CODEWITHSUNDEEP
node.jsprofilingstack-tracev8
Philipp Claßen
Philipp Claßen

Reputation: 43969

How to get a thread dump of a running Node.js process?

In the Java JVM, kill -3 forces the process to print the current stack traces of all running threads. I found it very effective to quickly locate bottlenecks.

Is there an equivalent in V8? Can I make V8 print the current stack trace?

Clarification: I assume, due to the asynchronous nature of node, it will be less useful than for a typical non-asynchronous program. Still, if there is an easy way to get access to a few stack traces, it does not take much time to look at it.

From my experience, some obvious bottlenecks can be quickly located that way before you need to switch to more advanced tools.

Upvotes: 18

Views: 10608

Answers (3)

zvi
zvi

Reputation: 4706

On this thread you have an idea using:

# node --debug-brk buggy.js
Debugger listening on port 5858

In another terminal:

# node debug -p $(pgrep -f 'node.*buggy')
connecting to 127.0.0.1:5858 ... ok
break in buggy.js:16
 14 }
 15 
>16 z();
 17 
 18 });
debug> cont

(wait for the node process to start using 100% CPU)

debug> step
break in buggy.js:3
  1 function x() {
  2     var i = 0;
> 3     while(1) {
  4             i++;
  5     }
debug> bt
#0 buggy.js:3:8
#1 buggy.js:9:2
#2 buggy.js:13:2
#3 buggy.js:16:1

Source: https://github.com/nodejs/node-v0.x-archive/issues/25263

Upvotes: 1

Viral Patel
Viral Patel

Reputation: 1156

You can accomplish the same using heapdump tool. I found the below article of the same which is below (It also works for me):

https://medium.com/better-programming/make-a-dump-of-the-v8-heap-and-inspect-for-your-node-app-b69f7b68c162

Upvotes: -2

Aditya Guru
Aditya Guru

Reputation: 712

Node has fully loaded diagnostics that tricks like above (if I understood correctly) would be redundant but feel free to correct me.

Must Read: Awesome blogs by NodeSource 1 2 3

I'll try to list down all the tools that I found useful:

Others (Just googled them.)

Upvotes: 2

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