| | | 1 | | using CounterpointCollective.Dataflow.Encapsulation; |
| | | 2 | | using CounterpointCollective.Dataflow.Internal; |
| | | 3 | | using System.Threading.Tasks.Dataflow; |
| | | 4 | | namespace CounterpointCollective.Dataflow |
| | | 5 | | { |
| | | 6 | | |
| | | 7 | | /// <summary> |
| | | 8 | | /// Hooks for controlling and observing admission into a block. |
| | | 9 | | /// </summary> |
| | | 10 | | /// <remarks> |
| | | 11 | | /// All hook callbacks are invoked serially: at most one hook method |
| | | 12 | | /// is executing at any given time. No hook is ever called concurrently |
| | | 13 | | /// with itself or with another hook. |
| | | 14 | | /// </remarks> |
| | 0 | 15 | | public record AdmissionGateHooks |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// When this returns true, always either Entering or FailingToEnter will be called afterwards. |
| | | 19 | | /// </summary> |
| | 2791995 | 20 | | public Func<bool>? MayTryToEnter { get; set; } |
| | | 21 | | |
| | | 22 | | /// <summary> |
| | | 23 | | /// A message is successfully entering the block. |
| | | 24 | | /// Allows you to commit state changes accordingly. |
| | | 25 | | /// </summary> |
| | 1128302 | 26 | | public Action? Entering { get; set; } |
| | | 27 | | |
| | | 28 | | /// <summary> |
| | | 29 | | /// Called when a message has successfully entered the block, and after all state changes. |
| | | 30 | | /// </summary> |
| | 1128274 | 31 | | public Action? HasEntered { get; set; } |
| | | 32 | | |
| | | 33 | | /// <summary> |
| | | 34 | | /// Although a message was allowed to enter, it failed to do so (e.g. because it could not be consumed from the |
| | | 35 | | /// Allows you to roll back any state changes made in MayTryToEnter. |
| | | 36 | | /// </summary> |
| | 551 | 37 | | public Action? FailingToEnter { get; set; } = () => { }; |
| | | 38 | | } |
| | | 39 | | |
| | | 40 | | /// <summary> |
| | | 41 | | /// A dataflow block that conditionally admits messages into an inner target block based on user-defined <see cref=" |
| | | 42 | | /// |
| | | 43 | | /// <para>Use this block when you want to control when/which messages are allowed to enter the block |
| | | 44 | | /// dynamically, e.g. by throttling rules.</para> |
| | | 45 | | /// |
| | | 46 | | /// <para>Features include:</para> |
| | | 47 | | /// <list type="bullet"> |
| | | 48 | | /// <item><description>Hooks to decide whether a message may enter, when it enters, and if entry fails.</descripti |
| | | 49 | | /// <item><description>Automatic postponement of messages that are not currently allowed to enter.</description></ |
| | | 50 | | /// <item><description>Processing of postponed messages when state changes allow them to be admitted.</description |
| | | 51 | | /// </list> |
| | | 52 | | /// </summary> |
| | | 53 | | public class AdmissionGateBlock<T> : AbstractEncapsulatedTargetBlock<T> |
| | | 54 | | { |
| | | 55 | | /// <exclude/> |
| | | 56 | | protected override ITargetBlock<T> TargetSide { get; } |
| | | 57 | | /// <exclude/> |
| | | 58 | | protected override IDataflowBlock CompletionSide => this; |
| | | 59 | | /// <exclude/> |
| | | 60 | | public override Task Completion { get; } |
| | | 61 | | private readonly UnboundedTargetBlock<T> _inner; |
| | | 62 | | |
| | | 63 | | private AdmissionGateHooks hooks; |
| | | 64 | | private readonly PostponedMessages<AdmissionGateBlock<T>, T> _postponedMessages; |
| | | 65 | | private readonly PostponedMessagesManager<AdmissionGateBlock<T>, T> _postponedMessagesManager; |
| | | 66 | | |
