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com.lutris.appserver.server.sql.standard
Class StandardConnectionAllocator  

java.lang.Object
  com.lutris.appserver.server.sql.standard.StandardConnectionAllocator

All Implemented Interfaces:

com.lutris.appserver.server.sql.ConnectionAllocator

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public class StandardConnectionAllocator

extends java.lang.Object

implements com.lutris.appserver.server.sql.ConnectionAllocator

Manages a pool (set) of connections to a database. The pool is named as a logical database. By naming a pool, this allows connection resource control to be on a finer grain that a database and allows for easier migration to multiple databases. One or more pools can map to the same actual database. A connection considered part of the pool, even if its allocated to a thread. These objects are all publicly accessed via the Database Manager, not directly.

If an error occurs in a connection, it is dropped from the pool. The process using the connection has already received an error which aborts the work in progress. By dropping the connection, waiting threads are restarted. If something is wrong with the database (e.g. server is down), they will recieve errors and also be aborted. A generation number is used to close down all connections that were open when the error occured, allowing new connections to be allocated.

The configuration data is specified in the section: DatabaseManager.DB.dbName.Connection

Configuration sub fields are:

• Url - The JDBC URLof the database. Manditary. E.g. "jdbc:sequelink://dbHost:4000/[Informix];Database=dummy"
• User - The database users used to access the database. Manditary.
• Password - The database user's password. Manditary.
• MaxPoolSize - The maximum number of open connections to the database. Optional, if not specified, then it default to 0. A value of 0 means that connections are allocated indefinitely or until the database (JDBC) refuses any new connections.
• Logging - Specify true to enable SQL logging, false to disable it. Optional, false if not specified.
• AllocationTimeout - The Maximum amount of time that a thread will wait for a connection from the connection allocator before an exception is thrown. This will prevent possible dead locks. The time out is in milliseconds. If the time out is <= 0, the allocation of connections will wait indefinitely. Optional, if not specified, then it defaults to 1000 (ms).
• QueryTimeout - The amount of time (in seconds) that a query will block before throwing an exception. If <= 0 then the query will not block. Optional, if not specified, then the value defaults to 0. This is not implemented by all logical databases.
• TransactionTimeout - The amount of time (in seconds) that a transaction will block before throwing an exception. If <= 0 then the transaction will not block. Optional, if not specified, then the value defaults to 0. This is not implemented by all logical databases.
• MaxPreparedStatements - If specified, overrides the JDBC Connection.getMetaData().getMaxStatements() value. If less than zero, use the meta data value. Optional, default is to use the meta data.

It would be nice to add a config parameter that would disable caching of PreparedStatements.

Since:

LBS1.8

Version:

$Revision: 1.10.12.1 $

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Field Summary
private  java.util.Date	biggestPoolDate           Date at which the biggest pool size occured.
private  int	biggestPoolSize           Maximum size the pool ever got to, regardless of generation.
private  int	currentPoolSize           Current size of the pool; includes allocated connections.
protected  int	generation           Generation number.
private  com.lutris.logging.LogChannel	log           The log channel.
protected  com.lutris.appserver.server.sql.LogicalDatabase	logicalDatabase           Reference to the logical database for easy access to the connection pool.
private  int	maxPoolSize           Maximum number of connections in the pool.
protected  int	maxPreparedStatements           Maximum number of prepared statements to use; if less-than zero, then JDBC is queried for this value.
protected  long	numRequests           Number of queries or transactions on this logical database.
protected  java.lang.String	password           SQL password..
private  java.util.Stack	pool           The actual pool of DBConnection objects.
protected  int	queryTimeOut           Maximum amount of time in seconds to block on a query.
protected  boolean	sqlLogging           Indicates if logging is enabled.
private  int	timeOut           Maximum amount of time in milliseconds to wait for a connection.
protected  int	transactionTimeOut           Maximum amount of time in seconds to block on a transaction.
protected  java.lang.String	url           JDBC URL of database.
protected  java.lang.String	user           SQL user name.

 

Constructor Summary
protected	StandardConnectionAllocator(com.lutris.appserver.server.sql.LogicalDatabase logicalDatabase, com.lutris.util.Config conConfig)           Initialize the connection allocator object.

 

Method Summary
com.lutris.appserver.server.sql.DBConnection	allocate()           Allocate a connection to a thread.
protected  com.lutris.appserver.server.sql.DBConnection	createConnection()           Create a new connection in the pool.
void	drop(com.lutris.appserver.server.sql.DBConnection dbConnection)           Called when a connection in this pool has an SQL error.
void	dropAllNow()           Called when the database manager is shutting down: Close all connections immediately.
protected  void	finalize()           Finalizer.
int	getActiveCount()           Return the number of currently active connections.
int	getMaxCount()           Return the maximum number of connections active at one time.
java.util.Date	getMaxCountDate()           Return the time when the maximum connection count occured.
long	getRequestCount()           Return the number of database requests.
void	release(com.lutris.appserver.server.sql.DBConnection dbConnection)           Return a connection to the pool.
void	resetMaxCount()           Reset the maximum connection count and date.

