Debugging nestjs application with --watch from vscode with docker stops on changed file

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I am trying to debug a typescript nestjs application in --watch mode (so it restarts when files are changed) in Visual Studio code (using the Docker extension). The code is mounted in docker through the use of a volume.

It almost works perfectly, the docker is correctly launched, the debugger can attach, however I have one problem that I can't seem to work out:

As soon as a file is changed, the watcher picks it up and I see the following in docker logs -f for the container:

[...]
[10:12:59 AM] File change detected. Starting incremental compilation...

[10:12:59 AM] Found 0 errors. Watching for file changes.

Debugger listening on ws://0.0.0.0:9229/af60f5e3-394d-4df3-a565-8d15898348bf
For help, see: https://nodejs.org/en/docs/inspector
user@system:~$
# (at this point the docker logs command stops and the docker is gone)

At that point vscode ends the debugging session, the docker stops (or vice versa?) and I have to manually restart it.

If I launch the exact same docker command (copy/pasted from the vscode terminal window) manually, it does not stop when changing a file. This is the command it generates:

docker run -dt --name "core-dev" -e "DEBUG=*" -e "NODE_ENV=development" --label "com.microsoft.created-by=visual-studio-code" -v "/home/user/projects/core:/usr/src/app" -p "4000:4000" -p "9229:9229" --workdir=/usr/src/app "node:14-buster" yarn run start:dev --debug 0.0.0.0:9229

I did try to look with strace what happens and this is what I see on the node process when I change any file:

strace: Process 28315 attached
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, si_pid=40, si_uid=0, si_status=SIGTERM, si_utime=79, si_stime=9} ---
+++ killed by SIGKILL +++

The killed by SIGKILL line does not happen when docker is run manually, it only happens when it's started from vscode when debugging.

Hopefully someone has an idea where I'm going wrong.

Here are the relevant configs:

launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Docker Node.js Launch",
            "type": "docker",
            "request": "launch",
            "preLaunchTask": "docker-run: debug",
            "platform": "node"
        }
    ]
}

tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "type": "docker-run",
            "label": "docker-run: debug",
            "dockerRun": {
                "customOptions": "--workdir=/usr/src/app",
                "image": "node:14-buster",
                "command": "yarn run start:dev --debug 0.0.0.0:9229",
                "ports": [{
                    "hostPort": 4000,
                    "containerPort": 4000
                }],
                "volumes": [
                    {
                        "localPath": "${workspaceFolder}",
                        "containerPath": "/usr/src/app"
                    }
                ],
                "env": {
                    "DEBUG": "*",
                    "NODE_ENV": "development"
                }
            },
            "node": {
                "enableDebugging": true,
            }
        }
    ]
}

Here is a hello world repo: https://github.com/strikernl/nestjs-docker-hello-world

nestjs visual-studio-code docker node.js watch
1 Answers

So here's what I found out. When you change code it restarts node's debugger process. VSCode kills Docker container when it loses connection to the debugger.

There is a nice feature which restarts debugger sessions on code changes (see this link) but the problem is - it is for "type": "node" launch configurations. Yours is "type": "docker". From it's options for node only autoAttachChildProcesses seems promising but it doesn't solve the problem (I've checked).

So my suggestion is:

  1. Create a docker-compose.yml file, which will start the container instead of VSCode.
  2. Edit your launch.json so that it attaches to the node in container and restarts debugger session on changes.
  3. Remove/rework tasks.json as it is not needed in it's current state.

docker-compose.yml:

version: "3.0"

services:
    node:
        image: node:14-buster
        working_dir: /usr/src/app
        command: yarn run start:dev --debug 0.0.0.0:9229
        ports:
            - 4000:4000
            - 9229:9229
        volumes:
            - ${PWD}:/usr/src/app
        environment:
            DEBUG: "*"
            NODE_ENV: "development"

launch.json:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Attach to node",
            "type": "node",
            "request": "attach",
            "restart": true,
            "port": 9229
        }
    ]
}

Save the docker-compose.yml in your project root and use docker-compose up to start the container (you may need to install it first https://docs.docker.com/compose/ ). Once it's working start the debugger as usual.

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