Package org.apache.lucene.misc.store

Class DirectIODirectory

java.lang.Object

org.apache.lucene.store.Directory

org.apache.lucene.store.FilterDirectory

org.apache.lucene.misc.store.DirectIODirectory

All Implemented Interfaces:

Closeable, AutoCloseable

public class DirectIODirectory
extends FilterDirectory

A Directory implementation for all Unixes and Windows that uses DIRECT I/O to bypass OS level IO caching during merging. For all other cases (searching, writing) we delegate to the provided Directory instance.

See Overview for more details.

WARNING: this code is very new and quite easily could contain horrible bugs.

This directory passes Solr and Lucene tests on Linux, OS X, and Windows; other systems should work but have not been tested! Use at your own risk.

@throws UnsupportedOperationException if the operating system, file system or JDK does not support Direct I/O or a sufficient equivalent.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field	Description
static int	DEFAULT_MERGE_BUFFER_SIZE	Default buffer size before writing to disk (256 KB); larger means less IO load but more RAM and direct buffer storage space consumed during merging.
static long	DEFAULT_MIN_BYTES_DIRECT	Default min expected merge size before direct IO is used (10 MB):

Fields inherited from class org.apache.lucene.store.FilterDirectory

in

Constructor Summary

Constructors

Constructor	Description
DirectIODirectory(FSDirectory delegate)	Create a new DirectIODirectory for the named location.
DirectIODirectory(FSDirectory delegate, int mergeBufferSize, long minBytesDirect)	Create a new DirectIODirectory for the named location.

Method Summary

Modifier and Type	Method	Description
void	close()
IndexOutput	createOutput(String name, IOContext context)
protected void	ensureOpen()
Path	getDirectory()
IndexInput	openInput(String name, IOContext context)
protected boolean	useDirectIO(String name, IOContext context, OptionalLong fileLength)	Determines if direct IO should be used for a file.

Methods inherited from class org.apache.lucene.store.FilterDirectory

createTempOutput, deleteFile, fileLength, getDelegate, getPendingDeletions, listAll, obtainLock, rename, sync, syncMetaData, toString, unwrap

Methods inherited from class org.apache.lucene.store.Directory

copyFrom, getTempFileName, openChecksumInput

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_MERGE_BUFFER_SIZE

public static final int DEFAULT_MERGE_BUFFER_SIZE

Default buffer size before writing to disk (256 KB); larger means less IO load but more RAM and direct buffer storage space consumed during merging.

See Also:

Constant Field Values

DEFAULT_MIN_BYTES_DIRECT

public static final long DEFAULT_MIN_BYTES_DIRECT

Default min expected merge size before direct IO is used (10 MB):

See Also:

Constant Field Values

Constructor Detail

DirectIODirectory

public DirectIODirectory(FSDirectory delegate,
                         int mergeBufferSize,
                         long minBytesDirect)
                  throws IOException

Create a new DirectIODirectory for the named location.

Parameters:

delegate - Directory for non-merges, also used as reference to file system path.

mergeBufferSize - Size of buffer to use for merging.

minBytesDirect - Merges, or files to be opened for reading, smaller than this will not use direct IO. See DEFAULT_MIN_BYTES_DIRECT and useDirectIO(java.lang.String, org.apache.lucene.store.IOContext, java.util.OptionalLong).

Throws:

IOException - If there is a low-level I/O error

DirectIODirectory

public DirectIODirectory(FSDirectory delegate)
                  throws IOException

Create a new DirectIODirectory for the named location.

Parameters:

delegate - Directory for non-merges, also used as reference to file system path.

Throws:

IOException - If there is a low-level I/O error

Method Detail

getDirectory

public Path getDirectory()

Returns:

the underlying file system directory

ensureOpen

protected void ensureOpen()
                   throws AlreadyClosedException

Overrides:

ensureOpen in class Directory

Throws:

AlreadyClosedException

useDirectIO

protected boolean useDirectIO(String name,
                              IOContext context,
                              OptionalLong fileLength)

Determines if direct IO should be used for a file. By default this tests if it is a merge context and if the merge or file length extends the minimum size (see DEFAULT_MIN_BYTES_DIRECT). Subclasses may override method to enforce direct IO for specific file types.

Parameters:

name - file name (unused by default implementation)

context - information about merge size

fileLength - if available, gives the file length. Will be empty when requesting an IndexOutput.

Returns:

true if direct IO should be used; false if input/output should be requested from delegate directory.

openInput

public IndexInput openInput(String name,
                            IOContext context)
                     throws IOException

Overrides:

openInput in class FilterDirectory

Throws:

IOException

createOutput

public IndexOutput createOutput(String name,
                                IOContext context)
                         throws IOException

Overrides:

createOutput in class FilterDirectory

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class FilterDirectory

Throws:

IOException