com.orientechnologies.orient.core.storage.cache.chm

Class AsyncReadCache

java.lang.Object

com.orientechnologies.orient.core.storage.cache.chm.AsyncReadCache

All Implemented Interfaces:

OReadCache

public final class AsyncReadCache
extends Object
implements OReadCache

Disk cache based on ConcurrentHashMap and eviction policy which is asynchronously processed by handling set of events logged in lock free event buffer. This feature first was introduced in Caffeine framework https://github.com/ben-manes/caffeine and in ConcurrentLinkedHashMap library https://github.com/ben-manes/concurrentlinkedhashmap . The difference is that if consumption of memory in cache is bigger than 1% disk cache is switched from asynchronous processing of stream of events to synchronous processing. But that is true only for threads which cause loading of additional pages from write cache to disk cache. Window TinyLFU policy is used as cache eviction policy because it prevents usage of ghost entries and as result considerably decrease usage of heap memory.

Constructor Summary

Constructors

Constructor and Description
AsyncReadCache(OByteBufferPool bufferPool, long maxCacheSizeInBytes, int pageSize, boolean trackHitRate)

Method Summary

Modifier and Type	Method and Description
long	addFile(String fileName, long fileId, OWriteCache writeCache)
long	addFile(String fileName, OWriteCache writeCache)
OCacheEntry	allocateNewPage(long fileId, OWriteCache writeCache, OLogSequenceNumber startLSN)
void	changeMaximumAmountOfMemory(long maxMemory)
void	clear()
void	closeFile(long fileId, boolean flush, OWriteCache writeCache)
void	closeStorage(OWriteCache writeCache) Closes all files inside of write cache and flushes all associated data.
void	deleteFile(long fileId, OWriteCache writeCache)
void	deleteStorage(OWriteCache writeCache)
long	getUsedMemory()
void	loadCacheState(OWriteCache writeCache) Load state of cache from file system if possible.
OCacheEntry	loadForRead(long fileId, long pageIndex, boolean checkPinnedPages, OWriteCache writeCache, int pageCount, boolean verifyChecksums)
OCacheEntry	loadForWrite(long fileId, long pageIndex, boolean checkPinnedPages, OWriteCache writeCache, int pageCount, boolean verifyChecksums, OLogSequenceNumber startLSN)
void	pinPage(OCacheEntry cacheEntry, OWriteCache writeCache)
void	releaseFromRead(OCacheEntry cacheEntry, OWriteCache writeCache)
void	releaseFromWrite(OCacheEntry cacheEntry, OWriteCache writeCache)
OCacheEntry	silentLoadForRead(long extFileId, int pageIndex, OWriteCache writeCache, boolean verifyChecksums) Loads page from the disk cache if it is already loaded otherwise loads it from disk but does not put it the disk cache.
void	storeCacheState(OWriteCache writeCache) Stores state of cache inside file if possible.
void	truncateFile(long fileId, OWriteCache writeCache)

Methods inherited from class java.lang.Object

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

Constructor Detail

AsyncReadCache

public AsyncReadCache(OByteBufferPool bufferPool,
                      long maxCacheSizeInBytes,
                      int pageSize,
                      boolean trackHitRate)

Method Detail

addFile

public final long addFile(String fileName,
                          OWriteCache writeCache)
                   throws IOException

Specified by:

addFile in interface OReadCache

Throws:

IOException

addFile

public final long addFile(String fileName,
                          long fileId,
                          OWriteCache writeCache)
                   throws IOException

Specified by:

addFile in interface OReadCache

Throws:

IOException

loadForWrite

public final OCacheEntry loadForWrite(long fileId,
                                      long pageIndex,
                                      boolean checkPinnedPages,
                                      OWriteCache writeCache,
                                      int pageCount,
                                      boolean verifyChecksums,
                                      OLogSequenceNumber startLSN)

Specified by:

loadForWrite in interface OReadCache

loadForRead

public final OCacheEntry loadForRead(long fileId,
                                     long pageIndex,
                                     boolean checkPinnedPages,
                                     OWriteCache writeCache,
                                     int pageCount,
                                     boolean verifyChecksums)

Specified by:

loadForRead in interface OReadCache

silentLoadForRead

public OCacheEntry silentLoadForRead(long extFileId,
                                     int pageIndex,
                                     OWriteCache writeCache,
                                     boolean verifyChecksums)

Description copied from interface: OReadCache

Loads page from the disk cache if it is already loaded otherwise loads it from disk but does not put it the disk cache. In some scenarios usage of this method can lead to concurrency issues so please use it carefully.

Specified by:

silentLoadForRead in interface OReadCache

changeMaximumAmountOfMemory

public final void changeMaximumAmountOfMemory(long maxMemory)

Specified by:

changeMaximumAmountOfMemory in interface OReadCache

releaseFromRead

public final void releaseFromRead(OCacheEntry cacheEntry,
                                  OWriteCache writeCache)

Specified by:

releaseFromRead in interface OReadCache

releaseFromWrite

public final void releaseFromWrite(OCacheEntry cacheEntry,
                                   OWriteCache writeCache)

Specified by:

releaseFromWrite in interface OReadCache

pinPage

public final void pinPage(OCacheEntry cacheEntry,
                          OWriteCache writeCache)

Specified by:

pinPage in interface OReadCache

allocateNewPage

public final OCacheEntry allocateNewPage(long fileId,
                                         OWriteCache writeCache,
                                         OLogSequenceNumber startLSN)
                                  throws IOException

Specified by:

allocateNewPage in interface OReadCache

Throws:

IOException

getUsedMemory

public final long getUsedMemory()

Specified by:

getUsedMemory in interface OReadCache

clear

public final void clear()

Specified by:

clear in interface OReadCache

truncateFile

public final void truncateFile(long fileId,
                               OWriteCache writeCache)
                        throws IOException

Specified by:

truncateFile in interface OReadCache

Throws:

IOException

closeFile

public final void closeFile(long fileId,
                            boolean flush,
                            OWriteCache writeCache)

Specified by:

closeFile in interface OReadCache

deleteFile

public final void deleteFile(long fileId,
                             OWriteCache writeCache)
                      throws IOException

Specified by:

deleteFile in interface OReadCache

Throws:

IOException

deleteStorage

public final void deleteStorage(OWriteCache writeCache)
                         throws IOException

Specified by:

deleteStorage in interface OReadCache

Throws:

IOException

closeStorage

public final void closeStorage(OWriteCache writeCache)
                        throws IOException

Description copied from interface: OReadCache

Closes all files inside of write cache and flushes all associated data.

Specified by:

closeStorage in interface OReadCache

Parameters:

writeCache - Write cache to close.

Throws:

IOException

loadCacheState

public final void loadCacheState(OWriteCache writeCache)

Description copied from interface: OReadCache

Load state of cache from file system if possible.

Specified by:

loadCacheState in interface OReadCache

Parameters:

writeCache - Write cache is used to load pages back into cache if possible.

storeCacheState

public final void storeCacheState(OWriteCache writeCache)

Description copied from interface: OReadCache

Stores state of cache inside file if possible.

Specified by:

storeCacheState in interface OReadCache

Parameters:

writeCache - Write cache which manages files cache state of which is going to be stored.