Class NRTCachingDirectory
- java.lang.Object
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- org.apache.lucene.store.Directory
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- org.apache.lucene.store.NRTCachingDirectory
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- All Implemented Interfaces:
Closeable
,AutoCloseable
public class NRTCachingDirectory extends Directory
Wraps aRAMDirectory
around any provided delegate directory, to be used during NRT search. Make sure you pull the merge scheduler usinggetMergeScheduler()
and pass that to yourIndexWriter
; this class uses that to keep track of which merges are being done by which threads, to decide when to cache each written file.This class is likely only useful in a near-real-time context, where indexing rate is lowish but reopen rate is highish, resulting in many tiny files being written. This directory keeps such segments (as well as the segments produced by merging them, as long as they are small enough), in RAM.
This is safe to use: when your app calls {IndexWriter#commit}, all cached files will be flushed from the cached and sync'd.
NOTE: this class is somewhat sneaky in its approach for spying on merges to determine the size of a merge: it records which threads are running which merges by watching ConcurrentMergeScheduler's doMerge method. While this works correctly, likely future versions of this class will take a more general approach.
Here's a simple example usage:
Directory fsDir = FSDirectory.open(new File("/path/to/index")); NRTCachingDirectory cachedFSDir = new NRTCachingDirectory(fsDir, 5.0, 60.0); IndexWriterConfig conf = new IndexWriterConfig(Version.LUCENE_32, analyzer); conf.setMergeScheduler(cachedFSDir.getMergeScheduler()); IndexWriter writer = new IndexWriter(cachedFSDir, conf);
This will cache all newly flushed segments, all merges whose expected segment size is <= 5 MB, unless the net cached bytes exceeds 60 MB at which point all writes will not be cached (until the net bytes falls below 60 MB).
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Field Summary
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Fields inherited from class org.apache.lucene.store.Directory
isOpen, lockFactory
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Constructor Summary
Constructors Constructor Description NRTCachingDirectory(Directory delegate, double maxMergeSizeMB, double maxCachedMB)
We will cache a newly created output if 1) it's a flush or a merge and the estimated size of the merged segment is <= maxMergeSizeMB, and 2) the total cached bytes is <= maxCachedMB
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description void
clearLock(String name)
Attempt to clear (forcefully unlock and remove) the specified lock.void
close()
Close this directory, which flushes any cached files to the delegate and then closes the delegate.IndexOutput
createOutput(String name)
Creates a new, empty file in the directory with the given name.void
deleteFile(String name)
Removes an existing file in the directory.protected boolean
doCacheWrite(String name)
Subclass can override this to customize logic; return true if this file should be written to the RAMDirectory.boolean
fileExists(String name)
Returns true iff a file with the given name exists.long
fileLength(String name)
Returns the length of a file in the directory.long
fileModified(String name)
Returns the time the named file was last modified.LockFactory
getLockFactory()
Get the LockFactory that this Directory instance is using for its locking implementation.String
getLockID()
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.MergeScheduler
getMergeScheduler()
String[]
listAll()
Returns an array of strings, one for each file in the directory.String[]
listCachedFiles()
Lock
makeLock(String name)
Construct aLock
.IndexInput
openInput(String name)
Returns a stream reading an existing file.IndexInput
openInput(String name, int bufferSize)
Returns a stream reading an existing file, with the specified read buffer size.void
setLockFactory(LockFactory lf)
Set the LockFactory that this Directory instance should use for its locking implementation.long
sizeInBytes()
Returns how many bytes are being used by the RAMDirectory cachevoid
sync(Collection<String> fileNames)
Ensure that any writes to these files are moved to stable storage.String
toString()
void
touchFile(String name)
Deprecated.-
Methods inherited from class org.apache.lucene.store.Directory
copy, copy, ensureOpen, sync
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Constructor Detail
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NRTCachingDirectory
public NRTCachingDirectory(Directory delegate, double maxMergeSizeMB, double maxCachedMB)
We will cache a newly created output if 1) it's a flush or a merge and the estimated size of the merged segment is <= maxMergeSizeMB, and 2) the total cached bytes is <= maxCachedMB
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Method Detail
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getLockFactory
public LockFactory getLockFactory()
Description copied from class:Directory
Get the LockFactory that this Directory instance is using for its locking implementation. Note that this may be null for Directory implementations that provide their own locking implementation.- Overrides:
getLockFactory
in classDirectory
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setLockFactory
public void setLockFactory(LockFactory lf) throws IOException
Description copied from class:Directory
Set the LockFactory that this Directory instance should use for its locking implementation. Each * instance of LockFactory should only be used for one directory (ie, do not share a single instance across multiple Directories).- Overrides:
setLockFactory
in classDirectory
- Parameters:
lf
- instance ofLockFactory
.- Throws:
IOException
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getLockID
public String getLockID()
Description copied from class:Directory
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances. This ID should be the same if two Directory instances (even in different JVMs and/or on different machines) are considered "the same index". This is how locking "scopes" to the right index.
