org.apache.beam.fn.harness

Class Caches

java.lang.Object

org.apache.beam.fn.harness.Caches

public final class Caches
extends java.lang.Object

Utility methods used to instantiate and operate over cache instances.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Caches.ClearableCache<K,V> A cache that tracks keys that have been inserted into the cache and supports clearing them.

Field Summary

Fields

Modifier and Type	Field and Description
static long	REFERENCE_SIZE The size of a reference.

Constructor Summary

Constructors

Constructor and Description
Caches()

Method Summary

Modifier and Type	Method and Description
static <K,V> Cache<K,V>	eternal() A cache that never evicts any values.
static <K,V> Cache<K,V>	fromOptions(org.apache.beam.sdk.options.PipelineOptions options) Uses the specified PipelineOptions to configure and return a cache instance based upon parameters within SdkHarnessOptions.
static <K,V> Cache<K,V>	noop() A cache that never stores any values.
static boolean	shouldUpdateOnSizeChange(long oldSize, long newSize) Returns whether the cache should be updated in the case where the objects size has changed.
static <K,V> Cache<K,V>	subCache(Cache<?,?> cache, java.lang.Object keyPrefix, java.lang.Object... additionalKeyPrefix) Returns a view of a cache that operates on keys with a specified key prefix.
static long	weigh(java.lang.Object o) Returns the amount of memory in bytes the provided object consumes.

Methods inherited from class java.lang.Object

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

Field Detail

REFERENCE_SIZE

public static final long REFERENCE_SIZE

The size of a reference.

See Also:

Constant Field Values

Constructor Detail

Caches

public Caches()

Method Detail

weigh

public static long weigh(java.lang.Object o)

Returns the amount of memory in bytes the provided object consumes.

shouldUpdateOnSizeChange

public static boolean shouldUpdateOnSizeChange(long oldSize,
                                               long newSize)

Returns whether the cache should be updated in the case where the objects size has changed.

Note that this should only be used in the case where the cache is being updated very often in a tight loop and is not a good fit for cases where the object being cached is the result of an expensive operation like a disk read or remote service call.

noop

public static <K,V> Cache<K,V> noop()

A cache that never stores any values.

eternal

public static <K,V> Cache<K,V> eternal()

A cache that never evicts any values.

fromOptions

public static <K,V> Cache<K,V> fromOptions(org.apache.beam.sdk.options.PipelineOptions options)

Uses the specified PipelineOptions to configure and return a cache instance based upon parameters within SdkHarnessOptions.

subCache

public static <K,V> Cache<K,V> subCache(Cache<?,?> cache,
                                        java.lang.Object keyPrefix,
                                        java.lang.Object... additionalKeyPrefix)

Returns a view of a cache that operates on keys with a specified key prefix.

All lookups, insertions, and removals into the parent Cache will be prefixed by the specified prefixes.