4.6.7.3 Using mysqlbinlog to Back Up Binary Log Files

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 --read-from-remote-server 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 --result-file=file_name option if that option is given.

• mysqlbinlog Backup Capabilities

• mysqlbinlog Backup Options

• Static and Live Backups

• Output File Naming

• Example: mysqldump + mysqlbinlog for Backup and Restore

• mysqlbinlog Backup Restrictions

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:

• The --read-from-remote-server (or -R) option tells mysqlbinlog to connect to a server and request its binary log. (This is similar to a replica server connecting to its replication source server.)

• The --raw option tells mysqlbinlog to write raw (binary) output, not text output.

Along with --read-from-remote-server, 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 --user and --password.

Several other options are useful in conjunction with --raw:

• --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=id: The server ID that mysqlbinlog reports to the server when --stop-never is 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 4.6.7.4, “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 SHOW 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.000130 through 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-log to read through the last. A difference between these commands is that if the server happens to open binlog.000133 before 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.000130 to 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

  With --stop-never, it is not necessary to specify --to-last-log to read to the last log file because that option is implied.

Output File Naming

Without --raw, 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 --raw, 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 conjunction with --raw, the --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 --result-file option 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.

--result-file Option	Output File Names
--result-file=x	xbinlog.000999 and up
--result-file=/tmp/	/tmp/binlog.000999 and up
--result-file=/tmp/x	/tmp/xbinlog.000999 and up

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 single line.

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 --all-databases, --events, and --routines to back up all data, and --master-data=2 to 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 like this:

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 root access.

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 replica server.