org.apache.ignite.internal.cdc

Interface CdcManager

All Superinterfaces:

DatabaseLifecycleListener, GridCacheSharedManager

All Known Implementing Classes:

CdcUtilityActiveCdcManager

public interface CdcManager
extends GridCacheSharedManager, DatabaseLifecycleListener

CDC manager responsible for logic of capturing data within Ignite node. Communication between CdcManager and CdcMain components is established through CDC management WAL records. CdcManager logs them, while CdcMain listens to them:

• This manager can log CdcManagerRecord with committed consumer state. This record will be handled by CdcMain the same way it handles CdcConsumer.onEvents(Iterator) when it returns true.
• This manager must log CdcManagerStopRecord after it stopped handling records by any reason. CdcMain will start consume records instead since CdcManagerRecord.walState() of last consumed CdcManagerRecord.
• Apache Ignite provides a default implementation - CdcUtilityActiveCdcManager. It is disabled from the beginning, logs the CdcManagerStopRecord after Ignite node started, and then delegates consuming CDC events to the CdcMain utility.

Apache Ignite can be extended with custom CDC manager. It's required to implement this interface, create own PluginProvider that will return the implementation with PluginProvider.createComponent(PluginContext, Class) method. The Class parameter in the method is CdcManager class.

See Also:

CdcConsumer.onEvents(Iterator), CdcConsumerState.saveCdcMode(CdcMode)

Method Summary

Modifier and Type	Method and Description
default void	afterBinaryMemoryRestore(IgniteCacheDatabaseSharedManager mgr, GridCacheDatabaseSharedManager.RestoreBinaryState restoreState) Callback is executed only once on Ignite node start when binary memory has fully restored and WAL logging is resumed.
void	collect(ByteBuffer dataBuf) Callback to collect written WAL records.
boolean	enabled() If this manager isn't enabled then Ignite skips notifying the manager with following methods.

Methods inherited from interface org.apache.ignite.internal.processors.cache.GridCacheSharedManager

onDisconnected, onKernalStart, onKernalStop, onReconnected, printMemoryStats, start, stop

Methods inherited from interface org.apache.ignite.internal.processors.cache.persistence.DatabaseLifecycleListener

afterInitialise, afterLogicalUpdatesApplied, beforeBinaryMemoryRestore, beforeResumeWalLogging, beforeStop, onBaselineChange, onInitDataRegions

Method Detail

enabled

boolean enabled()

If this manager isn't enabled then Ignite skips notifying the manager with following methods.

Returns:

true if manager is enabled, otherwise false.

afterBinaryMemoryRestore

default void afterBinaryMemoryRestore(IgniteCacheDatabaseSharedManager mgr,
                                      GridCacheDatabaseSharedManager.RestoreBinaryState restoreState)
                               throws IgniteCheckedException

Callback is executed only once on Ignite node start when binary memory has fully restored and WAL logging is resumed. It's executed before the first call of collect(ByteBuffer).

Implementation suggestions:

• Implementation must subscribe to the database events to get notified with this callback via GridInternalSubscriptionProcessor.registerDatabaseListener(DatabaseLifecycleListener)
• Callback can be used for restoring CDC state on Ignite node start, collecting missed events from WAL segments.
• Be aware, this method runs in the Ignite system thread and might get longer the Ignite start procedure.
• Ignite node will fail in case the method throws an exception.

Specified by:

afterBinaryMemoryRestore in interface DatabaseLifecycleListener

restoreState - Result of binary recovery.

Throws:

IgniteCheckedException - If failed.

collect

void collect(ByteBuffer dataBuf)

Callback to collect written WAL records. The provided buffer is a continuous part of WAL segment file. The buffer might contain full content of a segment or only piece of it. There are guarantees:

• This method is invoked sequentially.
• Provided dataBuf is a continuation of the previous one.
• dataBuf contains finite number of completed WAL records. No partially written WAL records are present.
• Records can be read from the buffer with RecordSerializer.readRecord(FileInput, WALPointer).
• dataBuf must not be changed within this method.

Implementation suggestions:

• Frequence of calling the method depends on frequence of fsyncing WAL segment. See IgniteSystemProperties.IGNITE_WAL_SEGMENT_SYNC_TIMEOUT.
• It must handle the content of the dataBuf within the calling thread. Content of the buffer will not be changed before this method returns.
• It must not block the calling thread and work quickly.
• Ignite will ignore any Throwable throwed from this method.

Parameters:

dataBuf - Buffer that contains data to collect.