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  • Per-machine decentralised DNS caching - nscd/lwresd/etc

    - by Dan Carley
    Preface: We have caching resolvers at each of our geographic network locations. These are clustered for resiliency and their locality reduces the latency of internal requests generated by our servers. This works well. Except that a vast quantity of the requests seen over the wire are lookups for the same records, generated by applications which don't perform any DNS caching of their own. Questions: Is there a significant benefit to running lightweight caching daemons on the individual servers in order to reduce repeated requests from hitting the network? Does anyone have experience of using [u]nscd, lwresd or dnscache to do such a thing? Are there any other packages worth looking at? Any caveats to beware of? Besides the obvious, caching and negative caching stale results.

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  • Python class representation under the hood

    - by decentralised
    OK, here is a simple Python class: class AddSomething(object): __metaclass__ = MyMetaClass x = 10 def __init__(self, a): self.a = a def add(self, a, b): return a + b We have specified a metaclass, and that means we could write something like this: class MyMetaClass(type): def __init__(cls, name, bases, cdict): # do something with the class Now, the cdict holds a representation of AddSomething: AddSomething = type('AddSomething', (object,), {'x' : 10, '__init__': __init__, 'add': add}) So my question is simple, are all Python classes represented in this second format internally? If not, how are they represented? EDIT - Python 2.7

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  • Interesting things – Twitter annotations and your phone as a web server

    - by jamiet
    I overheard/read a couple of things today that really made me, data junkie that I am, take a step back and think, “Hmmm, yeah, that could be really interesting” and I wanted to make a note of them here so that (a) I could bring them to the attention of anyone that happens to read this and (b) I can maybe come back here in a few years and see if either of these have come to fruition. Your phone as a web server While listening to Jon Udell’s (twitter) “Interviews with Innovators Podcast” today in which he interviewed Herbert Van de Sompel (twitter) about his Momento project. During the interview Jon and Herbert made the following remarks: Jon: [some people] really had this vision of a web of servers, the notion that every node on the internet, every connected entity, is potentially a server and a client…we can see where we’re getting to a point where these endpoint devices we have in our pockets are going to be massively capable and it may be in the not too distant future that significant chunks of the web archive will be cached all over the place including on your own machine… Herbert: wasn’t it Opera who at one point turned your browser into a server? That really got my brain ticking. We all carry a mobile phone with us and therefore we all potentially carry a mobile web server with us as well and to my mind the only thing really stopping that from happening is the capabilities of the phone hardware, the capabilities of the network infrastructure and the will to just bloody do it. Certainly all the standards required for addressing a web server on a phone already exist (to this uninitiated observer DNS and IPv6 seem to solve that problem) so why not? I tweeted about the idea and Rory Street answered back with “why would you want a phone to be a web server?”: Its a fair question and one that I would like to try and answer. Mobile phones are increasingly becoming our window onto the world as we use them to upload messages to Twitter, record our location on FourSquare or interact with our friends on Facebook but in each of these cases some other service is acting as our intermediary; to see what I’m thinking you have to go via Twitter, to see where I am you have to go to FourSquare (I’m using ‘I’ liberally, I don’t actually use FourSquare before you ask). Why should this have to be the case? Why can’t that data be decentralised? Why can’t we be masters of our own data universe? If my phone acted as a web server then I could expose all of that information without needing those intermediary services. I see a time when we can pass around URLs such as the following: http://jamiesphone.net/location/current - Where is Jamie right now? http://jamiesphone.net/location/2010-04-21 – Where was Jamie on 21st April 2010? http://jamiesphone.net/thoughts/current – What’s on Jamie’s mind right now? http://jamiesphone.net/blog – What documents is Jamie sharing with me? http://jamiesphone.net/calendar/next7days – Where is Jamie planning to be over the next 7 days? and those URLs get served off of the phone in our pockets. If we govern that data then we can control who has access to it and (crucially) how long its available for. Want to wipe yourself off the face of the web? its pretty easy if you’re in control of all the data – just turn your phone off. None of this exists today but I look forward to a time when it does. Opera really were onto something last June when they announced Opera Unite (admittedly Unite only works because Opera provide an intermediary DNS-alike system – it isn’t totally decentralised). Opening up Twitter annotations Last week Twitter held their first developer conference called Chirp where they announced an upcoming new feature called ‘Twitter Annotations’; in short this will allow us to attach metadata to a Tweet thus enhancing the tweet itself. Think of it as a richer version of hashtags. To think of it another way Twitter are turning their data into a humongous Entity-Attribute-Value or triple-tuple store. That alone has huge implications both for the web and Twitter as a whole – the ability to enrich that 140 characters data and thus make it more useful is indeed compelling however today I stumbled upon a blog post from Eugene Mandel entitled Tweet Annotations – a Way to a Metadata Marketplace? where he proposed the idea of allowing tweets to have metadata added by people other than the person who tweeted the original tweet. This idea really fascinated me especially when I read some of the potential uses that Eugene and his commenters suggested. They included: Amazon could attach an ISBN to a tweet that mentions a book. Specialist clients apps for book lovers could be built up around this metadata. Advertisers could pay to place adverts in metadata. The revenue generated from those adverts could be shared with the tweeter or people who add the metadata. Granted, allowing anyone to add metadata to a tweet has the potential to create a spam problem the like of which we haven’t even envisaged but spam hasn’t halted the growth of the web and neither should it halt the growth of data annotations either. The original tweeter should of course be able to determine who can add metadata and whether it should be moderated. As Eugene says himself: Opening publishing tweet annotations to anyone will open the way to a marketplace of metadata where client developers, data mining companies and advertisers can add new meaning to Twitter and build innovative businesses. What Eugene and his followers did not mention is what I think is potentially the most fascinating use of opening up annotations. Google’s success today is built on their page rank algorithm that measures the validity of a web page by the number of incoming links to it and the page rank of the sites containing those links – its a system built on reputation. Twitter annotations could open up a new paradigm however – let’s call it People rank- where reputation can be measured by the metadata that people choose to apply to links and the websites containing those links. Its not hard to see why Google and Microsoft have paid big bucks to get access to the Twitter firehose! Neither of these features, phones as a web server or the ability to add annotations to other people’s tweets, exist today but I strongly believe that they could dramatically enhance the web as we know it today. I hope to look back on this blog post in a few years in the knowledge that these ideas have been put into place. @Jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Pushing Windows Store apps silently

