com.facebook.buck.util.concurrent

Class ResourcePool<R extends AutoCloseable>

java.lang.Object

com.facebook.buck.util.concurrent.ResourcePool<R>

All Implemented Interfaces:

AutoCloseable

public class ResourcePool<R extends AutoCloseable>
extends Object
implements AutoCloseable

Allows multiple concurrently executing futures to share a constrained number of resources.

Resources are lazily created up till a fixed maximum. If more than max resources are requested the associated 'requests' are queued up in the resourceRequests field. As soon as a resource is returned it will be used to satisfy the first pending request, otherwise it is stored in the parkedResources queue.

If the resourceSupplier throws a RuntimeException the Future associated with the failed attempt to create the resource will contain the relevant exception. Any subsequent requests the pool will get will attempt to create a new resource.

If the ResourcePool.ResourceUsageErrorPolicy.RECYCLE error usage policy is specified then, in case of errors when "using" a resource it is assumed to be defective, will be retired and a new resource will be requested from the supplier. The Future associated with the failed attempt to use the resource will contain the relevant exception.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ResourcePool.ResourceUsageErrorPolicy Describes how to handle errors that take place during resource usage.
static interface	ResourcePool.ThrowingFunction<T,R>

Constructor Summary

Constructors

Constructor and Description
ResourcePool(int maxResources, ResourcePool.ResourceUsageErrorPolicy resourceUsageErrorPolicy, java.util.function.Supplier<R> resourceSupplier)

Method Summary

Modifier and Type	Method and Description
void	callOnEachResource(java.util.function.Consumer<R> withResource)
void	close()
com.google.common.util.concurrent.ListenableFuture<Unit>	getShutdownFullyCompleteFuture()
<T> com.google.common.util.concurrent.ListenableFuture<T>	scheduleOperationWithResource(ResourcePool.ThrowingFunction<R,T> withResource, com.google.common.util.concurrent.ListeningExecutorService executorService)

Methods inherited from class java.lang.Object

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

Constructor Detail

ResourcePool

public ResourcePool(int maxResources,
                    ResourcePool.ResourceUsageErrorPolicy resourceUsageErrorPolicy,
                    java.util.function.Supplier<R> resourceSupplier)

Parameters:

maxResources - maximum number of resources to use concurrently.

resourceSupplier - function used to create a new resource. It should never block, it may be called more than maxResources times if processing resources throws exceptions.

Method Detail

callOnEachResource

public void callOnEachResource(java.util.function.Consumer<R> withResource)

scheduleOperationWithResource

public <T> com.google.common.util.concurrent.ListenableFuture<T> scheduleOperationWithResource(ResourcePool.ThrowingFunction<R,T> withResource,
                                                                                               com.google.common.util.concurrent.ListeningExecutorService executorService)

Parameters:

executorService - where to perform the resource processing. Should really be a "real" executor (not a directExecutor).

Returns:

a ListenableFuture containing the result of the processing. The future will be cancelled if the close() method is called.

getShutdownFullyCompleteFuture

@Nullable
public com.google.common.util.concurrent.ListenableFuture<Unit> getShutdownFullyCompleteFuture()

close

public void close()

Specified by:

close in interface AutoCloseable