Debugging running node process

[Vivek Goel]

Hi,
I have node daemon (gearman worker). Sometime I am facing the problem that the process don't respond to some particular requests (gearman jobs).

I am using following modules

• gearman
• mysql
• redis
• aws sdk
• node-gcm
• node-apn

I don't know in which module the program is hanging. Is it hanging in my code or some of third party code.

Is there a way to find out in which module it is hanged  (while process is in running state) ?

What are the methods used for debugging already running process in node ?

[Andrey]

You can enable debugger agent in your process by sending SIGUSR1 ( see http://nodejs.org/api/debugger.html#debugger_advanced_usage )

[Vivek Goel]

But that will not give stack trace of all current callbacks.
I need to attach a breakpoint and wait,  but problem is I don't know where  is it  waiting. So breakpoint will be blind guess.

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[Andrey]

From debugger you have an option to 1) break on next js statement 2) enable statistical profiler (and later analyse with v8.log tick processor what functions are repeatedly executed)

[Alexey Petrushin]

node.js is extremely hard to debug, one method I found is - binary search - cut app in half and see in which half the problem is - and continue cutting in half until you found the source :).

[Alexey Petrushin]

But such approach applicable only if you can reproduce the problem, it's not always possible though ...

[Vivek Goel]

On Thursday, September 19, 2013 12:08:59 PM UTC+5:30, Andrey wrote:

From debugger you have an option to 1) break on next js statement 2) enable statistical profiler (and later analyse with v8.log tick processor what functions are repeatedly executed)

Sorry , If I am getting any thing wrong here.
My problem is callback hanged (lost some where). No next function is getting executed for particular one request here.
I think then attaching breakpoint on next statement or enabling statistical profile will not help here.

Please correct me if I am wrong.

 

[Jeremy Darling]

I'd suggest looking at Theseus (for Brackets) http://blog.brackets.io/2013/08/28/theseus-javascript-debugger-for-chrome-and-nodejs/

Has helped me debug callback soup more than once.  I use it frequently on my Lenovo IdeaPad u310 for debugging, but not for editing, so it doesn't require a ton of resources.  On my I7 desktop I use it for both editing and debugging.

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