org.oddjob.sql

Class SQLKeeperService

java.lang.Object

org.oddjob.sql.SQLKeeperService

public class SQLKeeperService
extends java.lang.Object

Description

Provides a Keeper that uses a database table.

The keeper uses a simple 'first to insert' a row wins methodology for deciding winner and looser. This is quite primitive and decides that any exception from the insert operation is a duplicate key exception and therefore a looser.

A LoosingOutcome will continue to Poll the database (for as long as it has listeners) until the work is complete. The default polling schedule polls every 5 seconds indefinitely. The pollSchedule property can be used to poll for a limited time, after which it flags an exception state. This could be used by loosing servers to flag the winner is taking too long and has possibly crashed.

This is an example of the SQL that would create a suitable table.

 CREATE TABLE oddjob_grabbable(
   key VARCHAR(32),
   instance VARCHAR(32),
   winner VARCHAR(32),
   complete boolean,
  CONSTRAINT oddjob_pk PRIMARY KEY (key, instance))
 

This service does not tidy up the database so rows will grow indefinitely. A separate tidy job should be implemented.

Example

See the User Guide.

Author:

Rob Gordon.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	TABLE_NAME The default table name.

Constructor Summary

Constructors

Constructor and Description
SQLKeeperService()

Method Summary

Modifier and Type	Method and Description
protected java.sql.PreparedStatement	createInsertStatementFor(java.sql.Connection connection, java.lang.String keeperKey, java.lang.String ourIdentifier, java.lang.Object instanceIdentifier) Provide a PreparedStatement for the insert operation.
protected java.sql.PreparedStatement	createQueryStatementFor(java.sql.Connection connection, java.lang.String keeperKey, java.lang.Object instanceIdentifier) Create the PreparedStatement for the query of who won and is work complete yet.
protected java.sql.PreparedStatement	createUpdateStatementFor(java.sql.Connection connection, java.lang.String keeperKey, java.lang.Object instanceIdentifier) Create the PreparedStatemenet for updating won work is complete.
Keeper	getKeeper(java.lang.String keeperKey) Provide a Keeper.
java.lang.String	getName()
int	getPollerCount()
Schedule	getPollSchedule()
java.lang.String	getTable()
void	setConnection(java.sql.Connection connection) Set the connection.
void	setName(java.lang.String name)
void	setPollSchedule(Schedule schedule)
void	setScheduleExecutorService(java.util.concurrent.ScheduledExecutorService scheduler)
void	setTable(java.lang.String table)
void	start() Start the service.
void	stop() Stop the service.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

TABLE_NAME

public static final java.lang.String TABLE_NAME

The default table name.

See Also:

Constant Field Values

Constructor Detail

SQLKeeperService

public SQLKeeperService()

Method Detail

start

public void start()
           throws java.sql.SQLException

Start the service.

Throws:

java.sql.SQLException

stop

public void stop()
          throws java.sql.SQLException

Stop the service.

Throws:

java.sql.SQLException

getKeeper

public Keeper getKeeper(java.lang.String keeperKey)

Provide a Keeper.

Parameters:

keeperKey - The keepers key. Must not be null.

Returns:

A keeper. Never null.

getName

public java.lang.String getName()

setName

public void setName(java.lang.String name)

setConnection

public void setConnection(java.sql.Connection connection)
                   throws java.sql.SQLException

Set the connection.

Parameters:

connection - The connection.

Throws:

java.sql.SQLException

getPollerCount

public int getPollerCount()

Property: pollerCount

Description: The number of outstanding loosing outcome's polling of the database that are still in progress.

Returns:

The number.

createInsertStatementFor

protected java.sql.PreparedStatement createInsertStatementFor(java.sql.Connection connection,
                                                              java.lang.String keeperKey,
                                                              java.lang.String ourIdentifier,
                                                              java.lang.Object instanceIdentifier)
                                                       throws java.sql.SQLException

Provide a PreparedStatement for the insert operation.

Parameters:

connection -

keeperKey -

ourIdentifier -

instanceIdentifier -

Returns:

Throws:

java.sql.SQLException

createQueryStatementFor

protected java.sql.PreparedStatement createQueryStatementFor(java.sql.Connection connection,
                                                             java.lang.String keeperKey,
                                                             java.lang.Object instanceIdentifier)
                                                      throws java.sql.SQLException

Create the PreparedStatement for the query of who won and is work complete yet.

Parameters:

connection -

keeperKey -

instanceIdentifier -

Returns:

Throws:

java.sql.SQLException

createUpdateStatementFor

protected java.sql.PreparedStatement createUpdateStatementFor(java.sql.Connection connection,
                                                              java.lang.String keeperKey,
                                                              java.lang.Object instanceIdentifier)
                                                       throws java.sql.SQLException

Create the PreparedStatemenet for updating won work is complete.

Parameters:

connection -

keeperKey -

instanceIdentifier -

Returns:

Throws:

java.sql.SQLException

getTable

public java.lang.String getTable()

setTable

public void setTable(java.lang.String table)

getPollSchedule

public Schedule getPollSchedule()

setPollSchedule

public void setPollSchedule(Schedule schedule)

setScheduleExecutorService

@Inject
public void setScheduleExecutorService(java.util.concurrent.ScheduledExecutorService scheduler)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object