Connector/J provides a useful load-balancing implementation for Cluster or multi-master deployments.  As of Connector/J 5.1.12, this same implementation is used under the hood for balancing load between read-only slaves with ReplicationDriver.  When trying to balance workload between multiple servers, though, the driver has to decide when it’s safe to swap servers – doing so in the middle of a transaction would not make applications very happy.  Many of the same principles which apply to autoReconnect also apply here – you don’t want to lose important state information.

As a result, Connector/J will only try to pick a new server when one of the following happen:

1. At transaction boundaries (transactions are explicitly committed or rolled back)
2. A communication …

Chances are, if you write Java applications using MySQL’s Connector/J driver, you’ve run across the autoReconnect property.  I remember that when I first found it, it seemed I had found the grail itself.  “No more nasty connection closed error messages,” I thought.  Except … it doesn’t really work that way, does it?  I’ve seen this question asked many times in many different contexts:  “Why doesn’t Connector/J just reconnect to MySQL and re-issue my statement, instead of throwing this Exception?”

There are actually a number of reasons, starting with loss of transactional integrity.  The …

Several things to think about in the next 10 days leading up to Kaleidoscope.

1. The Marriott Wardman Park is out of rooms. If you’re attending and haven’t reserved a room yet, you may get lucky with a cancellation, but there are several hotels on the Metro line that should have openings. The conference and location is very popular, and while I wish we could accommodate everyone, it’s not going to be possible. Here’s a good suggestion: when next year’s conference dates and location are announced, register and reserve your room as soon as possible (hint – these announcements will be made at our general session on Monday, June 28 starting at 8:30 AM).

2. The Java Bus is coming! Monday afternoon/evening, June 28, the Java “Code to …

Prologue: Long back there were golden days of post graduation in the “great” DDIT (Now Dharamsinh Desai University), Nadiad. Assignments, termwork and journals or everything similar was in demand – I attempted a java code as my termwork on Monday, October 03, 2005. [That’s created date of .java file, I don’t remember anything.] A “variable […]

We’ve long wondered what might happen to all of that open source software from Sun Microsystems now that it’s at Oracle? Obviously, some pieces continue to live at Oracle (Java, Solaris, MySQL), but there are a number of open source projects that Oracle has either neglected to talk about or have been overlooked, particularly as we focused on user reactions, implications and finally approval of Oracle’s acquisition of Sun.

One significant group of open source technologies from Sun is its OpenSSO single sign-on identity and access …

I’ve released version 1.1.7 of the Better Cacti Templates project. This release includes a bunch of bug fixes, some new graphs for MySQL, and two new sets of graphs, for Redis graphing and for JMX graphing.

There are upgrade instructions on the project wiki for this and all releases. There is also a comprehensive tutorial on how to create your own graphs and templates with this project. Use the project issue tracker to view and report issues, and use the project mailing list to discuss the …

Topics for this podcast:

*The latest in VC funding for open source
*VMware’s SpringSource buys cloud messenger Rabbit
*Open source monitoring vendors’ key cloud partnershps
*Oracle moves ahead, back on MySQL, OpenSolaris

iTunes or direct download (25:38, 7MB)

Fig. 1 Java access to MySQL Cluster

This is a follow up to the earlier post Using ClusterJ (part of MySQL Cluster Connector for Java) – a tutorial but covers the ClusterJPA interface rather than ClusterJ.

JPA is the Java standard for persistence and different vendors can implement their own implementation of this API and they can (and do) add proprietary extensions. Three of the most common implementations are OpenJPA, Hibernate and Toplink. JPA can be used within server containers or outside of them (i.e. with either J2EE or J2SE).

Typically a JPA implementation would access the database (for example, MySQL Cluster) using JDBC. JDBC gives a great deal of flexibility to the …