Yahoo Pipe to Google maps integration

Yahoo Maps are a bit rubbish, so I looked for a way to easily pull together a  map I don't dislike using.

The map's here; the original data's here; and the Yahoo pipe between is here.

This map is a handy reference to the Victorian state government's public register of convictions for food safety offences. It's also a nice example of how cloud services can be integrated and mixed, and matched - Yahoo does provide a map interface to this data, but their maps are terrible.



View Larger Map

Viewing D-Link DCS-932L IP camera from Ubuntu

In a word (line) ...

avconv -r 15 -f mjpeg -i http://USERNAME:PASSWORD@IP-ADDRESS/video.cgi -i http://USERNAME:PASSWORD@IP-ADDRESS/audio.cgi -vcodec mpeg4 -f mpegts file:///dev/stdout | vlc file:///dev/stdin

Now, if only the audio didn't crash avconv, we'd be cooking with gas! The silent version is here, and seems stable.

avconv -r 15 -f mjpeg -i http://USERNAME:PASSWORD@IP-ADDRESS/video.cgi -vcodec mpeg4 -f mpegts file:///dev/stdout | vlc file:///dev/stdin

File upload and copy pattern

I was asked a different question; but then ended up with this instead. Shame to waste it...

The pattern that I've used in the past has directories like this (under some root directory like /var/lib/uploads):

/partial
/ready
/working
/success
/error

This set of directories are required for all traffic to a given recipient. Essentially, a file makes its way through the directories, from top to bottom. All directories should be on a single file system. File uploaders/clients should be able to write to /partial and /ready. File receivers/servers should be able to write to everything, except /partial.

Step 1: A file is uploaded/copied into the /partial directory; with a (globally) unique file name. This step completes when there's sufficient confidence that the file has been copied (usually that just means that the expected number of bytes has been written without an error being thrown).
Step 2:  The file uploader/client moves the newly uploaded file into the /ready directory. DO NOT COPY THE FILE!!!! In general, moving/renaming a file within a file system is guaranteed to be an atomic operation, but copying is not. This signifies that the file is ready (from the perspective of the client).
Step 3: When the recipient application/process is ready to process a file in /ready, it should first move the file into its /working directory.
Step 4: When the recipient application has finished processing a file (due to completion, or error) it should move the file into the /success, or /error, directory.

Things to watch
- more than one file in the working directory is likely to indicate a failure.
- Any file in the error directory is likely to indicate a failure.
- "old" files in the partial directory indicate unsuccessful copies/uploads.
- "old" files in the ready directory indicate that processing has failed/slowed.
- "old" files in the working directory indicate a failure/ABEND.
- Make sure the file system doesn't fill.
- Archiving is not covered here; that's a different pattern.

Other notes;
- If there is more than one recipient (e.g.: a multi-process server) there should be multiple working directories (working01 working02, working03, etc. - one for each process.
- this is essentially a queue implementation with single phase commit transactions.
- You can implement exactly the same pattern using file renaming, rather than separate directories. I prefer directories.

VMware player 4.0.3 on Ubuntu 12.04

VMware player has some well-known issues with setting up the network for player under Ubuntu 12.04 (that is, where Ubuntu is the host OS).

With one small change, I followed the great instructions here: http://www.kartook.com/2012/05/vmware-virtual-network-device-unable-to-loadcompile-vm-player-4-0-2-in-ubuntu-12-04/

The change is that the script you download has the recognised version numbers hardcoded in the header.

Before you run the script (patch-modules_3.2.0.sh), open the file using your preferred text editor, and change the 4.0.2 to 4.0.3, so it looks like:

   plreqver=4.0.3

The script (and VMware player) seems to run fine for VMware Player 4.0.3 on Ubuntu 12.04. If it should make a difference, I'm running x86_64 Ubuntu 12.04.

USB dead device fix

I have a slug (NSLU2) at home, serving out a big USB hard disk. I like my slug. It's small, and it runs Debian, and so long as I remember that it's really small, it runs really well.

It looks like USB drives suffer from lots of issues with dodgey firmware and drivers. Certainly, I haven't escaped them. Every few months I lose the USB drive:
kern.log:

Apr 12 20:32:54 slug kernel: scsi 1:0:0:0: rejecting I/O to dead device

...

This can cause filesystem corruption as well, and is generally "A Bad Thing". Fixing this issue is (for me) a case of remounting the filesystem. I recall once I also had to cycle the power too. Fortunately, I found this page: http://www.mail-archive.com/linux-usb-users@lists.sourceforge.net/msg16510.html which has a very nifty technique for coaxing the USB stack back to life.

I've written a script to pull out the sysfs name of the USB device for a given mount point. At some point I'll add this in to my slug so that it "just works". That just leaves a log scraper to pick up each mount and get the sysfs name, wait for a failure, unmount the dead file system, rebind the USB device, check the file system for damage, and remount the filesystem. Easy!

#!/bin/bash
# get_usb_name.sh 
# e.g.: ./get_usb_name.sh /media/usb2

USB_DEV=$(mount | grep ${1} | cut -f 1 -d ' ' | sed -e 's/[0-9]$//' -e 's(^/dev/((')
USB_ADDR=$(ls -l /sys/block/${USB_DEV}/device | sed -e 's(/host.*$((' -e 's(^.*/((')
if [ -e /sys/bus/usb/drivers/usb-storage/${USB_ADDR} ]
then
echo $USB_ADDR
else
echo "could not verify usb address of ${USB_ADDR} for device ${USB_DEV}" >&2
fi