    - by seagull
    As part of a requirement I have been issued, I seek the ability to push apps from the Windows Store (.appx) to remote users. The framework surrounding the data transmission is sorted; What I need to know is if there is a script that can be sent out along with a URI or the package proper to facilitate installation on the user-side of the Windows Store app. I am well aware that numerous guides exist from Microsoft on pushing out Line-of-Business (LOB) (AKA Enterprise) applications -- that is, apps that have been developed in-house and are not for the consumption of the Windows store. This is inappropriate for my requirement, however; the customer wants their clients to receive apps that appear currently on the Windows Store, and for them to be installed in a silent manner. I've seen this guide; http://blogs.technet.com/b/keithmayer/archive/2013/02/25/step-by-step-deploying-windows-8-apps-with-system-center-2012-service-pack-1.aspx, which details doing exactly this, but it is only applicable to machines that are administered by a system running Windows Server 2012 R2 with the 'System Center 2012' bundle installed. The systems I target are considerably more decentralised than this, making this guide inappropriate. I have a hunch that Microsoft have deliberately designed the Windows Store to be this way, but I figured I ought to ask around before I resign myself to the requirement. Much obliged

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  • SVN supports historical merges so how is Mercurial better?

    - by radman
    Hi, I'm a long time SVN user and have been hearing a lot of brou ha ha with regard to mercurial and decentralised version control systems in general. The main touted feature that I am aware of is that merging in Mercurial is much easier because it records information for each merge so each successive merge is aware of the previous ones. Now as stated in the red book, in the section to do with merging, SVN already supports this with mergeinfo. Now I have not actually used this feature (although I wanted to, our repo version wasn't recent enough) but is this SVN feature particularly different to what Mercurial offers? For anyone who is not aware the suggested work flow for historical merging in svn is this: branch from the development trunk to do your own thing. Regularly merge changes from trunk into your branch to stay up to date. Merge back when your done with the mergeinfo to smooth the process. Without historical data merging this is a nightmare because the comparison is strictly on the differences in the files and does not take into account the steps taken on the way. So each change in the development trunk puts you further into possible conflict when you merge back. Now what I would like to know is: Does merging using Mercurial provide a significant advantage when compared with mergeinfo in SVN or is this just a lot of hot air about nothing? Has anyone used the mergeinfo feature in SVN and how good is it actually in practice?

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