Package org.apache.lucene.store

Class NRTCachingDirectory

java.lang.Object
org.apache.lucene.store.Directory
org.apache.lucene.store.NRTCachingDirectory
All Implemented Interfaces:
Closeable, AutoCloseable
public class NRTCachingDirectory extends Directory
Wraps a RAMDirectory around any provided delegate directory, to be used during NRT search.

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.

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_47, analyzer);
   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).

  • Constructor Details

    • 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

  • Method Details

    • getDelegate

      public Directory getDelegate()

    • 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.
      Specified by:
      getLockFactory in class Directory

    • 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).
      Specified by:
      setLockFactory in class Directory
      Parameters:
      lf - instance of LockFactory.
      Throws:
      IOException

    • 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.
      Overrides:
      getLockID in class Directory

    • makeLock

      public Lock makeLock(String name)
      Description copied from class: Directory
      Construct a Lock.
      Specified by:
      makeLock in class Directory
      Parameters:
      name - the name of the lock file

    • 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.
      Specified by:
      clearLock in class Directory
      Parameters:
      name - name of the lock to be cleared.
      Throws:
      IOException

    • toString

      public String toString()
      Overrides:
      toString in class Directory

    • 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 class Directory
      Throws:
      NoSuchDirectoryException - if the directory is not prepared for any write operations (such as Directory.createOutput(String, IOContext)).
      IOException - in case of other IO errors

    • sizeInBytes

      public long sizeInBytes()
      Returns how many bytes are being used by the RAMDirectory cache

    • 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 class Directory
      Throws:
      IOException

    • deleteFile

      public void deleteFile(String name) throws IOException
      Description copied from class: Directory
      Removes an existing file in the directory.
      Specified by:
      deleteFile in class Directory
      Throws:
      IOException

    • 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:
      • Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).
      • Returns a value ≥0 if the file exists, which specifies its length.
      Specified by:
      fileLength in class Directory
      Parameters:
      name - the name of the file for which to return the length.
      Throws:
      IOException - if there was an IO error while retrieving the file's length.

    • listCachedFiles

      public String[] listCachedFiles()

    • createOutput

      public IndexOutput createOutput(String name, IOContext context) 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 class Directory
      Throws:
      IOException

    • 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.
      Specified by:
      sync in class Directory
      Throws:
      IOException

    • openInput

      public IndexInput openInput(String name, IOContext context) 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 are FSDirectory and CompoundFileDirectory.
    • Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).
      • Specified by:
      openInput in class Directory
      Throws:
      IOException

    • createSlicer

      public Directory.IndexInputSlicer createSlicer(String name, IOContext context) throws IOException
      Description copied from class: Directory
      Creates an Directory.IndexInputSlicer for the given file name. IndexInputSlicer allows other Directory implementations to efficiently open one or more sliced IndexInput instances from a single file handle. The underlying file handle is kept open until the Directory.IndexInputSlicer is closed.
    • Must throw FileNotFoundException if the file does not exist (not java.nio.file.NoSuchFileException of Java 7).
      • Overrides:
      createSlicer in class Directory
      Throws:
      IOException - if an IOException occurs

    • 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 interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in class Directory
      Throws:
      IOException

    • doCacheWrite

      protected boolean doCacheWrite(String name, IOContext context)
      Subclass can override this to customize logic; return true if this file should be written to the RAMDirectory.