Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.impl.store.replication.master.AsynchronousLogShipper

Field Summary

Modifier and Type	Field and Description
public static final int	DEFAULT_FORCEFLUSH_TIMEOUT The number of millis a call to forceFlush will wait before giving up sending a chunk of log to the slave
private ReplicationMessage	failedChunk Store the log chunk that failed during a previous shipping attempt so that it can be re-shipped to the slave.
private long	failedChunkHighestInstant The highest log instant in failedChunk
private static final int	FI_HIGH Fill information value indicative of a high load in the log buffer.
private static final int	FI_LOW Fill information value indicative of a low load in the log buffer.
private Object	forceFlushSemaphore Used to synchronize forceFlush calls
private long	highestShippedInstant The highest log instant shipped so far
private long	lastShippingTime Will store the time at which the last shipping happened.
private final ReplicationLogBuffer	logBuffer Replication log buffer that contains the log records that need to be transmitted to the slave.
private MasterController	masterController The master controller that initialized this log shipper.
private static final long	MAX If the fill information is less than FI_LOW the log shipper will ship with a MAX ms delay or when a buffer becomes full whichever comes first.
private long	maxShippingInterval Minimum interval (in milliseconds) between log shipping.
private static final long	MIN If the fill information (obtained from the log buffer) is less than FI_HIGH but greater than FI_LOW the log shipper will ship with a MIN ms delay.
private long	minShippingInterval Minimum interval (in milliseconds) between log shipping.
private Object	objLSTSync Object used to synchronize on while the log shipper thread is moved into the wait state, or while notifying it.
private final ReplicationLogger	repLogger
private long	shippingInterval Time interval (in milliseconds) at which the log shipping takes place.
private volatile boolean	stopShipping Indicates whether a stop shipping request has been sent.
private ReplicationMessageTransmit	transmitter Replication message transmitter that is used for the network transmission of the log records retrieved from the log buffer (on the master) to the slave being replicated to.

Inherited from java.lang.Thread:: MAX_PRIORITY MIN_PRIORITY NORM_PRIORITY

Constructor Summary

Access	Constructor and Description
public	AsynchronousLogShipper(ReplicationLogBuffer the replication log buffer that contains the log record chunks to be transmitted to the slave. logBuffer, ReplicationMessageTransmit the replication message transmitter that is used for network transmission of retrieved log records. transmitter, MasterController The master controller that initialized this log shipper. masterController, ReplicationLogger The replication logger that will write messages to the log file (typically derby.log) repLogger) Constructor initializes the log buffer, the replication message transmitter, the shipping interval and the master controller.

Access

Constructor and Description

public

AsynchronousLogShipper(ReplicationLogBuffer

the replication log buffer that contains the log record chunks to be transmitted to the slave.

logBuffer, ReplicationMessageTransmit

the replication message transmitter that is used for network transmission of retrieved log records.

transmitter, MasterController

The master controller that initialized this log shipper.

masterController, ReplicationLogger

The replication logger that will write messages to the log file (typically derby.log)

repLogger)

Constructor initializes the log buffer, the replication message transmitter, the shipping interval and the master controller.

Method Summary

Modifier and Type	Method and Description
private long	Returns: the shipping interval based on the fill information. calculateSIfromFI() Will be used to calculate the shipping interval based on the fill information obtained from the log buffer.
public void	flushBuffer() Implements org.apache.derby.impl.store.replication.master.LogShipper.flushBuffer. Transmits all the log records in the log buffer to the slave.
public void	flushedInstance(long a long that contains the latest instance of the log record that has been flushed to the disk. latestInstanceFlushedToDisk) Implements org.apache.derby.impl.store.replication.master.LogShipper.flushedInstance. updates the information about the latest instance of the log record that has been flushed to the disk.
public void	forceFlush() Implements org.apache.derby.impl.store.replication.master.LogShipper.forceFlush. Transmits a chunk of log record from the log buffer to the slave, used by the master controller when the log buffer is full and some space needs to be freed for further log records.
public long	Returns: the highest log instant shipped so far getHighestShippedInstant() Get the highest log instant shipped so far
private void	getLogShipperProperties() Load relevant system properties: max and min log shipping interval
public void	run() Overrides java.lang.Thread.run. Implements java.lang.Runnable.run. Ships log records from the log buffer to the slave being replicated to.
private synchronized boolean	Returns: true if a chunk of log records was shipped. false if no log records were shipped because log buffer is empty. shipALogChunk() Retrieves a chunk of log records, if available, from the log buffer and transmits them to the slave.
public void	stopLogShipment() Stop shipping log records.
public void	workToDo() Implements org.apache.derby.impl.store.replication.master.LogShipper.workToDo. Used to notify the log shipper that a log buffer element is full.

