Debugger doesn't work for processes which fork other processes

I'm running:

$ node --inspect some-node-script.js

Where some-node-script.js uses plain child_process.fork (run with defaults mostly) calls to initialize few other processes internally. Right after that I receive message Unable to open devtools socket: address already in use:

$ node -v
v7.0.0
$ node --inspect some-node-script.js
Debugger listening on port 9229.
Warning: This is an experimental feature and could change at any time.
To start debugging, open the following URL in Chrome:
    chrome-devtools://devtools/remote/serve_file/@60cd6e859b9f557d2312f5bf532f6aec5f284980/inspector.html?experiments=true&v8only=true&ws=localhost:9229/edbce9e9-0a9d-4c24-8f2b-bcaaeb4a5965
Unable to open devtools socket: address already in use

Also forked process crashes so technically application doesn't run (I've skipped that part of a log to avoid not related noise).

Behavior is same in both latest Node.js v7 and v6 (Tested on OSX, both El Captain and Sierra, with latest Chrome on board)

Am I doing something wrong, or there's no support currently for multi-process Node.js apps?

I've found similar issue which states that this probably should just work, but gives no clue why it actually doesn't.

I'll be happy to provide simple test case if needed

/cc @nodejs/v8-inspector

I've found similar issue which states that this probably should just work, but gives no clue why it actually doesn't.

child_process.fork() doesn't fix up execArgv, only cluster.fork() does. See #8495 (comment).

child_process.fork() doesn't fix up execArgv, only cluster.fork() does. See #8495 (comment).

Thanks, that clearer now. Is there a plan to fix it for child_process.fork?

After reading this comment I see that probably #5025 is meant to fix this issue

with v8 landing RemoteExecutionContext, it should be possible for a debugger to work for multiple processes. I don't know if we are ready for that and it requires v8 version >=55 which isn't going to land on Node v6

V8 inspector protocol has support for the "subtargets" - we are currently
looking into leveraging that for the node processes that fork children.
#9630 updates the HTTP transport for the
inspector, now it should be able to track multiple "sessions" and also list
multiple targets.

Currently we are considering introducing a special "inspector" pipe from
the parent to a child so the child does not have to run the HTTP server.
All communications with the children will happen through the parent, parent
will also be able to list individual children.

Note that this work is in experimental stage and the design will likely
change a lot.

On Thu, Nov 17, 2016 at 1:21 PM Bradley Meck notifications@github.com
wrote:

with v8 landing RemoteExecutionContext, it should be possible for a
debugger to work for multiple processes. I don't know if we are ready for
that and it requires v8 version >=55 which isn't going to land on Node v6

—
You are receiving this because you are on a team that was mentioned.

Reply to this email directly, view it on GitHub
#9435 (comment), or mute
the thread
https://github.com/notifications/unsubscribe-auth/AARkrb9lYhslDNRD2jh8KnSe5jJ03pspks5q_MVegaJpZM4KoFlU
.

@eugeneo

@eugeneo Should this remain open?

I believe it can be closed.

Does it mean, there's no plan to fix it?

Multi-process Node.js configurations are not that uncommon, and currently debugger functionality is not usable having such setup. I see it as quite important issue.

@bnoordhuis

/ping @bnoordhuis Is the reasoning in #8495 (comment) basically an explanation of why the behavior observed here is the way it is, and why it is unlikely to be changed?

@medikoo Does it work in Node.js 8.x if you invoke the script like this?:

$ node --inspect --inspect-port=0 some-node-script.js

I've opened https://groups.google.com/forum/#!forum/google-chrome-developer-tools to start discussion on things, but all these non-chrome approaches such as IDEs would need to adopt any solution that would be agreed upon if the feature is seen as safe/valuable enough to implement.

this problem still exists on node 8.11.3, is there a plan for fixing this?

@bmeck

@bmeck this is the link to the actual post, right?

Chrome DevTools › [for Node] Expand chrome:inspect discovery for debuggable targets

@CFKevinRef

@CFKevinRef yes, but it looks like Google is working on https://github.com/GoogleChromeLabs/ndb (recently made public) which should supercede that

Even if it works in ndb, it would be great to have in the command line debugger. I'm a huge fan of it as it involves less context switching.

I'm sure once it's fleshed out it will find its way in. But prepending ndb to any command is so easy!👍

@ilijaz

@ilijaz Thanks!

const options = {
  execArgv: []
};
const child = Child.fork(program, options);

Although not an ideal fix, this was a great workaround.

There has been no activity on this feature request for 5 months and it is unlikely to be implemented. It will be closed 6 months after the last non-automated comment.

For more information on how the project manages feature requests, please consult the feature request management document.

There has been no activity on this feature request and it is being closed. If you feel closing this issue is not the right thing to do, please leave a comment.

For more information on how the project manages feature requests, please consult the feature request management document.

Navigation Menu

Repository navigation

Debugger doesn't work for processes which fork other processes #9435

21 remaining items

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Debugger doesn't work for processes which fork other processes #9435

Description

Activity

mscdex commented on Nov 3, 2016

bnoordhuis commented on Nov 3, 2016

medikoo commented on Nov 3, 2016

medikoo commented on Nov 3, 2016

bmeck commented on Nov 17, 2016

eugeneo commented on Nov 17, 2016

Trott commented on Jul 15, 2017

eugeneo commented on Jul 17, 2017

medikoo commented on Jul 17, 2017

Trott commented on Jul 18, 2017

21 remaining items

bmeck commented on Jul 2, 2018

eason-shsf commented on Jul 4, 2018

CFKevinRef commented on Jul 30, 2018

bmeck commented on Jul 30, 2018

CADBOT commented on Aug 21, 2018

trusktr commented on Sep 4, 2018

mdrichardson commented on Dec 18, 2019

github-actions commented on Mar 4, 2022

github-actions commented on Apr 4, 2022

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions