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UTOSC 2012 talks of interest

By Jon Jensen
May 18, 2012

It’s been two weeks now since the Utah Open Source Conference for 2012. My fellow End Pointers wrote previously about it: Josh Ausborne about the mini Liquid Galaxy we set up there for everyone to play with, and Josh Tolley with a write-up of his talks on database constraints and KML for geographic mapping markup.

There were a lot of interesting talks planned, and I could only attend some of them. I really enjoyed these:

• Rob Taylor on AngularJS

• Brandon Johnson on Red Hat’s virtualization with oVirt, Spacewalk, Katello, and Aeolus

• Clint Savage about RPM packaging with Mock & Koji

• Daniel Evans on testing web applications with Capybara, embedded WebKit, and Selenium (which End Pointer Mike Farmer wrote about here back in December)

• Aaron Toponce on breaking full-disk encryption (I missed this talk, but learned about it from Aaron in the hallway track and his slides afterwards)

• Matt Harrison’s tutorial Hands-on intermediate Python, covering doctest, function parameters and introspection, closures, function and class decorators, and more.

I gave a talk on GNU Screen vs. tmux, which was fun (and ends with a live demo that predictably fell apart, and audience questions …

Keeping Your Apps Neat & Tidy With RequireJS

By Greg Davidson
May 17, 2012

RequireJS is a very handy tool for loading files and modules in JavaScript. A short time ago I used it to add a feature to Whiskey Militia that promoted a new section of the site. By developing the feature as a RequireJS module, I was able to keep all of its JavaScript, HTML and CSS files neatly organized. Another benefit to this approach was the ability to turn the new feature “on” or “off” on the site by editing a single line of code. In this post I’ll run through a similar example to demonstrate how you could use RequireJS to improve your next project.

File Structure

The following is the file structure I used for this project:

├── index.html
└── scripts
    ├── main.js
    ├── my
    │   ├── module.js
    │   ├── styles.css
    │   └── template.html
    ├── require-jquery.js
    ├── requirejs.mustache.js
    └── text.js

The dependencies included RequireJS bundled together with jQuery, mustache.js for templates and the RequireJS text plugin to include my HTML template file.

Configuration

RequireJS is included in the page with a script tag and the data-main attribute is used to specify additional files to load. In this case “scripts/main” tells RequireJS to load the main.js file …

Vim — working with encryption

By Terry Grant
May 16, 2012

On occasion I have to work with encrypted files for work or personal use. I am partial to a Linux environment and I prefer Vim as my text editor, even when I am only reading a file. Vim supports quite a few different ways of interfacing with external encryption packages. I only use two of those variations as described below.

Vim comes packaged with a default encryption mechanism referred to as VimCrypt in the documentation. I typically use this functionality as a temporary solution in a situation where my GPG is not immediately available, like a remote system that is not mine.

Using Vim’s default VimCrypt feature

Creating a new encrypted file or open a plain text file you wish to encrypt:

vim -x <filename></filename>

This will create a new file if it does not exist or open an existing file and then prompt you for a password. This password is then used as the key to encrypt and decrypt the specified file. Upon saving and exiting this file, it will be saved in this encrypted format using your crypt key.

You can also save and encrypt an open file you are currently working on like so. Please note this is a capital X:

:X 

This will also ask you for a password to encrypt …

Points of Interest

By Brian Buchalter
May 15, 2012

It’s been a fairly straight forward week at work, but I have stumbled a few interesting finds along the way this week.

Vim Adventures

Finally! A game based approach to learning Vim keyboard commands. I was hoping someone would do this. It’s just getting started (only two levels) and sadly, it looks like it’ll be charging money to unlock higher levels. However, some things are worth paying for. I’ve found just playing the first two levels a few times have helped retrain my brain to not take my fingers off the home row. It’s still quite buggy and seems to only work in Chrome. I found several times I needed to close all my Chrome windows after playing. Also, incognito mode seems to help with the bugs, as it disables all extensions you may have installed.

MySQL query comments in Rails

Ever wanted to know where that slow query was being called from? Well, if you’re using MySQL with your Rails 2.3.x or 3.x.x app, you can get debug information about what controller’s action made the call. Check out 37Signals new marginalia gem.

