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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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In my day...

Web development has changed a lot . I was aware that there have been many changes in the last few years, and I’ve seen maturity come to web platforms in the form of standardisation and common reusable libraries and frameworks - and I don’t mean reusable in the way we used to “reuse” stuff by nicking it off other people’s websites when we saw something cool. I used to be a web developer.  Sort of.  Some times I’ve been on the bleeding edge, and others… I remember using JavaScript to call back-end services with an XML payload before people were using the term AJAX, but I also remember working on an enterprise um… “classic”… JSP application only “recently” - in fact that was probably the last job where I did anything that looked like web development. So this blog post is going to chart the progress of web development through my own experience.  Of course, this doesn’t by any means cover the whole spectrum, but I think my experience has been not unusual for...
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GWT: Why VerticalPanel is Evil

At LMAX we adopted Google Web Toolkit pretty early on.  One of the motivations for using it was so we only had to worry about recruiting Java guys, and then we could all work on every part of the application including the web UI.  Sure, you can learn a bunch of different skills if you want to, but it reduced context-switching and kept the skill set we were hiring for to a nice short list. The problem is that GWT does a very nice job of pretending to be Java whilst actually compiling down to HTML and JavaScript.  If you don't have some understanding of the end result (the DOM the browser is going to be rendering) it's going to be hard to get the performance you need from a low-latency trading application . My number one bug-bear with GWT is VerticalPanel .  To the uninitiated developer, this seems like the sort of thing that will be useful everywhere.  You often want stuff stacked on top of each other - think menus, lists, the layout of a dialog.  What...
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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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