Thinking Outloud

Interesting hibernate transaction issue

The Bull — Thu, 22 Oct 2009 19:52:41 +0000

I’m working on a new Grails based project and came across a transaction issue. The application is an ecommerce app and as such the placing of the order has a lot going on that should all reside in a transaction.

Being a Grails app I decided to put the processing inside a transactional service method. So far so good. The flow looks something like this:

Create billing address
Create credit card
Assign billing address to card
Create shipping address
Loop through the cart items and for each item find stock(inventory) to fulfill each
Mark the stock as sold as applied
Add each order item to the order
Assign order to customer
Save order and customer

That is a little oversimplified, but you get the idea. So, what was the problem?

The problem came in during the select for the stock. This select would cause a hibernate exception about the address being a transient object. Well that made no sense at all.

At first I started down the road of abandoning the whole transaction thing and doing it manually. Naturally that was ugly and very error prone, so I did some research to find out what the cause might be. Came up empty.

My gut said that a select should not cause a problem with unsaved data. Then I thought that maybe hibernate was enforcing some sort of isolation level mechanism. Most of us never bother with database isolation levels (and fewer even know what they are sadly enough), but perhaps that was causing it. So what I did was move all the save() calls from the end to where they were being used.

In other words I called save on the two addresses and the credit card before the loops on getting and assigning stock.

Worked like a charm. I now have the whole thing in a transaction as it should be.

My new app minus the RDBMS

The Bull — Wed, 16 Sep 2009 02:20:21 +0000

I’ve been intrigued for some time about building an application on using a datastore that wasn’t a relational database. This “movement” as it were is being called “noSQL”.

My application is a search engine service. As such I don’t need much actual data that is stored in a database and I decided to forgo using trusty old MySQL for this job and try something different.

SimpleDB

So I decided to go with Amazon’s SimpleDB for this project. It has come a long way since I first looked at it and has all the query capabilities that I need.

If you aren’t familiar with SimpleDB, it is a schema-less setup where domains act as tables. The schema-less design means that the schema can accommodate new columns as needed. While not really necessary for my particular application, it is a feature.

What do I gain with SimpleDB? As traffic increases, I can spool up more servers (can you say Amazon’s EC2?) and since they communicate with SimpleDB, I don’t have to worry about a load on a central RDBMS.

The App

The app itself is built on Grails. For those familiar with Grails, it uses Hibernate under the covers as part of GORM. Well, I’m not using that obviously for this project. However since my query requirements are pretty minimal, that is not an issue. I only have a few domain objects and in most cases I get them by id.

Behind the grails app is Solr, the web app front end to Lucence indexing engine.

Initial development is about done and will be alpha tested behind an existing site that receives ~100k pageviews a month. I’ll give that a month or so and expand into beta testing.

New gun bag for my AK

The Bull — Fri, 17 Jul 2009 14:59:11 +0000

I finally got a gun bag for my AK. Got it from Desert Tactical and it is a 36″ bag with plenty of pockets and storage.

Here are some pics:

Still waiting for the new tapco magazines to come in as well as the lula loader.

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Sarah Palin’s new assault rifle

The Bull — Mon, 04 May 2009 18:17:33 +0000

I wrote about it here, but the NRA is giving the governor a beautiful custom built .50 AR-15 style assault rifle in honor of her defense of the second amendment. Whether you like guns or not, the workmanship on this one is pretty spectacular.

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Shooting an AR15

The Bull — Mon, 04 May 2009 18:14:48 +0000

This weekend I had a good time shooting my friend’s AR15 out the Nevada desert. All told we put 470 round through it over the course of a couple hours. The video below wasn’t my best shooting, but both us did manage to hit the pins every time it was our turn to shoot.

Not too shabby considering I was standing, unsupported shooting through iron sights with a slight wind.

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More Americans think global warming is natural

The Bull — Sat, 18 Apr 2009 20:07:19 +0000

Despite the best efforts of Al Gore and his legion of leftist alarmists, most Americans believe that global warming is a natural thing.

According to Rasmussen reports, only one out of three voters believe global warming is caused by human activity.

The rest of the story is here.

My new XD 45

The Bull — Sat, 18 Apr 2009 18:21:54 +0000

A few weekends ago I wrote about going shooting with a friend and his new Springfield XD 45. It had been a long time since I had shot a gun and I enjoyed it thoroughly.

Well, I had so much fun that my wife and I went shooting. She brought her .22 Magnum revolver that she got from her brother and we also rented a Glock 17 (9mm). We had a good time and I was hooked. I wanted my own handgun.

I did some research and it seemed like the XD was the hot thing out there now. I enjoyed the Glock, but I liked the XD just a bit more. It also came with more for the money, and I told my wife I wanted one.

