io.js remote debuging is EXTREMELY slow compared to Node.js 0.10

[unbornchikken]

Hello,

If I run a debugging session in WebStorm or the recently fixed (node-inspector/node-inspector#563) node-inspector (--debug-brk), booting of the application takes forever. Even processing of the few require lines on top of my app.js file takes forever. I can se that io.js process is eating up a whole core of my i7 CPU. It takes almost two minutes to get the server started. In Node.js 0.10 this was around 7-10 seconds. I've tried Node.js 0.12. It's interesting because it's very slow too, but a slightly faster than what I'm experiencing in io.js.

Are there some parameters to speed thing out?

[Ndrou]

I have exactly the same problem... more than one minute to start my express project with --debug-brk in Webstorm :-(

[Ndrou]

I tested many versions of node. The problem seems to appear from 0.11.15.

[unbornchikken]

Sadly this bug makes node-inspector kinda useless POS with io.js. I don't even know a sane method to debug my applications in io.js, I simply don't have hours to wait for a breakpoint get hit. Switched back to Node.js 0.10 :(

I can confirm that this issue present with io.js 1.2 on Linux x64, Linux x86, Windows 8 x64 (and with Node.js 0.12 on those platforms).

[bnoordhuis]

I can't reproduce with the built-in debugger on a medium-sized application. What does the WebStorm debugger do that the built-in one doesn't?

Also, /cc @bajtos.

[unbornchikken]

It's using remote debugging exactly like node-inspector, it opens io.js with --debug-brk. This issue is not related to WebStorm it's related to remote debugging. I can reproduce this bug with node-inpector, which has an io.js compatible version in a PR there: node-inspector/node-inspector#563

[bnoordhuis]

That's why I cc'd @bajtos, he's the maintainer of node-inspector. It's still unclear to me why external debuggers are problematic when the built-in debugger seems to be working fine.

EDIT: To be clear, the built-in debugger is a 'remote' debugger as well; it runs in a separate process.

[unbornchikken]

I get it, sorry. I've just tested one of our medium sized express application with node-inspector and WebStorm on Linux (by using debug-brk and manual start). It was 7 seconds to get server started with Node.js 0.10 on both debuggers. It was 37 seconds to get server started on node-inpector. It was 43 seconds to get server started on WebStorm debugger (I think it's slower slightly because of the nolazy flag).

[bajtos]

@unbornchikken can you try the following please?

Install node-inspector@0.7 and run it with DEBUG=node-inspector:protocol:*. Save the logs for both 0.10 and 0.12. Then compare the logs and look for requests/responses that take unreasonable long time to complete in 0.12 compared to 0.10.

You can also upload the logs as a gist, so that we can take a look too. Please don't paste them as a comment in this issue, because they are long and they would make the comment page difficult to read.

[unbornchikken]

I've tried my best, but there was some issues. I was not able to log anything with Node.js 0.12, because it didn't honoured debug-brk, it started the application immediately. So I created logs with Node.js 0.10.30 + node-inspector@0.7, and with io.js 1.2 + node-inspector@node-inspector/node-inspector#563.

It's uploaded the results along with shell scripts there: http://1drv.ms/1AX33g8

This time Node.js 0.10 server startup time was slightly slower, maybe because it was debug mode enabled, but WebStorm started the server within 7 seconds in debug mode as a said before. io.js was the same as before.

[unbornchikken]

Tomorrow I'm gonna make logs by using Fiddler when debugging my project in WebStorm. Its debugger consistently supports all versions of node and io.js, maybe we will figure out what's the cause of this better with it.

[unbornchikken]

Ok, guys, there is the stuff. I have full pcap captures of Node.js 0.10.36 and io.js 1.2.0 debugging sessions. I've made it with RawCap, it shows a WebStorm debugging session from beginning to get a restify server started. I placed a breakpoint there.

io.js: http://1drv.ms/1w4n04n
Node.js 0.10.36: http://1drv.ms/1w4nyXW

You can open them in Wireshark, and can filter to communication streams by using the following filter:

tcp.stream eq 0 && tcp.len > 0

The whole session length is:

• node.js 0.10.36: 11 seconds
• io.js 1.2.0: 78 secons

This mean it takes 7x more time to get breakpoint hit in io.js! If this is not a bug, then what?

I cannot se any notable difference between the communication (Follow TCP stream in Wireshark), in io.js it just slow.

I'd appreciate if someone with deep v8 debugger knowledge could take a look at this, thanks!

[unbornchikken]

I've opened a discussing on JetBrains board too: https://devnet.jetbrains.com/thread/460705

[develar]

I am developer of JetBrains JS debuggers.

WebStorm (IDEA) is slower (start) than node inspector due to two reasons:

1. V8 debugger protocol is ugly (compare to WIP). So, we bootstrap our own implementation (using evaluate) on start. Yes, our protocol should be pulled to V8 (or node/io.js), but it works without problems.
2. WebStorm loads global variables on start (it is required for live console). You can disable it — pass vm property: -Djs.debugger.load.global.variables.on.start=false

I don't experience slow down on Mac OS X, but we have user report https://youtrack.jetbrains.com/issue/WEB-14539#comment=27-925591

There is some difference between WebStorm 9 and WebStorm 10 (139 branch and 140), but in this area nothing was changed in the past 6 months.

[unbornchikken]

Do you have any idea why does WebStorm debugger hit the same breakpoint in the same project much slower in io.js than in node 0.10?