com.cosylab.logging.client.cache

Class LogBufferedFileCache

java.lang.Object

com.cosylab.logging.client.cache.LogFileCache

com.cosylab.logging.client.cache.LogBufferedFileCache

All Implemented Interfaces:

ILogMap

public class LogBufferedFileCache
extends LogFileCache
implements ILogMap

This class extends the LogFileCache adding the buffering of the logs that must be written on disk. It uses a WriteBuffer to store the logs to write on disk. The purpose of this class is to write several logs at once reducing the write operations on disk. The buffer stores the logs when they are added. It flushes the buffer on disk when the number of logs in memory exceeds the maximum size. This means that the number of chars written on the file cache at once is not fixed but depends on the lengths of the logs stored in this buffer. To enhance performance and to have the size of the file always available, the buffer stores the log together with other info in Map of BufferedCacheItem

Author:

acaproni

Nested Class Summary

Nested classes/interfaces inherited from class com.cosylab.logging.client.cache.LogFileCache

LogFileCache.LogCacheInfo

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_WRITEBUFFERSIZE
static java.lang.String	WRITEBUFFERSIZE_PROPERTY_NAME

Fields inherited from class com.cosylab.logging.client.cache.LogFileCache

file, index, logID, replacedLogs

Constructor Summary

Constructors

Constructor and Description
LogBufferedFileCache() Build a LogBufferedFileCache with the default sizes for the write buffer
LogBufferedFileCache(int writeBufferSize) Build a LogBufferedFileCache with the given size for the cache and the write buffer.

Method Summary

Modifier and Type	Method and Description
int	add(ILogEntry log) Append a log to the cache
void	clear() Empty the cache
void	deleteLog(java.lang.Integer key) Delete a log with the given key
void	deleteLogs(java.util.Collection<java.lang.Integer> keys) Delete a collection of logs
void	flushBuffer() Flush all the logs on file
int	getBufferSize()
long	getFileSize() Return the length of the file on disk taking into account the length of the string to write on the disk for the logs in the buffer.
java.lang.Integer	getFirstLog() Return the key of the first valid log (FIFO).
int	getFirstLogs(int n, java.util.Collection<java.lang.Integer> keys) Append at most n keys from the first valid logs to the collection.
java.lang.Integer	getLastLog() Return the key of the last valid log (FIFO) The key of the last log is the key of the last inserted log but it can cheang if such log has been deleted
ILogEntry	getLog(java.lang.Integer key) Return the log with the given key
int	getSize() Return the number of logs in cache
java.util.Iterator<ILogEntry>	iterator() Return an iterator over the logs in cache
java.util.Set<java.lang.Integer>	keySet() Return a set with all the keys of the logs in cache
void	replaceLog(java.lang.Integer key, ILogEntry log) Replace the log in the given position with the new one

Methods inherited from class com.cosylab.logging.client.cache.LogFileCache

initCache, toCacheString

Methods inherited from class java.lang.Object

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

Field Detail

WRITEBUFFERSIZE_PROPERTY_NAME

public static final java.lang.String WRITEBUFFERSIZE_PROPERTY_NAME

See Also:

Constant Field Values

DEFAULT_WRITEBUFFERSIZE

public static final int DEFAULT_WRITEBUFFERSIZE

See Also:

Constant Field Values

Constructor Detail

LogBufferedFileCache

public LogBufferedFileCache(int writeBufferSize)
                     throws LogCacheException

Build a LogBufferedFileCache with the given size for the cache and the write buffer. If there isn't enough memory for the cache, tries with a smmaller size.

