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Name: James Taylor
Member since: 2002-04-15 13:29:20
Last Login: 2013-04-30 15:34:22

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Homepage: www.imen.org.uk

Notes:

Working in Norwich UK for a technology company, working on interesting products for various markets. The work involves some web programming for both Websites and applications requiring data from a centralized server system. Also a fully licensed Radio Ham, holding the licenses: M0OUZ, 2E0OUZ and M3OUZ (in decreasing order of relevance). Undergoing personal development with the IET.

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21 Jul 2012 (updated 30 Apr 2013 at 12:57 UTC) »

Now Your All Dreams Will Going To Become Reality with Your Own Home Business

Post removed as was spam through aggregator.

Syndicated 2012-07-21 02:55:23 from jejt / jmons

Continual Integration Development and the Cloud

One of the big buzz phrases at the moment seems to be Continual Integration Development. If you’re developing and wanting to deploy ‘as the features are ready’, and you have a cloud you have two main options, which both have pros and con’s but:

New Image per Milestone

Most cloud systems work by you taking an ‘image’ of a pre-setup machine, then booting new instances of these images. Each time you get to a milestone, you setup a new image, and then setup your auto scaling system to launch these instances rather then the old one, but you have to shut down all your old images and bring them up as new ones.

Pro’s: The machines come up in the new state quickly.
Con’s: For each deployment, you have to do quite a bit more work making the new image. Each deployment requires shutting down all the old images and bringing up new replacements.

SCM Pull on Boot

Make one image, and give it access to your SCM (i.e. git / svn etc). Build in a boot process that brings up the service but also fetches the most recent copy of the ‘live’ branch.

Pro’s: You save a lot of time in deployments – deployments are triggered by people committing to the live branch, rather then by system administrators performing the deployments. Because they are running SCM, updating all the currently running images is as simple as just running the fetch procedure again.
Con’s: You do need to maintain two branches: a live and a dev branch, and merge (some SCM’s might not like this). Also, your SCM hosting has to be able to cope with when you get loads (i.e. when new computers get added). Your machines come up a little slower as they have to do the fetch before they are usable.

I opted for the second route: we use Git, so we can clone quickly to the right branch. We’ve also added in git hooks that make sure any setup procedures (copying the right settings file in) are done when the computer comes up. Combining this with a fabric script to update all the currently running boxes is a dream.


Syndicated 2011-03-20 11:10:17 from jejt / jmons

What Cloud Computing System to Use?

So you’re sitting at work, and you have to build a new system, and for once you don’t have any previous code or language forcing you to write one way or another, and you know this is going to get big – maybe not Twitter or Google big, but certainly big enough to give you a good old headache. The big question becomes what technology to use. Firstly, I apologise that this is early 2011, so if you’re reading this in two or three years (or even six months) then the technology will all change again – I’m not planning on updating this particular post as the stuff changes, but I might make new ones.

So the first decision to make is what Cloud Computing system you’re going to use – are you doing lots of queries, or just a few queries and lots of processing. I’m presuming the first one, but the latter one is quite interesting – it deals with universities and researchers trying to run on massive data sets and producing reports.

Your main contenders are:

  • Some collection of *nux or Windows servers
  • Proprietary cloud compute services

The first category might mean more work for you and your sysadmins – it really does point towards the requirements of a sysadmin but gives you a lot more flexibility in your choice of languages and systems, where as the latter might mean that you are able to do with out those, and also (depending on the service) have access to a lot of tools and power without having to use any other third party services.

The main propietary services at the moment seem to be:

  • Google’s Apps
  • Microsoft Azure

Now – both of these platforms are quite seductive, they have a lot of benefits – mainly that you don’t have to be a sysadmin to deploy and maintain the system, that you can access quite complicated things such as shared and persistent storage, caching and database pooling without having to actually spend days reading various manuals for everything.

