com::cosylab::logging::engine::cache::EngineCache Class Reference

Collaboration diagram for com::cosylab::logging::engine::cache::EngineCache:

Public Member Functions
	EngineCache ()
	EngineCache (long size)
void	run ()
int	size ()
int	getActiveFilesSize ()
void	push (String string) throws IOException
String	pop () throws IOException, InterruptedException
void	close (boolean sync)
Static Public Attributes
static long	DEFAULT_SIZE = 1073741824
static String	MAXSIZE_PROPERTY_NAME = "jlog.enine.cache.maxFilesSize"
Private Member Functions
File	getNewFile () throws IOException
boolean	releaseFile (CacheFile itemToDel)
Integer	getNextFileKey ()
Static Private Member Functions
static long	getDefaultMaxFileSize ()
Private Attributes
long	maxSize
int	fileKey = 0
volatile CacheFile	outCacheFile = null
volatile CacheFile	inCacheFile = null
CacheEntriesQueue	entries = new CacheEntriesQueue()
LinkedBlockingQueue< CacheFile >	filesToDelete = new LinkedBlockingQueue<CacheFile>()
LinkedHashMap< Integer, CacheFile >	files = new LinkedHashMap<Integer,CacheFile>()
volatile boolean	closed = false

Detailed Description

Objects from this class implement a FIFO cache of String objects. The strings are written on disk by using several files: a new file is created whenever the dimension of the current file becomes greater then a fixed size. For each entry in cache, a record is created and kept in a in-memory list.

The cache is used by com.cosylab.logging.engine.ACS.ACSLogRetrieval, but can be used wherever a set of strings needs to be stored because there is no assumption about the content of the strings.

The logs are stored in a set of files and their ending position saved. When all the logs in a file have been red, the file is deleted optimizing the usage disk space. The deletion of unused files is done by a thread.

The length of each file of cache can be specified by a parameter in the constructor or by a java property. If both those values are not given, a default length is used.

files contains all the files used by the cache, identified by a key. When a file does not contain unread entries then its key is pushed into filesToDelete and deleted. The thread that deletes the files from disk, removes the CacheFile object from files too.

entries contains all the entries of in cache.

Author:: acaproni

Constructor & Destructor Documentation

com::cosylab::logging::engine::cache::EngineCache::EngineCache ( ) [inline]

Build a cache.

The max size of each file of the cache is calculated in the following way: 1. if the java property is present, the size is taken from suc a property 2. the default size is used

References getDefaultMaxFileSize().

com::cosylab::logging::engine::cache::EngineCache::EngineCache ( long size ) [inline]

Build the cache with the passed maximum size for each file of the cache

Parameters:

size

The max size of each file of the cache

References maxSize.

Member Function Documentation

void com::cosylab::logging::engine::cache::EngineCache::close ( boolean sync ) [inline]

Close the cache: delete all the entries and all the files the exit.

Note: this must be the last operation executed by the cache

Parameters:

sync true if must wait the termination of the threads before exiting

References com::cosylab::logging::engine::cache::CacheFile::close(), closed, files, inCacheFile, and outCacheFile.

Referenced by com::cosylab::logging::engine::ACS::ACSLogRetrieval::close(), and alma::acs::jlog::test::EngineCacheTest::tearDown().

int com::cosylab::logging::engine::cache::EngineCache::getActiveFilesSize ( ) [inline]

Returns:: The number of files used by the cache

References files.

Referenced by alma::acs::jlog::test::EngineCacheTest::setUp(), alma::acs::jlog::test::EngineCacheTest::testPushPopSeveralFiles(), and alma::acs::jlog::test::EngineCacheTest::testPushPopSingleFile().

static long com::cosylab::logging::engine::cache::EngineCache::getDefaultMaxFileSize ( ) [inline, static, private]

Get the max size of the files out of the system properties or uses the default value if the property does not exist

References DEFAULT_SIZE, and MAXSIZE_PROPERTY_NAME.

Referenced by EngineCache().

File com::cosylab::logging::engine::cache::EngineCache::getNewFile ( ) throws IOException [inline, private]

Attempts to create the file for the strings in several places before giving up.

Returns:: A new temporary file null if it was not possible to create a new file

Exceptions:

If

it was not possible to create a temporary file

Referenced by push().

Integer com::cosylab::logging::engine::cache::EngineCache::getNextFileKey ( ) [inline, private]

Generate a new key for a file.

Each new key is generated by increasing the value of the current key. If the max integer value is reached then the key rests to the min value.

Returns:: A new key for a file

References fileKey, and files.

Referenced by push().

String com::cosylab::logging::engine::cache::EngineCache::pop ( ) throws IOException, InterruptedException [inline]

Get and remove the next string from the cache.