So she ended up getting me one for my birthday, along with a UpLULA speed loader, a couple of extra magazines and cleaning kit. It wasn’t easy finding one as they sell out pretty quickly, but find one we did.

XD 45 with UpLULA loaders and cleaning kit

First 100 Rounds

Today I got to shoot it for the first time and I put two boxes of round through it. I am very pleased to say the least. The picture below shows about 4 mags worth of rounds. With the exception of a few stragglers most are in pretty a good group. If my math is correct, I put 73% in a 5″ grouping. All of these were at 10 yards.

First 100 rounds with XD 45

For a little fun I put a couple mags into some head shots. Only one miss. Again at 10 yards.

2 mags into the heads

I then hooked up a smaller target, put it at ten yards and shot about a mag and half (the rest of my .45 rounds). I was a bit off on that one and wasn’t too pleased. Maybe it was a little fatigue, who knows. I also shot my wife’s .22 for a little variety. It is quite accurate and I managed a couple of 2″ groups with it at 7 yards.

All around, I am very happy with the gun and my shooting. I plan on going at least twice a month and working on those groupings.

Upgrading to Grails 1.1

The Bull — Fri, 10 Apr 2009 15:00:27 +0000

I spent about a day’s worth of work upgrading PatriotRoom.com from Grails 1.0.4 to Grails 1.1.

There were two areas that I had trouble with. The first was the plugins and was the easiest to overcome. I just had to reinstall them. The second however was logging which was completely revamped in Grails 1.1.

Personally I always had mixed results with logging settings in different environments. Turns out this site was the worst. However I like the new approach although it took the longest to get right. Some of it is because the documentation is a bit light in the area, especially with regards to custom appenders. I use two appenders, a daily rolling appender and an email appender for errors.

My file appender now looks like this:

appenders {
  console name:'stdout', layout:pattern(conversionPattern: '%d{ISO8601} [%p] -%X{user} %X{ip} # %X{sessionid} - %c{2} - %m%n')

appender new org.apache.log4j.DailyRollingFileAppender(name:'rollingfile', datePattern:"'.'yyyy-MM-dd",layout:pattern(conversionPattern: '%d{ISO8601} [%p] -%X{user} %X{ip} # %X{sessionid} - %c{2} - %m%n'), file:'../logs/patriotroom.log');
}

I still haven’t gotten the email appender working yet though.

Besides that, I also had to turn off the nice warning about the createLinkTo tag being deprecated. Guess I should fix those

The best part of the upgrade though is the –nojars build option. This is a real timesaver. My war file went from 25mb down to 6mb, which means my upload times went from just over 2 minutes down to 18 seconds. Now that is nice!

Will Google App Engine Revolutionize Java Development?

The Bull — Fri, 10 Apr 2009 01:16:31 +0000

There is a lot of buzz in the Java community concerning the announcement over the availability of Java on the Google App Engine. It is a big boon for Java developers for sure, but there are some drawbacks for serious applications.

Logging

Seems you are stuck with using the JDK logging. Let’s face it, no developer in his right mind chooses that over Log4j. There just isn’t enough functionality there to make it worthwhile (reporting anyone?).

Persistence

You are limited to JDO. This can be both good and bad. JDO and related technologies, are fine for many applications, but there are times when you just need more power than object queries allow. The upside is that you probably don’t have to worry about data scaling needs.

Threading

You can’t create your own threads, nor presumably can anything else. This may be a big hindrance for many applications. For example I use the Quartz library all the time for various scheduling needs (especially in Grails).

There are a few other things you can and can’t do, but the ones above require some serious consideration before choosing to deploy on the app engine. On some brighter news, it looks like the Grails group is working on making Grails compatible with GAE. That alone will probably be the biggest use on GAE, and that isn’t a bad thing at all.

Java is safe. For now…

The Bull — Mon, 06 Apr 2009 14:45:07 +0000

IBM has pulled its offer to buy Sun according the NYT:

I.B.M. withdrew its $7 billion bid for Sun Microsystems on Sunday, one day after Sun’s board balked at a reduced offer, according to three people close to the talks.

The article goes on to say that other possible suitors could be HP and Cisco. I think with HP it would be similar to IBM in that HP would buy and dissolve the company with the possible exception of Java. As for Cisco, which is just entering the server business it would be a definite expansion of products all around.

Granted, Java has never really been a money maker for Sun but for IBM Sun’s Java software is a big competitor all the way from JVM to JEE servers. The other two companies don’t have a Java stack at all and would most likely leave the Java side alone, keeping out of Big Blue’s death.

Although IBM has pulled out, there is nothing from them getting back into it, and if Sun’s upcoming earnings report looks bad IBM may be the only one willing to buy them. Let’s hope for the best.