I am looking after an app built with Node JS that's producing some interesting issues. It was originally running on Node JS v0.3.0 and I've since upgraded to v0.10.12. We're using Node JS to render charts on the server and we've noticed the memory usage keeps climbing chart after chart.
Q1: I've been monitoring the RES column in top for the Node JS process, is this correct or should I be monitoring something else?
I've been setting variables to null to try and reallocate memory back to the system resources (I read this somewhere as a solution) and it makes only a slight difference.
I've pushed the app all the way to 1.5gb and it then ceases to function and the process doesn't appear to die. No error messages which I found odd.
Q2: Is there anything else I can do?
Thanks Steve
That is a massive jump in versions. You may want to share what code changes you may have made to get it working on latest stable. The api is not the same as back in v0.3, so that may be part of the problem.
If not then the issue you see it more likely from heap fragmentation than from an actual leak. In later v8 versions garbage collection is more liberal with cleanup to improve performance. (see http://code.google.com/p/chromium/issues/detail?id=112386 for some discussion on this)
You may try running the application with --max_old_space_size=32 which will limit the amount of memory v8 can use to around 32MB. Note the docs say "max size of the old generation", so it won't be exactly 32MB. Just around it, for lack of a better technical explanation.
Also you can track the amount of external memory usage with --trace_external_memory. This will allow you to know if external memory (i.e. Buffers) are being retained in your application.
You're note on the application hanging around 1.5GB would tell me you're probably on a 64-bit system. You only mentioned it ceases to function, but didn't note if the CPU is spinning during that time. Also since I don't have example code I'm not sure of what might be causing this to happen.
I'd try running on latest development (v0.11.3 at the time of this writing) and see if the issue is fixed. A lot of performance/memory enhancements are being worked on that may help your issue.
I guess you have somewhere a memory leak (in form of a closure?) that keeps the (not longer used?) diagrams(?) somewhere in memory.
The v8 sometimes needs a bit tweaking when it comes to > 1 GB of memory. Try out --noincremental_marking and/or --max_old_space_size=81920000 (if you have 8 GB available).
Check for more options with node --v8-options and go through the --trace*-parameters to find out what slows down/stops node.