1263 lines
67 KiB
C#
1263 lines
67 KiB
C#
// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE file in the project root for full license information.
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// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
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//
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// BroadcastBlock.cs
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//
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//
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// A propagator that broadcasts incoming messages to all targets, overwriting the current
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// message in the process.
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//
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// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Diagnostics.CodeAnalysis;
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using System.Diagnostics.Contracts;
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using System.Linq;
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using System.Security;
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using System.Threading.Tasks.Dataflow.Internal;
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namespace System.Threading.Tasks.Dataflow
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{
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/// <summary>
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/// Provides a buffer for storing at most one element at time, overwriting each message with the next as it arrives.
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/// Messages are broadcast to all linked targets, all of which may consume a clone of the message.
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/// </summary>
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/// <typeparam name="T">Specifies the type of the data buffered by this dataflow block.</typeparam>
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/// <remarks>
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/// <see cref="BroadcastBlock{T}"/> exposes at most one element at a time. However, unlike
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/// <see cref="WriteOnceBlock{T}"/>, that element will be overwritten as new elements are provided
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/// to the block. <see cref="BroadcastBlock{T}"/> ensures that the current element is broadcast to any
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/// linked targets before allowing the element to be overwritten.
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/// </remarks>
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[DebuggerDisplay("{DebuggerDisplayContent,nq}")]
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[DebuggerTypeProxy(typeof(BroadcastBlock<>.DebugView))]
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public sealed class BroadcastBlock<T> : IPropagatorBlock<T, T>, IReceivableSourceBlock<T>, IDebuggerDisplay
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{
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/// <summary>The source side.</summary>
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private readonly BroadcastingSourceCore<T> _source;
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/// <summary>Bounding state for when the block is executing in bounded mode.</summary>
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private readonly BoundingStateWithPostponedAndTask<T> _boundingState;
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/// <summary>Whether all future messages should be declined.</summary>
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private bool _decliningPermanently;
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/// <summary>A task has reserved the right to run the completion routine.</summary>
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private bool _completionReserved;
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/// <summary>Gets the lock used to synchronize incoming requests.</summary>
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private object IncomingLock { get { return _source; } }
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/// <summary>Initializes the <see cref="BroadcastBlock{T}"/> with the specified cloning function.</summary>
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/// <param name="cloningFunction">
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/// The function to use to clone the data when offered to other blocks.
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/// This may be null to indicate that no cloning need be performed.
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/// </param>
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public BroadcastBlock(Func<T, T> cloningFunction) :
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this(cloningFunction, DataflowBlockOptions.Default)
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{ }
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/// <summary>Initializes the <see cref="BroadcastBlock{T}"/> with the specified cloning function and <see cref="DataflowBlockOptions"/>.</summary>
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/// <param name="cloningFunction">
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/// The function to use to clone the data when offered to other blocks.
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/// This may be null to indicate that no cloning need be performed.
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/// </param>
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/// <param name="dataflowBlockOptions">The options with which to configure this <see cref="BroadcastBlock{T}"/>.</param>
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/// <exception cref="System.ArgumentNullException">The <paramref name="dataflowBlockOptions"/> is null (Nothing in Visual Basic).</exception>
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public BroadcastBlock(Func<T, T> cloningFunction, DataflowBlockOptions dataflowBlockOptions)
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{
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// Validate arguments
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if (dataflowBlockOptions == null) throw new ArgumentNullException("dataflowBlockOptions");
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Contract.EndContractBlock();
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// Ensure we have options that can't be changed by the caller
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dataflowBlockOptions = dataflowBlockOptions.DefaultOrClone();
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// Initialize bounding state if necessary
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Action<int> onItemsRemoved = null;
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if (dataflowBlockOptions.BoundedCapacity > 0)
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{
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Debug.Assert(dataflowBlockOptions.BoundedCapacity > 0, "Positive bounding count expected; should have been verified by options ctor");
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onItemsRemoved = OnItemsRemoved;
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_boundingState = new BoundingStateWithPostponedAndTask<T>(dataflowBlockOptions.BoundedCapacity);
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}
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// Initialize the source side
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_source = new BroadcastingSourceCore<T>(this, cloningFunction, dataflowBlockOptions, onItemsRemoved);
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// It is possible that the source half may fault on its own, e.g. due to a task scheduler exception.
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// In those cases we need to fault the target half to drop its buffered messages and to release its
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// reservations. This should not create an infinite loop, because all our implementations are designed
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// to handle multiple completion requests and to carry over only one.
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_source.Completion.ContinueWith((completed, state) =>
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{
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var thisBlock = ((BroadcastBlock<T>)state) as IDataflowBlock;
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Debug.Assert(completed.IsFaulted, "The source must be faulted in order to trigger a target completion.");
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thisBlock.Fault(completed.Exception);
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}, this, CancellationToken.None, Common.GetContinuationOptions() | TaskContinuationOptions.OnlyOnFaulted, TaskScheduler.Default);
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// Handle async cancellation requests by declining on the target
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Common.WireCancellationToComplete(
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dataflowBlockOptions.CancellationToken, _source.Completion, state => ((BroadcastBlock<T>)state).Complete(), this);
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#if FEATURE_TRACING
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DataflowEtwProvider etwLog = DataflowEtwProvider.Log;
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if (etwLog.IsEnabled())
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{
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etwLog.DataflowBlockCreated(this, dataflowBlockOptions);
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}
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#endif
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Blocks/Member[@name="Complete"]/*' />
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public void Complete()
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{
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CompleteCore(exception: null, storeExceptionEvenIfAlreadyCompleting: false);
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Blocks/Member[@name="Fault"]/*' />
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void IDataflowBlock.Fault(Exception exception)
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{
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if (exception == null) throw new ArgumentNullException("exception");
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Contract.EndContractBlock();
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CompleteCore(exception, storeExceptionEvenIfAlreadyCompleting: false);
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}
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internal void CompleteCore(Exception exception, bool storeExceptionEvenIfAlreadyCompleting, bool revertProcessingState = false)
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{
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Contract.Requires(storeExceptionEvenIfAlreadyCompleting || !revertProcessingState,
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"Indicating dirty processing state may only come with storeExceptionEvenIfAlreadyCompleting==true.");
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Contract.EndContractBlock();
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lock (IncomingLock)
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{
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// Faulting from outside is allowed until we start declining permanently.
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// Faulting from inside is allowed at any time.
