java.lang.Object
org.rrd4j.core.RrdBackend
org.rrd4j.core.ByteBufferBackend
org.rrd4j.core.RrdNioBackend
All Implemented Interfaces:
RrdFileBackend
public class RrdNioBackendextends ByteBufferBackend implements RrdFileBackend
Backend which is used to store RRD data to ordinary disk files using java.nio.* package. This is the default backend engine.

This version buffers all stat files in a single temporary buffer file sequentially, keeping track of each file's offset and length, then flushes all to the mapped file in batch.

  • Field Summary

    Fields inherited from class RrdBackend

    BYTEORDER
    Modifier and Type
    Field
    Description
    protected static final ByteOrder
    BYTEORDER
    All ByteBuffer usage should use this standard order.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    RrdNioBackend(String path, boolean readOnly, RrdSyncThreadPool threadPool, int syncPeriod)
    Creates RrdFileBackend object for the given file path, backed by java.nio.* classes.

  • Method Summary

    All Methods
    Modifier and Type
    Method
    Description
    void
    bufferStatFile(ByteBuffer data, long targetFileOffset)
    Buffers one stat file's data into the single temp buffer file sequentially.
    void
    close()
    Closes the underlying RRD file.
    void
    flushBufferedStatFiles()
    Flushes all buffered stat files sequentially from the temp buffer file into their designated positions in the mapped RRD file in one batch operation.
    String
    getCanonicalPath()
    Returns canonical path to the file on the disk.
    long
    getLength()
    Returns the number of RRD bytes in the underlying storage.
    protected void
    setLength(long newLength)
    Sets the number of bytes in the underlying RRD storage.
    protected void
    sync()
    Override sync to disable unbuffered flush.

    Methods inherited from class ByteBufferBackend

    getCharBuffer, isDirty, read, readDouble, readDouble, readInt, readLong, readShort, rrdClose, setByteBuffer, write, writeDouble, writeDouble, writeDouble, writeInt, writeLong, writeShort, writeString
    Modifier and Type
    Method
    Description
    protected CharBuffer
    getCharBuffer(long offset, int size)
    Extract a CharBuffer from the backend, used by readString
    protected boolean
    isDirty()
    Check whether the buffer has been modified since the last sync.
    protected void
    read(long offset, byte[] b)
    Reads a number of bytes from the RRD file on the disk
    double
    readDouble(long offset)
    Reads a double value from the underlying storage at the given offset.
    double[]
    readDouble(long offset, int count)
    Reads an array of double values from the underlying storage at the given offset.
    protected int
    readInt(long offset)
    Reads an integer value from the underlying storage at the given offset.
    protected long
    readLong(long offset)
    Reads a long value from the underlying storage at the given offset.
    protected short
    readShort(long offset)
    Reads a short value from the underlying storage at the given offset.
    protected void
    rrdClose()
    Closes the underlying backend.
    protected void
    setByteBuffer(ByteBuffer byteBuffer)
    Set the byte buffer to use for backing storage.
    protected void
    write(long offset, byte[] b)
    Writes bytes to the underlying RRD file on the disk
    protected void
    writeDouble(long offset, double value)
    Writes a double value to the underlying storage at the given offset.
    protected void
    writeDouble(long offset, double[] values)
    Writes an array of double values to the underlying storage at the given offset.
    protected void
    writeDouble(long offset, double value, int count)
    Writes multiple copies of a double value to the underlying storage at the given offset.
    protected void
    writeInt(long offset, int value)
    Writes an integer value to the underlying storage at the given offset.
    protected void
    writeLong(long offset, long value)
    Writes a long value to the underlying storage at the given offset.
    protected void
    writeShort(long offset, short value)
    Writes a short value to the underlying storage at the given offset.
    protected void
    writeString(long offset, String value, int length)
    Writes a string to the underlying storage at the given offset with a fixed length.

    Methods inherited from class RrdBackend

    done, getFactory, getPath, getUri, isCachingAllowed, isInstanceCreated, readAll, readString, writeString
    Modifier and Type
    Method
    Description
    (package private) void
    done(RrdBackendFactory factory, PhantomReference<RrdDb> ref)
    Set the factory and reference for this backend.
    RrdBackendFactory
    getFactory()
    Get the factory for this backend.
    String
    getPath()
    Returns path to the storage.
    URI
    getUri()
    Return the URI associated to this backend, using the factory to generate it from the path.
    protected boolean
    isCachingAllowed()
    This method suggests the caching policy to the Rrd4j frontend (high-level) classes.
    (package private) static boolean
    isInstanceCreated()
    Checks if a backend instance has been created.
    final byte[]
    readAll()
    Reads all RRD bytes from the underlying storage.
    protected final String
    readString(long offset)
    Reads a string from the underlying storage at the given offset.
    protected final void
    writeString(long offset, String value)
    Writes a string to the underlying storage at the given offset.

    Methods inherited from class Object

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

  • Constructor Details

    • RrdNioBackend

      protected RrdNioBackend(String path, boolean readOnly, RrdSyncThreadPool threadPool, int syncPeriod) throws IOException
      Creates RrdFileBackend object for the given file path, backed by java.nio.* classes.
      Parameters:
      path - Path to a file
      readOnly - True, if file should be open in read-only mode. False otherwise
      threadPool - Sync thread pool; can be null
      syncPeriod - Sync period in seconds
      Throws:
      IOException - On I/O error

  • Method Details

    • setLength

      protected void setLength(long newLength) throws IOException
      Sets the number of bytes in the underlying RRD storage. This method is called only once, immediately after a new RRD storage gets created. Sets length of the underlying RRD file. This method is called only once, immediately after new RRD creation.
      Specified by:
      setLength in class RrdBackend
      Parameters:
      newLength - Length of the underlying RRD storage in bytes.
      Throws:
      IllegalArgumentException - if the length is bigger than the possible mapping position (2GiB).
      IOException - Thrown in case of I/O error.

    • close

      public void close() throws IOException
      Closes the underlying RRD file. Also closes and deletes the temporary buffer file used for buffering.
      Overrides:
      close in class ByteBufferBackend
      Throws:
      IOException - On I/O error

    • bufferStatFile

      public void bufferStatFile(ByteBuffer data, long targetFileOffset) throws IOException
      Buffers one stat file's data into the single temp buffer file sequentially. This method appends the data to the temp file and records the offset and length, including the target offset in the mapped file where this stat file belongs.
      Parameters:
      data - ByteBuffer containing the stat file's bytes to buffer
      targetFileOffset - Position in the mapped RRD file to write this stat file to on flush
      Throws:
      IOException - If writing to temp file fails

    • flushBufferedStatFiles

      public void flushBufferedStatFiles()
      Flushes all buffered stat files sequentially from the temp buffer file into their designated positions in the mapped RRD file in one batch operation. After flushing, the temp buffer file and index are cleared for the next batch.

    • sync

      protected void sync()
      Override sync to disable unbuffered flush.

    • getLength

      public long getLength() throws IOException
      Description copied from class: RrdBackend
      Returns the number of RRD bytes in the underlying storage.
      Specified by:
      getLength in class RrdBackend
      Returns:
      Number of RRD bytes in the storage.
      Throws:
      IOException - Thrown in case of I/O error.

    • getCanonicalPath

      public String getCanonicalPath()
      Description copied from interface: RrdFileBackend
      Returns canonical path to the file on the disk.
      Specified by:
      getCanonicalPath in interface RrdFileBackend
      Returns:
      Canonical file path