memcached is not a clustered solution, so each server is completely independent. if you need to keep consistency you need to do this by using client. great example is Facebook McRouter: https://code.facebook.com/posts/296442737213493/introducing-mcrouter-a-memcached-protocol-router-for-scaling-memcached-deployments/ it allows to setup show copy.
also, keep in mind if you do not use "leases" memcached is pretty "evential" consistency solution. Other option is to use Redis instead of Memcached, it has replication (and some other advanced features). But replication brings tons of other problems (especially in a way how it is implemented in Redis) On Friday, October 17, 2014 11:23:45 AM UTC-7, Karim Tawfik wrote: > > Hi, > > I am new to memcached, and try to introduce it on our company as a caching > layer, but there is a question came up to my mind, how memcached handle the > consistency of data to all are the same in all clusters. > > For example: > say I have 2 clusters, each have memcached is installed on it, and clients > started to send requests (e.g.updating some data), how the other memcached > server would know about such update if it is already caching an old version > before it got updated. > > I am asking this question as i read 2 contradicting statements on the > website, which are: > > 1. Under ==> https://code.google.com/p/memcached/wiki/NewOverview, > section. > - Servers are Disconnected From Each Other : Memcached servers are > generally unaware of each other. There is no crosstalk, no > syncronization, > no broadcasting > 2. Under ==> > https://code.google.com/p/memcached/wiki/TutorialCachingStory > - > > So again, he takes keys that the Programmer uses and looks for them > on his memcached servers. 'get this_key' 'get that_key' But each time > he > does this, he only finds each key on one memcached! Now WHY would you > do > this, he thinks? And he puzzles all night. That's silly! Don't you want > the > keys to be on all memcacheds? > > "But wait", he thinks "I gave each memcached 1 gigabyte of memory, > and that means, in total, I can cache three gigabytes of my database, > instead of just ONE! Oh man, this is great," he thinks. "This'll save > me a > ton of cash. Brad Fitzpatrick, I love your ass!" > > Could you please give me the clear directions, if i have incorrect view. > > The last thing is, does memcached get affected by anymeans of replications > between server? > > Thanks, > Karim > -- --- You received this message because you are subscribed to the Google Groups "memcached" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