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if (exception != null && (!_decliningPermanently || storeExceptionEvenIfAlreadyCompleting))
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{
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_source.AddException(exception);
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}
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// Revert the dirty processing state if requested
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if (revertProcessingState)
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{
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Debug.Assert(_boundingState != null && _boundingState.TaskForInputProcessing != null,
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"The processing state must be dirty when revertProcessingState==true.");
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_boundingState.TaskForInputProcessing = null;
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}
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// Trigger completion if possible
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_decliningPermanently = true;
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CompleteTargetIfPossible();
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}
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="LinkTo"]/*' />
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public IDisposable LinkTo(ITargetBlock<T> target, DataflowLinkOptions linkOptions) { return _source.LinkTo(target, linkOptions); }
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceive"]/*' />
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public Boolean TryReceive(Predicate<T> filter, out T item) { return _source.TryReceive(filter, out item); }
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceiveAll"]/*' />
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Boolean IReceivableSourceBlock<T>.TryReceiveAll(out IList<T> items) { return _source.TryReceiveAll(out items); }
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Blocks/Member[@name="Completion"]/*' />
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public Task Completion { get { return _source.Completion; } }
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Targets/Member[@name="OfferMessage"]/*' />
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DataflowMessageStatus ITargetBlock<T>.OfferMessage(DataflowMessageHeader messageHeader, T messageValue, ISourceBlock<T> source, Boolean consumeToAccept)
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{
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// Validate arguments
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if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, "messageHeader");
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if (source == null && consumeToAccept) throw new ArgumentException(SR.Argument_CantConsumeFromANullSource, "consumeToAccept");
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Contract.EndContractBlock();
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lock (IncomingLock)
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{
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// If we've already stopped accepting messages, decline permanently
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if (_decliningPermanently)
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{
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CompleteTargetIfPossible();
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return DataflowMessageStatus.DecliningPermanently;
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}
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// We can directly accept the message if:
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// 1) we are not bounding, OR
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// 2) we are bounding AND there is room available AND there are no postponed messages AND we are not currently processing.
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// (If there were any postponed messages, we would need to postpone so that ordering would be maintained.)
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// (We should also postpone if we are currently processing, because there may be a race between consuming postponed messages and
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// accepting new ones directly into the queue.)
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if (_boundingState == null
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||
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(_boundingState.CountIsLessThanBound && _boundingState.PostponedMessages.Count == 0 && _boundingState.TaskForInputProcessing == null))
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{
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// Consume the message from the source if necessary
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if (consumeToAccept)
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{
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Debug.Assert(source != null, "We must have thrown if source == null && consumeToAccept == true.");
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bool consumed;
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messageValue = source.ConsumeMessage(messageHeader, this, out consumed);
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if (!consumed) return DataflowMessageStatus.NotAvailable;
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}
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// Once consumed, pass it to the delegate
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_source.AddMessage(messageValue);
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if (_boundingState != null) _boundingState.CurrentCount += 1; // track this new item against our bound
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return DataflowMessageStatus.Accepted;
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}
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// Otherwise, we try to postpone if a source was provided
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else if (source != null)
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{
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Debug.Assert(_boundingState != null && _boundingState.PostponedMessages != null,
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"PostponedMessages must have been initialized during construction in bounding mode.");
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_boundingState.PostponedMessages.Push(source, messageHeader);
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return DataflowMessageStatus.Postponed;
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}
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// We can't do anything else about this message
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return DataflowMessageStatus.Declined;
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}
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}
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/// <summary>Notifies the block that one or more items was removed from the queue.</summary>
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/// <param name="numItemsRemoved">The number of items removed.</param>
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private void OnItemsRemoved(int numItemsRemoved)
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{
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Contract.Requires(numItemsRemoved > 0, "Should only be called for a positive number of items removed.");
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Common.ContractAssertMonitorStatus(IncomingLock, held: false);
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// If we're bounding, we need to know when an item is removed so that we
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// can update the count that's mirroring the actual count in the source's queue,
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// and potentially kick off processing to start consuming postponed messages.
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if (_boundingState != null)
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{
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lock (IncomingLock)
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{
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// Decrement the count, which mirrors the count in the source half
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Debug.Assert(_boundingState.CurrentCount - numItemsRemoved >= 0,
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"It should be impossible to have a negative number of items.");
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_boundingState.CurrentCount -= numItemsRemoved;
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ConsumeAsyncIfNecessary();
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CompleteTargetIfPossible();
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}
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}
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}
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/// <summary>Called when postponed messages may need to be consumed.</summary>
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/// <param name="isReplacementReplica">Whether this call is the continuation of a previous message loop.</param>
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internal void ConsumeAsyncIfNecessary(bool isReplacementReplica = false)
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{
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Common.ContractAssertMonitorStatus(IncomingLock, held: true);
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Debug.Assert(_boundingState != null, "Must be in bounded mode.");
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if (!_decliningPermanently &&
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_boundingState.TaskForInputProcessing == null &&
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_boundingState.PostponedMessages.Count > 0 &&
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_boundingState.CountIsLessThanBound)
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{
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// Create task and store into _taskForInputProcessing prior to scheduling the task
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// so that _taskForInputProcessing will be visibly set in the task loop.
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_boundingState.TaskForInputProcessing =
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new Task(state => ((BroadcastBlock<T>)state).ConsumeMessagesLoopCore(), this,
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Common.GetCreationOptionsForTask(isReplacementReplica));
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#if FEATURE_TRACING
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DataflowEtwProvider etwLog = DataflowEtwProvider.Log;
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if (etwLog.IsEnabled())
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{
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etwLog.TaskLaunchedForMessageHandling(
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this, _boundingState.TaskForInputProcessing, DataflowEtwProvider.TaskLaunchedReason.ProcessingInputMessages,
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_boundingState.PostponedMessages.Count);
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}
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#endif
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// Start the task handling scheduling exceptions
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Exception exception = Common.StartTaskSafe(_boundingState.TaskForInputProcessing, _source.DataflowBlockOptions.TaskScheduler);
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if (exception != null)
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{
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// Get out from under currently held locks. Complete re-acquires the locks it needs.
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Task.Factory.StartNew(exc => CompleteCore(exception: (Exception)exc, storeExceptionEvenIfAlreadyCompleting: true, revertProcessingState: true),
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exception, CancellationToken.None, Common.GetCreationOptionsForTask(), TaskScheduler.Default);
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}
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}
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}
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/// <summary>Task body used to consume postponed messages.</summary>
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[SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
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private void ConsumeMessagesLoopCore()
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{
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Contract.Requires(_boundingState != null && _boundingState.TaskForInputProcessing != null,
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"May only be called in bounded mode and when a task is in flight.");
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Debug.Assert(_boundingState.TaskForInputProcessing.Id == Task.CurrentId,
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"This must only be called from the in-flight processing task.");
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Common.ContractAssertMonitorStatus(IncomingLock, held: false);
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try
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{
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int maxMessagesPerTask = _source.DataflowBlockOptions.ActualMaxMessagesPerTask;
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for (int i = 0;
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i < maxMessagesPerTask && ConsumeAndStoreOneMessageIfAvailable();
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i++)
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;
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}
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catch (Exception exception)
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{
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// Prevent the creation of new processing tasks
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CompleteCore(exception, storeExceptionEvenIfAlreadyCompleting: true);
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}
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finally
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{
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lock (IncomingLock)
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{
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// We're no longer processing, so null out the processing task
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_boundingState.TaskForInputProcessing = null;
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// However, we may have given up early because we hit our own configured
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// processing limits rather than because we ran out of work to do. If that's
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// the case, make sure we spin up another task to keep going.
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ConsumeAsyncIfNecessary(isReplacementReplica: true);
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// If, however, we stopped because we ran out of work to do and we
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// know we'll never get more, then complete.
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CompleteTargetIfPossible();
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}
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}
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}
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/// <summary>
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/// Retrieves one postponed message if there's room and if we can consume a postponed message.
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/// Stores any consumed message into the source half.
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/// </summary>
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/// <returns>true if a message could be consumed and stored; otherwise, false.</returns>
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/// <remarks>This must only be called from the asynchronous processing loop.</remarks>
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private bool ConsumeAndStoreOneMessageIfAvailable()
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{
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Contract.Requires(_boundingState != null && _boundingState.TaskForInputProcessing != null,
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"May only be called in bounded mode and when a task is in flight.");
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Debug.Assert(_boundingState.TaskForInputProcessing.Id == Task.CurrentId,
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"This must only be called from the in-flight processing task.");
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Common.ContractAssertMonitorStatus(IncomingLock, held: false);
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// Loop through the postponed messages until we get one.
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while (true)
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{
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// Get the next item to retrieve. If there are no more, bail.
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KeyValuePair<ISourceBlock<T>, DataflowMessageHeader> sourceAndMessage;
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lock (IncomingLock)
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{
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if (!_boundingState.CountIsLessThanBound) return false;
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if (!_boundingState.PostponedMessages.TryPop(out sourceAndMessage)) return false;
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// Optimistically assume we're going to get the item. This avoids taking the lock
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// again if we're right. If we're wrong, we decrement it later under lock.
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_boundingState.CurrentCount++;
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}
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// Consume the item
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bool consumed = false;
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try
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{
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T consumedValue = sourceAndMessage.Key.ConsumeMessage(sourceAndMessage.Value, this, out consumed);
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if (consumed)
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{
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_source.AddMessage(consumedValue);
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return true;
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}
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}
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finally
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{
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// We didn't get the item, so decrement the count to counteract our optimistic assumption.
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if (!consumed)
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{
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lock (IncomingLock) _boundingState.CurrentCount--;
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}
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}
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}
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}
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/// <summary>Completes the target, notifying the source, once all completion conditions are met.</summary>
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private void CompleteTargetIfPossible()
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{
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Common.ContractAssertMonitorStatus(IncomingLock, held: true);
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if (_decliningPermanently &&
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!_completionReserved &&
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(_boundingState == null || _boundingState.TaskForInputProcessing == null))
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{
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_completionReserved = true;
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// If we're in bounding mode and we have any postponed messages, we need to clear them,
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// which means calling back to the source, which means we need to escape the incoming lock.
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if (_boundingState != null && _boundingState.PostponedMessages.Count > 0)
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{
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Task.Factory.StartNew(state =>
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{
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var thisBroadcastBlock = (BroadcastBlock<T>)state;
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// Release any postponed messages
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List<Exception> exceptions = null;
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if (thisBroadcastBlock._boundingState != null)
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{
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// Note: No locks should be held at this point
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Common.ReleaseAllPostponedMessages(thisBroadcastBlock,
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thisBroadcastBlock._boundingState.PostponedMessages,
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ref exceptions);
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}
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if (exceptions != null)
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{
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// It is important to migrate these exceptions to the source part of the owning batch,
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// because that is the completion task that is publically exposed.
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thisBroadcastBlock._source.AddExceptions(exceptions);
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}
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thisBroadcastBlock._source.Complete();
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}, this, CancellationToken.None, Common.GetCreationOptionsForTask(), TaskScheduler.Default);
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}
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// Otherwise, we can just decline the source directly.
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else
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{
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_source.Complete();
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}
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}
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ConsumeMessage"]/*' />
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T ISourceBlock<T>.ConsumeMessage(DataflowMessageHeader messageHeader, ITargetBlock<T> target, out Boolean messageConsumed)
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{
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return _source.ConsumeMessage(messageHeader, target, out messageConsumed);
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ReserveMessage"]/*' />
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bool ISourceBlock<T>.ReserveMessage(DataflowMessageHeader messageHeader, ITargetBlock<T> target)
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{
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return _source.ReserveMessage(messageHeader, target);
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}
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/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ReleaseReservation"]/*' />
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void ISourceBlock<T>.ReleaseReservation(DataflowMessageHeader messageHeader, ITargetBlock<T> target)
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{
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_source.ReleaseReservation(messageHeader, target);
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}
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/// <summary>Gets a value to be used for the DebuggerDisplayAttribute. This must not throw even if HasValue is false.</summary>
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private bool HasValueForDebugger { get { return _source.GetDebuggingInformation().HasValue; } }
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/// <summary>Gets a value to be used for the DebuggerDisplayAttribute. This must not throw even if HasValue is false.</summary>
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private T ValueForDebugger { get { return _source.GetDebuggingInformation().Value; } }
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|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Blocks/Member[@name="ToString"]/*' />
|
|
public override string ToString() { return Common.GetNameForDebugger(this, _source.DataflowBlockOptions); }
|
|
|
|
/// <summary>The data to display in the debugger display attribute.</summary>
|
|
[SuppressMessage("Microsoft.Globalization", "CA1305:SpecifyIFormatProvider")]
|
|
private object DebuggerDisplayContent
|
|
{
|
|
get
|
|
{
|
|
return string.Format("{0}, HasValue={1}, Value={2}",
|
|
Common.GetNameForDebugger(this, _source.DataflowBlockOptions),
|
|
HasValueForDebugger,
|
|
ValueForDebugger);
|
|
}
|
|
}
|
|
/// <summary>Gets the data to display in the debugger display attribute for this instance.</summary>
|
|
object IDebuggerDisplay.Content { get { return DebuggerDisplayContent; } }
|
|
|
|
/// <summary>Provides a debugger type proxy for the BroadcastBlock.</summary>
|
|
private sealed class DebugView
|
|
{
|
|
/// <summary>The BroadcastBlock being debugged.</summary>
|
|
private readonly BroadcastBlock<T> _broadcastBlock;
|
|
/// <summary>Debug info about the source side of the broadcast.</summary>
|
|
private readonly BroadcastingSourceCore<T>.DebuggingInformation _sourceDebuggingInformation;
|
|
|
|
/// <summary>Initializes the debug view.</summary>
|
|
/// <param name="broadcastBlock">The BroadcastBlock being debugged.</param>
|
|
public DebugView(BroadcastBlock<T> broadcastBlock)
|
|
{
|
|
Contract.Requires(broadcastBlock != null, "Need a block with which to construct the debug view.");
|
|
_broadcastBlock = broadcastBlock;
|
|
_sourceDebuggingInformation = broadcastBlock._source.GetDebuggingInformation();
|
|
}
|
|
|
|
/// <summary>Gets the messages waiting to be processed.</summary>
|
|
public IEnumerable<T> InputQueue { get { return _sourceDebuggingInformation.InputQueue; } }
|
|
/// <summary>Gets whether the broadcast has a current value.</summary>
|
|
public bool HasValue { get { return _broadcastBlock.HasValueForDebugger; } }
|
|
/// <summary>Gets the broadcast's current value.</summary>
|
|
public T Value { get { return _broadcastBlock.ValueForDebugger; } }
|
|
|
|
/// <summary>Gets the task being used for output processing.</summary>
|
|
public Task TaskForOutputProcessing { get { return _sourceDebuggingInformation.TaskForOutputProcessing; } }
|
|
|
|
/// <summary>Gets the DataflowBlockOptions used to configure this block.</summary>
|
|
public DataflowBlockOptions DataflowBlockOptions { get { return _sourceDebuggingInformation.DataflowBlockOptions; } }
|
|
/// <summary>Gets whether the block is declining further messages.</summary>
|
|
public bool IsDecliningPermanently { get { return _broadcastBlock._decliningPermanently; } }
|
|
/// <summary>Gets whether the block is completed.</summary>
|
|
public bool IsCompleted { get { return _sourceDebuggingInformation.IsCompleted; } }
|
|
/// <summary>Gets the block's Id.</summary>
|
|
public int Id { get { return Common.GetBlockId(_broadcastBlock); } }
|
|
|
|
/// <summary>Gets the set of all targets linked from this block.</summary>
|
|
public TargetRegistry<T> LinkedTargets { get { return _sourceDebuggingInformation.LinkedTargets; } }
|
|
/// <summary>Gets the set of all targets linked from this block.</summary>
|
|
public ITargetBlock<T> NextMessageReservedFor { get { return _sourceDebuggingInformation.NextMessageReservedFor; } }
|
|
}
|
|
|
|
/// <summary>Provides a core implementation for blocks that implement <see cref="ISourceBlock{TOutput}"/>.</summary>
|
|
/// <typeparam name="TOutput">Specifies the type of data supplied by the <see cref="SourceCore{TOutput}"/>.</typeparam>
|
|
[SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable")]
|
|
[DebuggerDisplay("{DebuggerDisplayContent,nq}")]
|
|
private sealed class BroadcastingSourceCore<TOutput>
|
|
{
|
|
/// <summary>A registry used to store all linked targets and information about them.</summary>
|
|
private readonly TargetRegistry<TOutput> _targetRegistry;
|
|
/// <summary>All of the output messages queued up to be received by consumers/targets.</summary>
|
|
private readonly Queue<TOutput> _messages = new Queue<TOutput>();
|
|
/// <summary>A TaskCompletionSource that represents the completion of this block.</summary>
|
|
private readonly TaskCompletionSource<VoidResult> _completionTask = new TaskCompletionSource<VoidResult>();
|
|
/// <summary>
|
|
/// An action to be invoked on the owner block when an item is removed.
|
|
/// This may be null if the owner block doesn't need to be notified.
|
|
/// </summary>
|
|
private readonly Action<int> _itemsRemovedAction;
|
|
|
|
/// <summary>Gets the object to use as the outgoing lock.</summary>
|
|
private object OutgoingLock { get { return _completionTask; } }
|
|
/// <summary>Gets the object to use as the value lock.</summary>
|
|
private object ValueLock { get { return _targetRegistry; } }
|
|
|
|
/// <summary>The source utilize this helper.</summary>
|
|
private readonly BroadcastBlock<TOutput> _owningSource;
|
|
/// <summary>The options used to configure this block's execution.</summary>
|
|
private readonly DataflowBlockOptions _dataflowBlockOptions;
|
|
/// <summary>The cloning function to use.</summary>
|
|
private readonly Func<TOutput, TOutput> _cloningFunction;
|
|
|
|
/// <summary>An indicator whether _currentMessage has a value.</summary>
|
|
private bool _currentMessageIsValid;
|
|
/// <summary>The message currently being broadcast.</summary>
|
|
private TOutput _currentMessage;
|
|
/// <summary>The target that the next message is reserved for, or null if nothing is reserved.</summary>
|
|
private ITargetBlock<TOutput> _nextMessageReservedFor;
|
|
/// <summary>Whether this block should again attempt to offer messages to targets.</summary>
|
|
private bool _enableOffering;
|
|
/// <summary>Whether all future messages should be declined.</summary>
|
|
private bool _decliningPermanently;
|
|
/// <summary>The task used to process the output and offer it to targets.</summary>
|
|
private Task _taskForOutputProcessing;
|
|
/// <summary>Exceptions that may have occurred and gone unhandled during processing.</summary>
|
|
private List<Exception> _exceptions;
|
|
/// <summary>Counter for message IDs unique within this source block.</summary>
|
|
private long _nextMessageId = 1; // We are going to use this value before incrementing.
|
|
/// <summary>Whether someone has reserved the right to call CompleteBlockOncePossible.</summary>
|
|
private bool _completionReserved;
|
|
|
|
/// <summary>Initializes the source core.</summary>
|
|
/// <param name="owningSource">The source utilizing this core.</param>
|
|
/// <param name="cloningFunction">The function to use to clone the data when offered to other blocks. May be null.</param>
|
|
/// <param name="dataflowBlockOptions">The options to use to configure the block.</param>
|
|
/// <param name="itemsRemovedAction">Action to invoke when an item is removed.</param>
|
|
internal BroadcastingSourceCore(
|
|
BroadcastBlock<TOutput> owningSource,
|
|
Func<TOutput, TOutput> cloningFunction,
|
|
DataflowBlockOptions dataflowBlockOptions,
|
|
Action<int> itemsRemovedAction)
|
|
{
|
|
Contract.Requires(owningSource != null, "Must be associated with a broadcast block.");
|
|
Contract.Requires(dataflowBlockOptions != null, "Options are required to configure this block.");
|
|
|
|
// Store the arguments
|
|
_owningSource = owningSource;
|
|
_cloningFunction = cloningFunction;
|
|
_dataflowBlockOptions = dataflowBlockOptions;
|
|
_itemsRemovedAction = itemsRemovedAction;
|
|
|
|
// Construct members that depend on the arguments
|
|
_targetRegistry = new TargetRegistry<TOutput>(_owningSource);
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceive"]/*' />
|
|
internal Boolean TryReceive(Predicate<TOutput> filter, out TOutput item)
|
|
{
|
|
// Take the lock only long enough to get the message,
|
|
// synchronizing with other activities on the block.
|
|
// We don't want to execute the user-provided cloning delegate
|
|
// while holding the lock.
|
|
TOutput message;
|
|
bool isValid;
|
|
lock (OutgoingLock)
|
|
{
|
|
lock (ValueLock)
|
|
{
|
|
message = _currentMessage;
|
|
isValid = _currentMessageIsValid;
|
|
}
|
|
}
|
|
|
|
// Clone and hand back a message if we have one and if it passes the filter.
|
|
// (A null filter means all messages pass.)
|
|
if (isValid && (filter == null || filter(message)))
|
|
{
|
|
item = CloneItem(message);
|
|
return true;
|
|
}
|
|
else
|
|
{
|
|
item = default(TOutput);
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="TryReceiveAll"]/*' />
|
|
internal Boolean TryReceiveAll(out IList<TOutput> items)
|
|
{
|
|
// Try to receive the one item this block may have.
|
|
// If we can, give back an array of one item. Otherwise, give back null.
|
|
TOutput item;
|
|
if (TryReceive(null, out item))
|
|
{
|
|
items = new TOutput[] { item };
|
|
return true;
|
|
}
|
|
else
|
|
{
|
|
items = null;
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/// <summary>Adds a message to the source block for propagation.</summary>
|
|
/// <param name="item">The item to be wrapped in a message to be added.</param>
|
|
internal void AddMessage(TOutput item)
|
|
{
|
|
// This method must not take the outgoing lock, as it will be called in situations
|
|
// where a derived type's incoming lock is held. The lock leveling structure
|
|
// we're employing is such that outgoing may be held while acquiring incoming, but
|
|
// of course not the other way around. This is the reason why DataflowSourceBlock
|
|
// needs ValueLock as well. Otherwise, it would be pure overhead.
|
|
lock (ValueLock)
|
|
{
|
|
if (_decliningPermanently) return;
|
|
_messages.Enqueue(item);
|
|
if (_messages.Count == 1) _enableOffering = true;
|
|
OfferAsyncIfNecessary();
|
|
}
|
|
}
|
|
|
|
/// <summary>Informs the block that it will not be receiving additional messages.</summary>
|
|
internal void Complete()
|
|
{
|
|
lock (ValueLock)
|
|
{
|
|
_decliningPermanently = true;
|
|
|
|
// Complete may be called in a context where an incoming lock is held. We need to
|
|
// call CompleteBlockIfPossible, but we can't do so if the incoming lock is held.
|
|
// However, now that _decliningPermanently has been set, the timing of
|
|
// CompleteBlockIfPossible doesn't matter, so we schedule it to run asynchronously
|
|
// and take the necessary locks in a situation where we're sure it won't cause a problem.
|
|
Task.Factory.StartNew(state =>
|
|
{
|
|
var thisSourceCore = (BroadcastingSourceCore<TOutput>)state;
|
|
lock (thisSourceCore.OutgoingLock)
|
|
{
|
|
lock (thisSourceCore.ValueLock)
|
|
{
|
|
thisSourceCore.CompleteBlockIfPossible();
|
|
}
|
|
}
|
|
}, this, CancellationToken.None, Common.GetCreationOptionsForTask(), TaskScheduler.Default);
|
|
}
|
|
}
|
|
|
|
/// <summary>Clones the item.</summary>
|
|
/// <param name="item">The item to clone.</param>
|
|
/// <returns>The cloned item.</returns>
|
|
private TOutput CloneItem(TOutput item)
|
|
{
|
|
return _cloningFunction != null ?
|
|
_cloningFunction(item) :
|
|
item;
|
|
}
|
|
|
|
/// <summary>Offers the current message to a specific target.</summary>
|
|
/// <param name="target">The target to which to offer the current message.</param>
|
|
private void OfferCurrentMessageToNewTarget(ITargetBlock<TOutput> target)
|
|
{
|
|
Contract.Requires(target != null, "Target required to offer messages to.");
|
|
Common.ContractAssertMonitorStatus(OutgoingLock, held: true);
|
|
Common.ContractAssertMonitorStatus(ValueLock, held: false);
|
|
|
|
// Get the current message if there is one
|
|
TOutput currentMessage;
|
|
bool isValid;
|
|
lock (ValueLock)
|
|
{
|
|
currentMessage = _currentMessage;
|
|
isValid = _currentMessageIsValid;
|
|
}
|
|
|
|
// If there is no valid message yet, there is nothing to offer
|
|
if (!isValid) return;
|
|
|
|
// Offer it to the target.
|
|
// We must not increment the message ID here. We only do that when we populate _currentMessage, i.e. when we dequeue.
|
|
bool useCloning = _cloningFunction != null;
|
|
DataflowMessageStatus result = target.OfferMessage(new DataflowMessageHeader(_nextMessageId), currentMessage, _owningSource, consumeToAccept: useCloning);
|
|
|
|
// If accepted and the target was linked as "unlinkAfterOne", remove it
|
|
if (result == DataflowMessageStatus.Accepted)
|
|
{
|
|
if (!useCloning)
|
|
{
|
|
// If accepted and the target was linked as "once", mark it for removal.
|
|
// If we were forcing consumption, this removal would have already
|
|
// happened in ConsumeMessage.
|
|
_targetRegistry.Remove(target, onlyIfReachedMaxMessages: true);
|
|
}
|
|
}
|
|
// If declined permanently, remove it
|
|
else if (result == DataflowMessageStatus.DecliningPermanently)
|
|
{
|
|
_targetRegistry.Remove(target);
|
|
}
|
|
else Debug.Assert(result != DataflowMessageStatus.NotAvailable, "Messages from a Broadcast should never be missed.");
|
|
}
|
|
|
|
/// <summary>Offers messages to targets.</summary>
|
|
private bool OfferToTargets()
|
|
{
|
|
Common.ContractAssertMonitorStatus(OutgoingLock, held: true);
|
|
Common.ContractAssertMonitorStatus(ValueLock, held: false);
|
|
|
|
DataflowMessageHeader header = default(DataflowMessageHeader);
|
|
TOutput message = default(TOutput);
|
|
int numDequeuedMessages = 0;
|
|
lock (ValueLock)
|
|
{
|
|
// If there's a reservation or there aren't any more messages,
|
|
// there's nothing for us to do. If there's no reservation
|
|
// and a message is available, dequeue the next one and store it
|
|
// as the new current. If we're now at 0 message, disable further
|
|
// propagation until more messages arrive.
|
|
if (_nextMessageReservedFor == null && _messages.Count > 0)
|
|
{
|
|
// If there are no targets registered, we might as well empty out the broadcast,
|
|
// keeping just the last. Otherwise, it'll happen anyway, but much more expensively.
|
|
if (_targetRegistry.FirstTargetNode == null)
|
|
{
|
|
while (_messages.Count > 1)
|
|
{
|
|
_messages.Dequeue();
|
|
numDequeuedMessages++;
|
|
}
|
|
}
|
|
|
|
// Get the next message to offer
|
|
Debug.Assert(_messages.Count > 0, "There must be at least one message to dequeue.");
|
|
_currentMessage = message = _messages.Dequeue();
|
|
numDequeuedMessages++;
|
|
_currentMessageIsValid = true;
|
|
header = new DataflowMessageHeader(++_nextMessageId);
|
|
if (_messages.Count == 0) _enableOffering = false;
|
|
}
|
|
else
|
|
{
|
|
_enableOffering = false;
|
|
return false;
|
|
}
|
|
} // must not hold ValueLock when calling out to targets
|
|
|
|
// Offer the message
|
|
if (header.IsValid)
|
|
{
|
|
// Notify the owner block that our count has decreased
|
|
if (_itemsRemovedAction != null) _itemsRemovedAction(numDequeuedMessages);
|
|
|
|
// Offer it to each target, unless a soleTarget was provided, which case just offer it to that one.
|
|
TargetRegistry<TOutput>.LinkedTargetInfo cur = _targetRegistry.FirstTargetNode;
|
|
while (cur != null)
|
|
{
|
|
// Note that during OfferMessage, a target may call ConsumeMessage, which may unlink the target
|
|
// if the target is registered as "once". Doing so will remove the target from the targets list.
|
|
// As such, we avoid using an enumerator over _targetRegistry and instead walk from back to front,
|
|
// so that if an element is removed, it won't affect the rest of our walk.
|
|
TargetRegistry<TOutput>.LinkedTargetInfo next = cur.Next;
|
|
ITargetBlock<TOutput> target = cur.Target;
|
|
OfferMessageToTarget(header, message, target);
|
|
cur = next;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// <summary>Offers the specified message to the specified target.</summary>
|
|
/// <param name="header">The header of the message to offer.</param>
|
|
/// <param name="message">The message to offer.</param>
|
|
/// <param name="target">The target to which the message should be offered.</param>
|
|
/// <remarks>
|
|
/// This will remove the target from the target registry if the result of the propagation demands it.
|
|
/// </remarks>
|
|
private void OfferMessageToTarget(DataflowMessageHeader header, TOutput message, ITargetBlock<TOutput> target)
|
|
{
|
|
Common.ContractAssertMonitorStatus(OutgoingLock, held: true);
|
|
Common.ContractAssertMonitorStatus(ValueLock, held: false);
|
|
|
|
// Offer the message. If there's a cloning function, we force the target to
|
|
// come back to us to consume the message, allowing us the opportunity to run
|
|
// the cloning function once we know they want the data. If there is no cloning
|
|
// function, there's no reason for them to call back here.
|
|
bool useCloning = _cloningFunction != null;
|
|
switch (target.OfferMessage(header, message, _owningSource, consumeToAccept: useCloning))
|
|
{
|
|
case DataflowMessageStatus.Accepted:
|
|
if (!useCloning)
|
|
{
|
|
// If accepted and the target was linked as "once", mark it for removal.
|
|
// If we were forcing consumption, this removal would have already
|
|
// happened in ConsumeMessage.
|
|
_targetRegistry.Remove(target, onlyIfReachedMaxMessages: true);
|
|
}
|
|
break;
|
|
|
|
case DataflowMessageStatus.DecliningPermanently:
|
|
// If declined permanently, mark the target for removal
|
|
_targetRegistry.Remove(target);
|
|
break;
|
|
|
|
case DataflowMessageStatus.NotAvailable:
|
|
Debug.Assert(false, "Messages from a Broadcast should never be missed.");
|
|
break;
|
|
// No action required for Postponed or Declined
|
|
}
|
|
}
|
|
|
|
/// <summary>Called when we want to enable asynchronously offering message to targets.</summary>
|
|
/// <param name="isReplacementReplica">Whether this call is the continuation of a previous message loop.</param>
|
|
private void OfferAsyncIfNecessary(bool isReplacementReplica = false)
|
|
{
|
|
Common.ContractAssertMonitorStatus(ValueLock, held: true);
|
|
// This method must not take the OutgoingLock.
|
|
|
|
bool currentlyProcessing = _taskForOutputProcessing != null;
|
|
bool processingToDo = _enableOffering && _messages.Count > 0;
|
|
|
|
// If there's any work to be done...
|
|
if (!currentlyProcessing && processingToDo && !CanceledOrFaulted)
|
|
{
|
|
// Create task and store into _taskForOutputProcessing prior to scheduling the task
|
|
// so that _taskForOutputProcessing will be visibly set in the task loop.
|
|
_taskForOutputProcessing = new Task(thisSourceCore => ((BroadcastingSourceCore<TOutput>)thisSourceCore).OfferMessagesLoopCore(), this,
|
|
Common.GetCreationOptionsForTask(isReplacementReplica));
|
|
|
|
#if FEATURE_TRACING
|
|
DataflowEtwProvider etwLog = DataflowEtwProvider.Log;
|
|
if (etwLog.IsEnabled())
|
|
{
|
|
etwLog.TaskLaunchedForMessageHandling(
|
|
_owningSource, _taskForOutputProcessing, DataflowEtwProvider.TaskLaunchedReason.OfferingOutputMessages, _messages.Count);
|
|
}
|
|
#endif
|
|
|
|
// Start the task handling scheduling exceptions
|
|
Exception exception = Common.StartTaskSafe(_taskForOutputProcessing, _dataflowBlockOptions.TaskScheduler);
|
|
if (exception != null)
|
|
{
|
|
// First, log the exception while the processing state is dirty which is preventing the block from completing.
|
|
// Then revert the proactive processing state changes.
|
|
// And last, try to complete the block.
|
|
AddException(exception);
|
|
_decliningPermanently = true;
|
|
_taskForOutputProcessing = null;
|
|
|
|
// Get out from under currently held locks - ValueLock is taken, but OutgoingLock may not be.
|
|
// Re-take the locks on a separate thread.
|
|
Task.Factory.StartNew(state =>
|
|
{
|
|
var thisSourceCore = (BroadcastingSourceCore<TOutput>)state;
|
|
lock (thisSourceCore.OutgoingLock)
|
|
{
|
|
lock (thisSourceCore.ValueLock)
|
|
{
|
|
thisSourceCore.CompleteBlockIfPossible();
|
|
}
|
|
}
|
|
}, this, CancellationToken.None, Common.GetCreationOptionsForTask(), TaskScheduler.Default);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// <summary>Task body used to process messages.</summary>
|
|
[SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
|
|
private void OfferMessagesLoopCore()
|
|
{
|
|
try
|
|
{
|
|
int maxMessagesPerTask = _dataflowBlockOptions.ActualMaxMessagesPerTask;
|
|
lock (OutgoingLock)
|
|
{
|
|
// Offer as many messages as we can
|
|
for (int counter = 0;
|
|
counter < maxMessagesPerTask && !CanceledOrFaulted;
|
|
counter++)
|
|
{
|
|
if (!OfferToTargets()) break;
|
|
}
|
|
}
|
|
}
|
|
catch (Exception exception)
|
|
{
|
|
_owningSource.CompleteCore(exception, storeExceptionEvenIfAlreadyCompleting: true);
|
|
}
|
|
finally
|
|
{
|
|
lock (OutgoingLock)
|
|
{
|
|
lock (ValueLock)
|
|
{
|
|
// We're no longer processing, so null out the processing task
|
|
_taskForOutputProcessing = null;
|
|
|
|
// However, we may have given up early because we hit our own configured
|
|
// processing limits rather than because we ran out of work to do. If that's
|
|
// the case, make sure we spin up another task to keep going.
|
|
OfferAsyncIfNecessary(isReplacementReplica: true);
|
|
|
|
// If, however, we stopped because we ran out of work to do and we
|
|
// know we'll never get more, then complete.
|
|
CompleteBlockIfPossible();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// <summary>Completes the block's processing if there's nothing left to do and never will be.</summary>
|
|
private void CompleteBlockIfPossible()
|
|
{
|
|
Common.ContractAssertMonitorStatus(OutgoingLock, held: true);
|
|
Common.ContractAssertMonitorStatus(ValueLock, held: true);
|
|
|
|
if (!_completionReserved)
|
|
{
|
|
bool currentlyProcessing = _taskForOutputProcessing != null;
|
|
bool noMoreMessages = _decliningPermanently && _messages.Count == 0;
|
|
|
|
// Are we done forever?
