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In two previous posts (first here and second here) I reported about Java 5 VM crashes on Linux machines.

Digging deeper into the problem with external support led to some new evidence. Apparently the problem is in some way related to regular garbage collects initiated by the so called "GC Daemon" thread. It gets spawned when you use some fashion or other of RMI and calls full GCs in order to get rid of unreachable remote objects.

One can specify the interval (in milliseconds) between calls to the garbage collector using -Dsun.rmi.dgc.server|client.gcInterval. With our application using RMI to call remote services we reduced this value to as little as 6 seconds. As we expected this let us reproduce the problem we have much more …

In two previous posts (first here and second here) I reported about Java 5 VM crashes on Linux machines.

Digging deeper into the problem with external support led to some new evidence. Apparently the problem is in some way related to regular garbage collects initiated by the so called "GC Daemon" thread. It gets spawned when you use some fashion or other of RMI and calls full GCs in order to get rid of unreachable remote objects.

One can specify the interval (in milliseconds) between calls to the garbage collector using -Dsun.rmi.dgc.server|client.gcInterval. With our application using RMI to call remote services we reduced this value to as little as 6 seconds. As we expected this let us reproduce the problem we have much more …

We are currently evaluating the consequences of migrating our application from Java 1.4 to Java 5. While initial tests revealed only simple issues (like variables called enum etc.) we are now seeing a much more severe problem: Random VM crashes.

Currently we only see this on Linux (Kernel 2.4) only, however even there we cannot reliably reproduce the problem. On a single machine we have seen two crashes in a week. Notably the application was not being used, it was just started and waiting for user input. Some background threads are running in this situation, however they do not do any work, either. They just poll some database tables for external changes, but there were none.

All of a sudden a VM would crash, leaving a hs_err_pid1234.txt behind. This is what they look like (shortened):

#
# An unexpected error has been detected by HotSpot Virtual Machine:
#
#  SIGSEGV (0xb) at pc=0x402989b9, …

We are currently evaluating the consequences of migrating our application from Java 1.4 to Java 5. While initial tests revealed only simple issues (like variables called enum etc.) we are now seeing a much more severe problem: Random VM crashes.

Currently we only see this on Linux (Kernel 2.4) only, however even there we cannot reliably reproduce the problem. On a single machine we have seen two crashes in a week. Notably the application was not being used, it was just started and waiting for user input. Some background threads are running in this situation, however they do not do any work, either. They just poll some database tables for external changes, but there were none.

All of a sudden a VM would crash, leaving a hs_err_pid1234.txt behind. This is what they look like (shortened):

#
# An unexpected error has been detected by HotSpot Virtual Machine:
#
#  SIGSEGV (0xb) at pc=0x402989b9, …

I got asked (being a Java developer) about what was involved in creating an Eclipse Plugin for Mercurial. Well in true Google style, why invent when somebody probably already has. A quick check finds Mercurial Eclipse by VecTrace.

Now until last week, I’d never heard of Mercurial, so this is really an introduction to somebody that has no idea.

What is Mercurial?

Mercurial is a fast, lightweight Source Control Management system designed for efficient handling of very large distributed projects.

Ok, so big deal, I use CVS. I also use Subversion (SVN) for my Apache contributions, and also for MySQL GUI products. Why do we need another Version Control Product? Mercurial is a Distributed Software Configuration Management Tool. …

Last week I was notified that my article about how to install and configure MySQL and the MySQL Connector/J was published in the Java Starter Magazine, a special edition of the german Java Magazin. It covers the basic installation of MySQL and Connector/J on Windows and Linux and how to write a small example program to connect to to MySQL with Java using the Eclipse framework. They were kind enough to send me a number of copies that I plan to give away at tonight's Hamburg MySQL User Group Meeting.

I’ve yet to find any Java project that doesn’t have dependancies on some other Open Source external libraries. I’ve yet to find a Java project that manages these external dependencies appropiately for support and integration at an enterprise level.

As with most projects, understanding an applying sound principles that scale will help you at a later date, and generally the cost of implementation is minimual at the start, but of course becomes more expensive when it’s really needed. The classic case is Version Control. For over 10 years, even on small single developer projects, I’ve used Version Control, it should be taught at university as an introduction to good programming design, it would greatly benefit software development and maintenance.

Back onto the topic of hand. Let’s use a moderate Java Web Based application, and for the purposes of this discussion the following Open Source external libraries are incoporated. …

C.J. Blathers about recent major changes in his life.

https://colliertech.com/~cjcollier/confidential/sateOfTheCJ20060625.ogg
https://colliertech.com/~cjcollier/confidential/sateOfTheCJ20060625.mp3

Mail me for credentials.

Today, will go down in my professional history as quite possibly the lowest I would ever think of a software developer. I’ve carefully avoided the term “fellow coder”, speaking of a IT industry sticking by fellow IT people, but not today.

I presently support an existing production system, some 1000+ users that’s been in place around 3 years in which I’ve had no prior involvement until recently. Integration with other external parties within the system have provided an esclation in errors being reported in this external communication, and lack of adequate feedback to the user is another topic. Email is the means of reporting administratively of user errors, again another topic of issue. Within these emails, which are almost impossible to manage due to the limited internal GUI only toolset and lack of access to actual email account files to automate scripting (yet another topic? Do you see a trend here), is some relevent information …