| | | 67 | | private readonly TaskCompletionSource _tcsCompletionRequest = new(); |
| | | 68 | | |
| | | 69 | | /// <summary> |
| | | 70 | | /// Whether a completion request has been made. |
| | | 71 | | /// </summary> |
| | | 72 | | public bool IsCompletionRequested => _tcsCompletionRequest.Task.IsCompleted; |
| | | 73 | | |
| | | 74 | | /// <summary> |
| | | 75 | | /// Whether a completion request has been made and there are no more buffered messages waiting to enter. |
| | | 76 | | /// </summary> |
| | | 77 | | public Task InputCompletion => _inner.InputCompletion; |
| | | 78 | | |
| | | 79 | | public void ConfigureHooks(AdmissionGateHooks h) |
| | | 80 | | { |
| | | 81 | | lock(_postponedMessagesManager.IncomingLock) |
| | | 82 | | { |
| | | 83 | | hooks = Clone(h); |
| | | 84 | | _postponedMessagesManager.ProcessPostponedMessages(); |
| | | 85 | | } |
| | | 86 | | } |
| | | 87 | | |
| | | 88 | | public AdmissionGateBlock(ITargetBlock<T> buffer, AdmissionGateHooks h) |
| | | 89 | | { |
| | | 90 | | TargetSide = new Target(this); |
| | | 91 | | hooks = Clone(h); |
| | | 92 | | |
| | | 93 | | _inner = new UnboundedTargetBlock<T>(buffer); |
| | | 94 | | |
| | | 95 | | _postponedMessages = new(this); |
| | | 96 | | _postponedMessagesManager = new( |
| | | 97 | | (out PostponedMessage<AdmissionGateBlock<T>, T> p) => |
| | | 98 | | { |
| | | 99 | | if ( |
| | | 100 | | !_postponedMessages.IsEmpty |
| | | 101 | | && hooks.MayTryToEnter != null |
| | | 102 | | && hooks.MayTryToEnter() |
| | | 103 | | && _postponedMessages.TryDequeuePostponed(out p)) |
| | | 104 | | { |
| | | 105 | | return true; |
| | | 106 | | } |
| | | 107 | | else |
| | | 108 | | { |
| | | 109 | | p = default; |
| | | 110 | | return false; |
| | | 111 | | } |
| | | 112 | | } |
| | | 113 | | ); |
| | | 114 | | |
| | | 115 | | |
| | | 116 | | _postponedMessagesManager.Consume = |
| | | 117 | | (in PostponedMessage<AdmissionGateBlock<T>, T> postponedMessage) => |
| | | 118 | | { |
| | | 119 | | var succ = postponedMessage.Consume(out var msg); |
| | | 120 | | { |
| | | 121 | | //Lock to prevent hooks from being updated concurrently while we are invoking them. |
| | | 122 | | lock (_postponedMessagesManager.IncomingLock) |
| | | 123 | | { |
| | | 124 | | if (succ) |
| | | 125 | | { |
| | | 126 | | hooks.Entering?.Invoke(); |
| | | 127 | | _inner.PostAsserted(msg!); |
| | | 128 | | hooks.HasEntered?.Invoke(); |
| | | 129 | | } |
| | | 130 | | else |
| | | 131 | | { |
| | | 132 | | hooks.FailingToEnter?.Invoke(); |
| | | 133 | | } |
| | | 134 | | } |
| | | 135 | | } |
| | | 136 | | }; |
| | | 137 | | |
| | | 138 | | var tcs = new TaskCompletionSource(); |
| | | 139 | | Completion = tcs.Task; |
| | | 140 | | Task.Run(async () => |
| | | 141 | | { |
| | | 142 | | var t1 = await Task.WhenAny(_tcsCompletionRequest.Task); |
| | | 143 | | var t2 = await Task.WhenAny(_postponedMessagesManager.ShutdownAsync()); |
| | | 144 | | _ = t1.PropagateCompletion(_inner); |
| | | 145 | | var t3 = await Task.WhenAny(_inner.Completion); |
| | | 146 | | await Task.WhenAll(t3).PropagateCompletionAsync(tcs); |
| | | 147 | | }, CancellationToken.None); |
| | | 148 | | |
| | | 149 | | _inner.Completion.ContinueWith(_ => |
| | | 150 | | { |
| | | 151 | | if (!IsCompletionRequested) |
| | | 152 | | { |
| | | 153 | | Fault(new InvalidOperationException("Source side completed unexpectedly.")); |
| | | 154 | | } |
| | | 155 | | }); |
| | | 156 | | } |
| | | 157 | | |
| | | 158 | | /// <summary> |
