AbstractStringCache (mongodb-async-driver 2.0.1 API)

java.lang.Object
- com.allanbank.mongodb.bson.io.AbstractStringCache

Direct Known Subclasses:

StringDecoderCache, StringEncoderCache
```
public abstract class AbstractStringCache
extends Object
```
AbstractStringCache provides the basic functionality for tracking string usage and triggering rebuilds of the cache over time.
The basic function of the cache is to maintain two structures. The first (provided by this class) tracks the usage of strings in the cache via a 'seen' ConcurrentMap. As the cache sees more usage it will periodically trim entries from the map that are not being used often (this is to limit memory usage). Once the cache thinks it has seen enough usage it will trigger the building of the runtime cache. This runtime cache does not require any locking as it is read-only after being constructed.

There are two controls on the amount of caching instances of this class will do:
1. getMaxCacheLength() limits the length of the encoded bytes this class will try and retrieve from the cache. Setting this value to zero disables the cache and limit any memory overhead.
2. getMaxCacheEntries() controls the number of cached entries in the runtime-cache and how often the accumulated statistics are trimmed. Each entry represents a single encoded string.
API Warning:

This class is NOT part of the drivers API. This class may be mutated in incompatible ways between any two releases of the driver.

Copyright ©:

2014, Allanbank Consulting, Inc., All Rights Reserved

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`AbstractStringCache.ReverseIntegerComparator` ReverseIntegerComparator provides a `Comparator` that considers higher value integers to be less then lower value integers.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`DEFAULT_MAX_CACHE_ENTRIES` The default maximum number of entries to keep in the cache.
`static int`	`DEFAULT_MAX_CACHE_LENGTH` The default maximum length byte array to cache.
`protected static int`	`MAX_MULTIPLIER` The maximum value for the multiplier.
`protected int`	`myMaxCacheLength` The maximum length of a string to cache.
`protected int`	`myMaxCachEntries` The maximum number of entries to have in the cache.
`protected int`	`myMaxCachEntriesMultiplier` The multiplier for the number of times the cache is used before we re-load the cache.
`protected ConcurrentMap<String,com.allanbank.mongodb.bson.io.SeenString>`	`mySeen` The map of seen strings that will be used periodically to build the cache cache.
`protected AtomicInteger`	`myUseCount` The number of time the cache has been used since the last re-load of runtime, read-only cache.

Constructor Summary

Constructors
Constructor and Description

AbstractStringCache()
Creates a new AbstractStringCache.

Constructors
Constructor and Description
`AbstractStringCache()` Creates a new AbstractStringCache.

Method Summary

Methods
Modifier and Type	Method and Description
`protected SortedMap<Integer,List<com.allanbank.mongodb.bson.io.SeenString>>`	`buildCacheGroups()` Builds a map of the seen strings at each count.
`protected void`	`clear()` Clears the cache.
`int`	`getMaxCacheEntries()` Returns the maximum node count.
`int`	`getMaxCacheLength()` Returns the maximum length of strings to cache.
`protected abstract void`	`rebuildCache()` Rebuilds the cache from the current `mySeen` map.
`void`	`setMaxCacheEntries(int maxCacheEntries)` Sets the value of maximum number of cached strings.
`void`	`setMaxCacheLength(int maxlength)` Sets the value of maximum length of strings to cache to the new value.
`void`	`used(String decoded, byte[] source, int offset, int length)` Notification that a string/byte[] have been used.

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

- Field Detail
  - DEFAULT_MAX_CACHE_ENTRIES
```
public static final int DEFAULT_MAX_CACHE_ENTRIES
```
    The default maximum number of entries to keep in the cache.
    
    See Also:
    Constant Field Values
  - DEFAULT_MAX_CACHE_LENGTH
```
public static final int DEFAULT_MAX_CACHE_LENGTH
```
    The default maximum length byte array to cache.
    
    See Also:
    Constant Field Values
  - MAX_MULTIPLIER
```
protected static final int MAX_MULTIPLIER
```
    The maximum value for the multiplier.
    
    See Also:
    Constant Field Values
  - myMaxCacheLength
```
protected int myMaxCacheLength
```
    The maximum length of a string to cache. This can be used to stop a single long string from pushing useful values out of the cache.
  - myMaxCachEntries
```
protected int myMaxCachEntries
```
    The maximum number of entries to have in the cache.
  - myMaxCachEntriesMultiplier
```
protected volatile int myMaxCachEntriesMultiplier
```
    The multiplier for the number of times the cache is used before we re-load the cache.
  - mySeen
```
protected final ConcurrentMap<String,com.allanbank.mongodb.bson.io.SeenString> mySeen
```
    The map of seen strings that will be used periodically to build the cache cache.
  - myUseCount
```
protected final AtomicInteger myUseCount
```
    The number of time the cache has been used since the last re-load of runtime, read-only cache.
- Constructor Detail
  - AbstractStringCache
```
public AbstractStringCache()
```
    Creates a new AbstractStringCache.
- Method Detail
  - getMaxCacheEntries
```
public int getMaxCacheEntries()
```
    Returns the maximum node count.
    
    Returns:
    The maximum node count.
  - getMaxCacheLength
```
public int getMaxCacheLength()
```
    Returns the maximum length of strings to cache. This can be used to stop a single long string from pushing useful values out of the cache.
    
    Returns:
    The maximum length of strings to cache.
  - setMaxCacheEntries
```
public void setMaxCacheEntries(int maxCacheEntries)
```
    Sets the value of maximum number of cached strings.
    
    Parameters:
    maxCacheEntries - The new value for the maximum number of cached strings.
  - setMaxCacheLength
```
public void setMaxCacheLength(int maxlength)
```
    Sets the value of maximum length of strings to cache to the new value. This can be used to stop a single long string from pushing useful values out of the cache.
    
    Parameters:
    maxlength - The new value for the maximum length of strings to cache.
  - used
```
public void used(String decoded,
        byte[] source,
        int offset,
        int length)
```
    Notification that a string/byte[] have been used.
    
    Parameters:
    source - The bytes in the string.
    offset - The offset of the first byte.
    length - The length of the bytes with a terminal zero byte.
    decoded - The decoded string.
  - buildCacheGroups
```
protected SortedMap<Integer,List<com.allanbank.mongodb.bson.io.SeenString>> buildCacheGroups()
```
    Builds a map of the seen strings at each count. The order of the map is reversed so that higher counts are first in the map.
    
    Returns:
    A map of the seen strings at each count.
  - clear
```
protected void clear()
```
    Clears the cache.
  - rebuildCache
```
protected abstract void rebuildCache()
```
    Rebuilds the cache from the current mySeen map. By the end of the method the caceh should have been rebuild and the mySeen map cleared.

Class AbstractStringCache

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_MAX_CACHE_ENTRIES

DEFAULT_MAX_CACHE_LENGTH

MAX_MULTIPLIER

myMaxCacheLength

myMaxCachEntries

myMaxCachEntriesMultiplier

mySeen

myUseCount

Constructor Detail

AbstractStringCache

Method Detail

getMaxCacheEntries

getMaxCacheLength

setMaxCacheEntries

setMaxCacheLength

used

buildCacheGroups

clear

rebuildCache