Lazy Garbage Collection Question

Philip Neustrom philipn at
Sun Apr 30 04:35:39 UTC 2006

Sorry, one more thing I forgot to mention: They just wanted to 'clear
all their caches' without having to reboot the clients, figuring this
reaping method was safer for the reasons I mentioned.

--Philip Neustrom

On 4/29/06, Philip Neustrom <philipn at> wrote:
> The reaper was necessary because of the server fall-back implemented
> in memcached clients.  The individual wanted a safe way to reset a
> bunch of machines' caches without worrying about machine X's items
> falling to machine Y and then machine X coming back online, receiving
> the items and having the items in both X and Y -- which can lead to
> out-of-date items being served up.  Realistically it shouldn't be a
> problem because you can usually set clients up (no fall-back
> temporarily, things like that) so that a restart across a bunch of
> servers all at once is possible without a chance for corruption.
> --Philip Neustrom
> On 4/29/06, Adam Hiatt <adam.hiatt at> wrote:
> > I've noticed a couple threads in the mailing list archives with
> > questions concerning the lazy garbage collection for expiring
> > entries. One user attempted to write a 'reaper' agent that
> > specifically cleaned up their cache. Now this clearly should not be
> > necessary, but from what I read it appears that they felt that it was
> > critical because the memcached processes kept using memory until it
> > had to swap to disk. I wasn't able to determine this from the
> > threads, so, is the consensus that these deployments of memcached are
> > configured to use more memory than the system will provide to it and
> > that when the configured level is approached the OS is forced to swap
> > to disk? Or, is there some actual problem that prevents deallocation
> > and causes memory leaks force these swaps. I am concerned because I
> > am looking into using memcached in a production environment and on at
> > least one of the threads I referenced, I noticed that the
> > administrators had to restart the boxes every couple of days or so.
> >
> > ___________________________
> > Adam Hiatt (adam.hiatt at
> >
> >
> >

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