How to implement memcached using a database ?

Question

As far as I know, memcached runs in-memory and does not have a persistent backing-store.

Currently my team is not ready yet to use memcached.

So, I plan to write a simple database backed alternative.

My question is pretty much in similar vein to this other question

http://stackoverflow.com/questions/33619/concurrent-logins-in-a-web-farm

My webapp has clear entry (login) and exit (logout) points.

The plan:

1. On login, I will add the userid into a table.
2. On logout, I will delete the row containing the userid.

Issues:

Is there a well-used method to timeout a row in Mysql ? By method, I mean a best practice. Once a timeout has been reached, the row is removed.

Thanks

J

Answer 1

there is already a variant for memcache which is persistent:

http://memcachedb.org/

also check out tokyo cabinet: http://1978th.net/ which supposedly is much faster

R

EDIT: rereading your question. Let me add this: the way to implement a timetolive, is just add a timestamp column to your db. The next time when you get the cached item, check if the timestamp is too old, and delete the entry at that time, get a fresh copy, and put it back in the DB cache with a current timestamp

This is also the way memcache does it

Answer 2

Not sure what u meant by

Is there a well-used method to timeout a row in Mysql ?

we use Memcache as a means for Object based caching, it can be set to a timetolive value

for eg.;

MemcachedClient c= // get memcachedclient reference...

      if (c != null) {
      c.set(key, timeToLiveInSeconds, objectToCache);
     }

After a stipulated time period it will be removed automatically