal -p 1 config-reload == SIGHUP)
+#   - check broker process state
+#
+# Release 1 ships validate/activate/reload/status only; restarts are a
+# Release 2 concern (reload-vs-restart classification, spec §28).
+
+FROM eclipse-mosquitto:2.1.2-alpine
+
+# Same image as the broker → --test-config validates with the exact
+# broker binary that will load the config.
+
+# The base image ships NO Python. control.py is stdlib-only, so the
+# distro package is sufficient (no pip, no venv needed).
+RUN apk add --no-cache python3
+
+COPY control.py /app/control.py
+
+# The base image has no USER directive, so this sidecar runs as root.
+# Deliberate: it writes /mosquitto/config (owned by uid 1883 in the fresh
+# volume) and signals the broker via the shared PID namespace. The API
+# is token-guarded, internal-network-only, and no docker.sock is mounted
+# (spec §29).
+
+# Clear the CMD inherited from the base image — its default CMD
+# (`mosquitto -c ...`) would otherwise be appended to our entrypoint.
+CMD []
+
+EXPOSE 8090
+
+ENTRYPOINT ["python3", "/app/control.py"]