|
|
bool complete = !currentlyProcessing && (noMoreMessages || CanceledOrFaulted);
|
|
if (complete)
|
|
{
|
|
CompleteBlockIfPossible_Slow();
|
|
}
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Slow path for CompleteBlockIfPossible.
|
|
/// Separating out the slow path into its own method makes it more likely that the fast path method will get inlined.
|
|
/// </summary>
|
|
private void CompleteBlockIfPossible_Slow()
|
|
{
|
|
Contract.Requires(_taskForOutputProcessing == null, "There must be no processing tasks.");
|
|
Contract.Requires(
|
|
(_decliningPermanently && _messages.Count == 0) || CanceledOrFaulted,
|
|
"There must be no more messages or the block must be canceled or faulted.");
|
|
|
|
_completionReserved = true;
|
|
|
|
// Run asynchronously to get out of the currently held locks
|
|
Task.Factory.StartNew(thisSourceCore => ((BroadcastingSourceCore<TOutput>)thisSourceCore).CompleteBlockOncePossible(),
|
|
this, CancellationToken.None, Common.GetCreationOptionsForTask(), TaskScheduler.Default);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Completes the block. This must only be called once, and only once all of the completion conditions are met.
|
|
/// As such, it must only be called from CompleteBlockIfPossible.
|
|
/// </summary>
|
|
private void CompleteBlockOncePossible()
|
|
{
|
|
TargetRegistry<TOutput>.LinkedTargetInfo linkedTargets;
|
|
List<Exception> exceptions;
|
|
|
|
// Clear out the target registry and buffers to help avoid memory leaks.
|
|
// We do not clear _currentMessage, which should remain as that message forever.
|
|
lock (OutgoingLock)
|
|
{
|
|
// Save the linked list of targets so that it could be traversed later to propagate completion
|
|
linkedTargets = _targetRegistry.ClearEntryPoints();
|
|
lock (ValueLock)
|
|
{
|
|
_messages.Clear();
|
|
|
|
// Save a local reference to the exceptions list and null out the field,
|
|
// so that if the target side tries to add an exception this late,
|
|
// it will go to a separate list (that will be ignored.)
|
|
exceptions = _exceptions;
|
|
_exceptions = null;
|
|
}
|
|
}
|
|
|
|
// If it's due to an exception, finish in a faulted state
|
|
if (exceptions != null)
|
|
{
|
|
_completionTask.TrySetException(exceptions);
|
|
}
|
|
// It's due to cancellation, finish in a canceled state
|
|
else if (_dataflowBlockOptions.CancellationToken.IsCancellationRequested)
|
|
{
|
|
_completionTask.TrySetCanceled();
|
|
}
|
|
// Otherwise, finish in a successful state.
|
|
else
|
|
{
|
|
_completionTask.TrySetResult(default(VoidResult));
|
|
}
|
|
|
|
// Now that the completion task is completed, we may propagate completion to the linked targets
|
|
_targetRegistry.PropagateCompletion(linkedTargets);
|
|
#if FEATURE_TRACING
|
|
DataflowEtwProvider etwLog = DataflowEtwProvider.Log;
|
|
if (etwLog.IsEnabled())
|
|
{
|
|
etwLog.DataflowBlockCompleted(_owningSource);
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="LinkTo"]/*' />
|
|
[SuppressMessage("Microsoft.Reliability", "CA2000:Dispose objects before losing scope")]
|
|
internal IDisposable LinkTo(ITargetBlock<TOutput> target, DataflowLinkOptions linkOptions)
|
|
{
|
|
// Validate arguments
|
|
if (target == null) throw new ArgumentNullException("target");
|
|
if (linkOptions == null) throw new ArgumentNullException("linkOptions");
|
|
Contract.EndContractBlock();
|
|
|
|
lock (OutgoingLock)
|
|
{
|
|
// If we've completed or completion has at least started, offer the message to this target,
|
|
// and propagate completion if that was requested.
|
|
// Then there's nothing more to be done.
|
|
if (_completionReserved)
|
|
{
|
|
OfferCurrentMessageToNewTarget(target);
|
|
if (linkOptions.PropagateCompletion) Common.PropagateCompletionOnceCompleted(_completionTask.Task, target);
|
|
return Disposables.Nop;
|
|
}
|
|
|
|
// Otherwise, add the target and then offer it the current
|
|
// message. We do this in this order because offering may
|
|
// cause the target to be removed if it's unlinkAfterOne,
|
|
// and in the reverse order we would end up adding the target
|
|
// after it was "removed".
|
|
_targetRegistry.Add(ref target, linkOptions);
|
|
OfferCurrentMessageToNewTarget(target);
|
|
return Common.CreateUnlinker(OutgoingLock, _targetRegistry, target);
|
|
}
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ConsumeMessage"]/*' />
|
|
internal TOutput ConsumeMessage(DataflowMessageHeader messageHeader, ITargetBlock<TOutput> target, out Boolean messageConsumed)
|
|
{
|
|
// Validate arguments
|
|
if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, "messageHeader");
|
|
if (target == null) throw new ArgumentNullException("target");
|
|
Contract.EndContractBlock();
|
|
|
|
TOutput valueToClone;
|
|
lock (OutgoingLock) // We may currently be calling out under this lock to the target; requires it to be reentrant
|
|
{
|
|
lock (ValueLock)
|
|
{
|
|
// If this isn't the next message to be served up, bail
|
|
if (messageHeader.Id != _nextMessageId)
|
|
{
|
|
messageConsumed = false;
|
|
return default(TOutput);
|
|
}
|
|
|
|
// If the caller has the reservation, release the reservation.
|
|
// We still allow others to take the message if there's a reservation.
|
|
if (_nextMessageReservedFor == target)
|
|
{
|
|
_nextMessageReservedFor = null;
|
|
_enableOffering = true;
|
|
}
|
|
_targetRegistry.Remove(target, onlyIfReachedMaxMessages: true);
|
|
|
|
OfferAsyncIfNecessary();
|
|
CompleteBlockIfPossible();
|
|
|
|
// Return a clone of the consumed message.
|
|
valueToClone = _currentMessage;
|
|
}
|
|
}
|
|
|
|
messageConsumed = true;
|
|
return CloneItem(valueToClone);
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ReserveMessage"]/*' />
|
|
internal Boolean ReserveMessage(DataflowMessageHeader messageHeader, ITargetBlock<TOutput> target)
|
|
{
|
|
// Validate arguments
|
|
if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, "messageHeader");
|
|
if (target == null) throw new ArgumentNullException("target");
|
|
Contract.EndContractBlock();
|
|
|
|
lock (OutgoingLock)
|
|
{
|
|
// If no one currently holds a reservation...
