Diagnostics WG Meeting - 2016-07-13

[joshgav]

Time

UTC Wed 13-July-2016 19:00 (1 hour before weekly CTC meeting)
Click for your local time.

San Francisco: Wed 13-July-2016 12:00
New York: Wed 13-July-2016 15:00
Amsterdam: Wed 13-July-2016 21:00
Moscow: Wed 13-July-2016 22:00
Sydney: Thu 14-July-2016 05:00
Tokyo: Thu 14-July-2016 04:00

Join/Watch

YouTube: https://youtu.be/QQ65Y4dfv84

Minutes

• Minutes: https://docs.google.com/document/d/1rq2VXKb4gj4RBTI1ZfAhRXmMDgO7LDCcLiDeI0FlErI
• Previous minutes: https://github.com/nodejs/tracing-wg/blob/master/wg-meetings/2016-06-01.md

Agenda

• AsyncWrap - AsyncWrap public API proposal node-eps#18
• Trace system for Node - update from @matthewloring and @ofrobots (see Trace Events trace system in Node.js #53, Trace module WIP - Request for feedback #50)
• Inspector Protocol (inspector: support non-V8 dispatchers node#7393, Subset of CDP as profile for Node.js tools and VMs #52, Updated info on Inspector Protocol (CDP) #59)
• APM Summit (APM summit #58)
• Topics from APM Summit thread? - ES6 module patching, trace system, F2F meetings

/cc @nodejs/diagnostics

[joshgav]

Agenda subject to this discussion. I think we should start with AsyncWrap since we missed it last time. @trevnorris @AndreasMadsen can you present status and next actions and lead a discussion for 10-15 minutes?

I'm working on something related to the Inspector stuff, will share soon.

[AndreasMadsen]

@trevnorris should do the status update this time. I haven't been following the EP that closely, since the initial discussion was mostly reserved to CTC members. Besides the EP, the only thing that is new is:

• uid is now a double
• backport to 4.x

On future work that is discussion worth, I think it is mostly about getting handle context bugs fixed. #29 contains an overview of that. The status is (my opinions)

• Microtask: difficult, but @ofrobots @jeisinger are optimistic about getting visibility from v8.
• timers: should be relatively easy
• addon modules integration: very difficult, at least without major breaking changes to how MakeCallback work.

[ofrobots]

I am away during the week of July 4, so I won't be able to make it.

[joshgav]

@ofrobots - good point. Would you be able to attend on 7/13? Would others also prefer to postpone a week?

I'm +1 :)

[MylesBorins]

I'm +1 on postponing a week

[pmuellr]

Makes sense, w/ July 4th holiday

[joshgav]

Great, July 13 it is. Thanks!

[joshgav]

@nodejs/diagnostics: reminder: meeting is this Wednesday July 13 at 12pm Pacific

@ofrobots @matthewloring - can you discuss the trace system? #53
@pavelfeldman - can you discuss progress on inspector integration? #52
@trevnorris - do you want to discuss AsyncWrap? /cc @bnoordhuis

I'd like to briefly discuss potential goals of nodejs/node#7393.

[matthewloring]

We'll be there to discuss the tracing controller.

[trevnorris]

@joshgav Not sure I have anything to discuss, but I'll be happy to take any questions.

[AndreasMadsen]

@trevnorris I think this will be a good opportunity to get an update on the v8 microtask hooks and for you to explain the MakeCallback solution.

[rvagg]

@Fishrock123 has an update about the microtask hooks .. not great news afaik

[Jeff-Lewis]

I'm not sure if this means anything but v8 ticket 4643 MicrotaskQueue lacking introspection APIs was just assigned last night.

[jmealo]

@nodejs/diagnostics If anyone from the diagnostics group could provide some guidance on getting debugging/inspector support back into pl/v8 it would be much appreciated!

plv8/plv8#131

[ofrobots]

@jmealo: At this point, v8_inspector is the best bet for implementing debugging for V8; the older JSON based protocol has been deprecated for ~2 years now. From skimming the issue it seems like plv8 might be on V8 ~4.3 which would be unfortunately too old (you need atleast V8 5.0+ for v8_inspector to work).

To use v8_inspector in your project, here's a rough outline of what you will have to do:

1. Get v8_inspector from https://github.com/pavelfeldman/v8_inspector. We are keeping this repo as a convenient location for integration with Node.js. You can pick this code up directly from upstream Chromium too if you prefer. Note that at some point in the near-ish future this code will be merged directly into V8 and you won't have to pick it up externally.
2. A websockets implementation that would serve your debugger endpoint. You should look at src/inspector_agent.cc in Node.js as an example to see how this is wired up.

[jmealo]

@ofrobots Thanks for the reply. The master branch is at 5.1.281.14. I haven't coded any serious C++ but I can take a look at it. I'm trying to get an implementation plan and do the footwork at the very least; so, this was very helpful.

[joshgav]

Would be great if I could get a couple LGTMs on the notes from this meeting. Thanks!