Some Random Upstart Debugging Notes…

…just so I don’t lose them…

dmesg spews out messages a Linux kernel has been issuing… which should also appear in /var/log/syslog (h/t Rod Norfor)

/var/log/upstart/SERVICE.log has log messages from trying to start a service SERVICE.

/etc/init.d should contain what looks like a generic sort of file, filename SERVICE, with the actual config file that contains the command you want to start the service in a file SERVICE.conf in /etc/init.

To generate the files that will have a go at auto-running the service, run the command update-rc.d SERVICE defaults.

Start a service with service SERVICE start, stop it with service SERVICE stop, and restart (stop if started, then start) with service SERVICE restart. Find out what’s going on with it using service SERVICE status.


Previewing the Contents of a JSON Feed in Yahoo Pipes

This post builds on the previous one (Grabbing the Output of a Yahoo Pipe into a Web Page) by describing a strategy that can help you explore the structure of a JSON feed that you may be pulling in to a web page so that you can identify how to address the separate elements contained within it.

This strategy is not so much for developers as for folk who don’t really get coding, and don’t want to install developer tools into their browser.

As the “Grabbing the Output of a Yahoo Pipe into a Web Page” post described, it’s easy enough to use JQuery to get a JSON feed into a web page, but what happens then? How do you work out how to “address” the various parts of the Javascript object so that you can get the information or data you want out of it?

Here’s part of a typical JSON feed out of a Yahoo pipe:

{“count”:17,”value”:{“title”:”Proxy”,”description”:”Pipes Output”,”link”:”http:\/\/\/pipes\/″,”pubDate”:”Mon, 19 Jul 2010 05:15:55 -0700″,”generator”:”http:\/\/\/pipes\/”,”callback”:””,”items”:[{“link”:”http:\/\/\/~r\/ouseful\/~3\/9WBAQqRtH58\/”,”y:id”:{“value”:”http:\/\/\/?p=3800″,”permalink”:”false”},”feedburner:origLink”:”http:\/\/\/2010\/07\/19\/grabbing-the-output-of-a-yahoo-pipe-into-a-web-page\/”,”slash:comments”:”0″,”wfw:commentRss”:”http:\/\/\/2010\/07\/19\/grabbing-the-output-of-a-yahoo-pipe-into-a-web-page\/feed\/”,”description”:”One of the things I tend to take for granted about using Yahoo Pipes is how to actaully grab the output of a Yahoo Pipe into a webpage. Here’s a simple recipe using the JQuery Javascript framework to do just that. The example demonstrates how to add a bit of code to a web page […]“,”comments”:”http:\/\/\/2010\/07\/19\/grabbing-the-output-of-a-yahoo-pipe-into-a-web-page\/#comments”,”dc:creator”:”Tony Hirst”,”y:title”:”Grabbing the Output of a Yahoo Pipe into a Web Page”,”content:encoded”:”

One of the things I tend to take for granted about using Yahoo Pipes is how to actaully grab the output of a Yahoo Pipe into a


However, we can can use the Yahoo pipes environment to help us understand the structure and make up of this feed. Create a new pipe, and just add a “Fetch Data” block to it. Paste the URL of the JSON feed into the block, and now you can preview the feed – the image below show a preview of the JSON output from a simple RSS proxy pipe, that just takes in the URL of an RSS feed and then emits it as a JSON feed:

Yahoo pipes JSON browser

(Note that if you find yourself using the Yahoo Pipes V2 engine, you may have to wire the output of the Fetch Data block to the output block before the preview works. You shouldn’t need to save the pipe though…)

When you load the feed in to a webpage, if you assign the whole object to the variable data, then you will find the output of the pipe in the object data.value.

In the example shown above, the title of the feed as a whole will be in data.value.title. The separate feed items will be in the collection of data.value.items; data.value.items[0] gives the first item, data.value.items[1] the second, and so on up to data.value.items[data.value.items.length-1]. The title of the third feed item will be data.value.items[2].title and the description of the 10th feed item will be data.value.items[9].description.

This style of referencing the different components of the javascript object loaded into the page is known as the javascript object dot notation.

Here’s a preview of a council feed from OpenlyLocal:

Preview an openly local council feed

In this case, we start to address the data at data.council, find the population at data.council.population, index the wards using data.council.wards[i] and so on.