com.ibm.di.queue
Class MemBufferQ

java.lang.Object
  com.ibm.di.queue.MemBufferQ

All Implemented Interfaces:

ActionListener, EventListener

public class MemBufferQ
extends Object
implements ActionListener

A FIFO queue

Constructor Summary

MemBufferQ(int nEntries)
Constructor Initializes the memory buffer pipe when paging is disabled

MemBufferQ(int nEntries, int pagesize)
Constructor Initializes the memory buffer pipe when paging is enabled

Method Summary

void	actionPerformed(ActionEvent e)
void	AddToChunk(Object x)
void	blockAdd(boolean enable) Enable disable blocking add this is used only when paging support is disabled.
void	enablePersistence(boolean enable) enablePersistence : enable/disable paging support using system store
void	handle(int purpose) handle : issues triggers to the registered callbacks
void	initDB(String sDBName, String jdbcLogin, String jdbcPassword, String sTblName) Initializes the system store paramemters.
boolean	isEmpty()
Object	peek() Same as read but does not remove data from the memq never use peek() for polling the memq in reader thread this is because the memq id implemented using a synchronized data structure and polling memq continuously would not relinquish control of memq to the writer thread as a result the reader will wait infinitely and writer would fail leading to loss of data.
Object	peekPage()
void	purgeQueue() Purges the queue.
Object	read() synchronized method: The first item inserted in the queue and not yet removed.
Object	read(int timeout) synchronized method: The first item inserted in the queue and not yet removed.
void	register(QCallback a, int purpose) Registers a callback which will be called when memQ is empty/full/data available it is assumed that the callback implements the handle()function.
int	size()
void	terminate() Terminates the system store threads.
void	terminate(boolean dropSystemStore) terminates the system store threads and drops table if dropSystemStore set to true
void	unregister(QCallback a, int purpose) unregister : unregisters a callback
void	write(Object x) write : add an object to the end of memq contains embedded logic that would trigger whenever memQ is full/empty or when an object is added to empty queue so that objects waiting for data can be triggered

Methods inherited from class java.lang.Object

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

Constructor Detail

MemBufferQ

public MemBufferQ(int nEntries,
                  int pagesize)

Constructor Initializes the memory buffer pipe when paging is enabled

MemBufferQ

public MemBufferQ(int nEntries)

Constructor Initializes the memory buffer pipe when paging is disabled

Method Detail

AddToChunk

public void AddToChunk(Object x)

initDB

public void initDB(String sDBName,
                   String jdbcLogin,
                   String jdbcPassword,
                   String sTblName)
            throws Exception

Initializes the system store paramemters.

Parameters:

sDBName - system store database name

jdbcLogin - username to connect to the db

jdbcPassword - password to connect to the db

sTblName - table name

Throws:

Exception - if system store is not initialized properly

isEmpty

public boolean isEmpty()

Returns:

True if memQ is empty

size

public int size()

Returns:

Number of items in the memq.

read

public Object read()

synchronized method: The first item inserted in the queue and not yet removed. Requires !isEmpty (). Reading removes the item from the queue. read with no timeout.

read

public Object read(int timeout)

synchronized method: The first item inserted in the queue and not yet removed. Requires !isEmpty (). Reading removes the item from the queue. Waits for timeout

peekPage

public Object peekPage()

write

public void write(Object x)
           throws Exception

write : add an object to the end of memq contains embedded logic that would trigger whenever memQ is full/empty or when an object is added to empty queue so that objects waiting for data can be triggered

Parameters:

x - object to be added

Throws:

Exception - if add fails

peek

public Object peek()

Same as read but does not remove data from the memq never use peek() for polling the memq in reader thread this is because the memq id implemented using a synchronized data structure and polling memq continuously would not relinquish control of memq to the writer thread as a result the reader will wait infinitely and writer would fail leading to loss of data. Use callbacks functionality by registering your object to receive a trigger when data is available for reading in the memq.

Returns:

object read

See Also:

register(QCallback a, int purpose)

register

public void register(QCallback a,
                     int purpose)

Registers a callback which will be called when memQ is empty/full/data available it is assumed that the callback implements the handle()function.

Parameters:

a - object to be triggered

purpose - full/empty/data available

unregister

public void unregister(QCallback a,
                       int purpose)
                throws Exception

unregister : unregisters a callback

Parameters:

a - object to be unregistered

purpose - full/empty/data available if -1 unregister the object from all callbacks

Throws:

Exception - if callback object is not found

handle

public void handle(int purpose)

handle : issues triggers to the registered callbacks

Parameters:

purpose - full/empty/data available

enablePersistence

public void enablePersistence(boolean enable)

enablePersistence : enable/disable paging support using system store

Parameters:

enable - paging support enabled if true and disabled if false

blockAdd

public void blockAdd(boolean enable)

Enable disable blocking add this is used only when paging support is disabled.

Parameters:

enable - if true, add to memq blocks infinitely until there is space for an object to be added to memq if false, add throws an exception if memq is full

actionPerformed

public void actionPerformed(ActionEvent e)

Specified by:

actionPerformed in interface ActionListener

terminate

public void terminate()

Terminates the system store threads.

terminate

public void terminate(boolean dropSystemStore)

terminates the system store threads and drops table if dropSystemStore set to true

Parameters:

dropSystemStore -

purgeQueue

public void purgeQueue()

Purges the queue. The isBeingPurged Flag is set which blocks all reader or writer threads until the purge operation is not completed. Deletes all data from the associated table in System Store if this queue has paging enabled.