The downside though? You are locked to one provider and their billing methods – Apps has a very strange billing mechanism to do with the number of users (Which if you’re producing something for a lot of users, that might be very expensive), and because you’re locked into that service provider, there isn’t another provider who you can goto for alternative pricing, and because of this, I think a lot of smaller businesses make a commercial decision to go with the more traditional style hosting.

Traditional clusters (such as provided by Amazon and Rackspace) seem to provide a collection of tools along side. Content distribution networks for static content such as images and javascipt, as well as tools for monitoring and automatically scaling the systems. The advantages of the traditional route is that its easy to run up a local copy at your location and develop away, which means when you are looking at doing architectural changes, these are much easier to stage to live.

In my opinion, it seems that commercial reasons for going down cloud hosting of systems which are ‘traditional linux/windows’ boxes have massive advantages, but do require more systems-administration work.


Syndicated 2011-03-20 10:05:01 from jejt / jmons

Hissing Noise from Speakers Fixed


So recently a friend at work (the esteemed DJ Hedflux) had a problem with his speakers – he has a pair of powered speakers, and he outputs sound down a normal stereo cable into the speakers. Being a professional DJ, nothing in his system is particually cheap (he’s not spending £100 on cables, but he’s not buying £1.50 speaker modules from the market) so we can quickly rule out shoddy work and bad connections inside of the devices.

Anyways, he worked out that it was a combination of his computer and his touch lamp causing it – doing things on his computer that required lots of processing, and having the dimmer lamp “dimmed” caused the noise to appear and dissapear.

This is very common, and also, very easy to fix.

How to fix:

Ferrite ring filter

The solution is very simple, and very cheap. You’ll need a ferrite ring, which you wind the audio cable in just a couple of times, like in the above picture.

Maplins sell these for a couple of pounds, usually find them in the Radio section:

http://www.maplin.co.uk/Module.aspx?ModuleNo=29788

Image stolen from http://www.gbrcaa.org/ntoa/Filters,%20Chokes%20and%20OIs.htm on which site you can also find more information about other kinds of chokes.

The science:

In Hedflux’s case, its possible that his computer internals arn’t all grounded to the case correctly, or the case to the power supply, so its generating more electrical noise then ideal. The dimmer lamp however is a common source of Electromagnetic Interferance (EMI).

Because he’s using a set of powered speakers, the loudspeaker cable is acting as an antenna, and the amplification circuit is having a side effect of acting as a little radio, which is picking up the EMI from the computer and the lamp, and turning it into the annoying hissing noise.

The ferrite bands that he added to the audio cable basically change the frequencies of that cable, effectivly filtering the annoying frequencies out.

Why don’t these cables come with the bands installed? Well, the point is that it dosn’t STOP the frequencies, it shifts the resonance frequency of the cable. The cable and speakers will still produce noise if the EMI comes in on a different frequency, so it was just bad luck that the EMI in his room was the same frequency as the cable / speaker setup.

Syndicated 2009-09-10 19:25:39 from Holding the Soldering Iron by the Cold End

Mud/Mush/Moo


So I’ve started on a tinymush server, and its quite interesting scripting objects together, so here is my first object (which is actually version two of it) because the first version was a little cumbersome. Please note this is ready for copy and pasting into the mush (I’ve escaped the ; with backslashes)

@create Board
@desc Board=An oak framed chalk board ready to be written on. It contains the words of wisdom from the teachers, or doodles from the students.[ifelse([hasattr(me,text)],It currently reads: [eval(me,text)],It is currently blank)]. Feel free to "write on board z" or "erase board"
@lock Board==me
@set BOARD = COMMANDS
&C_WRITE Board=$write on board *:&text me=%0\;pose has just been written on
&C_ERASE Board=$erase board:&text me\;pose causes clouds of dust to rise as it is erased

It has two commands “write on board x” and “erase board” which reset an attribute &text. I suspect I should change the pose lines to emit lines. But apart from that, I think its pretty cool.

Syndicated 2009-06-25 08:47:47 from Holding the Soldering Iron by the Cold End

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