key expiration for many memcached clients and DB stress

[Ben Suffolk]

Victor,

I would be set it never to expire, then have a separate process  
updating the cache with the new data every x time period (your old  
expiry time say).

This way you always have valid data in the cache, and when it time to  
update you only get one process hitting the database not every  
connection that suddenly finds its not got what it wants in the cache  
(which I think is your main problem)

Ben
On 20 Oct 2006, at 12:36, Victor Gumayunov wrote:

> Hello everybody,
> please advise how to solve our problem.
>
> We're using memcached in our web project.
> The site is actually a frond-end to some database.
> Since number of users is very high, we cache DB info in memcached.
> But when some memcached key expires, many users simultaneously rush to
> the DB server stressing it to the edge.
>
> Obvious solution is to notify in some way 1 web client that certain  
> key
> is about to expire, so the client re-fetches it from DB and updates in
> memcached, while other clients still use cached value until it is
> updated by notified client.
>
> We tried several client-side approaches to implement this scenario,
> but no one gives 100% good result.
>
> So we changed server's logics for key processing.
> Our modified memcached recognizes specially formatted key names
> and does what I described above (formatted key name contains
> various parameters for such a behavior).
>
> This works almost well, but now we (of cause) run into expected
> problem that our memcached server cannot be updated when new
> memcached version is released.
>
> Can you advise how to solve our problem (key expiration for many
> memcached clients simultaneously, which causes DB stress) without
> patches and various complicated client-side tricks?
>
> Thanks in advance.
>