Raible Designs

Weather.com: WebSphere to Tomcat and Oracle to MySQL

At my current client we're going to migrate our application from Tomcat to WebSphere 5 in May. I'm dreading the move and really don't see the point, but alas - the client is always right. However, since my client reads this website, I thought maybe they'd be interested to see that Weather.com recently migrated from WebSphere to Tomcat.

"It was hard to run WebSphere and an IDE [integrated development environment] because of all the resources WebSphere took," recalls Jeff Cunningham, who leads the Internet application development team at Weather.com. "You had to run an instance of DB2 on your machine because WebSphere stored its configurations in DB2, so you had to have all that overhead. It was just really slow. I just started using Tomcat for development because it was so much faster."

The article goes on to say that they evaluated other app servers as well, but chose Tomcat because of the team's preference. They also discovered that Tomcat served up pages significantly faster than WebSphere.

Weather.com is also working on swapping out its Oracle database for the open-source MySQL.
...
"Now when I talk to senior management about moving from Oracle to MySQL they don't ask me, 'Are you sure?'" he says. "They ask me, 'When?'"

It's a great time to be an Open Source Consultant. ;-)

Why Hibernate Rocks - easy database switching

The app I've been developing over the last 6 months is going live next week. As part of that process, my client decided they wanted to put the production database on their AS400, rather than their JDE/WebSphere/DB2 Server. Hibernate and AppFuse made this super-easy. Add the JDBC Driver, specify a new dialect/jdbc url/driver name, and voila - we're talking to DB2400! After creating the initial tables using Ant we noticed that the table names were too long since the 400 has a limit of 10 characters. To fix this, I simply modified my XDoclet @hibernate.class table="..." to have shorter table names. After that, I simply had to re-arrange a few tables in my sample-data.xml file (for DBUnit) to avoid referential integrity issues. All-in-all, we migrated from MySQL to DB2 on an AS400 in a little under an hour this morning. Hibernate makes my development life soooo much easier.

What should we do with Tiles?

There's some discussions taking place on the Struts Developer Mailing List about what to do with Tiles. Tiles is gaining popularity in frameworks other than Struts - i.e. Spring and JSF. Personally, I don't mind that Tiles is buried deep inside struts.jar b/c it's basically the difference between a 500 KB JAR and a 100 KB JAR - and disc space is cheap! However, an advantage of extracting Tiles from Struts is that it then has the opportunity to become friendlier to other web frameworks. I'd even like to see a Sitemesh-like Filter so you could do Sitemesh stuff with Tiles. Or maybe just bundle Sitemesh with Tiles as a kick-ass templating engine.

So the question is: What should we do with it? Should it become a Jakarta Commons project or a Jakarta Project? Or even a java.net project? Tiles Users - we need your feedback!

Setting the heap size on your JVM

Cameron has posted a comment on my Performance Tuning MySQL article. The reason I'm highlighting this because it's something I wasn't are of:

From the article:

    -Xms128m -Xmx256m

The Sun JVM will run significantly faster with the following config instead:

    -Xms256m -Xmx256m

That's because the Sun implementation acquires and releases memory from / to the OS way too aggresively if the "ms != mx". Furthermore, either your server has the 256MB available or it doesn't. If you don't have it available, don't set the max that high. If you do have it available, you gain nothing from setting the min lower. This isn't a desktop system, it's a server -- make sure you have the necessary resources and if you do then use them!

Time to change all my heap size setting since I've been using the first setting (128/256) for quite some time. Thanks Cameron! The real question is: will changing "-Xms256m -Xmx512m" to "-Xms512m -Xmx512m" speed up my slow-ass PowerBook? ;-)

[ANN] Hibernate 2.1.3 Released

Download · Release Notes. It's been awhile since the last Hibernate release (approx 2.5 months) - most likely because the last one has been rock solid - at least it has been on my projects. All tests pass in AppFuse.

Goals for the week with XDoclet, Spring and AppFuse

I have a lot that I want to accomplish this week. Hopefully a few late nights will make it possible. I'm posting this list here in case someone has already done some of this.

