Nx: Address already in use while forking a script.

[annsk]

Expected Behavior

A inspection port should be other than 7777 for child process.

Current Behavior

Child process using the port 7777 for inspect, which is using by parent process.

Failure Information (for bugs)

Starting inspector on localhost:7777 failed: address already in use

Steps to Reproduce

1. Generate node application (eg. "backend")
2. In main.ts fork other script.
3. Run "ng serve backend"

The repo containing minimal reproduction of issue: https://github.com/annsk/nx-fork-issue

Context

• version of Nx used: 7.8.0
• version of Angular CLI used: 7.3.1
• angular.json configuration:
  https://github.com/annsk/nx-fork-issue/blob/master/angular.json
• version of Angular DevKit used: @angular-devkit/core: "7.3.8", @angular-devkit/build-angular: 0.13.8
• 3rd-party libraries and their versions - express: 4.16.3

Failure Logs

PS C:\Sites\nx-fork-problem\nx-fork-issue> ng serve server
Starting type checking service...
Using 2 workers with 2048MB memory limit
Type checking in progress...
Hash: c407198eb3585492d041
Version: webpack 4.29.0
Time: 265ms
Built at: 2019-04-11 07:41:24
      Asset      Size  Chunks             Chunk Names
    main.js  5.81 KiB    main  [emitted]  main
main.js.map  4.74 KiB    main  [emitted]  main
Entrypoint main = main.js main.js.map
[0] multi ./apps/server/src/main.ts 28 bytes {main} [built]
[./apps/server/src/main.ts] 509 bytes {main} [built]
[child_process] external "child_process" 42 bytes {main} [built]
[express] external "express" 42 bytes {main} [built]
Starting inspector on localhost:7777 failed: address already in use
No type errors found
Version: typescript 3.2.2
Time: 1834ms

[jfrazx]

A workaround if you can live without the inspector is to add a new configuration for your apps serve command in angular.json.

// find this for your app
"serve": {
  "builder": "@nrwl/builders:node-execute",
  "options": {
    "buildTarget": "backend:build"
  },
// add this
  "configurations": {
    "development": {
      "inspect": false
    }
  }
},

Then launch your app: ng serve backend --configuration=development

[vsavkin]

@annsk Thanks for submitting the issue. I'm getting the following when running ng serve server in the provided repo:

Debugger listening on ws://localhost:7777/ad7a2352-b0cc-4fb4-aa99-f9ad43002705
For help, see: https://nodejs.org/en/docs/inspector
Listening at http://localhost:3333
Debugger listening on ws://localhost:7777/7beb70b0-3b29-43f6-b1f1-d7fe1ac5810e
For help, see: https://nodejs.org/en/docs/inspector

What version of node are you using?

[annsk]

NodeJS v9.8.0 running on Windows 10 1809.

[vsavkin]

I was able to repro the issue (only on Windows). You should be able to fix it, like this:

      "serve": {
          "builder": "@nrwl/builders:node-execute",
          "options": {
            "buildTarget": "server:build",
            "port": 0
          }
        },

Port 0 will assign random free ports to all forked processes.

[annsk]

I think it should be an annotation about port 0 in the documentation.

[vsavkin]

@annsk would you like sending a PR updating the docs? It'd be awesome.

[vsavkin]

Updated the docs here: https://github.com/nrwl/nx/pull/1697

Closing this issue.