Bug: Dockerfile EXPOSE $MANAGER_URL passes URL build arg instead of port number

[LucasMaupin]

Summary

Dockerfile line 5 passes $MANAGER_URL (a URL build arg, e.g. http://host:8080) to the EXPOSE directive, which only accepts port numbers. This is silently ignored by Docker and means the intended port is never declared.

Affected file

Dockerfile:5

ARG MANAGER_URL        # e.g. "http://intercom-manager:8080"
EXPOSE $PORT           # ✓ correct — port number
EXPOSE $MANAGER_URL    # ✗ wrong  — URL string, not a port

EXPOSE only accepts integers (or integer/protocol). Passing a URL string causes Docker to either silently ignore the directive or error, depending on the version. The port embedded in $MANAGER_URL is never actually exposed.

Impact

• Any port-publishing that relies on docker run -P or Docker Compose expose: for the manager URL port will not work as expected.
• Docker image consumers may not realise the manager port is not exposed, causing silent connectivity failures.

Recommendation

Remove line 5 (EXPOSE $MANAGER_URL). If the manager backend port needs to be declared, extract just the port number as a separate ARG and expose that:

ARG MANAGER_PORT=8080
EXPOSE $PORT
EXPOSE $MANAGER_PORT

Or simply document the expected port in comments and let docker-compose.yml handle port mapping explicitly.

Related

• Security: Frontend Dockerfile runs nginx as root — add non-root USER directive #648 — Dockerfile runs as root
• Security: Refactor frontend Dockerfile to multi-stage build — remove Node.js from runtime image #640 — Refactor to multi-stage build