org.apache.http.impl.client.cache
Class CacheConfig

java.lang.Object
  org.apache.http.impl.client.cache.CacheConfig

public class CacheConfig
extends Object

Java Beans-style configuration for a CachingHttpClient. Any class in the caching module that has configuration options should take a CacheConfig argument in one of its constructors. A CacheConfig instance has sane and conservative defaults, so the easiest way to specify options is to get an instance and then set just the options you want to modify from their defaults.

N.B. This class is only for caching-specific configuration; to configure the behavior of the rest of the client, configure the HttpClient used as the "backend" for the CachingHttpClient.

Cache configuration can be grouped into the following categories:

Cache size. If the backend storage supports these limits, you can specify the maximum number of cache entries as well as the maximum cacheable response body size.

Public/private caching. By default, the caching module considers itself to be a shared (public) cache, and will not, for example, cache responses to requests with Authorization headers or responses marked with Cache-Control: private. If, however, the cache is only going to be used by one logical "user" (behaving similarly to a browser cache), then you will want to turn off the shared cache setting.

Heuristic caching. Per RFC2616, a cache may cache certain cache entries even if no explicit cache control headers are set by the origin. This behavior is off by default, but you may want to turn this on if you are working with an origin that doesn't set proper headers but where you still want to cache the responses. You will want to enable heuristic caching, then specify either a default freshness lifetime and/or a fraction of the time since the resource was last modified. See Sections 13.2.2 and 13.2.4 of the HTTP/1.1 RFC for more details on heuristic caching.

Background validation. The cache module supports the stale-while-revalidate directive of RFC5861, which allows certain cache entry revalidations to happen in the background. You may want to tweak the settings for the minimum and maximum number of background worker threads, as well as the maximum time they can be idle before being reclaimed. You can also control the size of the queue used for revalidations when there aren't enough workers to keep up with demand.

Field Summary

static int	DEFAULT_ASYNCHRONOUS_WORKER_IDLE_LIFETIME_SECS Default maximum idle lifetime for a background revalidation thread before it gets reclaimed.
static int	DEFAULT_ASYNCHRONOUS_WORKERS_CORE Default minimum number of worker threads to allow for background revalidations resulting from the stale-while-revalidate directive.
static int	DEFAULT_ASYNCHRONOUS_WORKERS_MAX Default number of worker threads to allow for background revalidations resulting from the stale-while-revalidate directive.
static boolean	DEFAULT_HEURISTIC_CACHING_ENABLED Default setting for heuristic caching
static float	DEFAULT_HEURISTIC_COEFFICIENT Default coefficient used to heuristically determine freshness lifetime from the Last-Modified time of a cache entry.
static long	DEFAULT_HEURISTIC_LIFETIME Default lifetime in seconds to be assumed when we cannot calculate freshness heuristically.
static int	DEFAULT_MAX_CACHE_ENTRIES Default setting for the maximum number of cache entries that will be retained.
static int	DEFAULT_MAX_OBJECT_SIZE_BYTES Default setting for the maximum object size that will be cached, in bytes.
static int	DEFAULT_MAX_UPDATE_RETRIES Default setting for the number of retries on a failed cache update
static int	DEFAULT_REVALIDATION_QUEUE_SIZE Default maximum queue length for background revalidation requests.

Constructor Summary

CacheConfig()

