Github user synhershko commented on a diff in the pull request: https://github.com/apache/lucenenet/pull/171#discussion_r62451346 --- Diff: src/Lucene.Net.Core/Index/TaskMergeScheduler.cs --- @@ -0,0 +1,665 @@ +using System; +using System.Collections.Generic; +using System.Text; +using System.Threading; + +namespace Lucene.Net.Index +{ + using Lucene.Net.Support; + using System.Linq; + using System.Threading.Tasks; + using Util; + + /* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + + using Directory = Lucene.Net.Store.Directory; + + /// <summary> + /// A <seealso cref="MergeScheduler"/> that runs each merge using + /// Tasks on the default TaskScheduler. + /// + /// <p>If more than <seealso cref="#GetMaxMergeCount"/> merges are + /// requested then this class will forcefully throttle the + /// incoming threads by pausing until one more more merges + /// complete.</p> + /// </summary> + public class TaskMergeScheduler : MergeScheduler, IConcurrentMergeScheduler + { + public const string COMPONENT_NAME = "CMS"; + + private readonly TaskScheduler _taskScheduler = TaskScheduler.Default; + private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim(); + private readonly ManualResetEventSlim _manualResetEvent = new ManualResetEventSlim(); + /// <summary> + /// List of currently active <seealso cref="MergeThread"/>s.</summary> + private readonly IList<MergeThread> _mergeThreads = new List<MergeThread>(); + + /// <summary> + /// How many <seealso cref="MergeThread"/>s have kicked off (this is use + /// to name them). + /// </summary> + private int _mergeThreadCount; + + /// <summary> + /// <seealso cref="Directory"/> that holds the index. </summary> + private Directory _directory; + + /// <summary> + /// <seealso cref="IndexWriter"/> that owns this instance. + /// </summary> + private IndexWriter _writer; + + /// <summary> + /// Sole constructor, with all settings set to default + /// values. + /// </summary> + public TaskMergeScheduler() : base() + { + MaxThreadCount = _taskScheduler.MaximumConcurrencyLevel; + MaxMergeCount = _taskScheduler.MaximumConcurrencyLevel; + } + + /// <summary> + /// Sets the maximum number of merge threads and simultaneous merges allowed. + /// </summary> + /// <param name="maxMergeCount"> the max # simultaneous merges that are allowed. + /// If a merge is necessary yet we already have this many + /// threads running, the incoming thread (that is calling + /// add/updateDocument) will block until a merge thread + /// has completed. Note that we will only run the + /// smallest <code>maxThreadCount</code> merges at a time. </param> + /// <param name="maxThreadCount"> the max # simultaneous merge threads that should + /// be running at once. this must be <= <code>maxMergeCount</code> </param> + public void SetMaxMergesAndThreads(int maxMergeCount, int maxThreadCount) + { + // This is handled by TaskScheduler.Default.MaximumConcurrencyLevel + } + + /// <summary> + /// Max number of merge threads allowed to be running at + /// once. When there are more merges then this, we + /// forcefully pause the larger ones, letting the smaller + /// ones run, up until maxMergeCount merges at which point + /// we forcefully pause incoming threads (that presumably + /// are the ones causing so much merging). + /// </summary> + /// <seealso cref= #setMaxMergesAndThreads(int, int) </seealso> + public int MaxThreadCount { get; private set; } + + /// <summary> + /// Max number of merges we accept before forcefully + /// throttling the incoming threads + /// </summary> + public int MaxMergeCount { get; private set; } + + /// <summary> + /// Return the priority that merge threads run at. This is always the same. + /// </summary> + public int MergeThreadPriority + { + get + { + return (int)ThreadPriority.Normal; + } + set + { + } + } + + /// <summary> + /// Called whenever the running merges have changed, to pause & unpause + /// threads. this method sorts the merge threads by their merge size in + /// descending order and then pauses/unpauses threads from first to last -- + /// that way, smaller merges are guaranteed to run before larger ones. + /// </summary> + private void UpdateMergeThreads() + { + foreach (var merge in _mergeThreads.ToArray()) + { + // Prune any dead threads + if (!merge.IsAlive) + { + _mergeThreads.Remove(merge); + merge.Dispose(); --- End diff -- yes, but wouldn't merge.Dispose() throw in some cases, if the same method is called concurrently by different threads? shouldn't you be checking if disposed before calling Dispose?
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