Using execArgv with worker_threads.Worker breaks 'NODE_PRESERVE_SYMLINKS' envvar usage in worker.

[arciisine]

• Version: 12.13.0
• Platform: Linux

I have a child_process.fork that I am converting to use the worker_threads module. Currently I need to conditionally preserve symlinks, and this information was being passed through environment variables to the forked process. Switching over to worker_threads, this seemed to no longer work by default.

When creating the Worker instance, I am passing the NODE_PRESERVE_SYMLINKS flag in the env object. This fails to to work when execArgv is used as well. By removing execArgv, everything works as expected.

Looking at the docs for Worker's execArgv

List of node CLI options passed to the worker. V8 options 
(such as --max-old-space-size) and  options that affect the process 
(such as --title) are not supported

I can pass the --preserve-symlinks flag as a CLI option, and I've verified that is working. Though this is less than ideal as I need to enforce this conditionally.

Ultimately I'm trying to see if there is something overriding the env usage, or if the env vars, regarding process creation are potentially being ignored.

[HarshithaKP]

@arciisine, I was able to recreate it with flag --throw_deprecation.

const { Worker, isMainThread, parentPort, workerData } = require('worker_threads');
const a = true
if (isMainThread) {
   new Worker(__filename, { execArgv:[a]});
} 
else {
  console.log('Inside Worker!');
  const k = new Buffer(10)
}

I debugged in worker threads and based on my observation, the property is set at lib/internal/bootstrap/pre_execution.js but later it is unset, do not know for whatever reason.

[HarshithaKP]

• just to clarify, the above code does not throw exception as expected, when export NODE_OPTIONS=--throw-deprecation is ON.
• drilling down a bit, process.throwDeprecation field is undefined in worker is the root cause of this. when execArgv is absent, this field is true as expected.
• I have evidence that process.throwDeprecation is good in

  node/lib/internal/bootstrap/pre_execution.js

  Line 102 in 2606e1e

  addReadOnlyProcessAlias('throwDeprecation', '--throw-deprecation');

  but later it is unset.
• debugged a bit in JS (worker constructor) and C++ (Worker::New and Worker::Worker) but they don’t take part in decision making for this field value
• I see the process object creation and population is treated differently for main and worker threads (lib/internal/bootstrap/switches...) but not able to follow the bootstrap sequence completely. @addaleax / @joyeecheung - any guidance?

[HarshithaKP]

Also, is there a way for me to print debug data in the bootstrap phase? console.log / process.stdout.write etc. do not work, because of the phase in which we are, where these objects are not fully bootstrapped?

[addaleax]

@HarshithaKP The reason that this is happening is that when execArgv is passed, it is assumed that that is the entire execArgv for the worker. The issue is that NODE_OPTIONS and other environment variables aren’t being taken into account when setting that up.

Also, is there a way for me to print debug data in the bootstrap phase? console.log / process.stdout.write etc. do not work, because of the phase in which we are, where these objects are not fully bootstrapped?

For debugging Node.js core, process._rawDebug() is a good choice.

[HarshithaKP]

@addaleax , thanks for the info on process._rawDebug, that is really useful.

The reason that this is happening is that when execArgv is passed, it is assumed that that is the entire execArgv for the worker.

I believe this is a bug, do you agree?

The issue is that NODE_OPTIONS and other environment variables aren’t being taken into account when setting that up.

I am trying to find out that location, but failed. I looked at these locations:

• bootstrap sequences
• parser
• worker constructor
• GetOptions()

Do you know where this decision is taken? my current debugging is halted with this finding:

node/lib/internal/options.js

Line 7 in f895b5a

const result = options.get(option);

It returns true for main thread and undefined for worker.

[addaleax]

The reason that this is happening is that when execArgv is passed, it is assumed that that is the entire execArgv for the worker.

I believe this is a bug, do you agree?

Yes.

The issue is that NODE_OPTIONS and other environment variables aren’t being taken into account when setting that up.

I am trying to find out that location, but failed. I looked at these locations:

The Worker::New() function (in src/node_worker.cc) should do this when putting together per_isolate_opts, imo.