org.apache.cassandra.utils.concurrent

Class FutureCombiner<T>

java.lang.Object

org.apache.cassandra.utils.concurrent.AbstractFuture<V>

org.apache.cassandra.utils.concurrent.AsyncFuture<T>

org.apache.cassandra.utils.concurrent.FutureCombiner<T>

All Implemented Interfaces:

com.google.common.util.concurrent.ListenableFuture<T>, java.util.concurrent.Future<T>, Awaitable

public class FutureCombiner<T>
extends AsyncFuture<T>

Netty's PromiseCombiner is not threadsafe, and we combine futures from multiple event executors. This class groups a number of Future into a single logical Future, by registering a listener to each that decrements a shared counter; if any of them fail, the FutureCombiner is completed with the first cause, but in all scenario only completes when all underlying future have completed (exceptionally or otherwise) This Future is always uncancellable. We extend AsyncFuture, and simply provide it an uncancellable Promise that will be completed by the listeners registered to the input futures.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.cassandra.utils.concurrent.Awaitable

Awaitable.AbstractAwaitable, Awaitable.AsyncAwaitable, Awaitable.Defaults, Awaitable.SyncAwaitable

Field Summary

Fields inherited from class org.apache.cassandra.utils.concurrent.AbstractFuture

CANCELLED, UNCANCELLABLE, UNSET

Method Summary

Modifier and Type	Method and Description
static <V> Future<java.util.List<V>>	allOf(java.util.Collection<? extends io.netty.util.concurrent.Future<? extends V>> futures) Waits only until the first failure, or until all have succeeded.
boolean	cancel(boolean b)
static FutureCombiner<java.lang.Void>	nettySuccessListener(java.util.Collection<? extends io.netty.util.concurrent.Future<?>> futures) Waits for all of futures to complete, only propagating failures on completion
protected boolean	setUncancellable()
protected boolean	setUncancellableExclusive()
static <V> Future<java.util.List<V>>	successfulOf(java.util.List<? extends io.netty.util.concurrent.Future<V>> futures) Waits for all futures to complete, returning a list containing values of all successful input futures.
protected boolean	tryFailure(java.lang.Throwable throwable)
protected boolean	trySuccess(T t)

Methods inherited from class org.apache.cassandra.utils.concurrent.AsyncFuture

await, awaitUntil, flatMap, map

Methods inherited from class org.apache.cassandra.utils.concurrent.AbstractFuture

addCallback, addCallback, addCallback, addCallback, addCallback, addCallback, addListener, addListener, addListener, addListeners, await, awaitThrowUncheckedOnInterrupt, awaitThrowUncheckedOnInterrupt, awaitUninterruptibly, awaitUninterruptibly, awaitUntilThrowUncheckedOnInterrupt, awaitUntilUninterruptibly, cause, description, flatMap, get, get, getNow, getWhenDone, isCancellable, isCancelled, isDone, isSuccess, isUncancellable, map, map, notifyExecutor, removeListener, removeListeners, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.cassandra.utils.concurrent.Future

await, awaitUninterruptibly, flatMap, rethrowIfFailed, sync, syncThrowUncheckedOnInterrupt, syncUninterruptibly

Method Detail

setUncancellable

protected boolean setUncancellable()

Overrides:

setUncancellable in class AbstractFuture<T>

setUncancellableExclusive

protected boolean setUncancellableExclusive()

Overrides:

setUncancellableExclusive in class AbstractFuture<T>

trySuccess

protected boolean trySuccess(T t)

Overrides:

trySuccess in class AbstractFuture<T>

tryFailure

protected boolean tryFailure(java.lang.Throwable throwable)

Overrides:

tryFailure in class AbstractFuture<T>

cancel

public boolean cancel(boolean b)

Specified by:

cancel in interface java.util.concurrent.Future<T>

Overrides:

cancel in class AbstractFuture<T>

nettySuccessListener

public static FutureCombiner<java.lang.Void> nettySuccessListener(java.util.Collection<? extends io.netty.util.concurrent.Future<?>> futures)

Waits for all of futures to complete, only propagating failures on completion

allOf

public static <V> Future<java.util.List<V>> allOf(java.util.Collection<? extends io.netty.util.concurrent.Future<? extends V>> futures)

Waits only until the first failure, or until all have succeeded. Returns a list of results if successful; an exception if any failed.

Parameters:

futures - futures to wait for completion of

Returns:

a Future containing all results of futures

successfulOf

public static <V> Future<java.util.List<V>> successfulOf(java.util.List<? extends io.netty.util.concurrent.Future<V>> futures)

Waits for all futures to complete, returning a list containing values of all successful input futures. This emulates Guava's Futures::successfulAsList in that results will be in the same order as inputs and any non-success value (e.g. failure or cancellation) will be replaced by null.

Parameters:

futures - futures to wait for completion of

Returns:

a Future containing all successful results of futures and nulls for non-successful futures