• XDoclet: duplicate the Struts-specific <validationxml> Ant task for Spring. Make it work with POJOs. This is primarily motivated by the fact that I got the commons validator stuff to work just like it does with Struts.
• XDoclet: create a new <strutsform> task that doesn't depend on ejbdoclet. This will allow me to remove AppFuse's dependency on j2ee.jar.
• Spring: extract the mock objects used in Spring's internal test suite so I can use them to test Spring Controllers (springtestcase? ;-)).
• AppFuse: finish Spring MVC integration and release 1.5 beta.

Phew - it's gonna be a rough week with very little sleep. Fortunately, it'll all be worth it if I can pull it off.

Update: Sometimes things just click: generate validation.xml for Spring and generate ActionForms from POJOs w/o an EJB dependency. I also discovered that <hibernatedoclet> requires that xdoclet.modules.ejb.EjbDocletTask is in the classpath. It doesn't make sense, but the compiler doesn't lie.

Logout your users automatically after their session times out

One of the common issues I see in webapps is a user leaves their computer, their session times out, and when they come back to do something - the app throws errors b/c their session is null. There are several easy ways to fix this. If you use Container Managed Authentication, the user will likely be prompted to do login and can continue as before. If you're using a slick Remember Me feature (like AppFuse has), the user won't even notice. However, you might not have these options available to you. For those circumstances, I recommend you put a meta-refresh in your app to automatically show the uses a timeout message when their session expires. It's as simple as the following:

<meta http-equiv="Refresh" 
  content="${pageContext.session.maxInactiveInterval}; url=timeout.jsp"/>

I used JSP 2.0's EL in this example for simplification. If you're using a JSP 1.2 container - you'll have to wrap that expression with a <c:out> tag.

Full Time vs. Contract

I talked with some folks yesterday about joining their company as a full-time employee. Their opportunity sounds awesome: using open source tools to develop a product. The opportunity certainly appeals to me. In a sense - I could get paid to work on AppFuse. I could get paid to do the stuff I wake up early and go to bed late for. I could spend more time with my family because I'm doing my "moonlighting" stuff during the daytime.

At least that was their sales pitch.

In reality, no company in their right mind is going to pay me to work on all the open source projects I contribute to: AppFuse, Roller, Struts Resume, Struts Menu and DisplayTag. Sure, they might allow me to work on AppFuse and Roller for a few hours a week, but I can guarantee that I'll still want to contribute to the others - and hence, continue to burn the midnight oil. I've also started to think that the main reason for doing stuff "after hours" is because I spend my evenings with Julie and Abbie - whereas I used to work in the evening.

More than anything, the opportunity really got me thinking about doing full-time work vs. contract work. I've been doing contract work for almost 3 years now - and I've only had 2 months of no work in that 3 year period. So that whole contracting is so unstable has been a myth for me. In fact, I see contracting as more stable than an employee position because I control my own destiny for the most part. NOTE: This post is likely a bit biased because my contract just got extended until the end of the year and I'm working on an AppFuse-based application. In other words, I love my job right now.

The thing I enjoy the most about contracting over full-time is freedom. I am planning to take 7 weeks off in the next few months (3 weeks for Spring Live, 4 weeks for the new baby) - and with a full-time gig, that would be impossible. I also like the ability (again, this is probably because my current client is so cool) to take a week off to attend a conference, or take a few days off to run off and do some training. The fact that I'm not tied down to one client/company is awesome. With the full-time opportunity I'm considering, I feel like I'd be marrying a woman I met just a few weeks ago. I guess most full-time gigs are like this after you've been set free with contracting.

One of the main reasons I'm considering this full-time gig is because I don't know where I want to be in 5 years. Most of my career aspirations have been met. When I started in this industry, I wanted to gain enough knowledge about what I do to speak at conferences and such. I did that last week and it was a blast - but I don't really want to do that every month - especially if I have to travel. Traveling away from my family is no fun - and happiness is more important than anything. The nice thing about the full-time gig is that its centered around a product, rather than services. Services (i.e. consulting) are great - but they're only good as long as I'm capable of working. Developing products that earn money while you're on vacation - that's the ideal situation.

