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Showing posts from February, 2014

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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Should you notice I'm a woman? Should I care?

So, following on from my observations of being an outsider at FOSDEM because I'm not an open source developer, I do have another story to tell where my female-ness is actually relevant. I'm going to give specifics, but it's not to name and shame or anything like that, it's just that anonymising it will probably erase some of the subtleties.  But I'm not telling this to make anyone feel bad, because this is not an oh-poor-me story, this is just the way it goes sometimes and I want to share what it feels like. At JFokus (a conference I really enjoyed, where I got a chance to spend time with some awesome people) I was on a panel (well, game-show really) about static vs dynamic languages.  Not unusually, I was the only woman on the panel.  Also not unusually, one of the reasons I agreed to take part is to do my bit in demonstrating that women have technical knowledge too (in my opinion, it's important where possible to avoid a stage full of white men of a...
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Feel like an outsider?

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So, FOSDEM. I've heard great things about this conference, so I was pretty exited to go The Java dev room Now I know people talk about impostor syndrome whenever they mention the woeful lack of diversity at tech conferences.  Interestingly, I felt like an impostor at FOSDEM - not because I'm a woman (there were quite a few techy women around at FOSDEM, more than I expected) but because I'm not an open source person. I mean, I am, technically - MongoDB and the Java driver are both open source, and I have real live code on github.  But I didn't get there via the open source community, I was hired to do a specific job that happens to be open source (for which I am extremely grateful).  So although I knew the MongoDB folks I was there with and a lot of people who were running or speaking in the Java room, I didn't feel really at home in this conference.  I think I feel more comfortable with the ones aimed at enterprise Java developers (by which I mean...
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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 hea...
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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: 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 n...
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