Remote Debugging TAS Apps
Want to be able to set breakpoints on an app that's running in TAS just like debugging on your local machine? The Tanzu Toolkit for Visual Studio extension adds a new button to the context menu for projects in Visual Studio which allows them to be deployed to TAS with remote debug capabilities.
Right-click on your project in the solution explorer & look for the "Remote Debug on Tanzu Application Service" button.
Visual learner? Here's a demo video that shows a net5.0 web app being debugged remotely on both linux and windows.
remote-debug-windows-linux-demo.mp4
Clicking the "Remote Debug on Tanzu Application Service" button will attempt to find an app running on TAS which -- by default -- has the same name as the project in the Solution Explorer. If no such app is found (among the list of apps visible to the TAS user who is logged in), a dialog window will prompt you to select an existing app in TAS (that may be named differently than the selected project) to start remotely debugging. If instead you'd prefer to push a new version of the selected project for remote debugging, click the 'Push New App to Debug' button to be shown options for configuring that new app deployment.
To stop remote debugging while keeping the app running, use the "Detach All" button found under Visual Studio's "Debug" menu
Be warned! Using the rectangular stop button 
will stop the debugging process, but it will also stop the running (app) process it's attached to. If this happens, Tanzu Application Service should restart the app as soon as it recognizes the crash & you should only notice a few seconds-minutes of app downtime.
In this context, configuring an app for remote debugging means including these additional components with the final app binaries that get pushed to TAS:
-
PDB files
- these are important because they provide a mapping between source code and the compiled binary -- this mapping is essential for allowing breakpoints to be hit at a particular point in the execution of the app, e.g.
- these are generated as a result of publishing the app in "Debug" mode via
dotnet publish -c Debug
- the visual studio remote debug agent ("vsdbg")
- this tool is responsible for starting the debugging process for an app that has PDB files associated with it -- it's a necessary prerequisite for attaching to a process for remote debugging from Visual Studio
- this is installed in a 2-step process: first, downloading an installer script from Microsoft, then invoking that installer script to acquire the right version of vsdbg for the app/IDE
Once an app is successfully running in TAS with PDB files included and vsdbg installed, Visual Studio can attempt to attach to the remote app process using the DebugAdapterHost.Launch command. This command attempts to establish communication with the remote process over ssh & is provided a configuration file that specifies how the connection should be made. Tanzu Toolkit for Visual Studio creates a temporary config file (named "launch.json") when setting up this connection & deletes it after the remote debugging session ends. Here is an example of a "launch.json" configuration file generated by this VS extension:
{
"version": "0.2.0",
"adapter": "c:\\users\\awoosnam\\appdata\\local\\microsoft\\visualstudio\\17.0_a4444530exp\\extensions\\vmware\\tanzu toolkit for visual studio 2022\\0.0.4\\Resources\\cf7.exe",
"adapterArgs": "ssh WebApplication1 -c \"c:\\Users\\vcap\\app\\vsdbg\\vsdbg.exe --interpreter=vscode\"",
"languageMappings": {
"C#": {
"languageId": "3F5162F8-07C6-11D3-9053-00C04FA302A1",
"extensions": [
"*"
]
}
},
"exceptionCategoryMappings": {
"CLR": "449EC4CC-30D2-4032-9256-EE18EB41B62B",
"MDA": "6ECE07A9-0EDE-45C4-8296-818D8FC401D4"
},
"configurations": [
{
"name": ".NET Core Launch",
"type": "coreclr",
"processName": "WebApplication1.exe",
"request": "attach",
"justMyCode": false,
"cwd": "/home/vcap/app/vsdbg",
"logging": {
"engineLogging": true
}
}
]
}