Friday, February 21, 2014

Software developer competency matrix

One of the ACCU mailing lists currently has a thread going where the challenges of hiring good C++ developers is being discussed. Someone posted a link to a software developer competency matrix. I thought it was rather good so decided to blog about so I didn't forget and so that I would have something to go back to for reference purposes.

Someone else in the thread posted that they had been inspired by another one but I found that was much more career/corporation oriented. The first one is much better for a techie to measure up against. It can be used to measure oneself or if you are involved the hiring game.

Tuesday, February 04, 2014

Reverse engineering a sybase database

The world seems to have decided on Oracle. But every now and then as a freelancer I come across a system that uses sybase. Usually it is an ancient legacy system that cannot be turned off for some reason, so sybase soldiers on. In such cases it is often useful to be able to reverse engineer the schema. This is where SchemaSpy comes in.

SchemaSpy requires graphviz, aka dot. The final generated output is a set of web pages and a set of dot files. I suspect that the dot is used to generate the image files used on the web pages, so dot is needed even if you never want to look at the dot files directly. Dot can be installed on windoze by merely unpacking the zip and adjusting PATH.

Some sybase installations have internationalisation set up in such a way that the URL needs to end in ?charset=iso_1. schemaSpy forms the URL based on a config it reads so the config must be extracted from the schemaSpy jar (a zip).

I first came across the charset issue when setting up database connections in DbVisualizer. I found
this web page which has the solution. This is also the solution for the same problem in schemaSpy.

Edit a copy of this config, appending ?charset=iso_1 to the name of the URL, then invoke schemaSpy with this command line (the sybase config filename is

Note that the schema dbo must be specified, otherwise it tries to use the username as the schema name.

java -jar schemaSpy_5.0.0.jar -t -db <dbName> -u <userid> -p  <password> 
  -o <outputDir> -host <stringFromSybaseInterfaceFile> -port <portNumber>
  -dp <pathnameTojconn3.jar> -s dbo

Saturday, February 01, 2014

a high-volume, low-latency market data processing system implemented with IBM middleware

Way back in 2003 I worked on a very interesting C++ CORBA project. It was to do with the near real-time distribution of market data to multiple subscribers. Most of the work was contracted out to that well known consultancy, Object Computing Inc. IMHO they did a very good job. One of the things that made it interesting was the way they used an XML configuration file to describe a pipeline of components through which the messages passed. This used the Configurator pattern described in POSA.

Back in January 2013 I came across a system that reminded me strongly of the one I worked on. I found an article in the Wiley Online Library (WOL). Unfortunately the WOL article is behind a paywall. Luckily, the authors also made it available in several other places including one where you get get it as a PDF.

This is a reminder to me that OCI aren't the only ones to develop a system like the one I saw and that there is very good write up about that other system. Here is what is says in the abstract:

A stock market data processing system that can handle high data volumes at low latencies is critical to market makers. Such systems play a critical role in algorithmic trading, risk analysis, market surveillance, and many other related areas. We show that such a system can be built with general-purpose middleware and run on commodity hardware. The middleware we use is IBM System S, which has been augmented with transport technology from IBM WebSphere MQ Low Latency Messaging. Using eight commodity x86 blades connected with Ethernet and Infiniband, this system can achieve 80 μsec average latency at 3 times the February 2008 options market data rate and 206 μsec average latency at 15 times the February 2008 rate.