Field Detail

DEFAULT_FORCEFLUSH_TIMEOUT	back to summary
public static final int DEFAULT_FORCEFLUSH_TIMEOUT The number of millis a call to forceFlush will wait before giving up sending a chunk of log to the slave

failedChunk	back to summary
private ReplicationMessage failedChunk Store the log chunk that failed during a previous shipping attempt so that it can be re-shipped to the slave.

failedChunkHighestInstant	back to summary
private long failedChunkHighestInstant The highest log instant in failedChunk

FI_HIGH	back to summary
private static final int FI_HIGH Fill information value indicative of a high load in the log buffer.

FI_LOW	back to summary
private static final int FI_LOW Fill information value indicative of a low load in the log buffer.

forceFlushSemaphore	back to summary
private Object forceFlushSemaphore Used to synchronize forceFlush calls

highestShippedInstant	back to summary
private long highestShippedInstant The highest log instant shipped so far

lastShippingTime	back to summary
private long lastShippingTime Will store the time at which the last shipping happened. Will be used to calculate the interval between the log ships upon receiving a notification from the log buffer.

logBuffer	back to summary
private final ReplicationLogBuffer logBuffer Replication log buffer that contains the log records that need to be transmitted to the slave.

masterController	back to summary
private MasterController masterController The master controller that initialized this log shipper.

MAX	back to summary
private static final long MAX If the fill information is less than FI_LOW the log shipper will ship with a MAX ms delay or when a buffer becomes full whichever comes first. The delay however will not be smaller than MIN. max(MAX, DEFAULT_NUMBER_LOG_BUFFERSMIN) is the maximum delay between a log record is committed at the master until it is replicated to the slave. Hence the default latency should be atleast greater than the maximum latency offered by the choice of MIN, hence MAX > DEFAULT_NUMBER_LOG_BUFFERSMIN.

MAX

back to summary

private static final long MAX

If the fill information is less than FI_LOW the log shipper will ship with a MAX ms delay or when a buffer becomes full whichever comes first. The delay however will not be smaller than MIN. max(MAX, DEFAULT_NUMBER_LOG_BUFFERS*MIN) is the maximum delay between a log record is committed at the master until it is replicated to the slave. Hence the default latency should be atleast greater than the maximum latency offered by the choice of MIN, hence MAX > DEFAULT_NUMBER_LOG_BUFFERS*MIN.

maxShippingInterval back to summary

maxShippingInterval	back to summary
private long maxShippingInterval Minimum interval (in milliseconds) between log shipping. Defaults to MAX, but can be configured using system property derby.replication.maxLogShippingInterval See Also `MAX`

private long maxShippingInterval

Minimum interval (in milliseconds) between log shipping. Defaults to MAX, but can be configured using system property derby.replication.maxLogShippingInterval

See Also: MAX

MIN	back to summary
private static final long MIN If the fill information (obtained from the log buffer) is less than FI_HIGH but greater than FI_LOW the log shipper will ship with a MIN ms delay. MIN is a value that is only as large as not to affect the performance of the master database significantly.

minShippingInterval back to summary

minShippingInterval	back to summary
private long minShippingInterval Minimum interval (in milliseconds) between log shipping. Defaults to MIN, but can be configured using system property derby.replication.minLogShippingInterval See Also `MIN`

private long minShippingInterval

Minimum interval (in milliseconds) between log shipping. Defaults to MIN, but can be configured using system property derby.replication.minLogShippingInterval

See Also: MIN

objLSTSync	back to summary
private Object objLSTSync Object used to synchronize on while the log shipper thread is moved into the wait state, or while notifying it.

repLogger	back to summary
private final ReplicationLogger repLogger

shippingInterval	back to summary
private long shippingInterval Time interval (in milliseconds) at which the log shipping takes place.

stopShipping	back to summary
private volatile boolean stopShipping Indicates whether a stop shipping request has been sent. true - stop shipping log records false - shipping can continue without interruption.

transmitter	back to summary
private ReplicationMessageTransmit transmitter Replication message transmitter that is used for the network transmission of the log records retrieved from the log buffer (on the master) to the slave being replicated to.

