Sharded pools setup

Once your dataset becomes too big to fit on one memcached server, you want to split it across multiple servers. This is called a horizontal partition of data or simply sharding.

Mcrouter supports this feature. It can send requests to different destinations based on key hash. This way different keys will be evenly distributed across different targets and same key will be served by the same destination.

Mcrouter uses this logic to send requests to a pool by default. So sample configuration of mcrouter is pretty straightforward: just route to some pool.

 {
   "pools": {
     "A": {
       "servers": [
         // your destination memcached boxes here, e.g.:
         "127.0.0.1:12345",
         "[::1]:12346"
       ]
     }
   },
   "route": "PoolRoute|A"
 }

Explanation: requests will be routed to boxes based on a consistent hashing of keys. For more on consistent hashing, see here.

See also:

• supported hash functions;
• mcrouter configuration.