alluxio.client.file.cache

Class LocalCacheManager

java.lang.Object

alluxio.client.file.cache.LocalCacheManager

All Implemented Interfaces:

CacheManager, AutoCloseable

@ThreadSafe
public class LocalCacheManager
extends Object
implements CacheManager

A class to manage & serve cached pages. This class coordinates various components to respond for thread-safety and enforce cache replacement policies. One of the motivations of creating a client-side cache is from "Improving In-Memory File System Reading Performance by Fine-Grained User-Space Cache Mechanisms" by Gu et al, which illustrates performance benefits for various read workloads. This class also introduces paging as a caching unit. Lock hierarchy in this class: All operations must follow this order to operate on pages:

1. Acquire corresponding page lock
2. Acquire metastore lock mMetaLock
3. Update metastore
4. Release metastore lock mMetaLock
5. Update the pagestore and evictor
6. Release corresponding page lock

Nested Class Summary

Nested classes/interfaces inherited from interface alluxio.client.file.cache.CacheManager

CacheManager.Factory

Method Summary

Modifier and Type	Method and Description
void	close()
static LocalCacheManager	create(AlluxioConfiguration conf)
boolean	delete(PageId pageId) Deletes a page from the cache.
int	get(PageId pageId, int pageOffset, int bytesToRead, byte[] buffer, int offsetInBuffer) Reads a part of a page if the queried page is found in the cache, stores the result in buffer.
boolean	put(PageId pageId, byte[] page) Puts a page into the cache manager.

Methods inherited from class java.lang.Object

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

Methods inherited from interface alluxio.client.file.cache.CacheManager

get

Method Detail

create

public static LocalCacheManager create(AlluxioConfiguration conf)
                                throws IOException

Parameters:

conf - the Alluxio configuration

Returns:

an instance of LocalCacheManager

Throws:

IOException

put

public boolean put(PageId pageId,
                   byte[] page)

Description copied from interface: CacheManager

Puts a page into the cache manager. This method is best effort. It is possible that this put operation returns without page written.

Specified by:

put in interface CacheManager

Parameters:

pageId - page identifier

page - page data

Returns:

true if the put was successful, false otherwise

get

public int get(PageId pageId,
               int pageOffset,
               int bytesToRead,
               byte[] buffer,
               int offsetInBuffer)

Description copied from interface: CacheManager

Reads a part of a page if the queried page is found in the cache, stores the result in buffer.

Specified by:

get in interface CacheManager

Parameters:

pageId - page identifier

pageOffset - offset into the page

bytesToRead - number of bytes to read in this page

buffer - destination buffer to write

offsetInBuffer - offset in the destination buffer to write

Returns:

number of bytes read, 0 if page is not found, -1 on errors

delete

public boolean delete(PageId pageId)

Description copied from interface: CacheManager

Deletes a page from the cache.

Specified by:

delete in interface CacheManager

Parameters:

pageId - page identifier

Returns:

true if the page is successfully deleted, false otherwise

close

public void close()
           throws Exception

Specified by:

close in interface AutoCloseable

Throws:

Exception