Constructor Detail

AsynchronousLogShipper	back to summary
public AsynchronousLogShipper(ReplicationLogBuffer logBuffer, ReplicationMessageTransmit transmitter, MasterController masterController, ReplicationLogger repLogger) Constructor initializes the log buffer, the replication message transmitter, the shipping interval and the master controller. Parameters logBuffer:ReplicationLogBuffer the replication log buffer that contains the log record chunks to be transmitted to the slave. transmitter:ReplicationMessageTransmit the replication message transmitter that is used for network transmission of retrieved log records. masterController:MasterController The master controller that initialized this log shipper. repLogger:ReplicationLogger The replication logger that will write messages to the log file (typically derby.log)

AsynchronousLogShipper

back to summary

public AsynchronousLogShipper(ReplicationLogBuffer logBuffer, ReplicationMessageTransmit transmitter, MasterController masterController, ReplicationLogger repLogger)

Constructor initializes the log buffer, the replication message transmitter, the shipping interval and the master controller.

Parameters

logBuffer:ReplicationLogBuffer: the replication log buffer that contains the log record chunks to be transmitted to the slave.
transmitter:ReplicationMessageTransmit: the replication message transmitter that is used for network transmission of retrieved log records.
masterController:MasterController: The master controller that initialized this log shipper.
repLogger:ReplicationLogger: The replication logger that will write messages to the log file (typically derby.log)

Method Detail

calculateSIfromFI	back to summary
private long calculateSIfromFI() Will be used to calculate the shipping interval based on the fill information obtained from the log buffer. This method uses the following steps to arrive at the shipping interval, a) FI >= FI_HIGH return -1 (signifies that the waiting time should be 0) b) FI > FI_LOW and FI < FI_HIGH return minShippingInterval c) FI <= FI_LOW return maxShippingInterval. Returns:long the shipping interval based on the fill information.

calculateSIfromFI

back to summary

private long calculateSIfromFI()

Will be used to calculate the shipping interval based on the fill information obtained from the log buffer. This method uses the following steps to arrive at the shipping interval, a) FI >= FI_HIGH return -1 (signifies that the waiting time should be 0) b) FI > FI_LOW and FI < FI_HIGH return minShippingInterval c) FI <= FI_LOW return maxShippingInterval.

Returns:long: the shipping interval based on the fill information.

flushBuffer	back to summary
public void flushBuffer() throws IOException, StandardException Implements org.apache.derby.impl.store.replication.master.LogShipper.flushBuffer. Transmits all the log records in the log buffer to the slave. Exceptions IOException: If an exception occurs while trying to ship the replication message (containing the log records) across the network. StandardException: If an exception occurs while trying to read log records from the log buffer.

flushBuffer

back to summary

public void flushBuffer() throws IOException, StandardException

Implements org.apache.derby.impl.store.replication.master.LogShipper.flushBuffer.

Transmits all the log records in the log buffer to the slave.

Exceptions

IOException:: If an exception occurs while trying to ship the replication message (containing the log records) across the network.
StandardException:: If an exception occurs while trying to read log records from the log buffer.

flushedInstance	back to summary
public void flushedInstance(long latestInstanceFlushedToDisk) Implements org.apache.derby.impl.store.replication.master.LogShipper.flushedInstance. updates the information about the latest instance of the log record that has been flushed to the disk. Calling this method has no effect in this asynchronous implementation of the log shipper. Parameters latestInstanceFlushedToDisk:long a long that contains the latest instance of the log record that has been flushed to the disk.

flushedInstance

back to summary

public void flushedInstance(long latestInstanceFlushedToDisk)

Implements org.apache.derby.impl.store.replication.master.LogShipper.flushedInstance.

updates the information about the latest instance of the log record that has been flushed to the disk. Calling this method has no effect in this asynchronous implementation of the log shipper.