 

Methods inherited from class java.lang.Object

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

 

Field Detail

logicalDatabase

protected com.lutris.appserver.server.sql.LogicalDatabase logicalDatabase

Reference to the logical database for easy access to the connection pool.

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url

protected java.lang.String url

JDBC URL of database.

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user

protected java.lang.String user

SQL user name.

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password

protected java.lang.String password

SQL password..

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maxPoolSize

private int maxPoolSize

Maximum number of connections in the pool. If this value is <= zero, then create as many connections as possible.

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currentPoolSize

private int currentPoolSize

Current size of the pool; includes allocated connections.

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biggestPoolSize

private int biggestPoolSize

Maximum size the pool ever got to, regardless of generation.

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biggestPoolDate

private java.util.Date biggestPoolDate

Date at which the biggest pool size occured.

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numRequests

protected long numRequests

Number of queries or transactions on this logical database.

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pool

private java.util.Stack pool

The actual pool of DBConnection objects.

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sqlLogging

protected boolean sqlLogging

Indicates if logging is enabled.

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timeOut

private int timeOut

Maximum amount of time in milliseconds to wait for a connection.

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queryTimeOut

protected int queryTimeOut

Maximum amount of time in seconds to block on a query. The DBQuery object will retrieve this value from the connection.

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transactionTimeOut

protected int transactionTimeOut

Maximum amount of time in seconds to block on a transaction. The DBTransaction object will retrieve this value from the connection.

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maxPreparedStatements

protected int maxPreparedStatements

Maximum number of prepared statements to use; if less-than zero, then JDBC is queried for this value.

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generation

protected int generation

Generation number. When an SQL error occurs, all objects of the same generation or earlier are dropped.

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log

private com.lutris.logging.LogChannel log

The log channel.

Constructor Detail

StandardConnectionAllocator

protected StandardConnectionAllocator(com.lutris.appserver.server.sql.LogicalDatabase logicalDatabase,
                                      com.lutris.util.Config conConfig)
                               throws com.lutris.util.ConfigException

Initialize the connection allocator object. Connections are opened on demand and stored in a pool.

Method Detail

createConnection

protected com.lutris.appserver.server.sql.DBConnection createConnection()
                                                                 throws java.sql.SQLException

Create a new connection in the pool.

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allocate

public com.lutris.appserver.server.sql.DBConnection allocate()
                                                      throws java.sql.SQLException

Allocate a connection to a thread. If none are available, grow the pool. If the pool is alredy its maximum size, then the thread waits.

Specified by:

allocate in interface com.lutris.appserver.server.sql.ConnectionAllocator

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release

public void release(com.lutris.appserver.server.sql.DBConnection dbConnection)

Return a connection to the pool. If it is of an old generation, close and drop.

Specified by:

release in interface com.lutris.appserver.server.sql.ConnectionAllocator

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drop

public void drop(com.lutris.appserver.server.sql.DBConnection dbConnection)

Called when a connection in this pool has an SQL error. All unallocated connections in the pool are dropped if they have a generation number less than or equal to the error connection. If the current generation number is the same as this generation number, increment it. This way so that all outstanding connections (including the one passed in) of the same generation are dropped when returned.

Specified by:

drop in interface com.lutris.appserver.server.sql.ConnectionAllocator

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dropAllNow

public void dropAllNow()

Called when the database manager is shutting down: Close all connections immediately.

Specified by:

dropAllNow in interface com.lutris.appserver.server.sql.ConnectionAllocator

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getActiveCount

public int getActiveCount()

Return the number of currently active connections.

Specified by:

getActiveCount in interface com.lutris.appserver.server.sql.ConnectionAllocator

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getMaxCount

public int getMaxCount()

Return the maximum number of connections active at one time.

Specified by:

getMaxCount in interface com.lutris.appserver.server.sql.ConnectionAllocator

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getMaxCountDate

public java.util.Date getMaxCountDate()

Return the time when the maximum connection count occured.

Specified by:

getMaxCountDate in interface com.lutris.appserver.server.sql.ConnectionAllocator

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resetMaxCount

public void resetMaxCount()

Reset the maximum connection count and date.

Specified by:

resetMaxCount in interface com.lutris.appserver.server.sql.ConnectionAllocator

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getRequestCount

public long getRequestCount()

Return the number of database requests.

Specified by:

getRequestCount in interface com.lutris.appserver.server.sql.ConnectionAllocator

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finalize

protected void finalize()

Finalizer. If any connections allocated by this object have not been closed, this method ensures that garbage collection does so.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> com >> lutris >> appserver >> server >> sql >> [ standard overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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