Probably …

I’ve been following the development of Tungsten Replicator for quiet some time now, and recently was fortunate enough to find the time to take a look at the product in more detail. If you haven’t heard of Tungsten Replicator yet, it’s an open source database replication engine that can be used to complement or completely [...]

MySQL Replication is a powerful tool and it’s hard to find a production system not using it. On the other hand debugging replication issues can be very hard and time consuming. Especially if your replication setup is not straightforward and you are using filtering of some kind.

Recently we got an alert from our monitoring system that replication stopped on production slave with the following error:

Can't find record in 'some_table', Error_code: 1032;
handler error HA_ERR_KEY_NOT_FOUND;
the event's master log binlog.000011, end_log_pos 735766642

This means that a ROW-based replication event was going to be applied on slave, but could not find the row it was supposed to be applied to. This is something I like about ROW format — it allows you to catch such data synchronization issues right away. In this particular case MIXED format was used, but if this event was written in STATEMENT format, slave would just apply it …

Earlier this month I published an article on this blog describing the system of record approach to multi-master replication.  As mentioned in that article my colleagues and I at Continuent have been working on improving Tungsten to make system of record design patterns easier to implement.  This article describes how to set up system of record using Tungsten Replicator shard filters, which are a new feature in Tungsten 2.0.4.  By doing so we will create a multi-master configuration that avoids replication loops and transaction conflicts.  On top of that, it is quite easy to set up.

There are many possible system of record patterns depending on how many schemas are shared and across how many masters.  The following diagram …

My recent post on setting up Tungsten parallel replication in a hurry got a lot of hits, though to be fair it was probably not the great writing but the fact that at least one popular MySQL blog posted a link to it.  (Thanks, we like you guys too.)  Anyway, I would like to invite anybody who is interested in parallel replication to attend a webinar on Thursday September 1st at 10am PDT to cover installing and using Tungsten.  It's straight-up technical talk to help you start quickly. 
Bringing up Tungsten on an existing MySQL slave only takes a few minutes, so once we have that out of the way I will explain how Tungsten works inside and show you some …

Multi-master database systems that span sites are an increasingly common requirement in business applications.  Yet the way such applications work in practice is not quite what you would think from accounts of NoSQL systems like Cassandra or SQL-based systems like Oracle RAC.  In this article I would like to introduce a versatile design pattern for multi-master SQL applications in which individual schemas are updated in a single location only but may have many copies elsewhere both locally as well as on other sites.  This pattern is known as a system of record architecture.  You can build it with off-the-shelf MySQL and master/slave replication.

Let's …

Why This Post
While testing Yoshinori Matsunobo's MHA agent I found that although the wiki has a very complete documentation, it was missing a some details. This article intends to close that gap and bring up some issues to keep in mind when you do your own installation. At the end of the article I added a Conclusions section, if you're not interested in the implementation details, but to read my take on the project, feel free to jump straight to the end from here.

My Test Case
Most of our production environments can be simplified to match the MHA's agent most simple use case: 1 master w/ 2 or more slaves and at least one more slave in an additional tier:

Master A --> …

A previous article on this blog described Tungsten parallel replication using on-disk queues.  On-disk queues are now more or less finished, and I just closed the covering issue for the feature.  The work is bug fixing and performance testing from here on out.  Speaking of performance, that looks fairly good.   A recent on-site test using production workloads showed 3.3X improvement over native MySQL replication while holding resources like memory down to much more reasonable levels than in-memory queues.  We have further optimizations on the way, so this should improve.

Now that parallel replication is working a lot better, what is it good for?  Here is a good start:  assuming your …

If you love a software product, you should try to improve it, and not be afraid of criticizing it. This principle has guided me with MySQL (where I have submitted many usability bugs, and discussed interface with developers for years), and it proves true for Tungsten Replicator as well. When I started working at Continuent, while I was impressed by the technology, I found the installation procedure and the product logs quite discouraging. I would almost say disturbing. Fortunately, my colleagues have agreed on my usability focus, and we can enjoy some tangible improvements. I have already mentioned the new installation procedure, which requires just one command to install a full master/slave cluster. I would like to show how you can use the new installer to deploy a multiple source …

About a month ago I needed to compare tens of thousands of tables in hundreds of databases between a few different servers. The obvious choice was, mk-table-checksum! The only problem was, that the tool needs to know the minimum and maximum value of the column by which each table is to be subdivided into chunks and checksummed. This select min(col), max(col) from table locks all write operations on the table and on a big table it meant downtime.

Looking at the source it was clear we could make mk-table-checksum run the select min(col), max(col) from table on the read-only slave and use the values to checksum the master.

It was subtle code changes in function:
get_range_statistics adding

my $cxn_string_dc = “DBI:mysql:;host=slavehost;port=3306;mysql_read_default_group=client”;
my $user = ‘user’;
my $pass = ‘password’;
my $dbh_slave = DBI->connect($cxn_string_dc, $user, $pass); …