com.continuent.tungsten.replicator.extractor
Class ExtractorWrapper

java.lang.Object
  com.continuent.tungsten.replicator.extractor.ExtractorWrapper

All Implemented Interfaces:

Extractor, ReplicatorPlugin

public class ExtractorWrapper
extends java.lang.Object
implements Extractor

This class wraps a basic Extractor so that it returns ReplDBMSEvent values with assigned sequence numbers. It contains logic to recognize that we have failed over; see setLastEvent(ReplDBMSHeader) for more information.

Version:

1.0

Author:

Robert Hodges

Constructor Summary

ExtractorWrapper(RawExtractor extractor)
Create a new instance to wrap Creates a new ExtractorWrapper object

Method Summary

void	configure(PluginContext context) Complete plug-in configuration.
ReplDBMSEvent	extract() Extracts a raw event and wraps it in a ReplDBMS complete with sequence number, which increments each time we process the last fragment.
java.lang.String	getCurrentResourceEventId() Delegates to underlying extractor.
RawExtractor	getExtractor() Return wrapped extractor.
boolean	hasMoreEvents() Returns false until we implement caching.
void	prepare(PluginContext context) Prepare plug-in for use.
void	release(PluginContext context) Release all resources used by plug-in.
void	setLastEvent(ReplDBMSHeader header) Set the value of the last event called.
void	setLastEventId(java.lang.String eventId) Provides a new native event ID that overrides the default value that the extractor would otherwise use.

Methods inherited from class java.lang.Object

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

Constructor Detail

ExtractorWrapper

public ExtractorWrapper(RawExtractor extractor)

Create a new instance to wrap Creates a new ExtractorWrapper object

Parameters:

extractor - Extractor to be wrapped

Method Detail

getExtractor

public RawExtractor getExtractor()

Return wrapped extractor.

extract

public ReplDBMSEvent extract()
                      throws ReplicatorException,
                             java.lang.InterruptedException

Extracts a raw event and wraps it in a ReplDBMS complete with sequence number, which increments each time we process the last fragment.

Specified by:

extract in interface Extractor

Returns:

next ReplDBMSEvent found in the logs or another ReplEvent subclass containing control data

Throws:

ReplicatorException

java.lang.InterruptedException

See Also:

Extractor.extract()

getCurrentResourceEventId

public java.lang.String getCurrentResourceEventId()
                                           throws ReplicatorException,
                                                  java.lang.InterruptedException

Delegates to underlying extractor. Returns the last event ID committed in a database from which we are extracting. It is used to help synchronize state between the database and the transaction history log. Values returned from this call must correspond with the last extracted DBMSEvent.eventId as follows:

1. If the returned value is greater than DBMSEvent.eventId, the database has more recent updates
2. If the returned value is equal to DBMSEvent.eventId, all events have been extracted

It should not be possible to receive a value that is less than the last extracted DBMSEvent.eventId as this implies that the extractor is somehow ahead of the state of the database, which would be inconsistent.

Specified by:

getCurrentResourceEventId in interface Extractor

Returns:

A current event ID that can be compared with event IDs in DBMSEvent or null if this type of extractor does not extract from a database

Throws:

ReplicatorException

java.lang.InterruptedException

See Also:

Extractor.getCurrentResourceEventId()

hasMoreEvents

public boolean hasMoreEvents()

Returns false until we implement caching.

Specified by:

hasMoreEvents in interface Extractor

See Also:

Extractor.hasMoreEvents()

setLastEvent

public void setLastEvent(ReplDBMSHeader header)
                  throws ReplicatorException

Set the value of the last event called. The extractor is responsible for returning the next event in sequence after this one the next time extract() is called.

Specified by:

setLastEvent in interface Extractor

Parameters:

header - Last event we extracted

Throws:

ReplicatorException

See Also:

Extractor.setLastEvent(com.continuent.tungsten.replicator.event.ReplDBMSHeader)

setLastEventId

public void setLastEventId(java.lang.String eventId)
                    throws ReplicatorException

Provides a new native event ID that overrides the default value that the extractor would otherwise use. This call is used to position raw extractors at a specific native event ID in the DBMS log. It can be ignored by other extractors that do not read from a data source.

Specified by:

setLastEventId in interface Extractor

Parameters:

eventId - Event ID at which to begin extracting

Throws:

ReplicatorException

See Also:

Extractor.setLastEventId(java.lang.String)

configure

public void configure(PluginContext context)
               throws ReplicatorException,
                      java.lang.InterruptedException

Complete plug-in configuration. This is called after setters are invoked at the time that the replicator goes through configuration.

Specified by:

configure in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if configuration is incomplete or fails

java.lang.InterruptedException

See Also:

ReplicatorPlugin.configure(com.continuent.tungsten.replicator.plugin.PluginContext)

prepare

public void prepare(PluginContext context)
             throws ReplicatorException,
                    java.lang.InterruptedException

Prepare plug-in for use. This method is assumed to allocate all required resources. It is called before the plug-in performs any operations.

Specified by:

prepare in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if resource allocation fails

java.lang.InterruptedException

See Also:

ReplicatorPlugin.prepare(com.continuent.tungsten.replicator.plugin.PluginContext)

release

public void release(PluginContext context)
             throws ReplicatorException,
                    java.lang.InterruptedException

Release all resources used by plug-in. This is called before the plug-in is deallocated.

Specified by:

release in interface ReplicatorPlugin

Throws:

ReplicatorException - Thrown if resource deallocation fails

java.lang.InterruptedException

See Also:

ReplicatorPlugin.release(com.continuent.tungsten.replicator.plugin.PluginContext)