Parameters:

cacheSize - The size of the cache

writeBufferSize - The size of the write buffer

Throws:

LogCacheException - If there is'nt enough memory for a buffer of at least 32 logs

LogBufferedFileCache

public LogBufferedFileCache()
                     throws LogCacheException

Build a LogBufferedFileCache with the default sizes for the write buffer

Throws:

LogCacheException

See Also:

LogBufferedFileCache.getDefaultWriteCacheSize

Method Detail

clear

public void clear()
           throws LogCacheException

Empty the cache

Specified by:

clear in interface ILogMap

Overrides:

clear in class LogFileCache

Throws:

java.io.IOException

LogCacheException

getLog

public ILogEntry getLog(java.lang.Integer key)
                 throws LogCacheException

Return the log with the given key

Specified by:

getLog in interface ILogMap

Overrides:

getLog in class LogFileCache

Parameters:

key - The key of the log

Returns:

The LogEntryXML or null in case of error

Throws:

LogCacheException

deleteLog

public void deleteLog(java.lang.Integer key)
               throws LogCacheException

Delete a log with the given key

Specified by:

deleteLog in interface ILogMap

Overrides:

deleteLog in class LogFileCache

Parameters:

pos - The key of the log to delete

Throws:

LogCacheException

deleteLogs

public void deleteLogs(java.util.Collection<java.lang.Integer> keys)
                throws LogCacheException

Delete a collection of logs

Specified by:

deleteLogs in interface ILogMap

Overrides:

deleteLogs in class LogFileCache

Parameters:

keys - The keys of the logs to remove from the cache

Throws:

LogCacheException

add

public int add(ILogEntry log)
        throws LogCacheException

Append a log to the cache

Specified by:

add in interface ILogMap

Overrides:

add in class LogFileCache

Parameters:

log - The log to append in the cache

Returns:

The key of the added log

Throws:

LogCacheException

flushBuffer

public void flushBuffer()
                 throws LogCacheException

Flush all the logs on file

Throws:

LogCacheException

getSize

public int getSize()

Return the number of logs in cache

Specified by:

getSize in interface ILogMap

Overrides:

getSize in class LogFileCache

Returns:

The number of logs in cache

getFileSize

public long getFileSize()
                 throws java.io.IOException

Return the length of the file on disk taking into account the length of the string to write on the disk for the logs in the buffer.

Overrides:

getFileSize in class LogFileCache

Returns:

The size of the file cache

Throws:

java.io.IOException - in case of I/O error

See Also:

RandomAccessFile

getBufferSize

public final int getBufferSize()

Returns:

The number of logs actually in the buffer

getFirstLog

public java.lang.Integer getFirstLog()

Return the key of the first valid log (FIFO). The key of the first log is 0 but it can change if the log 0 has been deleted.

Specified by:

getFirstLog in interface ILogMap

Overrides:

getFirstLog in class LogFileCache

Returns:

The key of the first log null if the cache is empty

getFirstLogs

public int getFirstLogs(int n,
                        java.util.Collection<java.lang.Integer> keys)

Append at most n keys from the first valid logs to the collection. First here means first in the FIFO policy. The number of added keys can be less then n if the cache doesn't contain enough logs.

Specified by:

getFirstLogs in interface ILogMap

Overrides:

getFirstLogs in class LogFileCache

Parameters:

n - The desired number of keys of first logs

keys - The collection to add they keys to

Returns:

The number of keys effectively added

getLastLog

public java.lang.Integer getLastLog()

Return the key of the last valid log (FIFO) The key of the last log is the key of the last inserted log but it can cheang if such log has been deleted

Specified by:

getLastLog in interface ILogMap

Overrides:

getLastLog in class LogFileCache

Returns:

The key of the last inserted log null if th cache is empty

keySet

public java.util.Set<java.lang.Integer> keySet()

Return a set with all the keys of the logs in cache

Specified by:

keySet in interface ILogMap

Overrides:

keySet in class LogFileCache

Returns:

The keys of the logs in cache

iterator

public java.util.Iterator<ILogEntry> iterator()

Return an iterator over the logs in cache

Specified by:

iterator in interface ILogMap

Overrides:

iterator in class LogFileCache

Returns:

an Iterator over the elements in this map

replaceLog

public void replaceLog(java.lang.Integer key,
                       ILogEntry log)
                throws LogCacheException

Replace the log in the given position with the new one

If the log to replace is not in the buffer, LogBufferedFileCache delegated to LogFileCache

Specified by:

replaceLog in interface ILogMap

Overrides:

replaceLog in class LogFileCache

Parameters:

position - The position of the log to replace

log - The key (identifier) of the log

Throws:

LogCacheException