org.janusgraph.diskstorage.log

Class ReadMarker

java.lang.Object

org.janusgraph.diskstorage.log.ReadMarker

public class ReadMarker
extends Object

Author:

Matthias Broecheler ([email protected])

Method Summary

Modifier and Type	Method and Description
static ReadMarker	fromIdentifierOrNow(String id) Like fromIdentifierOrTime(String id, Instant timestamp) but uses the current time point as the starting timestamp if the log has no record of the id.
static ReadMarker	fromIdentifierOrTime(String id, Instant timestamp) Starts reading the log from the last recorded point in the log for the given id.
static ReadMarker	fromNow() Starts reading the log such that it will start with the first entry written after now.
static ReadMarker	fromTime(Instant timestamp) Starts reading the log from the given timestamp onward.
String	getIdentifier() Returns the configured identifier of this marker or throws an exception if none exists.
Instant	getStartTime(TimestampProvider times) Returns the start time of this marker if such has been defined or the current time if not
boolean	hasIdentifier() Whether this read marker has a configured identifier
boolean	hasStartTime()
boolean	isCompatible(ReadMarker newMarker)

Methods inherited from class java.lang.Object

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

Method Detail

hasIdentifier

public boolean hasIdentifier()

Whether this read marker has a configured identifier

Returns:

getIdentifier

public String getIdentifier()

Returns the configured identifier of this marker or throws an exception if none exists.

Returns:

hasStartTime

public boolean hasStartTime()

getStartTime

public Instant getStartTime(TimestampProvider times)

Returns the start time of this marker if such has been defined or the current time if not

Returns:

isCompatible

public boolean isCompatible(ReadMarker newMarker)

Parameters:

newMarker -

Returns:

fromNow

public static ReadMarker fromNow()

Starts reading the log such that it will start with the first entry written after now.

Returns:

fromTime

public static ReadMarker fromTime(Instant timestamp)

Starts reading the log from the given timestamp onward. The specified timestamp is included.

Parameters:

timestamp -

Returns:

fromIdentifierOrTime

public static ReadMarker fromIdentifierOrTime(String id,
                                              Instant timestamp)

Starts reading the log from the last recorded point in the log for the given id. If the log has a record of such an id, it will use it as the starting point. If not, it will start from the given timestamp and set it as the first read record for the given id.

Identified read markers of this kind are useful to continuously read from the log. In the case of failure, the last read record can be recovered for the id and log reading can be resumed from there. Note, that some records might be read twice in that event depending on the guarantees made by a particular implementation.

Parameters:

id -

timestamp -

Returns:

fromIdentifierOrNow

public static ReadMarker fromIdentifierOrNow(String id)

Like fromIdentifierOrTime(String id, Instant timestamp) but uses the current time point as the starting timestamp if the log has no record of the id.

Parameters:

id -

Returns: