com.sleepycat.je.log.entry

Interface ReplicableLogEntry

All Superinterfaces:

Cloneable, LogEntry

All Known Implementing Classes:

AbortLogEntry, CommitLogEntry, DeletedDupLNLogEntry, LNLogEntry, MatchpointLogEntry, NameLNLogEntry, TraceLogEntry

public interface ReplicableLogEntry
extends LogEntry

A sub-interface of LogEntry that must be implemented by all log entries that can be replicated. Replicable log entries are all those entries for which the associated LogEntryType's LogEntryType.isReplicationPossible() method returns true. These are the log entries that can be included in the replication stream distributed from feeders to replicas during replication. See [#22336].

Starting with the release using log version 9, as specified by LogEntryType.LOG_VERSION_REPLICATE_OLDER, all replicable log entries need to support writing themselves in earlier log formats, to support replication during an upgrade when the master is replicated first. Any loggable objects that they reference should also implement VersionedWriteLoggable for the same reason.

The getLastFormatChange() method identifies the log version for which the entry's log format has most recently changed. This information is used to determine if the current log format is compatible with a non-upgraded replica.

The getSize(int, boolean) method overloading is used when creating the buffer that will be used to transmit the log entry data in the earlier format.

The writeEntry(ByteBuffer, int, boolean) method overloading is used to convert the in-memory format of the log entry into the log data in the earlier format.

To simplify the implementation of writing log entries in multiple log version formats, a log entry that needs to be written in a previous format will first be read into its in-memory format in the current version, and then written from there to the previous format.

Method Summary

Modifier and Type	Method and Description
Collection<VersionedWriteLoggable>	getEmbeddedLoggables() Returns all possible VersionedWriteLoggable objects that may be embedded in the binary data of this log entry.
int	getLastFormatChange() Returns the log version of the most recent format change for this log entry.
int	getSize(int logVersion, boolean forReplication) Returns the number of bytes needed to store this entry in the format for the specified log version.
boolean	hasReplicationFormat() Returns whether this format has a variant that is optimized for replication.
boolean	isReplicationFormatWorthwhile(ByteBuffer logBuffer, int srcVersion, int destVersion) Returns whether it is worthwhile to materialize and then re-serialize a log entry in a format optimized for replication.
void	writeEntry(ByteBuffer logBuffer, int logVersion, boolean forReplication) Serializes this object into the specified buffer in the format for the the specified log version.

Methods inherited from interface com.sleepycat.je.log.entry.LogEntry

clone, dumpEntry, dumpRep, getDbId, getLogType, getMainItem, getResolvedItem, getSize, getTransactionId, isDeleted, isImmediatelyObsolete, logicalEquals, postLogWork, readEntry, setLogType, writeEntry

Method Detail

getLastFormatChange

int getLastFormatChange()

Returns the log version of the most recent format change for this log entry.

Returns:

the log version of the most recent format change

getEmbeddedLoggables

Collection<VersionedWriteLoggable> getEmbeddedLoggables()

Returns all possible VersionedWriteLoggable objects that may be embedded in the binary data of this log entry.

This is used by tests to ensure that for each X:Y pair, where X is a ReplicableLogEntry and Y is a VersionedWriteLoggable, and X embeds Y either directly or indirectly, X.getLastFormatChange is greater than or equal to Y.getLastFormatChange.

Each ReplicableLogEntry and VersionedWriteLoggable class typically has a LAST_FORMAT_CHANGE constant that is returned by its getLastFormatChange method. When bumping this constant for an object X embedded by an log entry Y, Y.LAST_FORMAT_CHANGE should also be set to the minimum of its current value and X.LAST_FORMAT_CHANGE.

Enforcing this rule in a general way is made possible by the getEmbeddedLoggables method of each ReplicableLogEntry and VersionedWriteLoggable. Note that this method is not intended to be called outside of tests.

getSize

int getSize(int logVersion,
            boolean forReplication)

Returns the number of bytes needed to store this entry in the format for the specified log version. Earlier log versions only need to be supported for log entries with format changes made in LogEntryType.LOG_VERSION_REPLICATE_OLDER or greater.

Parameters:

logVersion - the log version

forReplication - whether the entry will be sent over the wire, and not written to the log.

Returns:

the number of bytes to store this entry for the log version

writeEntry

void writeEntry(ByteBuffer logBuffer,
                int logVersion,
                boolean forReplication)

Serializes this object into the specified buffer in the format for the the specified log version. Earlier log versions only need to be supported for log entries with format changes made in LogEntryType.LOG_VERSION_REPLICATE_OLDER or greater.

Parameters:

logBuffer - the destination buffer

forReplication - whether the entry will be sent over the wire, and not written to the log.

logVersion - the log version

hasReplicationFormat

boolean hasReplicationFormat()

Returns whether this format has a variant that is optimized for replication.

isReplicationFormatWorthwhile

boolean isReplicationFormatWorthwhile(ByteBuffer logBuffer,
                                      int srcVersion,
                                      int destVersion)

Returns whether it is worthwhile to materialize and then re-serialize a log entry in a format optimized for replication. Implementations should attempt to check efficiently, without instantiating the log entry object. Some implementations will simply return false.

WARNING: The logBuffer position must not be changed by this method.

WARNING: The shared LogEntry object is used for calling this method, and this method must not change any of the fields in the object.

Parameters:

logBuffer - contains the entry that would be re-serialized.

srcVersion - the log version of entry in logBuffer.

destVersion - the version that would be used for re-serialization.