com.orientechnologies.orient.core.storage.cache.local.twoq

Class O2QCache

java.lang.Object

com.orientechnologies.orient.core.storage.cache.local.twoq.O2QCache

All Implemented Interfaces:

OReadCache

public final class O2QCache
extends Object
implements OReadCache

Since:

7/24/13

Author:

Andrey Lomakin (a.lomakin-at-orientdb.com)

Field Summary

Fields

Modifier and Type	Field and Description
static String	CACHE_STATE_FILE File which contains stored state of disk cache after storage close.
static String	CACHE_STATISTIC_FILE_EXTENSION Extension for file which contains stored state of disk cache after storage close.
static int	MIN_CACHE_SIZE Minimum size of memory which may be allocated by cache (in pages).

Constructor Summary

Constructors

Constructor and Description
O2QCache(long readCacheMaxMemory, int pageSize, boolean checkMinSize, int percentOfPinnedPages, boolean printCacheStatistics, int cacheStatisticsInterval)

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 readCacheMaxMemory) Changes amount of memory which may be used by given cache.
void	clear()
void	closeFile(long fileId, boolean flush, OWriteCache writeCache)
void	closeStorage(OWriteCache writeCache) Performs following steps: If flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true saves state of all queues of 2Q cache into file CACHE_STATE_FILE.The only exception is pinned pages they need to pinned again. Closes all files and flushes all data associated to them.
void	deleteFile(long fileId, OWriteCache writeCache)
void	deleteStorage(OWriteCache writeCache)
long	getUsedMemory()
void	loadCacheState(OWriteCache writeCache) Loads state of 2Q cache queues stored during storage close closeStorage(OWriteCache) back into memory if flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true.
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 fileId, 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 queues of 2Q cache inside of CACHE_STATE_FILE file if flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true.
void	truncateFile(long fileId, OWriteCache writeCache)

Methods inherited from class java.lang.Object

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

Field Detail

MIN_CACHE_SIZE

public static final int MIN_CACHE_SIZE

Minimum size of memory which may be allocated by cache (in pages). This parameter is used only if related flag is set in constrictor of cache.

See Also:

Constant Field Values

CACHE_STATE_FILE

public static final String CACHE_STATE_FILE

File which contains stored state of disk cache after storage close.

See Also:

Constant Field Values

CACHE_STATISTIC_FILE_EXTENSION

public static final String CACHE_STATISTIC_FILE_EXTENSION

Extension for file which contains stored state of disk cache after storage close.

See Also:

Constant Field Values

Constructor Detail

O2QCache

public O2QCache(long readCacheMaxMemory,
                int pageSize,
                boolean checkMinSize,
                int percentOfPinnedPages,
                boolean printCacheStatistics,
                int cacheStatisticsInterval)

Parameters:

readCacheMaxMemory - Maximum amount of direct memory which can allocated by disk cache in bytes.

pageSize - Cache page size in bytes.

checkMinSize - If this flat is set size of cache may be MIN_CACHE_SIZE or bigger.

percentOfPinnedPages - Maximum percent of pinned pages which may be hold by this cache.

See Also:

MAX_PERCENT_OF_PINED_PAGES

Method Detail

addFile

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

Specified by:

addFile in interface OReadCache

Throws:

IOException

silentLoadForRead

public OCacheEntry silentLoadForRead(long fileId,
                                     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

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)
                               throws IOException

Specified by:

loadForWrite in interface OReadCache

Throws:

IOException

releaseFromWrite

public final void releaseFromWrite(OCacheEntry cacheEntry,
                                   OWriteCache writeCache)

Specified by:

releaseFromWrite in interface OReadCache

loadForRead

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

Specified by:

loadForRead in interface OReadCache

Throws:

IOException

releaseFromRead

public final void releaseFromRead(OCacheEntry cacheEntry,
                                  OWriteCache writeCache)

Specified by:

releaseFromRead in interface OReadCache

pinPage

public final void pinPage(OCacheEntry cacheEntry,
                          OWriteCache writeCache)

Specified by:

pinPage in interface OReadCache

changeMaximumAmountOfMemory

public void changeMaximumAmountOfMemory(long readCacheMaxMemory)
                                 throws IllegalStateException

Changes amount of memory which may be used by given cache. This method may consume many resources if amount of memory provided in parameter is much less than current amount of memory.

Specified by:

changeMaximumAmountOfMemory in interface OReadCache

Parameters:

readCacheMaxMemory - New maximum size of cache in bytes.

Throws:

IllegalStateException - In case of new size of disk cache is too small to hold existing pinned pages.

allocateNewPage

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

Specified by:

allocateNewPage in interface OReadCache

Throws:

IOException

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

closeStorage

public final void closeStorage(OWriteCache writeCache)
                        throws IOException

Performs following steps:

1. If flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true saves state of all queues of 2Q cache into file CACHE_STATE_FILE.The only exception is pinned pages they need to pinned again.
2. Closes all files and flushes all data associated to them.

Specified by:

closeStorage in interface OReadCache

Parameters:

writeCache - Write cache all files of which should be closed. In terms of cache write cache = storage.

Throws:

IOException

loadCacheState

public final void loadCacheState(OWriteCache writeCache)

Loads state of 2Q cache queues stored during storage close closeStorage(OWriteCache) back into memory if flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true. If maximum size of cache was decreased cache state will not be restored.

Specified by:

loadCacheState in interface OReadCache

Parameters:

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

See Also:

closeStorage(OWriteCache)

storeCacheState

public final void storeCacheState(OWriteCache writeCache)

Stores state of queues of 2Q cache inside of CACHE_STATE_FILE file if flag OGlobalConfiguration.STORAGE_KEEP_DISK_CACHE_STATE is set to true. Following format is used to store queue state:

1. Max cache size, single item (long)
2. File id or -1 if end of queue is reached (int)
3. Page index (long), is absent if end of the queue is reached

Specified by:

storeCacheState in interface OReadCache

Parameters:

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

deleteStorage

public final void deleteStorage(OWriteCache writeCache)
                         throws IOException

Specified by:

deleteStorage in interface OReadCache

Throws:

IOException

getUsedMemory

public final long getUsedMemory()

Specified by:

getUsedMemory in interface OReadCache