org.apache.ignite.cdc

Interface CdcConsumer

public interface CdcConsumer

Consumer of WAL data change events. This consumer will receive data change events during CdcMain application invocation. The lifecycle of the consumer is the following:

• Start of the consumer start(MetricRegistry).
• Notification of the consumer by the onEvents(Iterator) call.
• Stop of the consumer stop().

In case consumer implementation wants to use IgniteLogger, please, use, LoggerResource annotation:

 public class ChangeDataCaptureConsumer implements ChangeDataCaptureConsumer {
     @LoggerResource
     private IgniteLogger log;

     ...
 }
 

Note, consumption of the CdcEvent will be started from the last saved offset. The offset of consumptions is saved on the disk every time onEvents(Iterator) returns true. Note, order of notifications are following:

• onMappings(Iterator)
• onTypes(Iterator)
• onCacheChange(Iterator)
• onCacheDestroy(Iterator)

Note, CdcConsumer receive notifications on each running CDC application(node).

See Also:

CdcMain, CdcEvent, CacheEntryVersion

Method Summary

Modifier and Type	Method and Description
default boolean	alive() Checks that consumer still alive.
void	onCacheChange(Iterator<CdcCacheEvent> cacheEvents) Handles caches changes(create, edit) events.
void	onCacheDestroy(Iterator<Integer> caches) Handles cache destroy events.
boolean	onEvents(Iterator<CdcEvent> events) Handles entry changes events.
void	onMappings(Iterator<TypeMapping> mappings) Handles new mappings from type name to id.
void	onTypes(Iterator<BinaryType> types) Handles new binary types.
void	start(org.apache.ignite.internal.processors.metric.MetricRegistry mreg) Starts the consumer.
void	stop() Stops the consumer.

Method Detail

start

void start(org.apache.ignite.internal.processors.metric.MetricRegistry mreg)

Starts the consumer.

Parameters:

mreg - Metric registry for consumer specific metrics.

onEvents

boolean onEvents(Iterator<CdcEvent> events)

Handles entry changes events. If this method return true then current offset will be stored and ongoing notifications after CDC application fail/restart will be started from it.

Parameters:

events - Entry change events.

Returns:

True if current offset should be saved on the disk to continue from it in case any failures or restart.

onTypes

void onTypes(Iterator<BinaryType> types)

Handles new binary types. State of the types processing will be stored after method invocation and ongoing notifications after CDC application fail/restart will be continued for newly created/updates types. Note, unlike onEvents(Iterator) this method MUST process all types or CDC will fail. Because, in time of invocation onEvents(Iterator) all changed types must be available on destionation.

Parameters:

types - Binary types iterator.

See Also:

IgniteBinary, IgniteBinary.type(int), IgniteBinary.type(Class), IgniteBinary.type(String), IgniteBinary.types()

onMappings

void onMappings(Iterator<TypeMapping> mappings)

Handles new mappings from type name to id. State of the types processing will be stored after method invocation and ongoing notifications after CDC application fail/restart will be continued for newly created/updates mappings.

Parameters:

mappings - Binary mapping iterator.

See Also:

IgniteBinary, IgniteBinary.typeId(String), BinaryIdMapper

onCacheChange

void onCacheChange(Iterator<CdcCacheEvent> cacheEvents)

Handles caches changes(create, edit) events. State of cache processing will be stored after method invocation and ongoing notifications after CDC application fail/restart will be continued for newly changed caches.

Parameters:

cacheEvents - Cache change events.

See Also:

Ignite.createCache(String), Ignite.getOrCreateCache(String), CdcCacheEvent

onCacheDestroy

void onCacheDestroy(Iterator<Integer> caches)

Handles cache destroy events. State of cache processing will be stored after method invocation and ongoing notifications after CDC application fail/restart will be continued for newly changed caches.

Parameters:

caches - Destroyed caches.

See Also:

Ignite.destroyCache(String), CdcCacheEvent, CacheView.cacheId()

stop

void stop()

Stops the consumer. This method can be invoked only after start(MetricRegistry).

alive

default boolean alive()

Checks that consumer still alive. This method helps to determine CdcConsumer errors in case CdcEvent is rare or source cluster is down.

Returns:

True in case consumer alive, false otherwise.