curator-recipes/src/site/confluence/double-barrier.confluence

h1. Double Barrier

h2. Description
An implementation of the Distributed Double Barrier ZK recipe.

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.

h2. Participating Classes
* DistributedDoubleBarrier

h2. Usage
h3. Creating a DistributedBarrier
{code}
public DistributedDoubleBarrier(CuratorFramework client,
                                String barrierPath,
                                int memberQty)
Creates the barrier abstraction. memberQty is the number of members in the barrier. When enter() is called, it blocks until
all members have entered. When leave() is called, it blocks until all members have left.

Parameters:
client - the client
barrierPath - path to use
memberQty - the number of members in the barrier
{code}

h2. General Usage
To enter on the barrier:
{code}
public void     enter();
{code}

To leave on the barrier:
{code}
public void     leave();
{code}

h2. Error Handling
DistributedDoubleBarrier instances watch for connection loss and will throw an exception from {{enter()}} and/or {{leave()}}.