org.axonframework.mongo.eventsourcing.eventstore

Class MongoTrackingToken

java.lang.Object

org.axonframework.mongo.eventsourcing.eventstore.MongoTrackingToken

All Implemented Interfaces:

TrackingToken

public class MongoTrackingToken
extends Object
implements TrackingToken

Tracking token implementation produced by the MongoEventStorageEngine to keep track of the position in an event stream. Order is determined by comparing timestamp, sequence number and event id.

This tracking token implementation keeps track of all events retrieved in a period of time before the furthest position in the stream. This makes it possible to detect event entries that have a lower timestamp than that with the highest timestamp but are published at a later time (due to time differences between nodes).

Author:

Rene de Waele

Method Summary

Modifier and Type	Method and Description
MongoTrackingToken	advanceTo(Instant timestamp, String eventIdentifier, Duration lookBackTime) Returns a new MongoTrackingToken instance based on this token but which has advanced to the event with given timestamp, eventIdentifier and sequenceNumber.
boolean	covers(TrackingToken other) Indicates whether this token covers the other token completely.
boolean	equals(Object o)
Set<String>	getKnownEventIds() Returns an Iterable with all known identifiers of events tracked before and including this token.
Instant	getTimestamp() Get the timestamp of the last event tracked by this token.
int	hashCode()
TrackingToken	lowerBound(TrackingToken other) Returns a token that represents the lower bound between this and the other token.
static MongoTrackingToken	of(Instant timestamp, String eventIdentifier) Returns a new instance of a MongoTrackingToken with given timestamp, eventIdentifier and sequenceNumber for the initial event in a stream.
String	toString()
TrackingToken	upperBound(TrackingToken other) Returns the token that represents the furthest possible position in a stream that either this token or the given other represents.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

of

public static MongoTrackingToken of(Instant timestamp,
                                    String eventIdentifier)

Returns a new instance of a MongoTrackingToken with given timestamp, eventIdentifier and sequenceNumber for the initial event in a stream.

Parameters:

timestamp - the event's timestamp

eventIdentifier - the event's identifier

Returns:

initial Mongo tracking token instance

advanceTo

public MongoTrackingToken advanceTo(Instant timestamp,
                                    String eventIdentifier,
                                    Duration lookBackTime)

Returns a new MongoTrackingToken instance based on this token but which has advanced to the event with given timestamp, eventIdentifier and sequenceNumber. Prior events with a timestamp smaller or equal than the latest event timestamp minus the given lookBackTime will not be included in the new token.

Parameters:

timestamp - the timestamp of the next event

eventIdentifier - the maximum distance between a gap and the token's index

lookBackTime - the maximum time between the latest and oldest event stored in the new key

Returns:

the new token that has advanced from the current token

getTimestamp

public Instant getTimestamp()

Get the timestamp of the last event tracked by this token.

Returns:

the timestamp of the event with this token

getKnownEventIds

public Set<String> getKnownEventIds()

Returns an Iterable with all known identifiers of events tracked before and including this token. Note, the token only stores ids of prior events if they are not too old, see advanceTo(Instant, String, Duration).

Returns:

all known event identifiers

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

lowerBound

public TrackingToken lowerBound(TrackingToken other)

Description copied from interface: TrackingToken

Returns a token that represents the lower bound between this and the other token. Effectively, the returned token will cause messages not received by both this and the other token to be redelivered.

Specified by:

lowerBound in interface TrackingToken

Parameters:

other - The token to compare to this one

Returns:

The token representing the lower bound of the two

upperBound

public TrackingToken upperBound(TrackingToken other)

Description copied from interface: TrackingToken

Returns the token that represents the furthest possible position in a stream that either this token or the given other represents. Effectively, this means this token will only deliver messages that neither this, nor the other have been received.

Specified by:

upperBound in interface TrackingToken

Parameters:

other - The token to compare this token to

Returns:

a token that represents the furthest position of this or the other stream

covers

public boolean covers(TrackingToken other)

Description copied from interface: TrackingToken

Indicates whether this token covers the other token completely. That means that this token represents a position in a stream that has received all of the messages that a stream represented by the other token has received.

Specified by:

covers in interface TrackingToken

Parameters:

other - The token to compare to this one

Returns:

true if this token covers the other, otherwise false