Github user synhershko commented on a diff in the pull request:
https://github.com/apache/lucenenet/pull/171#discussion_r63999838
--- Diff: src/Lucene.Net.Core/Index/TaskMergeScheduler.cs ---
@@ -0,0 +1,664 @@
+/*
+ * 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 Lucene.Net.Support;
+using Lucene.Net.Util;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Directory = Lucene.Net.Store.Directory;
+
+namespace Lucene.Net.Index
+{
+ /// <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>
+ ///
+ /// LUCENENET specific
+ /// </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();
+ }
+ }
+ }
+
+ /// <summary>
+ /// Returns true if verbosing is enabled. this method is usually
used in
+ /// conjunction with <seealso cref="#message(String)"/>, like that:
+ ///
+ /// <pre class="prettyprint">
+ /// if (verbose()) {
+ /// message("your message");
+ /// }
+ /// </pre>
+ /// </summary>
+ protected internal bool Verbose()
+ {
+ return _writer != null &&
_writer.infoStream.IsEnabled(COMPONENT_NAME);
--- End diff --
cache return value (or calculate on init / assignment of `_writer`)
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