In domain driven design (DDD) we talk a lot about entities; objects that have identity and lifetimes that typically outlive their values. e.g. An account lives longer than the email address, name, postal address etc. Value types might be mentioned in discussion but then quickly fade. This is a shame because they are the fundamental building blocks, after all they hold the application data. One reason for this lack of attention is that we have some pretty powerful substitutes already supported by our implementation languages - int, double, string. But is that really good enough?
Working with small teams is a lot of fun and I find it fairly easy to keep track of what is happening with version control and build systems. Errors and failures don’t come up that often and when they do they can quite often get solved there and then. On larger projects or working in a large organisation it’s impossible to keep track of everything. There are too many moving parts and changes. Incidents are more frequent and their impact much larger. A broken build or build system can affect 10s or 100s of people. For these larger development projects I find I have to collect and chart data, looking for tends and anomalies and then delve deeper into the data if and systems if there are problems.
How can we get the benefits of IoC containers at a higher level - the services that we deploy into environments? Typical service tiers are implemented with a fronting load balancer that allocates servers to satisfy requests. Applications or services that need these services are give domain or IP information of the load balancers and the load balancers are given details of the servers running instances of the services that they need. Essentially each system with dependencies news an instance of its dependencies. Inverting this dependency requires a container but it leads to some interesting advantages.
In his keynote ‘This is water’ Neal Ford talks about “Yesterday’s best practices become tomorrow’s anti-patterns”. This seems to be the case for application servers like WebSphere, WebLogic and JBoss.
If Conway’s law applies the how we set up and organise teams should either be aligned to the architecture of the applicaiton or system being developed or application/system architecture will shift to match the team structure.
The idea for lazybuilder came up during a recent coding dojo doing code kata. We were using Vim and a separate terminal to run the tests. Switching back and forth between two windows when trying to move quickly seemed like a waste of time.
After a long wait CODE keyboards are available again and I received mine last night. I have to confess that I am a bit of a keyboard junkie. I am reluctant to count them all but I am edging into double digits :(.
Browsing some blogs recently I came across some interesting C++11 lambda code and thought it would be cool to try it out for myself. The idea of spinning up a project or even putting a new test in an existing project did not feel right. Wouldn’t a C++ REPL be useful for just these occasions?
I have been spending time recently writing command line apps in C++11. Each time I wanted a way of handling command line arguments flexibly. I chose to use the boost::program_options library. The documentation is pretty good but there are some assumptions (aliased namespace) and the example code is broken up with paragraphs of text explaining what the code does.
I am about to embark on a new Java project so I thought I would take a look at the current state of build tools for Java projects. First I thought I would draw up some assessment criteria to use as a loose guide. This is what I came up with:
I like to commit code frequently when working on a project. I also like to use the command line for building, testing and committing code. So I thought it would be nice to have a way to check the build status from the command line. I have been wanting to write something in C++11 and a small lightweight command line tool seemed like a good opportunity.
Continuous Deployment is the act of automatically deploying an application every time the build is successful. I am currently working with a development team that is working towards continuous deployment as part of their continuous delivery adoption plans. The system involves several internal web services which seemed like a good place to start working on not only automating the deployments but maintaining a very high degree of up-time during those deployments. Automating deployments involves both development and techops groups so I thought I would search for some worked examples that would help illustrate the techniques and steps required. I found several blogs and articles talking about different approaches but no worked examples.
Following up on the next_permutation from a couple of weeks ago word finder uses next_permutation to find words in character sequences. Uses the aspell C api to look up each permutation. Searching for 3,4,5 and 6 character words in a 6 character sequence takes about 200ms.
Graham Brooks: Architect, Software Engineer