public abstract class

RrdBackendFactory

extends Object
java.lang.Object
   ↳ org.rrd4j.core.RrdBackendFactory
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

Base (abstract) backend factory class which holds references to all concrete backend factories and defines abstract methods which must be implemented in all concrete factory implementations.

Factory classes are used to create concrete RrdBackend implementations. Each factory creates unlimited number of specific backend objects. Rrd4j supports four different backend types (backend factories) out of the box:

  • RrdFileBackend: objects of this class are created from the RrdFileBackendFactory class. This was the default backend used in all Rrd4j releases before 1.4.0 release. It uses java.io.* package and RandomAccessFile class to store RRD data in files on the disk.
  • RrdSafeFileBackend: objects of this class are created from the RrdSafeFileBackendFactory class. It uses java.io.* package and RandomAccessFile class to store RRD data in files on the disk. 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 *slow* since it does not use fast java.nio.* package (it's still based on the RandomAccessFile class).
  • RrdNioBackend: objects of this class are created from the RrdNioBackendFactory class. The backend uses java.io.* and java.nio.* classes (mapped ByteBuffer) to store RRD data in files on the disk. This is the default backend since 1.4.0 release.
  • RrdMemoryBackend: objects of this class are created from the RrdMemoryBackendFactory class. This backend stores all data in memory. Once JVM exits, all data gets lost. The backend is extremely fast and memory hungry.
Each backend factory is identified by its name. Constructors are provided in the RrdDb class to create RrdDb objects (RRD databases) backed with a specific backend.

See javadoc for RrdBackend to find out how to create your custom backends.

Summary

Public Constructors
RrdBackendFactory()
Public Methods
static RrdBackendFactory getDefaultFactory()
Returns the defaul backend factory.
static RrdBackendFactory getFactory(String name)
Returns backend factory for the given backend factory name.
abstract String getName()
Returns the name (primary ID) for the factory.
static void registerAndSetAsDefaultFactory(RrdBackendFactory factory)
Registers new (custom) backend factory within the Rrd4j framework and sets this factory as the default.
static void registerFactory(RrdBackendFactory factory)
Registers new (custom) backend factory within the Rrd4j framework.
static void setDefaultFactory(String factoryName)
Replaces the default backend factory with a new one.
Protected Methods
abstract boolean exists(String path)
Determines if a storage with the given path already exists.
abstract RrdBackend open(String path, boolean readOnly)
Creates RrdBackend object for the given storage path.
abstract boolean shouldValidateHeader(String path)
Determines if the header should be validated.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public RrdBackendFactory ()

Public Methods

public static RrdBackendFactory getDefaultFactory ()

Returns the defaul backend factory. This factory is used to construct RrdDb objects if no factory is specified in the RrdDb constructor.

Returns
  • Default backend factory.

public static RrdBackendFactory getFactory (String name)

Returns backend factory for the given backend factory name.

Parameters
name Backend factory name. Initially supported names are:

  • FILE: Default factory which creates backends based on the java.io.* package. RRD data is stored in files on the disk
  • SAFE: Default factory which creates backends based on the java.io.* package. RRD data is stored in files on the disk. This backend is "safe". Being safe means that RRD files can be safely shared between several JVM's.
  • NIO: Factory which creates backends based on the java.nio.* package. RRD data is stored in files on the disk
  • MEMORY: Factory which creates memory-oriented backends. RRD data is stored in memory, it gets lost as soon as JVM exits.
Returns
  • Backend factory for the given factory name

public abstract String getName ()

Returns the name (primary ID) for the factory.

Returns
  • Name of the factory.

public static void registerAndSetAsDefaultFactory (RrdBackendFactory factory)

Registers new (custom) backend factory within the Rrd4j framework and sets this factory as the default.

Parameters
factory Factory to be registered and set as default

public static void registerFactory (RrdBackendFactory factory)

Registers new (custom) backend factory within the Rrd4j framework.

Parameters
factory Factory to be registered

public static void setDefaultFactory (String factoryName)

Replaces the default backend factory with a new one. This method must be called before the first RRD gets created.

Parameters
factoryName Name of the default factory. Out of the box, Rrd4j supports four different RRD backends: "FILE" (java.io.* based), "SAFE" (java.io.* based - use this backend if RRD files may be accessed from several JVMs at the same time), "NIO" (java.nio.* based) and "MEMORY" (byte[] based).

Protected Methods

protected abstract boolean exists (String path)

Determines if a storage with the given path already exists.

Parameters
path Storage path
Returns
  • True, if such storage exists, false otherwise.
Throws
IOException

protected abstract RrdBackend open (String path, boolean readOnly)

Creates RrdBackend object for the given storage path.

Parameters
path Storage path
readOnly True, if the storage should be accessed in read/only mode. False otherwise.
Returns
  • Backend object which handles all I/O operations for the given storage path
Throws
IOException Thrown in case of I/O error.

protected abstract boolean shouldValidateHeader (String path)

Determines if the header should be validated.

Returns
  • True, if the header should be validated for this factory
Throws
IOException