Concurrentli (com.concurrentli) is a collection of classes for multithreading that have proven useful at LinkedIn that expand on java.util.concurrent, adding convenience, efficiency and new tools to multithreaded Java programs.
- FutureEpochEvent and ImminentEpochEvent allow the caller to wait for a particular epoch (a long) or higher to be set.
- ResettableEvent is inspired by C#'s AutoResetEvent and ManualResetEvent classes, providing a simple way to wait for an event to be "set" with or without automatic resetting of the event.
- SemaphoreMap associates semaphores with keys, storing only those semaphores that currently have available permits or waiting threads.
- SequentialQueue assigns queued items a sequentially-increasing index the corresponds with the order they will be dequeued while allowing for random-access enqueing of future items.
- UnsafeCircularIntegerBuffer and UnsafeCircularReferenceBuffer are high-performance, thread-safe circular (ring) buffers.
ParallelProcessor simplifies a common concurrency scenario where a single-threaded reader thread produces inputs (e.g. by reading a stream) which are then processed by many threads. ParallelProcessor provides an abstract class that handles the multithreading, synchronization, and returning of processed elements in the order in which they were read; all client code needs to do is implement the nextInput() and processInput() methods.
- AtomicWriteOnceReference provides cheap, lock- and synchronization-free (but still thread-safe) access to a value that is set only once (the naive alternative, reading directly from a volatile, requires a memory fence on each read).
- Singleton similarly provides cheap, lock- and synchronization-free (but still thread-safe) access to a value that is generated only once using a provided getValue() method. This is a cheaper alternative to standard double-checked locking (correct implementations of which will read a volatile on each access).
- ExclusiveIdempotentMethod provides a nonblocking, lock-free way to ensure that exactly one thread is exclusively running a particular method when tryRun() is called.
- Interrupted is a utility class that wraps methods throwing InterruptedException, either ignoring the error (appropriate for the top-level method in a thread, which will thus terminate when the method returns) or re-throwing it as an unchecked UncheckedInterruptedException.
Implementations of ForkJoinPool.ManagedBlocker for reading streams (ManagedStreamReadBlocker), acquiring locks
(ManagedLockBlocker), dequeueing (ManagedDequeueBlocker), and combining multiple blockers (ManagedMultiBlocker).
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