September 1, 2014

Don’t trust the query planner!

Filed under: Technical — Tags: , , — James Bunton @ 12:00 am

This is an experiment in cross-posting something from my internal blog with my employer Atlassian. I thought it may be be of general interest so I’ve edited it a bit and shared it here.

We recently did a regular zero downtime upgrade of our order processing system. This is a fairly routine event, we use Bamboo deployments to push from git master to our dev, staging and then production environments every day. The vast majority of these upgrades go smoothly without serious regressions or problems. On this particular day the application did not come back properly, we had an outage! We treat these very seriously because the ordering system is a big monolithic do-all-the-things type of application. An outage means customers cannot make new purchases, view their license keys, sign up for OnDemand, view prices on Marketplace and many other things.

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July 25, 2014

Introduction to the Linux Wireless Subsystem

Filed under: Technical — Tags: , , , — 7:26 pm

Guest post by lemnisca.

I’ve recently started getting into Linux wireless programming for work. I am a fairly experienced C programmer but don’t know much about kernel development so this is a new adventure for me. What I found was that while there is a lot of information available about how it all works — indeed, since it’s open source, one can at least in theory have complete information about the functioning of the system — there is not much in the way of an introduction. There’s no broad explanation of how it all works for someone completely new to the system. The documentation that does exist is largely focused on documenting individual functions, structs, etc. and is more of a reference for those already familiar with the system. I quickly found myself lost in a sea of source code, chasing down chains of function calls with no real feel for how the whole thing is put together. So I’ve decided to share what I’ve learnt, in the hopes that it might help someone else in the future.

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April 7, 2014

Bluplayer – Easy Bluray playback with MakeMKV and VLC

Filed under: Technical — Tags: , , , , — James Bunton @ 9:00 am

About a year ago when I first bought my Bluray drive for Linux I had a simple requirement. I wanted to be able to put a disc in, then with some graphical tool select a track and have it start playing. It turns out nothing on Linux can do this.

So I wrote a simple Python/Qt app which uses MakeMKV to decrypt and VLC to play it.

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March 24, 2014

Bluetooth DUN Tethering with Linux and a Nokia Symbian Phone

Filed under: Technical — Tags: , , , , , — James Bunton @ 6:06 pm

A small Python script to connect to the internet over Bluetooth DUN (dialup networking) using my Nokia Symbian phone and my Linux laptop.

This was written on Arch Linux but should work elsewhere too. It uses bluez5 to enable bluetooth, rfcomm to create the serial port and wvdial to create the PPP connection and manage routes/DNS. Many newer phones use Bluetooth PAN instead of DUN so this method won’t be applicable.

Once upon a time this all worked automagically with NetworkManager. Since bluez5 it fails with this error:

Method "Connect" with signature "s" on interface "org.bluez.Serial" doesn't exist

Apparently we’re supposed to use the new Serial.ConnectFD DBUS API instead.

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January 16, 2014

Bluetooth Audio A2DP Receiver with Raspberry Pi

Filed under: Technical — Tags: , , , , , — James Bunton @ 10:34 am

My latest project was to have wireless audio streaming from my Symbian mobile phone over Bluetooth to a a new set of speakers. I used PulseAudio, Bluez5 and Arch Linux running on a Raspberry Pi. It all works really well. I can connect/disconnect from the phone and everything is automatically started on boot. I’m enjoying it now as I type this.

Thanks to Greg & Helen for the Christmas present! :)

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