com.continuent.tungsten.replicator.event
Class EventMetadataFilter

java.lang.Object
  com.continuent.tungsten.replicator.event.EventMetadataFilter

All Implemented Interfaces:

Filter, ReplicatorPlugin

public class EventMetadataFilter
extends java.lang.Object
implements Filter

This filter events newly extracted from the database log to answer the following key questions. It must run as an auto-filter whenever we want sharding and multi-master replication to work.

• Is this an ordinary transaction or a Tungsten catalog update?
• What is the original service of this event?
• What is the shard ID of this event?

These questions are answered as follows. We begin with the assumption that any event is from the local service and does not contain Tungsten catalog metadata updates. We then modify assumptions and assign the shard ID as follows.

• Case 0: No database identified. Sadly, this is possible. Warn and assign to the default shard ID.
• Case 1: Single ordinary database. Mark shard with database name.
• Case 2: 1 or more dbs including a tungsten_ database. Mark the service, mark tungsten metadata, and assign the shard name using the tungsten_ database name.
• Case 3: Multiple ordinary databases. Assign the shard to the default ID.

Finally, we should note that this filter needs to be fast and to minimize memory usage. The indexing structure used in the implementation is a local hash table of database schema names and reference counts, which takes up virtually no space.

Version:

1.0

Author:

Robert Hodges

Constructor Summary

EventMetadataFilter()

Method Summary

void	configure(PluginContext context) Complete plug-in configuration.
ReplDBMSEvent	filter(ReplDBMSEvent event) Filter the event.
void	prepare(PluginContext context) Prepare plug-in for use.
void	release(PluginContext context) Release all resources used by plug-in.
void	setUnknownSqlUsesDefaultDb(boolean unknownSqlUsesDefaultDb) If set to true, use default database for unknown SQL operations.

Methods inherited from class java.lang.Object

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

Constructor Detail

EventMetadataFilter

public EventMetadataFilter()

Method Detail

setUnknownSqlUsesDefaultDb

public void setUnknownSqlUsesDefaultDb(boolean unknownSqlUsesDefaultDb)

If set to true, use default database for unknown SQL operations.

filter

public ReplDBMSEvent filter(ReplDBMSEvent event)
                     throws ReplicatorException,
                            java.lang.InterruptedException

Filter the event. Filters may transform the event or return null if the event should be discarded. Filters must be prepared to be interrupted, which mechanism is used to cancel processing.

Specified by:

filter in interface Filter

Parameters:

event - An event to be filtered

Returns:

Filtered ReplDBMSEvent or null

Throws:

ReplicatorException - Thrown if there is a processing error

java.lang.InterruptedException - Must be thrown if the filter is interrupted or the replicator may hang

See Also:

Filter.filter(com.continuent.tungsten.replicator.event.ReplDBMSEvent)

configure

public void configure(PluginContext context)
               throws ReplicatorException

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

See Also:

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

prepare

public void prepare(PluginContext context)
             throws ReplicatorException

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

See Also:

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

release

public void release(PluginContext context)
             throws ReplicatorException

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

See Also:

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