CachingAllocator (SNF4J/Core 1.7.0 API)

java.lang.Object
- org.snf4j.core.allocator.DefaultAllocator
- - org.snf4j.core.allocator.CachingAllocator

All Implemented Interfaces:

IByteBufferAllocator

Direct Known Subclasses:

ThreadLocalCachingAllocator
```
public class CachingAllocator
extends DefaultAllocator
```
A caching allocator for ByteBuffer allocations.
It uses N number of caches for storing released buffers. The caches are organized to store buffers of different capacities. The first N-1 caches are assigned to store buffers of fixed capacities according to the following rules:
```
 cache 1: stores buffers of capacity determined by the minCapacity 
 cache 2: stores buffers of capacity determined by the minCapacity * 2
 cache 3: stores buffers of capacity determined by the minCapacity * 4
 ...
 cache N-1: stores buffers of capacity determined by the minCapacity * 2 to the power (N-2)
 
```
The last N-th cache is assign to store buffers of capacities greater or equal to minCapacity * 2 to the power (N-1). Its current capacity adjusts to the capacities of released buffers. If the capacity of released buffer is greater than the current capacity then all currently stored buffers are garbage collected and the current capacity adjusts to the capacity of the buffer being just released.
It implements cache aging mechanism to reduce size of caches that are not used for longer time.
Performance and Scalability:
It uses one set of caches so it can significantly reduce memory consumption but on the other hand, due to a need for cache synchronization, it can introduce latency issues in multi-thread applications.
The behavior of the allocator can be customized by setting following system properties:
Author:

SNF4J.ORG

Field Summary
- Fields inherited from class org.snf4j.core.allocator.DefaultAllocator
  DEFAULT, direct

Constructor Summary

Constructors
Constructor and Description
`CachingAllocator(boolean direct)` Constructs a caching allocator with default minimal capacity (128).
`CachingAllocator(boolean direct, IDefaultAllocatorMetricCollector metric)` Constructs a caching allocator with default minimal capacity (128) and specified metric data collector.
`CachingAllocator(boolean direct, int minCapacity)` Constructs a caching allocator.
`CachingAllocator(boolean direct, int minCapacity, IDefaultAllocatorMetricCollector metric)` Constructs a caching allocator with specified metric data collector.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected ByteBuffer`	`allocate(int capacity, boolean direct)` Allocates a new buffer with given capacity and type
`protected ByteBuffer`	`allocate(int capacity, ByteBuffer buffer)` Allocates a new buffer that will replace the original not empty buffer.
`protected ByteBuffer`	`allocateEmpty(int capacity, ByteBuffer buffer)` Allocates a new buffer that will replace the original empty buffer.
`int`	`getMinCapacity()` Gets the minimal capacity for buffers allocated by this allocator.
`boolean`	`isReleasable()` Tells if an implementation of the allocator supports releasing of no longer used buffers.
`void`	`purge()` Purges all caches used by this allocator.
`void`	`release(ByteBuffer buffer)` Informs that given buffer that was allocated by this allocator is no longer used and can be released.

Methods inherited from class org.snf4j.core.allocator.DefaultAllocator
allocate, ensure, ensureSome, extend, reduce, usesArray

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - CachingAllocator
```
public CachingAllocator(boolean direct,
                        IDefaultAllocatorMetricCollector metric)
```
    Constructs a caching allocator with default minimal capacity (128) and specified metric data collector.
    
    Parameters:
    
    direct - true if the allocator should allocate direct buffers, or false to allocate non-direct buffers that have a backing array
    
    metric - a metric data collector
  - CachingAllocator
```
public CachingAllocator(boolean direct)
```
    Constructs a caching allocator with default minimal capacity (128).
    
    Parameters:
    
    direct - true if the allocator should allocate direct buffers, or false to allocate non-direct buffers that have a backing array
  - CachingAllocator
```
public CachingAllocator(boolean direct,
                        int minCapacity,
                        IDefaultAllocatorMetricCollector metric)
```
    Constructs a caching allocator with specified metric data collector.
    
    Parameters:
    
    direct - true if the allocator should allocate direct buffers, or false to allocate non-direct buffers that have a backing array
    
    minCapacity - the minimal capacity for buffers allocated by this allocator
    
    metric - a metric data collector
  - CachingAllocator
```
public CachingAllocator(boolean direct,
                        int minCapacity)
```
    Constructs a caching allocator.
    
    Parameters:
    
    direct - true if the allocator should allocate direct buffers, or false to allocate non-direct buffers that have a backing array
    
    minCapacity - the minimal capacity for buffers allocated by this allocator
- Method Detail
  - getMinCapacity
```
public final int getMinCapacity()
```
    Gets the minimal capacity for buffers allocated by this allocator.
    
    Returns:
    
    the minimal capacity
  - purge
```
public void purge()
```
    Purges all caches used by this allocator.
  - isReleasable
```
public boolean isReleasable()
```
    Description copied from class: DefaultAllocator
    
    Tells if an implementation of the allocator supports releasing of no longer used buffers.
    
    Specified by:
    
    isReleasable in interface IByteBufferAllocator
    
    Overrides:
    
    isReleasable in class DefaultAllocator
    
    Returns:
    
    false
  - release
```
public void release(ByteBuffer buffer)
```
    Description copied from interface: IByteBufferAllocator
    
    Informs that given buffer that was allocated by this allocator is no longer used and can be released.
    
    Specified by:
    
    release in interface IByteBufferAllocator
    
    Overrides:
    
    release in class DefaultAllocator
    
    Parameters:
    
    buffer - buffer to be released
  - allocate
```
protected ByteBuffer allocate(int capacity,
                              boolean direct)
```
    Description copied from class: DefaultAllocator
    
    Allocates a new buffer with given capacity and type
    
    Overrides:
    
    allocate in class DefaultAllocator
    
    Parameters:
    
    capacity - the capacity of the allocated buffer
    
    direct - the type of the allocated buffer
    
    Returns:
    
    the new buffer
  - allocateEmpty
```
protected ByteBuffer allocateEmpty(int capacity,
                                   ByteBuffer buffer)
```
    Description copied from class: DefaultAllocator
    
    Allocates a new buffer that will replace the original empty buffer.
    
    Overrides:
    
    allocateEmpty in class DefaultAllocator
    
    Parameters:
    
    capacity - the capacity of the allocated buffer
    
    buffer - the buffer to be replaced. If the allocator support releasing it can be safely released in this method.
    
    Returns:
    
    the new buffer
  - allocate
```
protected ByteBuffer allocate(int capacity,
                              ByteBuffer buffer)
```
    Description copied from class: DefaultAllocator
    
    Allocates a new buffer that will replace the original not empty buffer. The content of the original buffer must be preserved in the returned buffer.
    
    Overrides:
    
    allocate in class DefaultAllocator
    
    Parameters:
    
    capacity - the capacity of the allocated buffer
    
    buffer - the buffer to be replaced. If the allocator support releasing it can be safely released in this method.
    
    Returns:
    
    the new buffer

Class CachingAllocator

Field Summary

Fields inherited from class org.snf4j.core.allocator.DefaultAllocator

Constructor Summary

Method Summary

Methods inherited from class org.snf4j.core.allocator.DefaultAllocator

Methods inherited from class java.lang.Object

Constructor Detail

CachingAllocator

CachingAllocator

CachingAllocator

CachingAllocator

Method Detail

getMinCapacity

purge

isReleasable

release

allocate

allocateEmpty

allocate