azure-functions-host: [LanguageWorker][Debugging]Function Host fails to restart language worker process on file edit if debugger is attached

Any update on when this’ll be fixed? Makes it hard to follow a real flow of work

I’m also seeing this issue.

Work for this is currently in progress, but we expect completion to happen next sprint. Updated the target to reflect that.

This issue is resolved on the azure-functions-host side with host versions > 3.0.15149 (currently, this means our next release).

However, this will not automatically enable a continuous debugging experience on file change. Changes also need to be made to the VS Code Extension, and those can be tracked here: https://github.com/microsoft/vscode-azurefunctions/issues/781

In addition to a resolution for https://github.com/microsoft/vscode-azurefunctions/issues/781, for Python functions, this change needs to be made: https://github.com/microsoft/vscode-azurefunctions/pull/2576

Closing as issue described in title, “Function Host fails to restart language worker process on file edit if debugger is attached,” is resolved.

this is a surprisingly bad developer experience, which is weird, because the vs extensions seems polished otherwise.

But having to kill the process all the time is just annoying.

Didn’t get much time to work on this larger item with being on-call, pushing to next sprint. Apologies all, still definitely a priority 😃

After a discussion with @fabiocav @anthonychu @pragnagopa and @mhoeger, we believe that the issue occurs when there is an overlap while recycling processes, that results in the new process fails to open the debugging port as it is still being held by the process that is being brought down.

The current approach that we are thinking is to remove the overlapping condition when running the host in development environments.

@Wankishh - what’s the scenario you are creating js files for? From our perspective this is an issue that affects people debugging their local code and not a production issue. Remember that function invocations should be regarded as stateless. If you are trying to preserve state between function invocations, you should explore Durable Functions.

For anybody who may have an interest in how to get a decent workflow up and running in VSCode until this issue is resolved I’ve put the following together to allow me to automatically start/stop the functions host when I launch the debugger.

launch.json

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "node",
            "request": "attach",
            "name": "Run Functions host and attach",
            "protocol": "inspector",
            "preLaunchTask": "Compile TS, Run Functions (Shell)",
            "postDebugTask": "Stop Functions",
            "outFiles": [ "{workspaceRoot}/TypeScriptFunction/index.js" ],
            "port": 5858
        },
        {
            "type": "node",
            "request": "attach",
            "name": "Attach",
            "protocol": "inspector",
            "outFiles": [ "{workspaceRoot}/TypeScriptFunction/index.js" ],
            "port": 5858
        }
    ]
}

tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "Run Functions",
      "type": "shell",
      "command": "sh scripts/functions_host_background.sh",
      "problemMatcher": []
    },
    {
      "label": "Stop Functions",
      "type": "shell",
      "command": "tmux kill-session -t azure-functions-playground",
      "problemMatcher": []
    },
    {
      "label": "Compile TypeScript",
      "type": "shell",
      "command": "tsc --outDir TypeScriptFunction --sourceMap --lib es2015 TypeScriptFunction/index.ts",
      "problemMatcher": []
    },
    {
      "label": "Compile TS, Run Functions (Compound)",
      "type": "shell",
      "dependsOn": [
        "Compile TypeScript",
        "Run Functions"
      ],
      "problemMatcher": []
    },
    {
      "label": "Compile TS, Run Functions (Shell)",
      "type": "shell",
      "command": "tsc --outDir TypeScriptFunction --sourceMap --lib es2015 TypeScriptFunction/index.ts;sh scripts/functions_host_background.sh",
      "problemMatcher": []
    }
  ]
}

functions_host_background.sh

tmux kill-session -t azure-functions-playground
tmux start-server
tmux new-session -d -s azure-functions-playground -n host
tmux send-keys -t azure-functions-playground:host "func host start --language-worker -- \"--inspect=5858\"" C-m

You need tmux, but it makes life bearable…

Add the presentation options to your tasks to keep them out of sight.

I couldn’t use the compound key because of this bug: https://github.com/Microsoft/vscode/issues/52737