Recipes

Curator implements all (soon) of the recipes listed on the ZooKeeper recipes doc. Click on the recipe name below for detailed documentation.

Locks/Elections
Leader Election	In distributed computing, leader election is the process of designating a single process as the organizer of some task distributed among several computers (nodes). Before the task is begun, all network nodes are unaware which node will serve as the "leader," or coordinator, of the task. After a leader election algorithm has been run, however, each node throughout the network recognizes a particular, unique node as the task leader.
Shared Lock	Fully distributed locks that are globally synchronous, meaning at any snapshot in time no two clients think they hold the same lock.
Shared Semaphore	A counting semaphore that works across JVMs. All processes in all JVMs that use the same lock path will achieve an inter-process limited set of leases. Further, this semaphore is mostly "fair" - each user will get a lease in the order requested (from ZK's point of view).
Multi Shared Lock	A container that manages multiple locks as a single entity. When acquire() is called, all the locks are acquired. If that fails, any paths that were acquired are released. Similarly, when release() is called, all locks are released (failures are ignored).
Queues
Distributed Queue	An implementation of the Distributed Queue ZK recipe. Items put into the queue are guaranteed to be ordered (by means of ZK's PERSISTENT_SEQUENTIAL node). If a single consumer takes items out of the queue, they will be ordered FIFO. If ordering is important, use a LeaderSelector to nominate a single consumer.
Distributed Priority Queue	An implementation of the Distributed Priority Queue ZK recipe.
Barriers
Barrier	Distributed systems use barriers to block processing of a set of nodes until a condition is met at which time all the nodes are allowed to proceed.
Double Barrier	Double barriers enable clients to synchronize the beginning and the end of a computation. When enough processes have joined the barrier, processes start their computation and leave the barrier once they have finished.
Counters
Shared Counter	Manages a shared integer. All clients watching the same path will have the up-to-date value of the shared integer (considering ZK's normal consistency guarantees).
Distributed Atomic Long	A counter that attempts atomic increments. It first tries using optimistic locking. If that fails, an optional InterProcessMutex is taken. For both optimistic and mutex, a retry policy is used to retry the increment.