How to use EC2 as a web proxy

Kevin Burke provides a very detailed HOWTO article for working around restrictions you may experience in the course of an Internet …

SELinux Local Policy Modules

By Jon Jensen
May 11, 2012

If you don’t want to use SELinux, fair enough. But I find many system administrators would like to use it but get flustered at the first problem it causes, and disable it. That’s unfortunate, because often it’s simple to customize SELinux policy by creating what’s known as a local policy module. That way you allow the actions you need while retaining the added security SELinux brings to the system as a whole.

A few years ago my co-worker Adam Vollrath wrote an article on this same subject for Red Hat Enterprise Linux (RHEL) 5, and went into more detail on SELinux file contexts, booleans, etc. I recently went through the process of building an SELinux local policy module on RHEL 6 and RHEL 7 mail servers and found a few differences and want to document some of the details here. This applies to RHEL 5, RHEL 6, and RHEL 7, and near relatives CentOS, Scientific Linux, et al.

When under pressure …

If you’re tempted to disable SELinux, consider leaving it on, but in “permissive” mode. That will leave it running but stop it from blocking disallowed actions until you have time to deal with them properly. It’s as simple as:

setenforce 0

That will last until you reboot, unless otherwise …

Three Things: Rails, JOIN tip, and Responsiveness

By Steph Skardal
May 11, 2012

Here’s another entry in my Three Things series, where I share a few small tips I’ve picked up lately.

1. Rails and Dramas

Sometimes I think that since Rails allows you write code efficiently, [a few] members of the Rails community have time to overdramatize incidents that otherwise would go relatively unnoticed :) Someone with a good sense of humor created this website to track these dramas. While it’s probably a waste of time to get caught up on the personal aspects of the drama, some of the dramas have interesting technical aspects which are fiercely defended.

2. JOIN with concat

Recently I needed to perform a JOIN on a partial string match in MySQL. After some investigation, I found that I had use the CONCAT method in a conditional (in an implicit inner JOIN), which looked like this:

SELECT * FROM products p, related_items ri WHERE concat(p.sku, '%') = ri.id

In modern MVC frameworks with ORMs, databases are typically not designed to include data associations in this manner. However, in this situation, data returned from a third party service in a non-MVC, ORM-less application was only a substring of the original data. There may be alternative ways to perform this type …

UTOSC Recap

By Josh Tolley
May 10, 2012

I spent three days last week attending the Utah Open Source Conference, in company with Josh Ausborne and Jon Jensen. Since End Point is a “distributed company”, I’d never met Josh Ausborne before, and was glad to spend a few days helping and learning from him as we demonstrated the Liquid Galaxy he has already written about.

This time around, the conference schedule struck me as being particularly oriented toward front-end web development. The talks were chosen based on a vote taken on the conference website, so apparently that’s what everyone wanted, but front-end stuff is not generally my cup of tea. That fact notwithstanding, I found plenty to appeal to my particular interests, and a number of talks I didn’t make it to but wished I had.

I delivered two talks during the conference, the first on database constraints, and the second on Google Earth and the Liquid Galaxy as they apply to geospatial visualization (slides here and here, respectively). Though I couldn’t get past the feeling that my constraints talk dragged quite a bit, it was well received. Where possible I kept it as database-agnostic as possible, but no talk on the subject would be complete without mentioning …

Inherit an application by rewriting the test suite

By Brian Buchalter
May 8, 2012

One of my first tasks at End Point was to inherit a production application from the lead developer who was no longer going to be involved. It was a fairly complex domain model and had passed through many developers’ hands on a tight client budget. Adding to the challenge was the absence of any active development; it’s difficult to “own” an application which you’re not able to make changes to or work with users directly. Moreover, we had a short amount of time; the current developer was leaving in just 30 days. I needed to choose an effective strategy to understand and document the system on a budget.

Taking Responsibility

At the time I was reading Robert C. Martin’s The Clean Coder, which makes a case for the importance of taking responsibility as a “Professional Software Developer”. He defines responsibility for code in the broadest of terms.

Drawing from the Hippocratic oath may seem arrogant, but what better source is there? And, indeed, doesn’t it make sense that the first responsibility, and first goal, of an aspiring professional is to use his or her powers for good?

From there he continues to expound in his declarative style about how to do no harm to the function and …