Upgrading application rails version from 5.0 to 5.1 is easier than doing from 4.2 to 5.0, since it's only a minor version update. However, there might still be quite a few things to address either from framework changes or due to outdated gems dependency.

RSpec is a popular test framework in ruby.

Rails framework autoloads constants so that in environments like development or test, the app does not need to load everything into memory before serving requests. However, autoloading is known to be thread unsafe in rails (at least for versions less than 6), and if you happen to be using threaded servers like puma or webrick, it's very easy to step on unexpected issues caused by multiple threads.

Upgrading rails to a new major version can be tricky because there might be many breaking changes from the framework itself or from many gems used in project that will become either deprecated or unsupported. However, it can also go smooth if done in a right procedural way. This post shares the procedure based on my recent hands-on experience in upgrading rails from 4.2.11 to 5.0.7.2 for our API server. Please be kindly noted that depending on project configuration or dependencies, the upgrading steps might be slightly different for various projects.

Ruby http request with cookie.

Ruby parallel gem use cases.

Rack is the gem that provides the interface between web frameworks (ruby on rails, sinatra) and web servers (webrick, puma, unicorn) in ruby world.

Rake is a Make-like task runner in Ruby. First define a list of tasks in ruby syntax in a Rakefile and then invoke the task with rake command.

Bundler is for dependency management in ruby projects.

A ruby gem is a software package that contains a reusable ruby application or library.