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Showing posts from November, 2013

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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First presentation at the Virtual JUG!

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Yesterday I had the privilege of presenting the very first session for vJUG, a new virtual Java User Group that allows us to span geographies when sharing talks and stories.  I'm really interested in the vJUG idea, especially now I'm not in London - if we can find good ways to share knowledge without having to travel, that will help us reach people who don't normally go to conferences or don't have a local user group to go to.  Not to mention cutting travel costs and saving the environment. See the event, and the record of the IRC chat, here:   The slides are also online, but obviously they're part of the video as well: Design is a process, not a Document from Trisha Gee
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JAX London & MongoDB Tutorial

In previous years, JAX London would have been an easy, local conference to go to.  This time it took me most of Sunday to get there, and not because of the Super Storm .  Still, that gave me the day to finish off the tutorial I was running there on Monday morning.  Not that I would be so unprofessional as to leave preparing things until the last minute, oh no.... But as in previous years, the main benefit of this conference for me was meeting most of the usual suspects from the London Java Community.  For example, presenting were: Andy Piper ; Barry Cranford ; Jim Gough ; Peter Lawrey ; Sandro Mancuso ;  Simon Maple ;  Martijn Verburg ;  John Oliver : John Stevenson ; Richard Warburton . The Community Night in particular also drew a lot of LJC members (including some first-timers) to JAX, and it was a really good "networking opportunity" (i.e. chance to have free drinks, catch up with friends and make new ones).  I really enjoyed hanging out with everyone at JAX this year,
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LinkedIn Etiquette

For no reason other than LinkedIn communications are starting to irritate me, here's my personal LinkedIn Etiquette guide.  Feel free to disagree with it all. I'm not going to accept invitations from recruiters.  Not just because I'm not looking for a job (who knows what the future holds?), but because I believe it shows a lack of respect to my network to bring recruiters one step closer to being able to contact them all.  It's not about Evil or Good recruiters, but I really don't want to make it easier for lazy recruiters to spam people I respect (caveat: there are people who are technically recruiters who I have added into my network, either because I know them personally or because they have proved their worth). If I get an invite without an introduction message from someone who's name I don't immediately recognise, I'm going to check out that profile to see if we have employers in common or common connections, but usually I won't acce
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JavaOne 2013

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So, I thought a few months ago that my blog would become more of a travel blog than a tech blog because of the amount of conferences I was going to.  Turned out that I was so busy writing / updating / practicing talks and workshops and, er, travelling, that I never got around to doing retrospectives on the events I'd been to. So, JavaOne, again, my third year there.  I'll always have a fondness for it - because of Martin Thompson , it was the first conference I presented at.  I know people always start with "it's not what it used to be" or "why isn't it in the Moscone?".  But not having ever been in the good ol' pre-Oracle days, I don't have that to compare it to. I do have the previous two years to compare it to, however.  This year, I think the quality of the presentations was much better compared to the previous two years (although I can't accurately speak for last year as I spent the whole time running between my presentation
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Popular posts from this blog

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 heart of the patte
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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 the first bi
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Dissecting the Disruptor: How do I read from the ring buffer?

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The next in the series of understanding the Disruptor pattern developed at LMAX . After the last post we all understand ring buffers and how awesome they are.  Unfortunately for you, I have not said anything about how to actually populate them or read from them when you're using the Disruptor. ConsumerBarriers and Consumers I'm going to approach this slightly backwards, because it's probably easier to understand in the long run.  Assuming that some magic has populated it: how do you read something from the ring buffer? (OK, I'm starting to regret using Paint/ Gimp .  Although it's an excellent excuse to purchase a graphics tablet if I do continue down this road.  Also UML gurus are probably cursing my name right now.) Your Consumer is the thread that wants to get something off the buffer.  It has access to a ConsumerBarrier , which is created by the RingBuffer and interacts with it on behalf of the Consumer .  While the ring buffer obviously needs a se
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