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Download Maatkit

Maatkit contains essential command-line utilities for MySQL, such as a table checksum tool and query profiler. It provides missing features such as checking slaves for data consistency, with emphasis on quality and scriptability.

This release contains major bug fixes and new features. Some of the changes are not backwards-compatible. It also contains new tools to help you discover replication slaves and move them around the replication hierarchy.

Changelog for mk-archiver:

2008-03-16: version 1.0.8

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).
   * Changed short form of --analyze to -Z to avoid conflict with --charset.

Changelog for mk-deadlock-logger:

2008-03-16: version 1.0.9

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added 'A' part to DSNs (bug #1877548).

Changelog for mk-duplicate-key-checker:

2008-03-16: version 1.1.5

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-find:

2008-03-16: version 0.9.10

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-heartbeat:

2008-03-16: version 1.0.8

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-parallel-dump:

2008-03-16: version 1.0.7

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).
   * A global database connection was re-used by children, causing a hang.

Changelog for mk-parallel-restore:

2008-03-16: version 1.0.6

   * Added --setvars option (bug #1904689, bug #1911371).
   * Changed --charset to be compatible with other tools (bug #1877548).

Changelog for mk-query-profiler:

2008-03-16: version 1.1.9

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-show-grants:

2008-03-16: version 1.0.9

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-slave-delay:

2008-03-16: version 1.0.6

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added 'A' part to DSNs (bug #1877548).

Changelog for mk-slave-find:

2008-03-16: version 1.0.0

   * Initial release.

Changelog for mk-slave-move:

2008-03-16: version 0.9.0

   * Initial release.

Changelog for mk-slave-prefetch:

2008-03-16: version 1.0.1

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Changelog for mk-slave-restart:

2008-03-16: version 1.0.6

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).
   * Added logic to repair tables, and rewrote a lot of code.
   * Added --always option, disabled by default.  Not backwards compatible.
   * --daemonize did not work.
   * --quiet caused an undefined variable error.

Changelog for mk-table-checksum:

2008-03-16: version 1.1.26

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added 'A' part to DSNs (bug #1877548).
   * Added --unique option to mk-checksum-filter.
   * The exit status from mk-checksum-filter was always 0.
   * mk-table-checksum now prefers to discover slaves via SHOW PROCESSLIST.

Changelog for mk-table-sync:

2008-03-16: version 1.0.6

   * --chunksize was not being converted to rowcount (bug #1902341).
   * Added --setvars option (bug #1904689, bug #1911371).
   * Deprecated the --utf8 option in favor of the A part in DSNs.
   * Mixed-case identifiers caused case-sensitivity issues (bug #1910276).
   * Prefer SHOW PROCESSLIST when looking for slaves of a server.

Changelog for mk-visual-explain:

2008-03-16: version 1.0.7

   * Added --setvars option (bug #1904689, bug #1911371).
   * Added --charset option (bug #1877548).

Suppose you have a master-master replication setup, and you know one of the tables has the wrong data. How do you re-sync it with the other server?

Warning: don’t just use any tool for this job! You may destroy your good copy of the data.

If your table is large, you’ll probably want to use a tool that can smartly find the differences in a very large dataset, and fix only the rows that need to be fixed. There are several tools that are either able to do this, or claim to be able to do this. However, most of them are not replication-aware, and are likely to either break replication or destroy data.

To see why this is, let’s look at a typical scenario. You have server1 and server2 set up as co-masters. On server1, your copy of sakila.film has correct data. On server2, somehow you are missing a row in that table. A hypothetical sync tool will compare the two copies of the data and find the missing row, then insert it on server2. This INSERT statement will flow through replication to server1, where it will cause a duplicate key error and stop replication.

You can probably think of many other scenarios with lots of bad side effects, so I won’t list any more. I’ll leave it at this: when you are synchronizing data on a slave (even if it is also a master), you must not change data on the slave. Changing data on the slave can cause so much trouble in so many different ways! The correct way to do this is to make the changes on the master, and let them flow through replication to the slave.

As far as I know, there is only one tool that is capable of doing this. It is mk-table-sync, which is part of Maatkit. However, even this tool will let you point the gun at your foot and pull the trigger, if you don’t use it correctly.

The correct way to sync a master-master setup with mk-table-sync is with the --synctomaster option, which tells it to make changes on the master:

mk-table-sync --synctomaster h=server2,D=sakila,t=film

Notice that I’m connecting to the slave, but instructing it to make changes on the master. (Yes, it is able to find the master by inspecting the slave).

If you do the following, you’ll probably cause problems:

mk-table-sync h=server1,D=sakila,t=film h=server2

I’ve just updated the documentation to point out the subtleties with master-master replication. However, you should always keep in mind: it’s not just master-master replication. Any replication configuration is best synchronized by making the changes on the master, and you should always avoid changing data on a slave — even to “fix” the slave. I might also add a feature to mk-table-sync to warn you when it detects that you are trying to change data on a slave.

Download Maatkit

This release contains minor bug fixes and new features. Besides the little bug fixes, there’s a fun new feature in mk-heartbeat: it can auto-discover slaves recursively, and show the replication delay on all of them, to wit:

baron@keywest ~ $ mk-heartbeat --check --host master -D rkdb --recurse 10
master 0
slave1 1
slave2 1
slave3 4

(Not actual results. Your mileage may vary. Closed course, professional driver. Do not attempt).

Nothing else in this release is very exciting. I just wanted to get the bug fixes out there.

Changelog for mk-heartbeat:

2008-02-10: version 1.0.7

   * Added --recurse option to check slaves to any depth.
   * Made mk-heartbeat explicitly close DB connection when done.

Changelog for mk-parallel-dump:

2008-02-10: version 1.0.6

   * Added the --losslessfp option.
   * Fixed child process exit status on Solaris (bug #1886444).

Changelog for mk-parallel-restore:

2008-02-10: version 1.0.5

   * Fixed forking issues with File::Find on Solaris (bug #1887102).
   * Fixed child process exit status on Solaris (bug #1886444).
   * The --defaults-file option caused a mysql error (bug #1886866).

Changelog for mk-show-grants:

2008-02-10: version 1.0.8

   * Added --timestamp option.

Changelog for mk-table-checksum:

2008-02-10: version 1.1.25

   * The --lock option did not work correctly (bug #1884712).

Changelog for mk-table-sync:

2008-02-10: version 1.0.5

   * The Stream algorithm wasn't chosen when a table had no key.
   * Numeric strings beginning with 0 weren't quoted (bug #1883019).