don't forget mysql innodb/ndb memcache interface, it's a memcached protocol
with a mysql database as storage

2014-10-18 2:49 GMT-03:00 Denis Samoylov <[email protected]>:

> 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
>>
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