com.aoindustries.io

Class AOPool<C,E extends Exception,I extends Exception>

java.lang.Object

java.lang.Thread

com.aoindustries.io.AOPool<C,E,I>

All Implemented Interfaces:

Runnable

Direct Known Subclasses:

AOConnectionPool

public abstract class AOPool<C,E extends Exception,I extends Exception>
extends Thread

Reusable generic connection pooling with dynamic flaming tiger feature. Two lists of connections are maintained. The first is the list of connections that are ready unused, and the second is the list of connections that are currently checked-out. By using this strategy, an available connection can be found without searching the entire list. In addition to the global lists, a ThreadLocal list of connections checked-out by the current thread is maintained. When getting a new connection, this is used to check again maxConnections instead of checking the global lists. Idea: Add some sort of thread-connection affinity, where the same connection slot will be used by the same thread when it is available. This should help cache locality. Idea: When connections are closed due to maxConnectionAge, automatically reconnect in the background. This would avoid the latency of the reconnect for the connection-using thread.

Author:

AO Industries, Inc.

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_CONNECT_TIMEOUT
static int	DEFAULT_DELAY_TIME
static long	DEFAULT_MAX_CONNECTION_AGE
static int	DEFAULT_MAX_IDLE_TIME
static int	DEFAULT_SOCKET_SO_LINGER
protected Logger	logger All warnings are sent here if available, otherwise will be written to System.err.
static long	UNLIMITED_MAX_CONNECTION_AGE

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AOPool(int delayTime, int maxIdleTime, String name, int poolSize, long maxConnectionAge, Logger logger)
protected	AOPool(String name, int poolSize, long maxConnectionAge, Logger logger)

Method Summary

Modifier and Type	Method and Description
void	close() Shuts down the pool, exceptions during close will be logged as a warning and not thrown.
protected abstract void	close(C conn)
int	getConcurrency() Gets the number of connections that are currently busy.
C	getConnection() Gets a connection, warning of a connection is already used by this thread.
C	getConnection(int maxConnections) Gets either an available connection or creates a new connection.
int	getConnectionCount() Gets the number of connections currently connected.
protected abstract C	getConnectionObject() Creates a new connection.
long	getConnects() Gets the total number of connects for the entire pool.
Logger	getLogger()
int	getMaxConcurrency()
long	getMaxConnectionAge() Gets the maximum age for connections.
int	getPoolSize()
long	getTotalTime()
long	getTransactionCount()
protected abstract boolean	isClosed(C conn)
protected abstract E	newException(String message, Throwable cause)
protected abstract I	newInterruptedException(String message, Throwable cause)
protected abstract void	printConnectionStats(Appendable out) Prints additional connection pool details.
void	printStatisticsHTML(Appendable out) Prints complete statistics about connection pool use.
void	releaseConnection(C connection) Releases the database Connection to the Connection pool.
protected abstract void	resetConnection(C conn)
void	run() The RefreshConnection thread polls every connection in the connection pool.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, clone, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_DELAY_TIME

public static final int DEFAULT_DELAY_TIME

See Also:

Constant Field Values

DEFAULT_MAX_IDLE_TIME

public static final int DEFAULT_MAX_IDLE_TIME

See Also:

Constant Field Values

UNLIMITED_MAX_CONNECTION_AGE

public static final long UNLIMITED_MAX_CONNECTION_AGE

See Also:

Constant Field Values

DEFAULT_MAX_CONNECTION_AGE

public static final long DEFAULT_MAX_CONNECTION_AGE

See Also:

Constant Field Values

DEFAULT_CONNECT_TIMEOUT

public static final int DEFAULT_CONNECT_TIMEOUT

See Also:

Constant Field Values

DEFAULT_SOCKET_SO_LINGER

public static final int DEFAULT_SOCKET_SO_LINGER

See Also:

Constant Field Values

logger

protected final Logger logger

All warnings are sent here if available, otherwise will be written to System.err.

Constructor Detail

AOPool

protected AOPool(String name,
                 int poolSize,
                 long maxConnectionAge,
                 Logger logger)

AOPool

protected AOPool(int delayTime,
                 int maxIdleTime,
                 String name,
                 int poolSize,
                 long maxConnectionAge,
                 Logger logger)

Method Detail

close

protected abstract void close(C conn)
                       throws E extends Exception

Throws:

E extends Exception

close

public final void close()

Shuts down the pool, exceptions during close will be logged as a warning and not thrown.

getConcurrency

public final int getConcurrency()

Gets the number of connections that are currently busy.

getConnectionCount

public final int getConnectionCount()

Gets the number of connections currently connected.

getConnection

public C getConnection()
                throws I extends Exception,
                       E extends Exception

Gets a connection, warning of a connection is already used by this thread.

Throws:

I - when interrupted

E - when error

I extends Exception

See Also:

getConnection(int)

getConnection

public C getConnection(int maxConnections)
                throws I extends Exception,
                       E extends Exception

Gets either an available connection or creates a new connection. If all the connections in the pool are busy and the pool is at capacity, waits until a connection becomes available. Due to internal ThreadLocal optimizations, the connection returned must be released by the current thread, it should not be passed off to another thread before release.

Parameters:

maxConnections - The maximum number of connections expected to be used by the current thread. This should normally be one to avoid potential deadlock.

Returns:

either a reused or new connection

Throws:

I - when interrupted

E - when error

I extends Exception

getConnectionObject

protected abstract C getConnectionObject()
                                  throws I extends Exception,
                                         E extends Exception

Creates a new connection.

Throws:

I - when interrupted

E - when error

I extends Exception

getConnects

public final long getConnects()

Gets the total number of connects for the entire pool.

getMaxConnectionAge

public final long getMaxConnectionAge()

Gets the maximum age for connections.

getMaxConcurrency

public final int getMaxConcurrency()

getPoolSize

public final int getPoolSize()

getTotalTime

public final long getTotalTime()

getTransactionCount

public final long getTransactionCount()

isClosed

protected abstract boolean isClosed(C conn)
                             throws E extends Exception

Throws:

E extends Exception

printConnectionStats

protected abstract void printConnectionStats(Appendable out)
                                      throws IOException

Prints additional connection pool details.

Throws:

IOException

printStatisticsHTML

public final void printStatisticsHTML(Appendable out)
                               throws IOException,
                                      E extends Exception

Prints complete statistics about connection pool use.

Throws:

IOException

E extends Exception

releaseConnection

public final void releaseConnection(C connection)
                             throws E extends Exception

Releases the database Connection to the Connection pool. It is safe to call this method more than once, but only the first call will have any affect and the second release will log a warning.

Throws:

E extends Exception

resetConnection

protected abstract void resetConnection(C conn)
                                 throws I extends Exception,
                                        E extends Exception

Throws:

I extends Exception

run

public final void run()

The RefreshConnection thread polls every connection in the connection pool. If it detects a connection is idle for more than the pre-defined MAX_IDLE_TIME, it closes the connection. It will stop when the pool is flagged as closed.

Specified by:

run in interface Runnable

Overrides:

run in class Thread

newException

protected abstract E newException(String message,
                                  Throwable cause)

newInterruptedException

protected abstract I newInterruptedException(String message,
                                             Throwable cause)

getLogger

public final Logger getLogger()