Topology service is listening on prometheus default port 9090

Overview

By default, the gitlab-topology-service binds a prometheus exporter to port 9090 in its configuration file.

This is the default port for prometheus, so this causes an issue if that is enabled as well.

Impacted categories

The following categories relate to this issue:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Steps to replicate (optional)

1. Enable prometheus
2. gitlab-topology-service or prometheus will fail to start due to the port conflict

Proposal (optional)

I've worked around this by adding the following to `gitlab-topology-service/config.toml:

[metrics]
address = ":9011"

This should be exposed as a configuration option via gdk.yml, and a different default port should be chosen. It may be appropriate to push upstream to the gitlab-topology-service project to pick a new default port.

Environment (optional)

• Operating system name: `Darwin ibaum--20250805-L0DVQ 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:34:05 PDT 2025; root:xnu-12377.41.6~2/RELEASE_ARM64_T6041 arm64

• Architecture: <!-- output of `arch` or `uname -m` command -->

• The contents of your gdk.yml (if any)

  ---
  geo:
    enabled: true
    secondary: false
  hostname: primary.gdk.test
  listen_address: 172.16.123.1
  registry:
    enabled: true
  sshd:
    enabled: false
  telemetry:
    enabled: true
    username: FOO
  tool_version_manager:
    enabled: true
  vite:
    enabled: true
  webpack:
    enabled: false
  prometheus:
    enabled: true

• Ruby version: ruby 3.3.9 (2025-07-24 revision f5c772fc7c) [arm64-darwin24]

• GDK version: bf2eb177