Type Members

1.  case class Shard(id: Int, node: ZNode, permit: Permit) extends ShardPermit with Product with Serializable
2.  class ShardCoordinator extends AnyRef

   A rudimentary shard/partition coordinator.

   A rudimentary shard/partition coordinator. Provides ShardPermits by lowest available ID first (linear scan).

   val shardCoordinator = new ShardCoordinator(zkClient, "/testing/twitter/service/something/shards", numShards)
   log.trace("Waiting for shard permit...")
   shardCoordinator.acquire flatMap { shard =>
     log.trace("Working as shard %d", shard.id)
     { // inside some Future
       if (Hashing.consistentHash(item, numShards) == shard.id) action
     } ensure { shard.release }
   }

3.  sealed trait ShardPermit extends AnyRef
4.  class ZkAsyncSemaphore extends AnyRef

   ZkAsyncSemaphore is a distributed semaphore with asynchronous execution.

   ZkAsyncSemaphore is a distributed semaphore with asynchronous execution. Grabbing a permit constitutes a vote on the number of permits the semaphore can permit and returns a Future[Permit]. If consensus on the number of permits is lost, an exception is raised when acquiring a permit (so expect it).

   Care must be taken to handle zookeeper client session expiry. A ZkAsyncSemaphore cannot be used after the zookeeper session has expired. Likewise, any permits acquired via the session must be considered invalid. Additionally, it is the client's responsibility to determine if a permit is still valid in the case that the zookeeper client becomes disconnected.

   Attempts to clone AsyncSemaphore

   Ex.

   implicit val timer = new JavaTimer(true)
   val connector = NativeConnector("localhost:2181", 5.seconds, 10.minutes)
   val zk = ZkClient(connector).withRetryPolicy(RetryPolicy.Basic(3))
   val path = "/testing/twitter/service/charm/shards"
   val sem = new ZkAsyncSemaphore(zk, path, 4)
   
   sem.acquire flatMap { permit =>
     Future { ... } ensure { permit.release }
   } // handle { ... }