cz.o2.proxima.direct.commitlog

Class RetryableLogObserver

java.lang.Object

cz.o2.proxima.direct.commitlog.RetryableLogObserver

All Implemented Interfaces:

LogObserver, java.io.Serializable

@Stable
public class RetryableLogObserver
extends java.lang.Object
implements LogObserver

LogObserver which is able to retry the observation on error. The number of retries is configurable.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface cz.o2.proxima.direct.commitlog.LogObserver

LogObserver.OffsetCommitter, LogObserver.OnIdleContext, LogObserver.OnNextContext, LogObserver.OnRepartitionContext

Field Summary

Fields

Modifier and Type	Field and Description
private LogObserver	delegate Underlying log observer.
private int	maxRetries Maximal number of retries.
private java.lang.String	name Name of the consumer.
private int	numFailures Current number of failures in a row.

Constructor Summary

Constructors

Modifier	Constructor and Description
private	RetryableLogObserver(java.lang.String name, int maxRetries, LogObserver delegate)

Method Summary

Modifier and Type	Method and Description
static RetryableLogObserver	of(java.lang.String name, int numRetries, LogObserver observer) Create online retryable log observer.
void	onCancelled() Notify that the processing has been canceled.
void	onCompleted() Notify that the processing has gracefully ended.
boolean	onError(java.lang.Throwable throwable) Called to notify there was an {@link Throwable error) in the commit reader.
void	onIdle(LogObserver.OnIdleContext context) Called when the observer is idle.
boolean	onNext(StreamElement ingest, LogObserver.OnNextContext context) Process next record in the commit log.
void	onRepartition(LogObserver.OnRepartitionContext context) Callback to notify of automatic repartitioning.

Methods inherited from class java.lang.Object

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

Methods inherited from interface cz.o2.proxima.direct.commitlog.LogObserver

onException, onFatalError

Field Detail

maxRetries

private final int maxRetries

Maximal number of retries.

name

private final java.lang.String name

Name of the consumer.

numFailures

private int numFailures

Current number of failures in a row.

delegate

private final LogObserver delegate

Underlying log observer.

Constructor Detail

RetryableLogObserver

private RetryableLogObserver(java.lang.String name,
                             int maxRetries,
                             LogObserver delegate)

Method Detail

of

public static RetryableLogObserver of(java.lang.String name,
                                      int numRetries,
                                      LogObserver observer)

Create online retryable log observer.

Parameters:

name - name of the consumer

numRetries - number of allowed successive failures

observer - observer of data

Returns:

the observer

onNext

public final boolean onNext(StreamElement ingest,
                            LogObserver.OnNextContext context)

Description copied from interface: LogObserver

Process next record in the commit log.

Specified by:

onNext in interface LogObserver

Parameters:

ingest - the ingested data written to the commit log

context - a context that the application must use to confirm processing of the ingest. If the application fails to do so, the result is undefined.

Returns:

true if the processing should continue, false otherwise

onError

public boolean onError(java.lang.Throwable throwable)

Description copied from interface: LogObserver

Called to notify there was an {@link Throwable error) in the commit reader.

Specified by:

onError in interface LogObserver

Parameters:

throwable - error caught during processing

Returns:

true to restart processing from last committed position, false to stop processing

onCompleted

public void onCompleted()

Description copied from interface: LogObserver

Notify that the processing has gracefully ended.

Specified by:

onCompleted in interface LogObserver

onCancelled

public void onCancelled()

Description copied from interface: LogObserver

Notify that the processing has been canceled.

Specified by:

onCancelled in interface LogObserver

onRepartition

public void onRepartition(LogObserver.OnRepartitionContext context)

Description copied from interface: LogObserver

Callback to notify of automatic repartitioning. This method is always called first before any LogObserver.onNext(cz.o2.proxima.storage.StreamElement, cz.o2.proxima.direct.commitlog.LogObserver.OnNextContext) call happens.

Specified by:

onRepartition in interface LogObserver

Parameters:

context - context of the repartition

onIdle

public void onIdle(LogObserver.OnIdleContext context)

Description copied from interface: LogObserver

Called when the observer is idle. Note that the definition of idle is commit-log dependent and it even might NOT be called at all, if the commit log guarantees that as long as there are *any* data flowing in, then LogObserver.onNext(cz.o2.proxima.storage.StreamElement, cz.o2.proxima.direct.commitlog.LogObserver.OnNextContext) will be called eventually.

Typical example of commit log with no need to call LogObserver.onIdle(cz.o2.proxima.direct.commitlog.LogObserver.OnIdleContext) is google PubSub, having virtually single shared partition which loads balances incoming data.

Specified by:

onIdle in interface LogObserver

Parameters:

context - the context for on idle processing