Cannot launch multiple Python debug sessions using VSC API

[kejxu]

Environment data

• VS Code version: 1.37.1
• Extension version (available under the Extensions sidebar): 2019.9.34474
• OS and version: Win10
• Python version (& distribution if applicable, e.g. Anaconda): 2.7
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): N/A
• Relevant/affected Python packages and their versions: N/A
• Jedi or Language Server? (i.e. what is "python.jediEnabled" set to; more info How to update the language server to the latest stable version #3977): N/A

Expected behaviour

multiple Python debug sessions get launched upon executing the following code inside an extension:

for (let request of launchRequests) {
    request.executable = request.executable.toLowerCase();
    if (request.executable.endsWith("python") || request.executable.endsWith("python.exe")) {
        const pythonScript: string = request.arguments.shift();
        const pythonlaunchdebugconfiguration: vscode.DebugConfiguration = {
            name: `Python: launch`,
            type: "python",
            request: "launch",
            program: pythonScript,
            args: request.arguments,
            env: request.env,
            stopOnEntry: true,
        };
        vscode.debug.startDebugging(undefined, pythonlaunchdebugconfiguration);
    }
}

Actual behaviour

only 1 debug session gets launched, other debug sessions would hit a timeout error like this:

Note

related to #6017

[kimadeline]

@karthiknadig Are we going to address this as part of the new debug adapter work?

[karthiknadig]

Correct, but not entirely. When we tried this, there seems to be some race condition in the extension itself, where only a sub set of connections end up going through the proper debugger hand shake. and the rest are left hanging waiting for a launch/attach request.

The new adapter addresses only part of the problem.

[DonJayamanne]

I'd block this issue, waiting for the new Debug Adapter work.
Else we'll end up doubling our work looking at issues in both debug adapters.

[luabud]

@karthiknadig is this still an issue in debugpy?

[karthiknadig]

We need to test this. It should not be a problem anymore, since we use the same mechanism as above to attach to multiple processes. The only thing that is concerning is that this is using integratedTerminal which is default. I am not sure how that impact will be when launching multiple processes.

[karthiknadig]

Tested this with debugpy... I was able to launch 5 successive session using the code above:

This is the code I used to launch:

        ['code1.py', 'code2.py', 'code3.py', 'code4.py', 'code5.py'].forEach(f => {
            const pythonlaunchdebugconfiguration: DebugConfiguration = {
                name: `Python: launch ${f}`,
                type: 'python',
                request: 'launch',
                program: `./${f}`,
                stopOnEntry: true
            };
            this.debugService.startDebugging(undefined, pythonlaunchdebugconfiguration);
        });

[karthiknadig]

Closing this, since this is now possible with debugpy. Currently debugpy is turned on for all users.