|
|
if (_nextMessageReservedFor == null)
|
|
{
|
|
lock (ValueLock)
|
|
{
|
|
// ...and the requested message is next in line, allow it
|
|
if (messageHeader.Id == _nextMessageId)
|
|
{
|
|
_nextMessageReservedFor = target;
|
|
_enableOffering = false;
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Sources/Member[@name="ReleaseReservation"]/*' />
|
|
internal void ReleaseReservation(DataflowMessageHeader messageHeader, ITargetBlock<TOutput> target)
|
|
{
|
|
// Validate arguments
|
|
if (!messageHeader.IsValid) throw new ArgumentException(SR.Argument_InvalidMessageHeader, "messageHeader");
|
|
if (target == null) throw new ArgumentNullException("target");
|
|
Contract.EndContractBlock();
|
|
|
|
lock (OutgoingLock)
|
|
{
|
|
// If someone else holds the reservation, bail.
|
|
if (_nextMessageReservedFor != target) throw new InvalidOperationException(SR.InvalidOperation_MessageNotReservedByTarget);
|
|
|
|
TOutput messageToReoffer;
|
|
lock (ValueLock)
|
|
{
|
|
// If this is not the message at the head of the queue, bail
|
|
if (messageHeader.Id != _nextMessageId) throw new InvalidOperationException(SR.InvalidOperation_MessageNotReservedByTarget);
|
|
|
|
// Otherwise, release the reservation, and reoffer the message to all targets.
|
|
_nextMessageReservedFor = null;
|
|
_enableOffering = true;
|
|
messageToReoffer = _currentMessage;
|
|
OfferAsyncIfNecessary();
|
|
}
|
|
|
|
// We need to explicitly reoffer this message to the releaser,
|
|
// as otherwise if the target has join behavior it could end up waiting for an offer from
|
|
// this broadcast forever, even though data is in fact available. We could only
|
|
// do this if _messages.Count == 0, as if it's > 0 the message will get overwritten
|
|
// as part of the asynchronous offering, but for consistency we should always reoffer
|
|
// the current message.
|
|
OfferMessageToTarget(messageHeader, messageToReoffer, target);
|
|
}
|
|
}
|
|
|
|
/// <summary>Gets whether the source has had cancellation requested or an exception has occurred.</summary>
|
|
private bool CanceledOrFaulted
|
|
{
|
|
get
|
|
{
|
|
// Cancellation is honored as soon as the CancellationToken has been signaled.
|
|
// Faulting is honored after an exception has been encountered and the owning block
|
|
// has invoked Complete on us.
|
|
return _dataflowBlockOptions.CancellationToken.IsCancellationRequested ||
|
|
(Volatile.Read(ref _exceptions) != null && _decliningPermanently);
|
|
}
|
|
}
|
|
|
|
/// <summary>Adds an individual exceptionto this source.</summary>
|
|
/// <param name="exception">The exception to add</param>
|
|
internal void AddException(Exception exception)
|
|
{
|
|
Contract.Requires(exception != null, "An exception to add is required.");
|
|
Contract.Requires(!Completion.IsCompleted || Completion.IsFaulted, "The block must either not be completed or be faulted if we're still storing exceptions.");
|
|
lock (ValueLock)
|
|
{
|
|
Common.AddException(ref _exceptions, exception);
|
|
}
|
|
}
|
|
|
|
/// <summary>Adds exceptions to this source.</summary>
|
|
/// <param name="exceptions">The exceptions to add</param>
|
|
internal void AddExceptions(List<Exception> exceptions)
|
|
{
|
|
Contract.Requires(exceptions != null, "A list of exceptions to add is required.");
|
|
Contract.Requires(!Completion.IsCompleted || Completion.IsFaulted, "The block must either not be completed or be faulted if we're still storing exceptions.");
|
|
lock (ValueLock)
|
|
{
|
|
foreach (Exception exception in exceptions)
|
|
{
|
|
Common.AddException(ref _exceptions, exception);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// <include file='XmlDocs/CommonXmlDocComments.xml' path='CommonXmlDocComments/Blocks/Member[@name="Completion"]/*' />
|
|
internal Task Completion { get { return _completionTask.Task; } }
|
|
|
|
/// <summary>Gets the DataflowBlockOptions used to configure this block.</summary>
|
|
internal DataflowBlockOptions DataflowBlockOptions { get { return _dataflowBlockOptions; } }
|
|
|
|
/// <summary>Gets the object to display in the debugger display attribute.</summary>
|
|
[SuppressMessage("Microsoft.Globalization", "CA1305:SpecifyIFormatProvider")]
|
|
private object DebuggerDisplayContent
|
|
{
|
|
get
|
|
{
|
|
var displaySource = _owningSource as IDebuggerDisplay;
|
|
return string.Format("Block=\"{0}\"",
|
|
displaySource != null ? displaySource.Content : _owningSource);
|
|
}
|
|
}
|
|
|
|
/// <summary>Gets information about this helper to be used for display in a debugger.</summary>
|
|
/// <returns>Debugging information about this source core.</returns>
|
|
internal DebuggingInformation GetDebuggingInformation() { return new DebuggingInformation(this); }
|
|
|
|
/// <summary>Provides debugging information about the source core.</summary>
|
|
internal sealed class DebuggingInformation
|
|
{
|
|
/// <summary>The source being viewed.</summary>
|
|
private BroadcastingSourceCore<TOutput> _source;
|
|
|
|
/// <summary>Initializes the type proxy.</summary>
|
|
/// <param name="source">The source being viewed.</param>
|
|
public DebuggingInformation(BroadcastingSourceCore<TOutput> source) { _source = source; }
|
|
|
|
/// <summary>Gets whether the source contains a current message.</summary>
|
|
public bool HasValue { get { return _source._currentMessageIsValid; } }
|
|
/// <summary>Gets the value of the source's current message.</summary>
|
|
public TOutput Value { get { return _source._currentMessage; } }
|
|
/// <summary>Gets the number of messages waiting to be made current.</summary>
|
|
public int InputCount { get { return _source._messages.Count; } }
|
|
/// <summary>Gets the messages available for receiving.</summary>
|
|
public IEnumerable<TOutput> InputQueue { get { return _source._messages.ToList(); } }
|
|
/// <summary>Gets the task being used for output processing.</summary>
|
|
public Task TaskForOutputProcessing { get { return _source._taskForOutputProcessing; } }
|
|
|
|
/// <summary>Gets the DataflowBlockOptions used to configure this block.</summary>
|
|
public DataflowBlockOptions DataflowBlockOptions { get { return _source._dataflowBlockOptions; } }
|
|
/// <summary>Gets whether the block is declining further messages.</summary>
|
|
public bool IsDecliningPermanently { get { return _source._decliningPermanently; } }
|
|
/// <summary>Gets whether the block is completed.</summary>
|
|
public bool IsCompleted { get { return _source.Completion.IsCompleted; } }
|
|
|
|
/// <summary>Gets the set of all targets linked from this block.</summary>
|
|
public TargetRegistry<TOutput> LinkedTargets { get { return _source._targetRegistry; } }
|
|
/// <summary>Gets the target that holds a reservation on the next message, if any.</summary>
|
|
public ITargetBlock<TOutput> NextMessageReservedFor { get { return _source._nextMessageReservedFor; } }
|
|
}
|
|
}
|
|
}
|
|
}
|