Thoughts of a geek

4 November 2009

Rubgy, a safe technical topic, and baking

Filed under: Computers, Me, Recipes — Tags: , , , , , , — qwandor @ 10:33 pm

Continuing on from my last post taking suggestions from Twitter, today I will be blogging about topics suggested by people on Facebook.

Allan Chesswas: Rugby

Here in New Zealand, and elsewhere I hear, some people like to run around a field jumping on each other and chasing an oddly-shaped ball. This activity seems to be more popular among boys than girls. Many other people like to watch them do so. Several of my flatmates are in the latter set, and one in the former. I have never seen the attraction of either activity. The running around does at least provide decent exercise, but at significant risk of injury. Watching seems even more pointless, and frequently people do so (via television) instead of partaking in more interesting and productive pastimes such as good conversation, programming, baking, listening to music or even reading. This can be something of a frustration.

Donald Gordon: Safe technical topics which no one will be offended by.

Well. Most of my ‘recreational’ programming of late has been on Fridge. Fridge is a co-operative honesty system for snackfood which originated in Memphis. The Memphis Fridge is something of an open secret, used by graduate students and their friends. The basic idea is that certain people buy pre-packaged food and drink in bulk. Everyone who uses fridge has an prepay account which they can put money into by putting cash in a drawer and crediting their account, and then they can use this balance to buy the food and drink. The software keeps track of users, money, the various items stocked, markups to make up for lost or damaged stock, various statistics, and so on.

I have made a few minor contributions to the Fridge software in the past (such as adding a QIF export feature to allow users to import their transaction history into their personal accounting software), but my substantial work on it now began with interfridge. Interfridge was an idea that I and others had some time ago, last year I think, to allow users on one fridge to use that account on another fridge. This was motivated by the fact that both Memphis and Innaworks (where I currently work) run the Fridge software, and several of us use both fridges from time to time. The idea of interfridge was that I could visit Memphis, login to their fridge with my Innaworks fridge account, and purchase items from Memphis just like any Memphis user.

At some point Donald wrote some notes on his ideas of how interfridge should be designed. I finally got around to implementing this (the server side in PHP as part of fridgeweb, the client side integrated into the Java fridge client) using a protocol on top of HTTP. After much discussion with lorne, Chris Andreae and Stephen Nelson and several iterations changing the protocol to fix potential security holes pointed out, we came up with the interfridge protocol that is now in use between Memphis and Innaworks.

However, we realised along the way that fridge really could do with being improved in other respects. Currently, the Java client talks directly to a PostgreSQL database which holds all the user, stock and transaction data. This means that the client must include the database password, which is really not a good thing to be giving out to all and sundry. A much better design would be to have a trusted fridge server which talks to the database, and then have the client perform all operations via the server. With an appropriately-designed protocol, this means that the client need not be trusted, and so anyone can write their own client to use with the fridge. I have thus begun to design and implement a fridge protocol based on the interfridge protocol (it can do everything the interfridge protocol can do and more, so will replace it when it is done). For this I scrapped the custom RPC protocol which I had been implementing for myself on top of HTTP, and went with XMLRPC to take care of all the details of procedure calls, encoding and decoding in a standard way. There are various implementation of XMLRPC available for many programming languages. I should note that the documentation linked above does not include all of the API currently implemented in the code, though it will eventually. I am currently still in the middle of designing it, implementing and documenting it at the same time.

As it currently stands, the fridge server has methods to login, check a user’s balance, transfer an amount to a local or remote (i.e. interfridge) user, make a purchase at the local fridge (I still have not yet decided the best way to handle interfridge purchases in the new scheme), list the current stock, and list other fridges with which the fridge is peered. I am writing a client library and simple command-line client in Ruby to test this as I go. The command-line client implements all the features just mentioned. I have not yet done much on the Java client, but that will come at some point. lorne has just started work on an iPhone client, which should be cool.

Felix Shi: You can always blog about cooking weird and wonderful dishes 😀

Weird and wonderful? Not sure about that. I made a batch of muesli and a chocolate cake on Sunday, as I mentioned. The weekend before I baked two batches of muffins (apple and sultana for the Skyline walk on Saturday, banana chocolate chip or something for a picnic on Labour Day with gringer, ja and xyzzy).

I am afraid my cooking of late has not been terribly interesting. Suggestions are welcomed, as are visitors interested in consuming baking. As always.



  1. I just realised I’d totally forgotten about that muffin recipe I was going to send you. Sorry – I’ll try to type it up over the weekend (the problem is it’s handwritten).

    Comment by fibby — 5 November 2009 @ 9:42 am

    • Oh yeah, I had forgotten too. Thanks, I should try baking those this weekend.

      Comment by qwandor — 5 November 2009 @ 10:49 am

  2. What about those weird sausage/spagetti things you made. Looked like worms eating the sausages!!

    Comment by Janet — 5 November 2009 @ 3:31 pm

    • True, though that was rather a while ago now and I cannot think of much more to say about them than I already have said.

      Comment by qwandor — 5 November 2009 @ 11:00 pm

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