RrdSafeFileBackend

org.rrd4j.core.RrdSafeFileBackend

All Implemented Interfaces:: RrdFileBackend

public class RrdSafeFileBackendextends RrdRandomAccessFileBackend

Backend which is used to store RRD data to ordinary files on the disk, using locking. This backend is SAFE: it locks the underlying RRD file during update/fetch operations, and caches only static parts of a RRD file in memory. Therefore, this backend is safe to be used when RRD files should be shared between several JVMs at the same time. However, this backend is a little bit slow since it does not use fast java.nio.* package (it's still based on the RandomAccessFile class).

Nested Class Summary
Nested Classes
Modifier and Type
Class
Description
(package private) static class
RrdSafeFileBackend.Counters
Internal counters for tracking file locking operations.
Field Summary
Fields inherited from class RrdRandomAccessFileBackend
rafile
Modifier and Type
Field
Description
protected final RandomAccessFile
rafile
Random access file handle.
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
Constructor
Description
RrdSafeFileBackend(String path, long lockWaitTime, long lockRetryPeriod)
Creates RrdFileBackend object for the given file path, backed by RandomAccessFile object.
Method Summary
Modifier and Type
Method
Description
void
close()
Releases the exclusive file lock, if held, then closes the underlying file.
static String
getLockInfo()
Returns a human readable summary of the file locking counters.
Methods inherited from class RrdRandomAccessFileBackend
getCanonicalPath, getLength, read, setLength, write
Modifier and Type
Method
Description
String
getCanonicalPath()
Returns canonical path to the file on the disk.
long
getLength()
Returns the number of RRD bytes in the underlying storage.
void
read(long offset, byte[] b)
Reads a number of bytes from the RRD file on the disk
protected void
setLength(long length)
Sets the number of bytes in the underlying RRD storage.
protected void
write(long offset, byte[] b)
Writes bytes to the underlying RRD file on the disk
Methods inherited from class RrdBackend
done, getCharBuffer, getFactory, getPath, getUri, isCachingAllowed, isInstanceCreated, readAll, readDouble, readDouble, readInt, readLong, readShort, readString, rrdClose, writeDouble, writeDouble, writeDouble, writeInt, writeLong, writeShort, writeString, writeString
Modifier and Type
Method
Description
(package private) void
done(RrdBackendFactory factory, PhantomReference<RrdDb> ref)
Set the factory and reference for this backend.
protected CharBuffer
getCharBuffer(long offset, int size)
Extract a CharBuffer from the backend, used by readString
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 double
readDouble(long offset)
Reads a double value from the underlying storage at the given offset.
protected 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 final String
readString(long offset)
Reads a string from the underlying storage at the given offset.
protected void
rrdClose()
Closes the underlying backend.
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 final void
writeString(long offset, String value)
Writes a string 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 Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details
- RrdSafeFileBackend
  public RrdSafeFileBackend(String path, long lockWaitTime, long lockRetryPeriod) throws IOException
  Creates RrdFileBackend object for the given file path, backed by RandomAccessFile object.
  Parameters:
  path - Path to a file
  lockWaitTime - lock waiting time in milliseconds.
  lockRetryPeriod - lock retry period in milliseconds.
  Throws:
  IOException - Thrown in case of I/O error.
Method Details
- close
  public void close() throws IOException
  Releases the exclusive file lock, if held, then closes the underlying file.
  Overrides:
  close in class RrdRandomAccessFileBackend
  Throws:
  IOException - if the lock cannot be released or the file cannot be closed.
- getLockInfo
  public static String getLockInfo()
  Returns a human readable summary of the file locking counters.
  Returns:
  a String object.

Nested Class Summary

Field Summary

Fields inherited from class RrdRandomAccessFileBackend

Fields inherited from class RrdBackend

Constructor Summary

Method Summary

Methods inherited from class RrdRandomAccessFileBackend

Methods inherited from class RrdBackend

Methods inherited from class Object

Constructor Details

Method Details

close

getLockInfo