Skip to main content

Static Variables: Grave Danger

I lost the whole last week on a very small issue. Issue of a kind that would be considered very silly if looked at later. Static variables for holding a Transactional object. This is probably a very naaive concept in Java (or any other language with statics). But mistakes are mistakes. We learn from them everyday. This time, I leart from some one else's. Not the static concept itself, but the sleepless nights it may drive you into for no reason.

The issue started last monday. We were seeing transactional attributes of an object replicated in other objects in the database. An application that stood well in multiple regression tests, load tests, stress tests, failed dramatically in production. To add to confusion, this was happenning exactly at a time where we had a batch job running, a lot of users logging in (of the order 50 logins/ sec), and most of these first time users.

To narrow down our variables, we stopped the batch job. that was in our control. Still There logins, a lot of them. We dint know what the users action was and what was causing it..

(To be continued..)

Popular posts from this blog

One page Stock

Alright.. That was a long absence. The whole last week I dint blog. I dint go away. I was "occupied". I was learning stock trading. Its very fascinating. I have a good weeeked blog for you all. Here is my experience. I can literally hyper-link every word from the following paragraphs, but I am writing it as simple as I can so you can look up the italicised words in wikipedia . I got a paper trading account from a brokerage firm . You need one brokerage account first. Then it can be an Equity account where all your money is yours or a Margin account , where some of the money is lent by the brokerage firm. Then I get Buying power , which is the dollor value of how much stocks you can buy. I can make profit by simple rules. Buy when Price is low. Sell when price is high. There is another more intersting way of earning money. Selling short . Thats when price is not high, per say, but when are confident that the price WILL go down. then buy back when its lowest. This is what

Appcache manifest file issues/caveats

Application cache (appcache) is a powerful feature in HTML5. However, it does come with baggage. Many (see links below) advocated ferociously against it due to tricky issues it comes with. For someone who is just testing waters, these issues may throw them off grid. Knowing them before hand helps reduce some unpredictable effects.

classpath*: making your Modular Spring Resources

Spring gives multiple options to load XML resources for building contexts. the reference documentation does explain this feature quite well. However, I am taking my shot at explaining the different practical scenarios ( by order of growing modularisation) For Example, A simplest Spring based web Context Loader can be configured with resources like this <context-param> <param-name>contextConfigLocation</param-name> <param-value>applicationContext.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> You just need to put applicationContext.xml in WEB-INF/ folder of your webapp. However, Typically an application is n-tiered. You can also have multiple files setup and in relative paths. like <param-value> context-files/applicationContext.xml context-files/dao.xml context-files/service.xml </param-value>