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com.bea.wlevs.ede.api
Interface EventChannel

public interface EventChannel

extends Stage, EventQueue, HeartbeatAware, com.bea.wlevs.ede.api.EventSinkManager, BatchRelationSink, BatchStreamSink

A event channel is a conduit for events.

Event channels support two types of modeling, streams and relations.

Streams are append-only, that is, events are always appended to the end of the stream. Relations support events that insert, delete, and update its content.

Events send to channels must have non-decreasing time-stamps.

Field Summary

static java.lang.String	RECOVERY_PRECISION_BEST_EFFORT Precision of recovery to be used for archived channels.
static java.lang.String	RECOVERY_PRECISION_NO_DUPS Precision of recovery to be used for archived channels.

Method Summary
abstract java.lang.String	getEventType() Only events of this event type are allowed to pass through this event channel.
abstract java.lang.String	getId() Returns the event channel identity
abstract java.lang.Integer	getPartitionOrderCapacity() The capacity (i.e.number of buckets) of partition used for partition-ordered sources (e.g. relation/stream).
abstract java.util.List	getPrimaryKey() Returns primary key of relation, or an empty list for streams.
abstract java.lang.String	getRecoveryPrecision() Returns the recovery precision for archived channel.
abstract java.lang.String	getTimestampExpression() Returns expression used to calculate the application timestamp.
abstract boolean	isApplicationTimestamped() Returns if channel is application timestamped, that is, application is responsible for assigning a timestamp to each event.
abstract boolean	isArchived() Returns if channel should handle archived events.
abstract boolean	isBatchEvents() Returns if channel is batching over timestamp
abstract boolean	isLocalPartitioner() Returns if channel partitions input stream into multiple substreams and push to a single downstream processor.
abstract boolean	isRelation() Returns if event channel is carrying relations, instead of streams.
abstract boolean	isSystemTimestamped() Returns if channel is system timestamped, that is, the system is responsible for assigning a timestamp to each event.
abstract boolean	isTotalOrder() Returns if application time published is always strictly greater than the last value used.

Methods inherited from interface com.bea.wlevs.ede.api.EventQueue

getCurrentSize, getMaxSize, getMaxThreads, getOfferTimeout, isFailWhenRejected, setFailWhenRejected, setMaxSize, setMaxThreads, setOfferTimeout

Methods inherited from interface com.bea.wlevs.ede.api.HeartbeatAware

onHeartbeat

Methods inherited from interface com.bea.wlevs.ede.api.BatchRelationSink

onEvents

Methods inherited from interface com.bea.wlevs.ede.api.BatchStreamSink

onInsertEvents

Methods inherited from interface com.bea.wlevs.ede.api.EventSender

sendEvent

Methods inherited from interface com.bea.wlevs.ede.api.BatchRelationSender

sendEvents

Methods inherited from interface com.bea.wlevs.ede.api.BatchStreamSender

sendInsertEvents

Methods inherited from interface com.bea.wlevs.ede.api.RelationSender

sendDeleteEvent, sendUpdateEvent

Methods inherited from interface com.bea.wlevs.ede.api.RelationSink

onDeleteEvent, onUpdateEvent

Field Detail

RECOVERY_PRECISION_BEST_EFFORT

public static final java.lang.String RECOVERY_PRECISION_BEST_EFFORT

Precision of recovery to be used for archived channels.

best-effort recovery entails that events may be lost, or you may get duplicate events while recovering an archived channel from failure.

RECOVERY_PRECISION_NO_DUPS

public static final java.lang.String RECOVERY_PRECISION_NO_DUPS

Precision of recovery to be used for archived channels.

no-dups recovery entails that the system will attempt to remove duplicate events by comparing their output event time.

Method Detail

getId

public java.lang.String getId()

Returns the event channel identity

Returns:

identity

getEventType

public java.lang.String getEventType()

Only events of this event type are allowed to pass through this event channel.

Returns:

event type name

getTimestampExpression

public java.lang.String getTimestampExpression()

Returns expression used to calculate the application timestamp.

Parameters:

expression -

isRelation

public boolean isRelation()

Returns if event channel is carrying relations, instead of streams.

Returns:

boolean

getPrimaryKey

public java.util.List getPrimaryKey()

Returns primary key of relation, or an empty list for streams.

Returns:

list of property names used as primary key for relation

isTotalOrder

public boolean isTotalOrder()

Returns if application time published is always strictly greater than the last value used.

Returns:

boolean

isSystemTimestamped

public boolean isSystemTimestamped()

Returns if channel is system timestamped, that is, the system is responsible for assigning a timestamp to each event. This is done using System.nanoTime().

Returns:

boolean

isApplicationTimestamped

public boolean isApplicationTimestamped()

Returns if channel is application timestamped, that is, application is responsible for assigning a timestamp to each event. Application may use any time domain.

Returns:

boolean

isBatchEvents

public boolean isBatchEvents()

Returns if channel is batching over timestamp

Returns:

boolean

getPartitionOrderCapacity

public java.lang.Integer getPartitionOrderCapacity()

The capacity (i.e.number of buckets) of partition used for partition-ordered sources (e.g. relation/stream). This is used by downstream processors when executing partition-ordered queries and views. If not set and max-threads is greater than zero, then it is assumed to be equal to max-threads. If max-threads is not greater than zero, then the server's global partition-buckets configuration in the 'cql' section is used. If this is not set, then a default of 4 is used. A channel that is not connected to a processor does not have a partition order capacity and therefore returns null if not explicitly configured with a value.

Returns:

Integer partition capacity, or null if not applicable

isArchived

public boolean isArchived()

Returns if channel should handle archived events.

Archived channels are channels that replay their events while recovering from a failure of the system in an attempt to revive the state of a downstream processor as it was before the failure.

The archiving of the events should be realized by the upstream stage to this channel.

Returns:

boolean

getRecoveryPrecision

public java.lang.String getRecoveryPrecision()

Returns the recovery precision for archived channel.

By default, recovery precision is best-effort. This means that events may be lost, and you may receive duplicates. If precision is set to no-dups, then the timestamp of the output events are used to remove duplicates.

Returns:

recovery precision of archived channel or null if not an archived channel

isLocalPartitioner

public boolean isLocalPartitioner()

Returns if channel partitions input stream into multiple substreams and push to a single downstream processor.

By default, the local partitioner flag will be false and channel will act as event partitioner if channel specifies partitionby attributes or user defined partition function.

Returns:

true if channel is a local partitioner, false otherwise.