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Showing posts with the label java 5

This Blog Has Moved!

Right, so yes, five years ago I moved to github pages, and never bothered to redirect any of these pages there. Now I've moved on from there, and... Finally I am using my real domain, trishagee.com . My blog is now at trishagee.com/blog .  See you there!
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AOP Caching

Today I would like to document my experiences implementing caching with Aspect Oriented Programming (AOP) and annotations.  Background context   Caching may need to be implemented in your application for a number of reasons. OK, actually usually only one: performance. I would like to add my own tuppence-worth to this though - if you can get away without caching (specifically in application that provide the ability to view and change data) then do so, unless you are using a cache implementation that will handle as much of the pain as possible for you. Implementing a home-grown cache from scratch is almost never the correct thing to do in my experience, you spend lots of time debugging and tweaking the cache when you should be working on your day-job, not re-inventing something that someone, somewhere, has already done a perfectly good job of .  The example I'm about to show you is for a web application created to let users read and edit values from a database (not an unusu...
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Java Specifics

When I first started playing with Java 1.5, I thought generics were the best thing since sliced bread. No more untidy casting, lovely type-safe Collections, and when combined with the new for loop , a lot of the tedious tasks associated with Collections became easier and, most importantly, aesthetically pleasing. Consider the old code: List list = new ArrayList(); list.add(new Integer(1)); Integer integer = (Integer)list.get(0); for (Iterator i = list.iterator(); i.hasNext(); ) { Integer number = (Integer)i.next(); number.intValue(); } And the new: List<Integer> list = new ArrayList<Integer>(); list.add(new Integer(2)); Integer integer = list.get(0); for (Integer number : list) { number.intValue(); } See? Much prettier. OK so it's a silly little example but when you apply it to all the places you use things like Collections it does make life a lot easier, especially when you consider that now you *k...
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Popular posts from this blog

Dissecting the Disruptor: Writing to the ring buffer

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This is the missing piece in the end-to-end view of the Disruptor.  Brace yourselves, it's quite long.  But I decided to keep it in a single blog so you could have the context in one place. The important areas are: not wrapping the ring; informing the consumers; batching for producers; and how multiple producers work. ProducerBarriers The Disruptor code has interfaces and helper classes for the Consumer s, but there's no interface for your producer, the thing that writes to the ring buffer.  That's because nothing else needs to access your producer, only you need to know about it.  However, like the consuming side, a ProducerBarrier is created by the ring buffer and your producer will use this to write to it. Writing to the ring buffer involves a two-phase commit.  First, your producer has to claim the next slot on the buffer.  Then, when the producer has finished writing to the slot, it will call commit on the ProducerBarrier . So let's look at...
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Dissecting the Disruptor: What's so special about a ring buffer?

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Recently we open sourced the LMAX Disruptor , the key to what makes our exchange so fast.  Why did we open source it?  Well, we've realised that conventional wisdom around high performance programming is... a bit wrong. We've come up with a better, faster way to share data between threads, and it would be selfish not to share it with the world.  Plus it makes us look dead clever. On the site you can download a technical article explaining what the Disruptor is and why it's so clever and fast.  I even get a writing credit on it, which is gratifying when all I really did is insert commas and re-phrase sentences I didn't understand. However I find the whole thing a bit much to digest all at once, so I'm going to explain it in smaller pieces, as suits my  NADD audience. First up - the ring buffer.  Initially I was under the impression the Disruptor was just the ring buffer.  But I've come to realise that while this data structure is at the hea...
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Dissecting the Disruptor: Demystifying Memory Barriers

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My recent slow-down in posting is because I've been trying to write a post explaining memory barriers and their applicability in the Disruptor . The problem is, no matter how much I read and no matter how many times I ask the ever-patient Martin and Mike questions trying to clarify some point, I just don't intuitively grasp the subject. I guess I don't have the deep background knowledge required to fully understand. So, rather than make an idiot of myself trying to explain something I don't really get, I'm going to try and cover, at an abstract / massive-simplification level, what I do understand in the area.  Martin has written a post  going into memory barriers  in some detail, so hopefully I can get away with skimming the subject. Disclaimer: any errors in the explanation are completely my own, and no reflection on the implementation of the Disruptor or on the LMAX guys who actually do know about this stuff. What's the point? My main aim in this s...
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