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makeLock
public Lock makeLock(String name)
Description copied from class:Directory
Construct aLock
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clearLock
public void clearLock(String name) throws IOException
Description copied from class:Directory
Attempt to clear (forcefully unlock and remove) the specified lock. Only call this at a time when you are certain this lock is no longer in use.- Overrides:
clearLock
in classDirectory
- Parameters:
name
- name of the lock to be cleared.- Throws:
IOException
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listAll
public String[] listAll() throws IOException
Description copied from class:Directory
Returns an array of strings, one for each file in the directory.- Specified by:
listAll
in classDirectory
- Throws:
NoSuchDirectoryException
- if the directory is not prepared for any write operations (such asDirectory.createOutput(String)
).IOException
- in case of other IO errors
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sizeInBytes
public long sizeInBytes()
Returns how many bytes are being used by the RAMDirectory cache
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fileExists
public boolean fileExists(String name) throws IOException
Description copied from class:Directory
Returns true iff a file with the given name exists.- Specified by:
fileExists
in classDirectory
- Throws:
IOException
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fileModified
public long fileModified(String name) throws IOException
Description copied from class:Directory
Returns the time the named file was last modified.- Specified by:
fileModified
in classDirectory
- Throws:
IOException
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touchFile
@Deprecated public void touchFile(String name) throws IOException
Deprecated.Description copied from class:Directory
Set the modified time of an existing file to now.- Specified by:
touchFile
in classDirectory
- Throws:
IOException
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deleteFile
public void deleteFile(String name) throws IOException
Description copied from class:Directory
Removes an existing file in the directory.- Specified by:
deleteFile
in classDirectory
- Throws:
IOException
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fileLength
public long fileLength(String name) throws IOException
Description copied from class:Directory
Returns the length of a file in the directory. This method follows the following contract:- Throws
FileNotFoundException
if the file does not exist - Returns a value ≥0 if the file exists, which specifies its length.
- Specified by:
fileLength
in classDirectory
- Parameters:
name
- the name of the file for which to return the length.- Throws:
FileNotFoundException
- if the file does not exist.IOException
- if there was an IO error while retrieving the file's length.
- Throws
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listCachedFiles
public String[] listCachedFiles()
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createOutput
public IndexOutput createOutput(String name) throws IOException
Description copied from class:Directory
Creates a new, empty file in the directory with the given name. Returns a stream writing this file.- Specified by:
createOutput
in classDirectory
- Throws:
IOException
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sync
public void sync(Collection<String> fileNames) throws IOException
Description copied from class:Directory
Ensure that any writes to these files are moved to stable storage. Lucene uses this to properly commit changes to the index, to prevent a machine/OS crash from corrupting the index.
NOTE: Clients may call this method for same files over and over again, so some impls might optimize for that. For other impls the operation can be a noop, for various reasons.- Overrides:
sync
in classDirectory
- Throws:
IOException
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openInput
public IndexInput openInput(String name) throws IOException
Description copied from class:Directory
Returns a stream reading an existing file.- Specified by:
openInput
in classDirectory
- Throws:
IOException
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openInput
public IndexInput openInput(String name, int bufferSize) throws IOException
Description copied from class:Directory
Returns a stream reading an existing file, with the specified read buffer size. The particular Directory implementation may ignore the buffer size. Currently the only Directory implementations that respect this parameter areFSDirectory
andCompoundFileReader
.- Overrides:
openInput
in classDirectory
- Throws:
IOException
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close
public void close() throws IOException
Close this directory, which flushes any cached files to the delegate and then closes the delegate.- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classDirectory
- Throws:
IOException
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getMergeScheduler
public MergeScheduler getMergeScheduler()
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doCacheWrite
protected boolean doCacheWrite(String name)
Subclass can override this to customize logic; return true if this file should be written to the RAMDirectory.
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