Tungsten parallel apply on slaves, or parallel replication for short, has been available for about a year.   Until recently we did not have many formal benchmarks of its performance.  Fortunately the excellent Percona Live Conference in London accepted my talk on Tungsten parallel replication (slides available here), so Giuseppe Maxia and I finally allocated a block of time for systematic performance testing.

In a nutshell, the results were quite good. In the best cases Tungsten parallel apply out-performs single-threaded native replication by about 4.5 to 1.  Both Giuseppe and I have verified this using slightly different test methodologies, which …

In the recent few weeks I have spent some time for creating yet another slave prefetching tool named "Replication Booster (for MySQL)", written in C/C++ and using Binlog API. Now I'm happy to say that I have released an initial version at GitHub repository.

The objective of Replication Booster is same as mk-slave-prefetch: avoiding or reducing replication delay under disk i/o bound workloads. This is done by prefetching relay logs events, converting to SELECT, and executing SELECT before SQL Thread executes the events. Then SQL thread can be much faster because target blocks are already cached.

On my benchmarking environment Replication Booster works pretty …

In my previous posts I introduced two new conflict detection functions, NDB$EPOCH and NDB$EPOCH_TRANS without explaining how these functions actually detect conflicts? To simplify the explanation I'll initially consider two circularly replicating MySQL Servers, A and B, rather than two replicating Clusters, but the principles are the same.

Commit ordering

Avoiding conflicts requires that data is only modified on one Server at a time. …

Blackhole tables are often used on a so-called “relay slave” where some operation needs to happen but no data needs to exist. This used to have a bug that prevented AUTO_INCREMENT columns from propagating the right values through replication, but that was fixed. It turns out there’s another bug, though, that has the same effect. This one is caused when there is an INSERT into a Blackhole table, where the source data is SELECT-ed from another Blackhole table.

I think it’s wise to keep it simple. MySQL has tons of cool little features that theoretically suit edge-case uses and make ninja tricks possible, but I really trust the core plain-Jane functionality so much more than these edge-case features. That’s precisely because they often have some edge-case bugs, especially with replication.

Typical MySQL environment involves one Master receiving writes and multiple slaves to scale the reads. The “slave” term has been used in MySQL because the Slave servers have to perform every task in copying from the Master binlog, then updating their relay logs and finally committing to the Slave databases. The Master plays no role in replication here other than storing the replication events in the binlog.
With this kind of Master- Slave set up, there are several limitations-
-       Slave lag -       Stale or old data -       Data loss -       Manual failover which is error-prone and time consuming
In SchoonerSQL, there is no concept of “Slaves” inside synchronous cluster. We refer to it as "Read Masters" because of our synchronous approach and different replication architecture. It is …

The Issue
I haven't blogged in a while an I have a long TODO list of things to publish: The repository for the SNMP Agent, video and slides of my OSCON talk and a quick overview of MHA master-master support. In the meantime, here's a little fact that I didn't know from MySQL CREATE VIEW documentation:

Although it is possible to create a view with a nonexistent DEFINER account, an error occurs when the view is referenced if the SQL SECURITY value is DEFINER but the definer account does not exist.How can this be possible?
The ProblemFor a number of reasons we don't have the same user accounts on the master than we have on the slaves (ie: developers shouldn't be querying the master). Our configuration files include the following line:

replicate-ignore-table=mysql.user

So if …

The MySQL Utilities project continues to evolve with key new features for
replication and export. The latest release, 1.0.3, is no exception.

MySQL Utilities is included in the MySQL Workbench product which can be
downloaded from HTTP://dev.mysql.com/downloads/workbench/5.2.html

If you want the latest developments for MySQL Utilities, you can create a
bazaar branch using the following command:

bzr branch lp:~mysql/mysql-utilities/trunk

New Utility - mysqlrplshow

You can now view a list of the slaves attached to your master with
mysqlrplshow. The utility displays a graph of the master and its slaves y
default but you can also get a list of the slaves in GRID, CSV, TAB, or
VERTICAL format as follows.

• GRID - Displays output formatted like that of the mysql monitor in a grid or table …

In my last post I described the motivation for the new NDB$EPOCH conflict detection function in MySQL Cluster. This function detects when a row has been concurrently updated on two asynchronously replicating MySQL Cluster databases, and takes steps to keep the databases in alignment.

With NDB$EPOCH, conflicts are detected and handled on a row granularity, as opposed to column granularity, as this is the granularity of the epoch metadata used to detect conflicts. Dealing with conflicts on a …

So, it has been a while since I’ve blogged.  As some of you may have read, I have a new job and Stewart and I have been busy planning all kinds of testing goodness for Percona >: ) (I’ve also been recovering from trying to keep up with Stewart!)

Rest assured, gentle readers, that I have not forgotten everyone’s favorite modular, community-driven database ; )  Not by a long-shot.  I have some major improvements to dbqp getting ready for a merge (think randgen in-tree / additional testing modes / multiple basedirs of multiple types).  Additionally, I’ve been …