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From synhershko <...@git.apache.org>
Subject [GitHub] lucenenet pull request: Adding a MergeScheduler that uses Tasks
Date Tue, 24 May 2016 20:59:23 GMT
Github user synhershko commented on a diff in the pull request:

    https://github.com/apache/lucenenet/pull/171#discussion_r64472893
  
    --- 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 &lt;= <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(&quot;your message&quot;);
    +        /// }
    +        /// </pre>
    +        /// </summary>
    +        protected internal bool Verbose()
    +        {
    +            return _writer != null && _writer.infoStream.IsEnabled(COMPONENT_NAME);
    --- End diff --
    
    sounds legit


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