The only thing I don't like about my current contract is that I'm a lone wolf. I'm the only guy developing the current app - which is great, but there's no "team spirit." My favorite job ever had awesome team spirit. This opportunity is a startup, which often leads to team spirit - but they also enticed me with ideas of working with a smart bunch of developers. If you've ever worked with smart people, you know that this is a real treat. Learning from your peers just by going into the office is quite a rush. When someone tries to find their answer on Google before asking you - it's refreshing. But is this worth giving up freedom for?

Another important consideration is compensation. Contracting tends to pay 50%-100% more than a full-time position. Of course, this full-time opportunity has options (which supposedly narrows the gap), but we all know that those rarely come to fruition. And if they do - it usually takes a couple of years. I am well aware that a cool job is waaayyy better than a good paying one, but still - getting paid well is nice.

Lastly, to throw a wrench into everything, someone sent me an e-mail last night suggesting they might (someday) be interested in paying me to do full-time AppFuse development. Heh - now that sounds like the ultimate dream job.

How does your MVC framework handle duplicate posts?

One of the problems that you'll often see in webapps is that when a record is added - hitting refresh on the browser will cause a 2nd record to be added. This is because the "Save" action usually does a forward, rather than a redirect, and the full post is re-created. I'm curious to know how other MVC Frameworks handle this issue, particularly Spring, WebWork, Tapestry and JSF. In Struts, it's pretty simple to solve. When the form is first displayed, you'll likely go through an Action. In AppFuse, this would be something like UserAction.edit(). In the edit method, you add a saveToken() call to put a token into the session:

Then in the save() method, you can check for a duplicate post using the isTokenValid() method:

How does your Java MVC framework handle this? Do you have to programmatically handle it like Struts - or is it built-in to the framework to handle it auto-magically?

Performance Tuning J2EE Applications deployed on MySQL

Last week I attended Mark Matthew's "Performance Tuning J2EE Applications deployed on MySQL" at the MySQL Conference (see Anthony's Review). Mark's presentation had a lot of tips and tricks with the MySQL JDBC Driver. I asked him to send me a copy - and he did. Below are a number of tips that you might be able to use in your apps. One thing that Mark forgot to mention (he did later over beers) was that MOST apps (with less than 50 tables) won't need this stuff. You should probably only performance tune your server (or JVM) if you *really* think it's not your app or database. The database, and its indexes, is the first thing to check for slow performance.

• To get JVM Metrics, i.e. Heap/Garbage Collection stats, add the following to your java command:

  -verbose:gc -XX:+PrintGCTimeStamps

• The default JVM heap size is 64MB, which is likely too small for most webapps. You can change the default min/max by adding the following to your JAVA_OPTS (or CATALINA_OPTS) environment variable:

  -Xms128m -Xmx256m

• Young generation sizing - let the JVM do it by specifying:

  -XX:+AggressiveHeap

• Connection Pool Size: 15-20 is more than enough to handle an average application. Never have more connections than threads that can use them. For MySQL, the pool size is resource throttling, not saving connection setup time. Click here for a chart that shows the number of connections used doesn't change between a pool size of 10 and 20.
• Connection/J 3.0 is 40-400% faster than 2.0.14 depending on the situation - use the latest driver!

Finally, here is the really good stuff. Below are a number of parameters you can add to your JDBC URL (like autoReconnect=true) to get information from MySQL's JDBC Driver:

• Logging Slow Queries: logSlowQueries=true and slowQueryThresholdMillis=n (2000 default)
• Reporting Performance Metrics: gatherPerfMetrics=true and reportMetricsIntervalMillis=n (30s default)
• Usage Advisor (abandoned objects, un-used columns in selects, incomplete ResultSet traversal): useUsageAdvisor=true

Reminder: if your app doesn't have performance issues - you probably don't need to modify anything. Mark said he'd put his presentation online soon, so I won't bother doing that. I'll try to link to it when he puts it up.

Update May 25th, 2004: Mark notified me that his slides have been posted.