By default, mysqlbinlog reads binary log
files and displays their contents in text format. This enables
you to examine events within the files more easily and to
re-execute them (for example, by using the output as input to
mysql). mysqlbinlog can
read log files directly from the local file system, or, with the
option, it can connect to a server and request binary log
contents from that server. mysqlbinlog writes
text output to its standard output, or to the file named as the
value of the
option if that option is given.
mysqlbinlog Backup Capabilities
mysqlbinlog can read binary log files and write new files containing the same content—that is, in binary format rather than text format. This capability enables you to easily back up a binary log in its original format. mysqlbinlog can make a static backup, backing up a set of log files and stopping when the end of the last file is reached. It can also make a continuous (“live”) backup, staying connected to the server when it reaches the end of the last log file and continuing to copy new events as they are generated. In continuous-backup operation, mysqlbinlog runs until the connection ends (for example, when the server exits) or mysqlbinlog is forcibly terminated. When the connection ends, mysqlbinlog does not wait and retry the connection, unlike a replica server. To continue a live backup after the server has been restarted, you must also restart mysqlbinlog.
mysqlbinlog Backup Options
Binary log backup requires that you invoke mysqlbinlog with two options at minimum:
-R) option tells mysqlbinlog to connect to a server and request its binary log. (This is similar to a replica replication server connecting to its source server.)
--rawoption tells mysqlbinlog to write raw (binary) output, not text output.
it is common to specify other options:
--host indicates where the
server is running, and you may also need to specify connection
options such as
Several other options are useful in conjunction with
--stop-never: Stay connected to the server after reaching the end of the last log file and continue to read new events.
--stop-never-slave-server-id=: The server ID that mysqlbinlog reports to the server when
--stop-neveris used. The default is 65535. This can be used to avoid a conflict with the ID of a replica server or another mysqlbinlog process. See Section 220.127.116.11, “Specifying the mysqlbinlog Server ID”.
--result-file: A prefix for output file names, as described later.
Static and Live Backups
To back up a server's binary log files with
mysqlbinlog, you must specify file names that
actually exist on the server. If you do not know the names,
connect to the server and use the
BINARY LOGS statement to see the current names.
Suppose that the statement produces this output:
mysql> SHOW BINARY LOGS; +---------------+-----------+ | Log_name | File_size | +---------------+-----------+ | binlog.000130 | 27459 | | binlog.000131 | 13719 | | binlog.000132 | 43268 | +---------------+-----------+
With that information, you can use mysqlbinlog to back up the binary log to the current directory as follows (enter each command on a single line):
To make a static backup of
binlog.000132, use either of these commands:
mysqlbinlog --read-from-remote-server --host=host_name --raw binlog.000130 binlog.000131 binlog.000132 mysqlbinlog --read-from-remote-server --host=host_name --raw --to-last-log binlog.000130
The first command specifies every file name explicitly. The second names only the first file and uses
--to-last-logto read through the last. A difference between these commands is that if the server happens to open
binlog.000133before mysqlbinlog reaches the end of
binlog.000132, the first command does not read it, but the second command does.
To make a live backup in which mysqlbinlog starts with
binlog.000130to copy existing log files, then stays connected to copy new events as the server generates them:
mysqlbinlog --read-from-remote-server --host=host_name --raw --stop-never binlog.000130
--stop-never, it is not necessary to specify
--to-last-logto read to the last log file because that option is implied.
Output File Naming
mysqlbinlog produces text output and the
--result-file option, if
given, specifies the name of the single file to which all output
is written. With
mysqlbinlog writes one binary output file for
each log file transferred from the server. By default,
mysqlbinlog writes the files in the current
directory with the same names as the original log files. To
modify the output file names, use the
--result-file option. In
--result-file option value
is treated as a prefix that modifies the output file names.
Suppose that a server currently has binary log files named
binlog.000999 and up. If you use
mysqlbinlog --raw to back up the files, the
produces output file names as shown in the following table. You
can write the files to a specific directory by beginning the
--result-file value with the
directory path. If the
--result-file value consists
only of a directory name, the value must end with the pathname
separator character. Output files are overwritten if they exist.
||Output File Names|
Example: mysqldump + mysqlbinlog for Backup and Restore
The following example describes a simple scenario that shows how
to use mysqldump and
mysqlbinlog together to back up a server's
data and binary log, and how to use the backup to restore the
server if data loss occurs. The example assumes that the server
is running on host
host_name and its
first binary log file is named
binlog.000999. Enter each command on a
Use mysqlbinlog to make a continuous backup of the binary log:
mysqlbinlog --read-from-remote-server --host=host_name --raw --stop-never binlog.000999
Use mysqldump to create a dump file as a
snapshot of the server's data. Use
--routines to back up all
include the current binary log coordinates in the dump file.
mysqldump --host=host_name --all-databases --events --routines --master-data=2> dump_file
Execute the mysqldump command periodically to create newer snapshots as desired.
If data loss occurs (for example, if the server unexpectedly exits), use the most recent dump file to restore the data:
mysql --host=host_name -u root -p < dump_file
Then use the binary log backup to re-execute events that were written after the coordinates listed in the dump file. Suppose that the coordinates in the file look like this:
-- CHANGE MASTER TO MASTER_LOG_FILE='binlog.001002', MASTER_LOG_POS=27284;
If the most recent backed-up log file is named
binlog.001004, re-execute the log events
mysqlbinlog --start-position=27284 binlog.001002 binlog.001003 binlog.001004 | mysql --host=host_name -u root -p
You might find it easier to copy the backup files (dump file and
binary log files) to the server host to make it easier to
perform the restore operation, or if MySQL does not allow remote
mysqlbinlog Backup Restrictions
Binary log backups with mysqlbinlog are subject to these restrictions:
mysqlbinlog does not automatically reconnect to the MySQL server if the connection is lost (for example, if a server restart occurs or there is a network outage).
Prior to MySQL 5.7.19, mysqlbinlog does not get all events as they are committed, even if the server is configured with
sync_binlog=1. This means that some of the most recent events may be missing. To ensure that mysqlbinlog sees the most recent events, flush the binary log on the server that you are backing up.
The delay for a backup is similar to the delay for a replication replica.