Returns:: The next string entry in cache. null If the timeout happened

Exceptions:

	IOException	In case of error reading from the file
	InterruptedException	When the call to `poll` is interrupted

References closed, entries, files, filesToDelete, com::cosylab::logging::engine::cache::CacheEntriesQueue::get(), inCacheFile, com::cosylab::logging::engine::cache::CacheFile::key, com::cosylab::logging::engine::cache::CacheEntry::key, com::cosylab::logging::engine::cache::CacheFile::readFromFile(), releaseFile(), and com::cosylab::logging::engine::cache::CacheFile::setReadingMode().

Referenced by com::cosylab::logging::engine::ACS::ACSLogRetrieval::run(), alma::acs::jlog::test::EngineCacheTest::testPushPopSeveralFiles(), and alma::acs::jlog::test::EngineCacheTest::testPushPopSingleFile().

void com::cosylab::logging::engine::cache::EngineCache::push ( String string ) throws IOException [inline]

Push an entry in the cache. If the current file is null or its size is greater then maxSize, then a new file is created.

Parameters:

string

The string to write in the cache

Exceptions:

IOException

In case of error writing the string on disk

References closed, entries, files, com::cosylab::logging::engine::cache::CacheFile::getFileLength(), getNewFile(), getNextFileKey(), com::cosylab::logging::engine::cache::CacheFile::key, maxSize, outCacheFile, com::cosylab::logging::engine::cache::CacheEntriesQueue::put(), com::cosylab::logging::engine::cache::CacheFile::setWritingMode(), and com::cosylab::logging::engine::cache::CacheFile::writeOnFile().

Referenced by com::cosylab::logging::engine::ACS::ACSLogRetrieval::addLog(), alma::acs::jlog::test::EngineCacheTest::testPushPopSeveralFiles(), and alma::acs::jlog::test::EngineCacheTest::testPushPopSingleFile().

boolean com::cosylab::logging::engine::cache::EngineCache::releaseFile ( CacheFile itemToDel ) [inline, private]

Close and delete a file.

Parameters:

itemToDel

The item to delete

Returns:: true if the file is deleted

References com::cosylab::logging::engine::cache::CacheFile::close(), com::cosylab::logging::engine::cache::CacheFile::fileName, com::cosylab::logging::engine::cache::CacheFile::getFile(), and com::cosylab::logging::engine::cache::CacheFile::key.

Referenced by pop(), and run().

void com::cosylab::logging::engine::cache::EngineCache::run ( ) [inline]

The method to get and delete unused files

References closed, filesToDelete, and releaseFile().

int com::cosylab::logging::engine::cache::EngineCache::size ( ) [inline]

Return the number of entries in cache.

Returns:: the number of entries in cache

References entries, and com::cosylab::logging::engine::cache::CacheEntriesQueue::size().

Referenced by com::cosylab::logging::engine::ACS::ACSLogRetrieval::hasPendingEntries(), com::cosylab::logging::engine::ACS::ACSLogRetrieval::run(), alma::acs::jlog::test::EngineCacheTest::setUp(), com::cosylab::logging::engine::ACS::ACSLogRetrieval::size(), alma::acs::jlog::test::EngineCacheTest::testPushPopSeveralFiles(), and alma::acs::jlog::test::EngineCacheTest::testPushPopSingleFile().

Member Data Documentation

volatile boolean com::cosylab::logging::engine::cache::EngineCache::closed = false [private]

true if the cache is closed. It signals the thread to terminate.

Referenced by close(), pop(), push(), and run().

long com::cosylab::logging::engine::cache::EngineCache::DEFAULT_SIZE = 1073741824 [static]

The default max size for each file of the cache. The default value is used when the java property is not found and the size is not given explicitly.

NFS could be limited to 2GB depending on the installed version

Referenced by getDefaultMaxFileSize().

CacheEntriesQueue com::cosylab::logging::engine::cache::EngineCache::entries = new CacheEntriesQueue() [private]

The entries in the cache.

The items of the list are organized in a FIFO policy. This is particularly important because this order is used to know when a file is not used anymore and can be deleted.

See also:: EngineCache.files

Referenced by pop(), push(), and size().

int com::cosylab::logging::engine::cache::EngineCache::fileKey = 0 [private]

Each file of the cache is identified by a key.

The key is always positive.

Referenced by getNextFileKey().

LinkedHashMap<Integer,CacheFile> com::cosylab::logging::engine::cache::EngineCache::files = new LinkedHashMap<Integer,CacheFile>() [private]

The files used by the cache.

The entries in this vector have the same order of the creation of the files: the last created file is in the last position of the vector.

This property can be used to verify for the correctness of the computation because every time we have to delete a file, it must be the first item of this vector