Question

If I use gcore to make a code dump of a Node.js process, what are the best tools to analyze it?

Inspired by:
Tool for analyzing java core dump

In my specific case, I’m interested in investigating some memory leaks, so I’m really curious to get some heap analysis. General tools and even instrumentation packages and techniques are also welcome. I’m finding Node.js to be very interesting, but the runtime analysis tools are just not there yet.

Answer 1

For investigating crashes, I’ve found node-segfault-handler to be invaluable. It’s a module I cooked up to get a native-code stack trace in the event of a hard-crash with a signal – eg deref of NULL leading to SIGSEGV

For investigating memory / allocation issues, here’s some of the data I’ve collected thus far:

1) Blog post by Dave Patheco – the author talks about using a plugin to MDB for getting JS stacks and such. Sadly, as far as I can tell, the source of that plugin was never released (nor any binary form).

2) Postmortem Debugging in Dynamic Environments – ACM Queue article also written by Dave Patheco (linked from the blog post). While it makes for GREAT background reading, the article doesn’t have many concrete tools and techniques in it.

3) node-panic – A pure-JS tool for dumping state in the event of an assert-failure type crash. Does nothing to help debug crashes that originate from native code faults (SIGSEGV, etc)

4) Joyent: Debugging Production Systems – talk by Bryan Cantrill on the tools and techniques he recommends (thx crickeys).