net.wicp.tams.common.binlog.parser.event

类 LogHeader

java.lang.Object

net.wicp.tams.common.binlog.parser.event.LogHeader

public final class LogHeader
extends Object

The Common-Header, documented in the table @ref Table_common_header "below", always has the same form and length within one version of MySQL. Each event type specifies a format and length of the Post-Header. The length of the Common-Header is the same for all events of the same type. The Body may be of different format and length even for different events of the same type. The binary formats of Post-Header and Body are documented separately in each subclass. The binary format of Common-Header is as follows.

Common-Header

Name	Format	Description
timestamp	4 byte unsigned integer	The time when the query started, in seconds since 1970.
type	1 byte enumeration	See enum #Log_event_type.
server_id	4 byte unsigned integer	Server ID of the server that created the event.
total_size	4 byte unsigned integer	The total size of this event, in bytes. In other words, this is the sum of the sizes of Common-Header, Post-Header, and Body.
master_position	4 byte unsigned integer	The position of the next event in the master binary log, in bytes from the beginning of the file. In a binlog that is not a relay log, this is just the position of the next event, in bytes from the beginning of the file. In a relay log, this is the position of the next event in the master's binlog.
flags	2 byte bitfield	See Log_event::flags.

Summing up the numbers above, we see that the total size of the common header is 19 bytes.

字段概要

字段

限定符和类型	字段和说明
protected int	checksumAlg The value is set by caller of FD constructor and Log_event::write_header() for the rest.
protected long	crc Placeholder for event checksum while writing to binlog.
protected int	eventLen Number of bytes written by write() function
protected int	flags Some 16 flags.
protected long	logPos The offset in the log where this event originally appeared (it is preserved in relay logs, making SHOW SLAVE STATUS able to print coordinates of the event in the master's binlog).
protected long	serverId The master's server id (is preserved in the relay log; used to prevent from infinite loops in circular replication).
protected int	type
protected long	when Timestamp on the master(for debugging and replication of NOW()/TIMESTAMP).

构造器概要

构造器

构造器和说明
LogHeader(int type)
LogHeader(LogBuffer buffer, FormatDescriptionLogEvent descriptionEvent)

方法概要

限定符和类型	方法和说明
int	getChecksumAlg()
long	getCrc()
int	getEventLen() The total size of this event, in bytes.
int	getFlags() Some 16 flags.
long	getLogPos() The position of the next event in the master binary log, in bytes from the beginning of the file.
long	getServerId() Server ID of the server that created the event.
int	getType() The different types of log events.
long	getWhen() The time when the query started, in seconds since 1970.

从类继承的方法 java.lang.Object

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

字段详细资料

type

protected final int type

logPos

protected long logPos

The offset in the log where this event originally appeared (it is preserved in relay logs, making SHOW SLAVE STATUS able to print coordinates of the event in the master's binlog). Note: when a transaction is written by the master to its binlog (wrapped in BEGIN/COMMIT) the log_pos of all the queries it contains is the one of the BEGIN (this way, when one does SHOW SLAVE STATUS it sees the offset of the BEGIN, which is logical as rollback may occur), except the COMMIT query which has its real offset.

when

protected long when

Timestamp on the master(for debugging and replication of NOW()/TIMESTAMP). It is important for queries and LOAD DATA INFILE. This is set at the event's creation time, except for Query and Load (et al.) events where this is set at the query's execution time, which guarantees good replication (otherwise, we could have a query and its event with different timestamps).

eventLen

protected int eventLen

Number of bytes written by write() function

serverId

protected long serverId

The master's server id (is preserved in the relay log; used to prevent from infinite loops in circular replication).

flags

protected int flags

Some 16 flags. See the definitions above for LOG_EVENT_TIME_F, LOG_EVENT_FORCED_ROTATE_F, LOG_EVENT_THREAD_SPECIFIC_F, and LOG_EVENT_SUPPRESS_USE_F for notes.

checksumAlg

protected int checksumAlg

The value is set by caller of FD constructor and Log_event::write_header() for the rest. In the FD case it's propagated into the last byte of post_header_len[] at FD::write(). On the slave side the value is assigned from post_header_len[last] of the last seen FD event.

crc

protected long crc

Placeholder for event checksum while writing to binlog.

构造器详细资料

LogHeader

public LogHeader(int type)

LogHeader

public LogHeader(LogBuffer buffer,
                 FormatDescriptionLogEvent descriptionEvent)

方法详细资料

getType

public final int getType()

The different types of log events.

getLogPos

public final long getLogPos()

The position of the next event in the master binary log, in bytes from the beginning of the file. In a binlog that is not a relay log, this is just the position of the next event, in bytes from the beginning of the file. In a relay log, this is the position of the next event in the master's binlog.

getEventLen

public final int getEventLen()

The total size of this event, in bytes. In other words, this is the sum of the sizes of Common-Header, Post-Header, and Body.

getWhen

public final long getWhen()

The time when the query started, in seconds since 1970.

getServerId

public final long getServerId()

Server ID of the server that created the event.

getFlags

public final int getFlags()

Some 16 flags. See the definitions above for LOG_EVENT_TIME_F, LOG_EVENT_FORCED_ROTATE_F, LOG_EVENT_THREAD_SPECIFIC_F, and LOG_EVENT_SUPPRESS_USE_F for notes.

getCrc

public long getCrc()

getChecksumAlg

public int getChecksumAlg()