Parameters

latestInstanceFlushedToDisk:long: a long that contains the latest instance of the log record that has been flushed to the disk.

forceFlush	back to summary
public void forceFlush() throws IOException, StandardException Implements org.apache.derby.impl.store.replication.master.LogShipper.forceFlush. Transmits a chunk of log record from the log buffer to the slave, used by the master controller when the log buffer is full and some space needs to be freed for further log records. Exceptions IOException: If an exception occurs while trying to ship the replication message (containing the log records) across the network. StandardException: If an exception occurs while trying to read log records from the log buffer.

forceFlush

back to summary

public void forceFlush() throws IOException, StandardException

Implements org.apache.derby.impl.store.replication.master.LogShipper.forceFlush.

Transmits a chunk of log record from the log buffer to the slave, used by the master controller when the log buffer is full and some space needs to be freed for further log records.

Exceptions

IOException:: If an exception occurs while trying to ship the replication message (containing the log records) across the network.
StandardException:: If an exception occurs while trying to read log records from the log buffer.

getHighestShippedInstant	back to summary
public long getHighestShippedInstant() Get the highest log instant shipped so far Returns:long the highest log instant shipped so far

getHighestShippedInstant

back to summary

public long getHighestShippedInstant()

Get the highest log instant shipped so far

Returns:long: the highest log instant shipped so far

getLogShipperProperties	back to summary
private void getLogShipperProperties() Load relevant system properties: max and min log shipping interval

run	back to summary
public void run() Overrides java.lang.Thread.run. Implements java.lang.Runnable.run. Ships log records from the log buffer to the slave being replicated to. The log shipping happens between shipping intervals of time, the shipping interval being derived from the fill information (an indicator of load in the log buffer) obtained from the log buffer. The shipping can also be triggered in the following situations, 1) Based on notifications from the log buffer, where the fill information is again used as the basis to decide whether a shipping should happen or not 2) On a forceFlush triggered by the log buffer becoming full and the LogBufferFullException being thrown.

run

back to summary

public void run()

Overrides java.lang.Thread.run.

Implements java.lang.Runnable.run.

Ships log records from the log buffer to the slave being replicated to. The log shipping happens between shipping intervals of time, the shipping interval being derived from the fill information (an indicator of load in the log buffer) obtained from the log buffer. The shipping can also be triggered in the following situations, 1) Based on notifications from the log buffer, where the fill information is again used as the basis to decide whether a shipping should happen or not 2) On a forceFlush triggered by the log buffer becoming full and the LogBufferFullException being thrown.

shipALogChunk	back to summary
private synchronized boolean shipALogChunk() throws IOException, StandardException Retrieves a chunk of log records, if available, from the log buffer and transmits them to the slave. Used for both periodic and forced shipping. Returns:boolean true if a chunk of log records was shipped. false if no log records were shipped because log buffer is empty. Exceptions IOException: If an exception occurs while trying to ship the replication message (containing the log records) across the network. StandardException: If an exception occurs while trying to read log records from the log buffer.

shipALogChunk

back to summary

private synchronized boolean shipALogChunk() throws IOException, StandardException

Retrieves a chunk of log records, if available, from the log buffer and transmits them to the slave. Used for both periodic and forced shipping.

Returns:boolean

true if a chunk of log records was shipped. false if no log records were shipped because log buffer is empty.

Exceptions

IOException:: If an exception occurs while trying to ship the replication message (containing the log records) across the network.
StandardException:: If an exception occurs while trying to read log records from the log buffer.

stopLogShipment	back to summary
public void stopLogShipment() Stop shipping log records. If a ship is currently in progress it will not be interrupted, shipping will stop only after the current shipment is done.

workToDo	back to summary
public void workToDo() Implements org.apache.derby.impl.store.replication.master.LogShipper.workToDo. Used to notify the log shipper that a log buffer element is full. This method would basically use the following steps to decide on the action to be taken when a notification from the log shipper is received, a) Get FI from log buffer b) If FI >= FI_HIGH b.1) notify the log shipper thread. c) Else If the time elapsed since last ship is greater than minShippingInterval c.1) notify the log shipper thread.

workToDo

back to summary

public void workToDo()

Implements org.apache.derby.impl.store.replication.master.LogShipper.workToDo.

Used to notify the log shipper that a log buffer element is full. This method would basically use the following steps to decide on the action to be taken when a notification from the log shipper is received, a) Get FI from log buffer b) If FI >= FI_HIGH b.1) notify the log shipper thread. c) Else If the time elapsed since last ship is greater than minShippingInterval c.1) notify the log shipper thread.

public Class AsynchronousLogShipper

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail