com.bigdata.service

Class AbstractIndexCache<T extends IRangeQuery>

java.lang.Object

com.bigdata.service.AbstractIndexCache<T>

Type Parameters:

T -

Direct Known Subclasses:

IndexCache, MetadataIndexCache

public abstract class AbstractIndexCache<T extends IRangeQuery>
extends Object

Abstract base class providing caching for IIndex like objects. A canonicalizing cache is used with weak references to the IIndexs back by a hard reference LRU cache. This tends to keep around views that are reused while letting references for unused views be cleared by the garbage collector in a timely manner.

Version:

$Id$

Author:

Bryan Thompson

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.apache.log4j.Logger	log

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractIndexCache(int capacity, long timeout)

Method Summary

Methods

Modifier and Type	Method and Description
protected void	dropIndexFromCache(String name) Drop the ITx.UNISOLATED and ITx.READ_COMMITTED entries for the named index from the cache.
T	getIndex(String name, long timestamp) Request a view of an index.
protected abstract T	newView(String name, long timestamp) Method is invoked on a cache miss and returns a view of the described index.
protected void	shutdown()

Methods inherited from class java.lang.Object

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

Field Detail

log

protected static final org.apache.log4j.Logger log

Constructor Detail

AbstractIndexCache

protected AbstractIndexCache(int capacity,
                  long timeout)

Parameters:

capacity - The capacity of the backing LRU hard reference cache.

timeout - The timeout in milliseconds for stale entries in the cache.

See Also:

IBigdataClient.Options.CLIENT_INDEX_CACHE_CAPACITY, IBigdataClient.Options.CLIENT_INDEX_CACHE_TIMEOUT

Method Detail

newView

protected abstract T newView(String name,
        long timestamp)

Method is invoked on a cache miss and returns a view of the described index.

Parameters:

name -

timestamp -

Returns:

The index view -or- null if the described index does not exist.

getIndex

public T getIndex(String name,
         long timestamp)

Request a view of an index. If there is a cache miss then a new view will be created.

Note: ITx.READ_COMMITTED views are cached. Read-committed semantics are obtained by the indirection imposed by the IClientIndex, which converts a request by the client into a request against the appropriate IDataServices via task(s) submitted against those services.

Parameters:

name - The index name.

timestamp - The timestamp of the view.

Returns:

The index view -or- null if the described index does not exist.

dropIndexFromCache

protected void dropIndexFromCache(String name)

Drop the ITx.UNISOLATED and ITx.READ_COMMITTED entries for the named index from the cache.

Historical and transactional reads are still allowed, but we remove the read-committed or unisolated views from the cache once the index has been dropped. If a client wants them, it needs to re-request. If they have been re-registered on the metadata service then they will become available again.

Note: Operations against unisolated or read-committed indices will throw exceptions if they execute after the index was dropped.

shutdown

protected void shutdown()