For what it's worth, I just went through an arduous process of tracking
down a memory leak for walmart, you can read about it
http://www.joyent.com/blog/walmart-node-js-memory-leak you could use the
techniques described there to help narrow down your issues. There are other
pieces of information available at
http://www.joyent.com/developers/node/debug#mdb
I will try and do a quick analysis for you, but if you have issues you can
hit me and others up on irc #node.js on freenode
On Fri, Nov 22, 2013 at 9:27 AM, Steve Freegard <st...@stevefreegard.com>wrote:
> Hi Ben,
>
> I managed to find the issue in Haraka - we were calling
> fs.unwatchFile/fs.watchFile instead of consulting our configuration
> cache which we should have been doing.
>
> However - this has pointed us to a rather large memory leak in the
> fs.unwatchFile and fs.watchFile functions. I've tested it on both 0.8
> and 0.10. This is on 0.10:
>
> [root@mta41 ~]# node --expose_gc watchfile_leak.js
> { rss: 8478720, heapTotal: 6163968, heapUsed: 1918824 }
> { rss: 827813888, heapTotal: 13387520, heapUsed: 4990520 }
>
> Testcase is attached.
>
> Kind regards,
> Steve.
>
>
> On 22/11/13 16:25, Ben Noordhuis wrote:
> > On Fri, Nov 22, 2013 at 12:37 PM, Steve Freegard
> > <st...@stevefreegard.com> wrote:
> >> Hi,
> >>
> >> I'm trying to debug and understand an issue on several of my Haraka
> servers
> >> after a recent update.
> >>
> >> I'm seeing large amounts of memory being used and never returned back
> to the
> >> operating system causing the machine to swap and eventually the Linux
> OOM
> >> killer shooting the processes.
> >>
> >> I thought that there must be a memory leak somewhere - but I've used
> >> node-heapdump and taken multiple snapshots and compared them and whilst
> I'm
> >> seeing a small growth I'm not seeing anything major. However the
> heapdump
> >> reports the size at ~97Mb whereas the RSS of the process at the time of
> the
> >> dump was 1.1Gb which is what I really don't understand at all.
> >>
> >> Would such a disparity between heap and RSS indicate that an external
> C++
> >> module that is being used is leaking memory?? If so, what is the best
> way
> >> of finding out which?
> >>
> >> I've tried the mtrace module - but it caused the process to completely
> hang
> >> after only a few minutes of running so I had to kill it. The output
> that I
> >> got from it is attached - I'm not really sure it tells me anything
> though.
> >>
> >> Any suggestions as to how to work out what is going on here and how to
> fix
> >> it would be gratefully received.
> >>
> >> Kind regards,
> >> Steve.
> > Tracking down memory leaks in garbage-collected environments is one of
> > the great unsolved problems of our generation. Okay, maybe not really
> > but there is no one-size-fits-all solution. Here are some things you
> > can try:
> >
> > * The mtrace log suggests you're using node.js v0.8. Consider upgrading.
> >
> > * Use Valgrind. Drawback: it's really, really slow and it uses a lot
> > of memory itself.
> >
> > * SystemTap. Write a small stap script that collects malloc/free/etc.
> > call graphs and aggregates them into histograms. Strong disparities
> > between calls to malloc() and free() generally show up quickly that
> > way.
> >
> > Apropos that heap snapshot, did you look at the self size or the
> > retained size? Buffer objects tend to have small self sizes (usually
> > on the order of a few hundred bytes) but can have massive retained
> > sizes. Note that Buffers in snapshots taken with node.js <= v0.8.11
> > don't report the true retained size.
> >
>
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