Class ConcurrentMergeScheduler

A MergeScheduler that runs each merge using a separate thread.

Specify the max number of threads that may run at once, and the maximum number of simultaneous merges with SetMaxMergesAndThreads(Int32, Int32).

If the number of merges exceeds the max number of threads then the largest merges are paused until one of the smaller merges completes.

If more than MaxMergeCount merges are requested then this class will forcefully throttle the incoming threads by pausing until one more more merges complete.

Inheritance

System.Object

MergeScheduler

ConcurrentMergeScheduler

Implements

IConcurrentMergeScheduler

IMergeScheduler

System.IDisposable

Inherited Members

MergeScheduler.Dispose()

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

Namespace: Lucene.Net.Index

Assembly: Lucene.Net.dll

Syntax

public class ConcurrentMergeScheduler : MergeScheduler, IConcurrentMergeScheduler, IMergeScheduler, IDisposable

Constructors

ConcurrentMergeScheduler()

Sole constructor, with all settings set to default values.

Declaration

public ConcurrentMergeScheduler()

Fields

compareByMergeDocCount

Sorts ConcurrentMergeScheduler.MergeThreads; larger merges come first.

Declaration

protected static readonly IComparer<ConcurrentMergeScheduler.MergeThread> compareByMergeDocCount

Field Value

Type	Description
System.Collections.Generic.IComparer<ConcurrentMergeScheduler.MergeThread>

DEFAULT_MAX_MERGE_COUNT

Default MaxMergeCount.

Declaration

public const int DEFAULT_MAX_MERGE_COUNT = 2

Field Value

Type	Description
System.Int32

DEFAULT_MAX_THREAD_COUNT

Default MaxThreadCount. We default to 1: tests on spinning-magnet drives showed slower indexing performance if more than one merge thread runs at once (though on an SSD it was faster)

Declaration

public const int DEFAULT_MAX_THREAD_COUNT = 1

Field Value

Type	Description
System.Int32

m_dir

Directory that holds the index.

Declaration

protected Directory m_dir

Field Value

Type	Description
Directory

m_mergeThreadCount

How many ConcurrentMergeScheduler.MergeThreads have kicked off (this is use to name them).

Declaration

protected int m_mergeThreadCount

Field Value

Type	Description
System.Int32

m_mergeThreads

List of currently active ConcurrentMergeScheduler.MergeThreads.

Declaration

protected IList<ConcurrentMergeScheduler.MergeThread> m_mergeThreads

Field Value

Type	Description
System.Collections.Generic.IList<ConcurrentMergeScheduler.MergeThread>

m_writer

IndexWriter that owns this instance.

Declaration

protected IndexWriter m_writer

Field Value

Type	Description
IndexWriter

Properties

IsVerbose

Returns true if verbosing is enabled. This method is usually used in conjunction with Message(String), like that:

if (IsVerbose) 
{
    Message("your message");
}

Declaration

protected virtual bool IsVerbose { get; }

Property Value

Type	Description
System.Boolean

MaxMergeCount

See SetMaxMergesAndThreads(Int32, Int32).

Declaration

public virtual int MaxMergeCount { get; }

Property Value

Type	Description
System.Int32

MaxThreadCount

Returns Lucene.Net.Index.ConcurrentMergeScheduler.maxThreadCount.

Declaration

public virtual int MaxThreadCount { get; }

Property Value

Type	Description
System.Int32

See Also

SetMaxMergesAndThreads(Int32, Int32)

MergeThreadCount

Returns the number of merge threads that are alive. Note that this number is <= m_mergeThreads size.

Declaration

protected virtual int MergeThreadCount { get; }

Property Value

Type	Description
System.Int32

MergeThreadPriority

Return the priority that merge threads run at. By default the priority is 1 plus the priority of (ie, slightly higher priority than) the first thread that calls merge.

Declaration

public virtual int MergeThreadPriority { get; }

Property Value

Type	Description
System.Int32

Methods

ClearSuppressExceptions()

Used for testing

Declaration

public virtual void ClearSuppressExceptions()

Clone()

Declaration

public override object Clone()

Returns

Type	Description
System.Object

Overrides

MergeScheduler.Clone()

Dispose(Boolean)

Declaration

protected override void Dispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing

Overrides

MergeScheduler.Dispose(Boolean)

DoMerge(MergePolicy.OneMerge)

Does the actual merge, by calling Merge(MergePolicy.OneMerge)

Declaration

protected virtual void DoMerge(MergePolicy.OneMerge merge)

Parameters

Type	Name	Description
MergePolicy.OneMerge	merge

GetMergeThread(IndexWriter, MergePolicy.OneMerge)

Create and return a new ConcurrentMergeScheduler.MergeThread

Declaration

protected virtual ConcurrentMergeScheduler.MergeThread GetMergeThread(IndexWriter writer, MergePolicy.OneMerge merge)

Parameters

Type	Name	Description
IndexWriter	writer
MergePolicy.OneMerge	merge

Returns

Type	Description
ConcurrentMergeScheduler.MergeThread

HandleMergeException(Exception)

Called when an exception is hit in a background merge thread

Declaration

protected virtual void HandleMergeException(Exception exc)

Parameters

Type	Name	Description
System.Exception	exc

Merge(IndexWriter, MergeTrigger, Boolean)

Declaration

public override void Merge(IndexWriter writer, MergeTrigger trigger, bool newMergesFound)

Parameters

Type	Name	Description
IndexWriter	writer
MergeTrigger	trigger
System.Boolean	newMergesFound

Overrides

MergeScheduler.Merge(IndexWriter, MergeTrigger, Boolean)

Message(String)

Outputs the given message - this method assumes IsVerbose was called and returned true.

Declaration

protected virtual void Message(string message)

Parameters

Type	Name	Description
System.String	message

SetMaxMergesAndThreads(Int32, Int32)

Sets the maximum number of merge threads and simultaneous merges allowed.

Declaration

public virtual void SetMaxMergesAndThreads(int maxMergeCount, int maxThreadCount)

Parameters

Type	Name	Description
System.Int32	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 maxThreadCount merges at a time.
System.Int32	maxThreadCount	The max # simultaneous merge threads that should be running at once. This must be <= maxMergeCount

SetMergeThreadPriority(Int32)

Set the base priority that merge threads run at. Note that CMS may increase priority of some merge threads beyond this base priority. It's best not to set this any higher than System.Threading.ThreadPriority.Highest(4)-maxThreadCount, so that CMS has room to set relative priority among threads.

Declaration

public virtual void SetMergeThreadPriority(int priority)

Parameters

Type	Name	Description
System.Int32	priority

SetSuppressExceptions()

Used for testing

Declaration

public virtual void SetSuppressExceptions()

Sync()

Wait for any running merge threads to finish. This call is not interruptible as used by Dispose(Boolean).

Declaration

public virtual void Sync()

ToString()

Declaration

public override string ToString()

Returns

Type	Description
System.String

Overrides

System.Object.ToString()

UpdateMergeThreads()

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.

Declaration

protected virtual void UpdateMergeThreads()

Implements

IConcurrentMergeScheduler

IMergeScheduler

System.IDisposable