io.debezium.connector.postgresql.connection

Class WalPositionLocator

java.lang.Object

io.debezium.connector.postgresql.connection.WalPositionLocator

public class WalPositionLocator
extends Object

This class is responsible for finding out a LSN from which Debezium should resume streaming after connector restarts. The LSNs are not guaranteed to be ordered in the WAL. LSN of commits are ordered and LSNs inside a transaction are ordered. It is thus necessary to find out the beginning of the unprocessed transaction and the LSN from which the streaming should start.

Author:

Jiri Pechanec

Field Summary

Fields

Modifier and Type	Field and Description
private Lsn	firstLsnReceived
private Lsn	lastCommitStoredLsn
private Lsn	lastEventStoredLsn
private static org.slf4j.Logger	LOGGER
private Lsn	lsnAfterLastEventStoredLsn
private boolean	passMessages
private Lsn	startStreamingLsn
private boolean	storeLsnAfterLastEventStoredLsn
private Lsn	txStartLsn

Constructor Summary

Constructors

Constructor and Description
WalPositionLocator()
WalPositionLocator(Lsn lastCommitStoredLsn, Lsn lastEventStoredLsn)

Method Summary

Modifier and Type	Method and Description
void	enableFiltering() Enables filtering of message LSNs based on calculated position.
Lsn	getLastEventStoredLsn()
Optional<Lsn>	resumeFromLsn(Lsn currentLsn, ReplicationMessage message)
boolean	searchingEnabled()
boolean	skipMessage(Lsn lsn) Decides whether the message with given LSN should be removed or not based on previously located LSN point.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

LOGGER

private static final org.slf4j.Logger LOGGER

lastCommitStoredLsn

private final Lsn lastCommitStoredLsn

lastEventStoredLsn

private final Lsn lastEventStoredLsn

txStartLsn

private Lsn txStartLsn

lsnAfterLastEventStoredLsn

private Lsn lsnAfterLastEventStoredLsn

firstLsnReceived

private Lsn firstLsnReceived

passMessages

private boolean passMessages

startStreamingLsn

private Lsn startStreamingLsn

storeLsnAfterLastEventStoredLsn

private boolean storeLsnAfterLastEventStoredLsn

Constructor Detail

WalPositionLocator

public WalPositionLocator(Lsn lastCommitStoredLsn,
                          Lsn lastEventStoredLsn)

WalPositionLocator

public WalPositionLocator()

Method Detail

resumeFromLsn

public Optional<Lsn> resumeFromLsn(Lsn currentLsn,
                                   ReplicationMessage message)

Returns:

the first LSN from which processing should be started or empty if the position has not been found yet

skipMessage

public boolean skipMessage(Lsn lsn)

Decides whether the message with given LSN should be removed or not based on previously located LSN point.

Parameters:

lsn -

Returns:

true if the message should be skipped, false otherwise

enableFiltering

public void enableFiltering()

Enables filtering of message LSNs based on calculated position.

searchingEnabled

public boolean searchingEnabled()

Returns:

true if searching of WAL position should be executed

getLastEventStoredLsn

public Lsn getLastEventStoredLsn()

toString

public String toString()

Overrides:

toString in class Object