VS Code debugging

This document describes how to set up Rails debugging in Visual Studio Code (VSCode) using the GitLab Development Kit (GDK).


  1. Install the debug gem by running gem install debug inside your gitlab folder.
  2. Install the VSCode Ruby rdbg Debugger extension to add support for the rdbg debugger type to VSCode.
  3. In case you want to automatically stop and start GitLab and its associated Ruby Rails server, you may add the following VSCode task to your configuration under the .vscode/tasks.json file:

       "version": "2.0.0",
       "tasks": [
             "label": "start rdbg",
             "type": "shell",
             "command": "gdk stop rails-web && GITLAB_RAILS_RACK_TIMEOUT_ENABLE_LOGGING=false PUMA_SINGLE_MODE=true rdbg --open -c bin/rails server",
             "isBackground": true,
             "problemMatcher": {
               "owner": "rails",
               "pattern": {
                 "regexp": "^.*$",
               "background": {
                 "activeOnStart": false,
                 "beginsPattern": "^(ok: down:).*$",
                 "endsPattern": "^(DEBUGGER: wait for debugger connection\\.\\.\\.)$"
  4. Add the following configuration to your .vscode/launch.json file:

         "version": "0.2.0",
         "configurations": [
             "type": "rdbg",
             "name": "Attach with rdbg",
             "request": "attach",
             // remove the following "preLaunchTask" if you do not wish to stop and start
             // GitLab via VS Code but manually on a separate terminal.
             "preLaunchTask": "start rdbg"
The VSCode Ruby extension might have issues finding the correct Ruby installation and the appropriate rdbg command. In this case, add "rdbgPath": "/home/user/.asdf/shims/ (in the case of asdf) to the launch configuration above.



  • You must have a running GDK instance.

To start debugging, do one of the following:

  • Press F5.
  • Run the Debug: Start Debugging command.