Feature request: Show event loop context in the debugger

[puzpuzpuz]

Hi guys.

I wonder if there is a way to see the current event loop phase and microtasks queues (and other task queues too) during debugging a node application? I haven't found such stuff on the net, but maybe it's possible.

By that I mean being able to put a breakpoint somewhere in your code and see the diagnostic context of the event loop (and other related stuff like the worker thread pool) execution.

It may be useful in certain cases like the example that is described in the recent blog post from V8's team:

const p = Promise.resolve();

(async () => {
  await p;
  console.log('after:await');
})();

p.then(() => console.log('tick:a'))
  .then(() => console.log('tick:b'));

I know that this particular example is quite synthetic. But there are quite many real-world scenarios when being able to put a breakpoint somewhere in your code and see the context of the event loop (and other related stuff like the worker thread pool) execution would be very helpful.

As far as I undestand Node.js' code and internals, V8 and libuv are orchestrated by Node.js, so it's node's (or other runtime's) responsibility to provide this context to V8. And with this context V8 debugger would be able to output this data further down the debugging chain. For me it sounds like a cross-component feature that will require certain changes in Node.js and V8. But I'd like to have a confirmation from you, guys.

So, I wonder if it's somehow available in the node or V8 itself, or any 3rd-party library, or it's a brand new feature?

I've seen the issue #1128, but it's a bit different.

This is a question that I've already posted an issue on nodejs/help repo and was adviced to address the question to V8 team: nodejs/help#1621. Though I'm not sure if it's a question for V8 team only.

[gberdzenishvili]

+1 it will be very helpful

[devsnek]

Duplicate of nodejs/help#1621