Method Summary

int	getAsynchronousWorkerIdleLifetimeSecs() Returns the current maximum idle lifetime in seconds for a background revalidation worker thread.
int	getAsynchronousWorkersCore() Returns the minimum number of threads to keep alive for background revalidations due to the stale-while-revalidate directive.
int	getAsynchronousWorkersMax() Returns the maximum number of threads to allow for background revalidations due to the stale-while-revalidate directive.
float	getHeuristicCoefficient() Returns lifetime coefficient used in heuristic freshness caching.
long	getHeuristicDefaultLifetime() Get the default lifetime to be used if heuristic freshness calculation is not possible.
int	getMaxCacheEntries() Returns the maximum number of cache entries the cache will retain.
long	getMaxObjectSize() Returns the current maximum response body size that will be cached.
int	getMaxObjectSizeBytes() Deprecated. (4.2) use getMaxObjectSize()
int	getMaxUpdateRetries() Returns the number of times to retry a cache update on failure
int	getRevalidationQueueSize() Returns the current maximum queue size for background revalidations.
boolean	isHeuristicCachingEnabled() Returns whether heuristic caching is enabled.
boolean	isSharedCache() Returns whether the cache will behave as a shared cache or not.
void	setAsynchronousWorkerIdleLifetimeSecs(int secs) Sets the current maximum idle lifetime in seconds for a background revalidation worker thread.
void	setAsynchronousWorkersCore(int min) Sets the minimum number of threads to keep alive for background revalidations due to the stale-while-revalidate directive.
void	setAsynchronousWorkersMax(int max) Sets the maximum number of threads to allow for background revalidations due to the stale-while-revalidate directive.
void	setHeuristicCachingEnabled(boolean heuristicCachingEnabled) Enables or disables heuristic caching.
void	setHeuristicCoefficient(float heuristicCoefficient) Sets coefficient to be used in heuristic freshness caching.
void	setHeuristicDefaultLifetime(long heuristicDefaultLifetimeSecs) Sets default lifetime in seconds to be used if heuristic freshness calculation is not possible.
void	setMaxCacheEntries(int maxCacheEntries) Sets the maximum number of cache entries the cache will retain.
void	setMaxObjectSize(long maxObjectSize) Specifies the maximum response body size that will be eligible for caching.
void	setMaxObjectSizeBytes(int maxObjectSizeBytes) Deprecated. (4.2) use setMaxObjectSize(long)
void	setMaxUpdateRetries(int maxUpdateRetries) Sets the number of times to retry a cache update on failure
void	setRevalidationQueueSize(int size) Sets the current maximum queue size for background revalidations.
void	setSharedCache(boolean isSharedCache) Sets whether the cache should behave as a shared cache or not.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_OBJECT_SIZE_BYTES

public static final int DEFAULT_MAX_OBJECT_SIZE_BYTES

Default setting for the maximum object size that will be cached, in bytes.

See Also:

Constant Field Values

DEFAULT_MAX_CACHE_ENTRIES

public static final int DEFAULT_MAX_CACHE_ENTRIES

Default setting for the maximum number of cache entries that will be retained.

See Also:

Constant Field Values

DEFAULT_MAX_UPDATE_RETRIES

public static final int DEFAULT_MAX_UPDATE_RETRIES

Default setting for the number of retries on a failed cache update

See Also:

Constant Field Values

DEFAULT_HEURISTIC_CACHING_ENABLED

public static final boolean DEFAULT_HEURISTIC_CACHING_ENABLED

Default setting for heuristic caching

See Also:

Constant Field Values

DEFAULT_HEURISTIC_COEFFICIENT

public static final float DEFAULT_HEURISTIC_COEFFICIENT

Default coefficient used to heuristically determine freshness lifetime from the Last-Modified time of a cache entry.

See Also:

Constant Field Values

DEFAULT_HEURISTIC_LIFETIME

public static final long DEFAULT_HEURISTIC_LIFETIME

Default lifetime in seconds to be assumed when we cannot calculate freshness heuristically.

See Also:

Constant Field Values

DEFAULT_ASYNCHRONOUS_WORKERS_MAX

public static final int DEFAULT_ASYNCHRONOUS_WORKERS_MAX

Default number of worker threads to allow for background revalidations resulting from the stale-while-revalidate directive.

See Also:

Constant Field Values

DEFAULT_ASYNCHRONOUS_WORKERS_CORE

public static final int DEFAULT_ASYNCHRONOUS_WORKERS_CORE

Default minimum number of worker threads to allow for background revalidations resulting from the stale-while-revalidate directive.

See Also:

Constant Field Values

DEFAULT_ASYNCHRONOUS_WORKER_IDLE_LIFETIME_SECS

public static final int DEFAULT_ASYNCHRONOUS_WORKER_IDLE_LIFETIME_SECS

Default maximum idle lifetime for a background revalidation thread before it gets reclaimed.

See Also:

Constant Field Values

DEFAULT_REVALIDATION_QUEUE_SIZE

public static final int DEFAULT_REVALIDATION_QUEUE_SIZE

Default maximum queue length for background revalidation requests.

See Also:

Constant Field Values

Constructor Detail

CacheConfig

public CacheConfig()

Method Detail

getMaxObjectSizeBytes

@Deprecated
public int getMaxObjectSizeBytes()

Deprecated. (4.2) use getMaxObjectSize()

Returns the current maximum response body size that will be cached.

Returns:

size in bytes

setMaxObjectSizeBytes

@Deprecated
public void setMaxObjectSizeBytes(int maxObjectSizeBytes)

Deprecated. (4.2) use setMaxObjectSize(long)

Specifies the maximum response body size that will be eligible for caching.

Parameters:

maxObjectSizeBytes - size in bytes

getMaxObjectSize

public long getMaxObjectSize()

Returns the current maximum response body size that will be cached.

