TaskIdsPermitsBarrier (Apache Giraph Parent 1.4.0-SNAPSHOT API)

```
public class TaskIdsPermitsBarrier
extends Object
```
This barrier is used when we don't know how many events are we waiting on from the start. Instead we have a set of task ids, and each of those will, at some point of time, give the information about how many events from it should we expect. Barrier will be waiting for all the tasks to notify it about that number of events, and than it will also wait for all the events to happen. requirePermits() corresponds to task notifying us how many events from it to expect, and releasePermits() notifies us about events happening. This class is currently used during preparation of aggregators. User must follow this protocol for concurrent access: (1) an object instance is constructed (2) arbitrarily many times (2a) concurrent calls to requirePermits(), releasePermits() and waitForRequiredPermits() are issued (2b) waitForRequiredPermits() returns Note that the next cycle of calls to requirePermits() or releasePermits() cannot start until the previous call to waitForRequiredPermits() has returned. Methods of this class are thread-safe.

Constructors
Constructor and Description
`TaskIdsPermitsBarrier(org.apache.hadoop.util.Progressable progressable)` Constructor

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`releaseOnePermit()` Release one permit.
`void`	`releasePermits(long permits)` Release some permits.
`void`	`requirePermits(long permits, int taskId)` Require more permits.
`void`	`waitForRequiredPermits(Set<Integer> expectedTaskIds)` Wait until permits have been required desired number of times, and all required permits are available

Class TaskIdsPermitsBarrier