Package org.postgresql.core.v3.replication

Class V3PGReplicationStream

java.lang.Object

org.postgresql.core.v3.replication.V3PGReplicationStream

All Implemented Interfaces:

AutoCloseable, PGReplicationStream

public class V3PGReplicationStream
extends Object
implements PGReplicationStream

Field Summary

Fields

Modifier and Type	Field	Description
static long	POSTGRES_EPOCH_2000_01_01

Constructor Summary

Constructors

Constructor	Description
V3PGReplicationStream(CopyDual copyDual, LogSequenceNumber startLSN, long updateIntervalMs, ReplicationType replicationType)

Method Summary

Modifier and Type	Method	Description
void	close()	Stop replication changes from server and free resources.
void	forceUpdateStatus()	Force send to backend status about last received, flushed and applied LSN.
LogSequenceNumber	getLastAppliedLSN()	Last applied lsn send in update message to backed.
LogSequenceNumber	getLastFlushedLSN()	Last flushed lsn send in update message to backend.
LogSequenceNumber	getLastReceiveLSN()	Parameter updates by execute PGReplicationStream.read() method.
boolean	isClosed()
ByteBuffer	read()	Read next wal record from backend.
ByteBuffer	readPending()	Read next wal record from backend.
void	setAppliedLSN(LogSequenceNumber applied)	Parameter used only physical replication and define which lsn already was apply on standby.
void	setFlushedLSN(LogSequenceNumber flushed)	Set flushed LSN.

Methods inherited from class java.lang.Object

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

Field Detail

POSTGRES_EPOCH_2000_01_01

public static final long POSTGRES_EPOCH_2000_01_01

See Also:

Constant Field Values

Constructor Detail

V3PGReplicationStream

public V3PGReplicationStream(CopyDual copyDual,
                             LogSequenceNumber startLSN,
                             long updateIntervalMs,
                             ReplicationType replicationType)

Parameters:

copyDual - bidirectional copy protocol

startLSN - the position in the WAL that we want to initiate replication from usually the currentLSN returned by calling pg_current_wal_lsn()for v10 above or pg_current_xlog_location() depending on the version of the server

updateIntervalMs - the number of millisecond between status packets sent back to the server. A value of zero disables the periodic status updates completely, although an update will still be sent when requested by the server, to avoid timeout disconnect.

replicationType - LOGICAL or PHYSICAL

Method Detail

read

public ByteBuffer read()
                throws SQLException

Description copied from interface: PGReplicationStream

Read next wal record from backend. It method can be block until new message will not get from server.

A single WAL record is never split across two XLogData messages. When a WAL record crosses a WAL page boundary, and is therefore already split using continuation records, it can be split at the page boundary. In other words, the first main WAL record and its continuation records can be sent in different XLogData messages.

Specified by:

read in interface PGReplicationStream

Returns:

not null byte array received by replication protocol, return ByteBuffer wrap around received byte array with use offset, so, use ByteBuffer.array() carefully

Throws:

SQLException - when some internal exception occurs during read from stream

readPending

public ByteBuffer readPending()
                       throws SQLException

Description copied from interface: PGReplicationStream

Read next wal record from backend. It method can't be block and in contrast to PGReplicationStream.read(). If message from backend absent return null. It allow periodically check message in stream and if they absent sleep some time, but it time should be less than CommonOptions.getStatusInterval() to avoid disconnect from the server.

A single WAL record is never split across two XLogData messages. When a WAL record crosses a WAL page boundary, and is therefore already split using continuation records, it can be split at the page boundary. In other words, the first main WAL record and its continuation records can be sent in different XLogData messages.

Specified by:

readPending in interface PGReplicationStream

Returns:

byte array received by replication protocol or null if pending message from server absent. Returns ByteBuffer wrap around received byte array with use offset, so, use ByteBuffer.array() carefully.

Throws:

SQLException - when some internal exception occurs during read from stream

getLastReceiveLSN

public LogSequenceNumber getLastReceiveLSN()

Description copied from interface: PGReplicationStream

Parameter updates by execute PGReplicationStream.read() method.

Specified by:

getLastReceiveLSN in interface PGReplicationStream

Returns:

not null LSN position that was receive last time via PGReplicationStream.read() method

getLastFlushedLSN

public LogSequenceNumber getLastFlushedLSN()

Description copied from interface: PGReplicationStream

Last flushed lsn send in update message to backend. Parameter updates only via PGReplicationStream.setFlushedLSN(LogSequenceNumber)

Specified by:

getLastFlushedLSN in interface PGReplicationStream

Returns:

not null location of the last WAL flushed to disk in the standby.

getLastAppliedLSN

public LogSequenceNumber getLastAppliedLSN()

Description copied from interface: PGReplicationStream

Last applied lsn send in update message to backed. Parameter updates only via PGReplicationStream.setAppliedLSN(LogSequenceNumber)

Specified by:

getLastAppliedLSN in interface PGReplicationStream

Returns:

not null location of the last WAL applied in the standby.

setFlushedLSN

public void setFlushedLSN(LogSequenceNumber flushed)

Description copied from interface: PGReplicationStream

Set flushed LSN. It parameter will be send to backend on next update status iteration. Flushed LSN position help backend define which wal can be recycle.

Specified by:

setFlushedLSN in interface PGReplicationStream

Parameters:

flushed - not null location of the last WAL flushed to disk in the standby.

See Also:

PGReplicationStream.forceUpdateStatus()

setAppliedLSN

public void setAppliedLSN(LogSequenceNumber applied)

Description copied from interface: PGReplicationStream

Parameter used only physical replication and define which lsn already was apply on standby. Feedback will send to backend on next update status iteration.

Specified by:

setAppliedLSN in interface PGReplicationStream

Parameters:

applied - not null location of the last WAL applied in the standby.

See Also:

PGReplicationStream.forceUpdateStatus()

forceUpdateStatus

public void forceUpdateStatus()
                       throws SQLException

Description copied from interface: PGReplicationStream

Force send to backend status about last received, flushed and applied LSN. You can not use it method explicit, because PGReplicationStream send status to backend periodical by configured interval via CommonOptions.getStatusInterval()

Specified by:

forceUpdateStatus in interface PGReplicationStream

Throws:

SQLException - when some internal exception occurs during read from stream

See Also:

CommonOptions.getStatusInterval()

isClosed

public boolean isClosed()

Specified by:

isClosed in interface PGReplicationStream

Returns:

true if replication stream was already close, otherwise return false

close

public void close()
           throws SQLException

Description copied from interface: PGReplicationStream

Stop replication changes from server and free resources. After that connection can be reuse to another queries. Also after close current stream they cannot be used anymore.

Note: This method can spend much time for logical replication stream on postgresql version 9.6 and lower, because postgresql have bug - during decode big transaction to logical form and during wait new changes postgresql ignore messages from client. As workaround you can close replication connection instead of close replication stream. For more information about it problem see mailing list thread Stopping logical replication protocol

Specified by:

close in interface AutoCloseable

Specified by:

close in interface PGReplicationStream

Throws:

SQLException - when some internal exception occurs during end streaming