Returns:

size in bytes

Since:

4.2

setMaxObjectSize

public void setMaxObjectSize(long maxObjectSize)

Specifies the maximum response body size that will be eligible for caching.

Parameters:

maxObjectSize - size in bytes

Since:

4.2

isSharedCache

public boolean isSharedCache()

Returns whether the cache will behave as a shared cache or not.

Returns:

true for a shared cache, false for a non- shared (private) cache

setSharedCache

public void setSharedCache(boolean isSharedCache)

Sets whether the cache should behave as a shared cache or not.

Parameters:

isSharedCache - true to behave as a shared cache, false to behave as a non-shared (private) cache. To have the cache behave like a browser cache, you want to set this to false.

getMaxCacheEntries

public int getMaxCacheEntries()

Returns the maximum number of cache entries the cache will retain.

setMaxCacheEntries

public void setMaxCacheEntries(int maxCacheEntries)

Sets the maximum number of cache entries the cache will retain.

getMaxUpdateRetries

public int getMaxUpdateRetries()

Returns the number of times to retry a cache update on failure

setMaxUpdateRetries

public void setMaxUpdateRetries(int maxUpdateRetries)

Sets the number of times to retry a cache update on failure

isHeuristicCachingEnabled

public boolean isHeuristicCachingEnabled()

Returns whether heuristic caching is enabled.

Returns:

true if it is enabled.

setHeuristicCachingEnabled

public void setHeuristicCachingEnabled(boolean heuristicCachingEnabled)

Enables or disables heuristic caching.

Parameters:

heuristicCachingEnabled - should be true to permit heuristic caching, false to enable it.

getHeuristicCoefficient

public float getHeuristicCoefficient()

Returns lifetime coefficient used in heuristic freshness caching.

setHeuristicCoefficient

public void setHeuristicCoefficient(float heuristicCoefficient)

Sets coefficient to be used in heuristic freshness caching. This is interpreted as the fraction of the time between the Last-Modified and Date headers of a cached response during which the cached response will be considered heuristically fresh.

Parameters:

heuristicCoefficient - should be between 0.0 and 1.0.

getHeuristicDefaultLifetime

public long getHeuristicDefaultLifetime()

Get the default lifetime to be used if heuristic freshness calculation is not possible.

setHeuristicDefaultLifetime

public void setHeuristicDefaultLifetime(long heuristicDefaultLifetimeSecs)

Sets default lifetime in seconds to be used if heuristic freshness calculation is not possible. Explicit cache control directives on either the request or origin response will override this, as will the heuristic Last-Modified freshness calculation if it is available.

Parameters:

heuristicDefaultLifetimeSecs - is the number of seconds to consider a cache-eligible response fresh in the absence of other information. Set this to 0 to disable this style of heuristic caching.

getAsynchronousWorkersMax

public int getAsynchronousWorkersMax()

Returns the maximum number of threads to allow for background revalidations due to the stale-while-revalidate directive. A value of 0 means background revalidations are disabled.

setAsynchronousWorkersMax

public void setAsynchronousWorkersMax(int max)

Sets the maximum number of threads to allow for background revalidations due to the stale-while-revalidate directive.

Parameters:

max - number of threads; a value of 0 disables background revalidations.

getAsynchronousWorkersCore

public int getAsynchronousWorkersCore()

Returns the minimum number of threads to keep alive for background revalidations due to the stale-while-revalidate directive.

setAsynchronousWorkersCore

public void setAsynchronousWorkersCore(int min)

Sets the minimum number of threads to keep alive for background revalidations due to the stale-while-revalidate directive.

Parameters:

min - should be greater than zero and less than or equal to getAsynchronousWorkersMax()

getAsynchronousWorkerIdleLifetimeSecs

public int getAsynchronousWorkerIdleLifetimeSecs()

Returns the current maximum idle lifetime in seconds for a background revalidation worker thread. If a worker thread is idle for this long, and there are more than the core number of worker threads alive, the worker will be reclaimed.

setAsynchronousWorkerIdleLifetimeSecs

public void setAsynchronousWorkerIdleLifetimeSecs(int secs)

Sets the current maximum idle lifetime in seconds for a background revalidation worker thread. If a worker thread is idle for this long, and there are more than the core number of worker threads alive, the worker will be reclaimed.

Parameters:

secs - idle lifetime in seconds

getRevalidationQueueSize

public int getRevalidationQueueSize()

Returns the current maximum queue size for background revalidations.

setRevalidationQueueSize

public void setRevalidationQueueSize(int size)

Sets the current maximum queue size for background revalidations.