Problem

Sometimes, when working with docker engine on CI systems, certain type of errors could arise from the challenging restrictions or limits on the environment. This is typical with the inherent server-client architecture of docker.

Here’s one of the problems that I’ve seen recently. When a client is connecting to dockerd in order to build an application image or prepare and pull external images, the server reports this issue:

failed to prepare a4mv4dh8qcq283c7x47a4nwpg: devmapper: Thin Pool has 161986 free data blocks which is less than minimum required 163840 free data blocks. Create more free space in thin pool or use dm.min_free_space option to change behavior

It’s advised that using universally unique identifiers (UUIDs) for exposed resource identifiers is more secure, and convenient for database distribution.

As expected, it’s relatively simple to configure Active Record to generate with UUID primary key based migrations.

Setup

Here are the steps:

1. Setup the default generation inside config/application.rb:

   # config/application.rb
      
   module SampleApp
     class Application < Rails::Application
       ...
       # Change the primary key default type to UUIDs.
       config.generators do |g|
         g.orm :active_record, primary_key_type: :uuid
       end
      end
   end
   

In many times you may find yourself in need for optimzing rapidly a bunch of images in your hands. There are handy utility libraries that can help you reduce image sizes with simple commands in the terminal. The following lists some of these tools:

1. OptiPNG: Advanced PNG Optimizer:

Get it for Mac OS X:

brew install optipng

For Linux Ubuntu:

apt-get install optipng

To optimize an image, run:

optipng <img-name>.png

In the past week, I’v been deploying a Sinatra app to AWS Elastic Beanstalk. In development environment, everything was working just fine, but when I published the application and tested it in production, I encountered a weird problem in one of the templates that was supposed to be supporting uft-8 text without any issues.

Symptoms

The error was appearing in one of the .erb view files that contains a textarea field. When it is populated with a non English text at the server, the application crashes with 500 code. Here’s a fragment of the error stack trace:

Recently, I’ve read Oslen Russ’s “Eloquent Ruby” and it was delightful read overall.

The book has a considerable reputation among the community programmers. It’s divided into (4) units on Ruby foundations and the software process practices.