| | | 159 | | /// Processes any messages that have been postponed and are now eligible for handling. |
| | | 160 | | /// |
| | | 161 | | /// You typically may want to call this method after changing the state that is checked in the MayTryToEnter hoo |
| | | 162 | | /// transitioned to allow messages to enter. |
| | | 163 | | /// </summary> |
| | | 164 | | public void ProcessPostponedMessages() |
| | | 165 | | { |
| | | 166 | | if (hooks.MayTryToEnter != null) |
| | | 167 | | { |
| | | 168 | | _postponedMessagesManager.ProcessPostponedMessages(); |
| | | 169 | | } else |
| | | 170 | | { |
| | | 171 | | //nothing to do because we always allow every message anyway. |
| | | 172 | | } |
| | | 173 | | } |
| | | 174 | | |
| | | 175 | | /// <exclude/> |
| | | 176 | | |
| | | 177 | | public override void Fault(Exception exception) => _tcsCompletionRequest.TrySetException(exception); |
| | | 178 | | |
| | | 179 | | /// <exclude/> |
| | | 180 | | public override void Complete() => _tcsCompletionRequest.TrySetResult(); |
| | | 181 | | |
| | | 182 | | private class Target(AdmissionGateBlock<T> outer) : ITargetBlock<T> |
| | | 183 | | { |
| | | 184 | | public Task Completion => outer.Completion; |
| | | 185 | | public void Complete() => outer.Complete(); |
| | | 186 | | public void Fault(Exception exception) => outer.Fault(exception); |
| | | 187 | | public DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader, T messageValue, ISourceBlock< |
| | | 188 | | { |
| | | 189 | | if (outer.IsCompletionRequested) |
| | | 190 | | { |
| | | 191 | | return DataflowMessageStatus.DecliningPermanently; |
| | | 192 | | } |
| | | 193 | | if (consumeToAccept && source == null) |
| | | 194 | | { |
| | | 195 | | return DataflowMessageStatus.Declined; //not allowed in protocol |
| | | 196 | | } |
| | | 197 | | |
| | | 198 | | lock (outer._postponedMessagesManager.IncomingLock) |
| | | 199 | | { |
| | | 200 | | var allow = |
| | | 201 | | !outer._postponedMessagesManager.IsRunningPostponedMessages && |
| | | 202 | | (outer.hooks.MayTryToEnter == null || outer.hooks.MayTryToEnter()); |
| | | 203 | | |
| | | 204 | | if (!allow) |
| | | 205 | | { |
| | | 206 | | if (source != null) |
| | | 207 | | { |
| | | 208 | | outer._postponedMessages.Postpone(source, messageHeader); |
| | | 209 | | return DataflowMessageStatus.Postponed; |
| | | 210 | | } |
| | | 211 | | else |
| | | 212 | | { |
| | | 213 | | return DataflowMessageStatus.Declined; |
| | | 214 | | } |
| | | 215 | | } |
| | | 216 | | else if (consumeToAccept) |
| | | 217 | | { |
| | | 218 | | var newValue = source!.ConsumeMessage(messageHeader, this, out var messageConsumed); |
| | | 219 | | if (!messageConsumed) |
| | | 220 | | { |
| | | 221 | | outer.hooks.FailingToEnter?.Invoke(); |
| | | 222 | | return DataflowMessageStatus.NotAvailable; |
| | | 223 | | } |
| | | 224 | | else |
| | | 225 | | { |
| | | 226 | | messageValue = newValue!; |
| | | 227 | | } |
| | | 228 | | } |
| | | 229 | | outer.hooks.Entering?.Invoke(); |
| | | 230 | | outer._inner.PostAsserted(messageValue); |
| | | 231 | | outer.hooks.HasEntered?.Invoke(); |
| | | 232 | | return DataflowMessageStatus.Accepted; |
| | | 233 | | } |
| | | 234 | | } |
| | | 235 | | } |
| | | 236 | | |
| | | 237 | | private static AdmissionGateHooks Clone(AdmissionGateHooks hooks) => new() |
| | | 238 | | { |
| | | 239 | | Entering = hooks.Entering, |
| | | 240 | | FailingToEnter = hooks.FailingToEnter, |
| | | 241 | | MayTryToEnter = hooks.MayTryToEnter, |
| | | 242 | | HasEntered = hooks.HasEntered, |
| | | 243 | | }; |
| | | 244 | | } |
| | | 245 | | } |