Question

Can anyone suggest any design pattern to dynamically differentiate the memcahce instances in java code?

Previously in my application there is only one memcache instance configured this way

Step-1:

dev.memcached.location=33.10.77.88:11211

dev.memcached.poolsize=5

Step-2:

Then i am accessing that memcache in code as follows,

private MemcachedInterface() throws IOException {

    String location =stringParam("memcached.location", "33.10.77.88:11211");

    MemcachedClientBuilder builder = new XMemcachedClientBuilder(AddrUtil.getAddresses(location));

}

Then i am invoking that memcache as follows in code using above MemcachedInterface(),

Step-3:

MemcachedInterface.getSoleInstance();

And then i am using that MemcachedInterface() to get/set data as follows,

MemcachedInterface.set(MEMCACHED_CUSTS, “{}”);
resp = MemcachedInterface.gets(MEMCACHED_CUSTS);

My question is if i introduce an new memcache instance in our architechture,configuration is done as follows,

Step-1:

dev.memcached.location=33.10.77.89:11211
dev.memcached.poolsize=5

So, first memcache instance is in 33.10.77.88:11211 and second memcache instance is in 33.10.77.89:11211

until this its ok…but….

how to handle Step-2 and Step-3 in this case,To get the MemcachedInterface dynamically.

1)should i use one more interface called MemcachedInterface2() in step-2

Now the actual problem comes in,

I am having 4 webservers in my application.Previoulsy all are writing to MemcachedInterface(),but now as i will introduce one more memcache instance ex:MemcachedInterface2() ws1 and ws2 should write in MemcachedInterface() and ws3 and ws4 should write in ex:MemcachedInterface2()

So,if i use one more interface called MemcachedInterface2() as mentioned above,

This an code burden as i should change all the classes using WS3 and WS4 to Ex:MemcachedInterface2() .

Can anyone suggest one approach with limited code changes??

Answer 1

xmemcached supports constistent hashing which will allow your client to choose the right memcached server instance from the pool. You can refer to this answer for a bit more detail Do client need to worry about multiple memcache servers?

So, if I understood correctly, you’ll have to

1. use only one memcached client in all your webapps
2. since you have your own wrapper class around the memcached client MemcachedInterface, you’ll have to add some method to this interface, that enables to add/remove server to an existing client. See the user guide (scroll down a little): https://code.google.com/p/xmemcached/wiki/User_Guide#JMX_Support