Question

I was thinking about using memcached to store sessions instead of mySQL, which seemed like a good idea, at first.

When it comes to the failover part of utilizing memcached servers, It’s a bit worrying that my sessions will stop working if the memcached would go offline. It will certainly affect my users.

There’s a few techniques that we already utilize to reduce failover, including having a pool of servers available to compensate in the event of downtime, utilizing sharding/consistent hashing across the server pool and so on. We would also do some sort of graceful degradation that tells the users that something have gone wrong and they are welcome to login again, in the event of them being kicked out due to memcached server failover.

So how does people generally deal with these issues when storing sessions on memcached servers?

Answer 1

You could create a fail safe method by using both the db and memcached. Check to see if your memcached object is in memory else store session in the db then create the memcache instance. Just make sure when log out / sign out, it flushes/removes the memcached…

So check memcached first, if fails, check db… 🙂