Using Thin for development (with SSL)

Note: These instructions are for a quick per-project setup and may require you to change code. If you generally need SSL for development, you probably want to use Passenger.


  1. Create a directory .ssl in your home directory. Go there and create a self-signed certificate. It is important to enter localhost.ssl as Common Name when asked. This is to mak...

MySQL 5.7.5 enables `ONLY_FULL_GROUP_BY` mode per default

When using GROUP BY, MySQL now complains if the SELECT includes columns which are not part of the GROUP BY.

Reason:

There could be multiple values for those columns per group but only one value can be picked for the results.

The default behaviour of MySQL prior to version 5.7 will not complain and arbitrarily choose a value. But this leads to non-deterministic results. So MySQL now has enabled the only_full_group_by setting by default to prevent this.

In Rails this could lead to some trouble, because scopes do not have sp...

Jasmine: Testing AJAX calls that manipulate the DOM

Here is a Javascript function reloadUsers() that fetches a HTML snippet from the server using AJAX and replaces the current .users container in the DOM:

window.reloadUsers = ->
  $.get('/users').then (html) ->
    $('.users').html(html)

Testing this simple function poses a number of challenges:

  • It only works if there is a <div class="users">...</div> container in the current DOM. Obviously the Jasmine spec runner has no such container.
  • The code requests /users and we want to prevent network interaction in our uni...

Virtual attributes for array fields

When a has_many association basically serves to store a list of associated strings (tags, categories, ...), it can be convenient to represent this association as a string array in the containing model. Here is an example for this pattern from the acts-as-taggable-on gem:

post = Post.last
p post.tag_list # ['foo', 'bar', 'baz']
post.tag_list = ['bam']
p post.tag_list # ['bam']

This string array tag_list is magical in several ways:

  • It is read from and written to a `has...

How to fix: Gems are unavailable although they are installed

  • If Rails or Rake are complaining about a missing gem that is listed in your Gemfile.lock and the listed version is properly installed, something is seriously wrong and needs to be fixed.
  • If you accidently executed bundle install some_gem although you wanted bundle update some_gem

What is wrong

Let's say your Gemfile asks for some-gem which you can see when running gem list but bundle show some-gem just gives you an error:

Could not find gem 'some-gem', in any of the sources

Another indicator: Doing a `...

Sharing cookies across subdomains with Rails 3

To achieve this goal you have to setup the session store like the following example:

  MyApp::Application.config.session_store(
    :cookie_store,
    {
      :key => '_myapp_session',
      :domain => :all, # :all defaults to da tld length of 1, '.web' has length of 1
      :tld_length => 2 # Top Level Domain (tld) length -> '*.myapp.web' has a length of 2
    }
  )

The invconvenient side effect for local development

… or: Why do I get "Can't verify CSRF token authenticity" even if csrf token is present?

As `:domain => :all...

Speed up file downloads with Rails, Apache and X-Sendfile

When you use the send_file method to send a local file to the browser, you can save resources on the application server by setting the :x_sendfile option to true. This option is activated by default for Rails 3, so you need to understand this.

What this option does is not to send any data at all, but rather set the local file path as a new response header:

X-Sendfile: /opt/www/awesome-project/shared/downloads/image.png

When the response comes back from Rails to...

Ruby constant lookup: The good, the bad and the ugly

In Ruby, classes and modules are called constants. This card explains how Ruby resolves the meaning of a constant.

The good

E. g. in the following example, Array could mean either Foo::Array or simply Array:

class Foo
  def list
    Array.new
  end
end

What Ruby does here is to see if the name Array makes sense inside of Foo::, and if that fails, resolves it to ::Array (without a namespace).

The bad

This is relevant for old Ruby versions. Ruby 2.5+ removes top-level constant lookup whi...

Howto: Select2 with AJAX

Select2 comes with AJAX support built in, using jQuery's AJAX methods.
...
For remote data sources only, Select2 does not create a new element until the item has been selected for the first time. This is done for performance reasons. Once an has been created, it will remain in the DOM even if the selection is later changed.

If you have a huge collection of records for your select2 input, you can populate it via AJAX in order to not pollute your HTML with lots of <option> elements.

All you have to do is to provide...

Dump your database with dumple

This tool is used on our application servers (and called when deploying) but it also works locally.
Just call dumple development from your project directory to dump your database.


This script is part of our geordi gem on github.

Yarn: How to recognize that you are using a different node version than your colleagues

The issue in this card can occur if the node_modules directory is checked into your Git repository. We usually recommend to exclude node_modules from version control.

In any case you should document which version of node to use in your project in a .nvmrc file.


I saw a strange behaviour after we introduced webpack in one of our projects and finally found out the reason: The person who committed the files used a node version that is older than mine.

Every time I wanted to run my rai...

Plotting graphs in Ruby with Gruff

Geoffrey Grosenbach has created Gruff for easily plotting graphs. It is written in pure Ruby and integrates with Rails applications.

It provides features as automatic sizing of dots and lines (the more values, the thinner the graph's elements), custom or predefined themes, different styles (bar, line, dot and many more) and multiple graphs in one chart.

Installation

In your Gemfile:

gem 'rmagick', :require => false
gem 'gruff'

Then run bundle install (and don't forget to restart your development server.)

Usage

This i...

How to: Client-side language detection

When you have a localized website, you may want to redirect users to their preferred language when they visit the root path.
Here is how to do it without a server-side component (like a Rails application).

  • Use JavaScript's navigator.language (real browsers and IE11+) and navigator.userLanguage (old IEs).
  • Use a <meta> refresh as fallback
  • Provide buttons for paranoid users that disabled JavaScript and meta refreshs.

JavaScript

The following JavaScript will try to auto-detect a user's preferred language.

It understands string...

Speeding up ssh session creation

Establishing a new SSH connection usually takes only a few seconds, but if you’re connecting to a server multiple times in succession the overhead starts to add up. If you do a lot of Git pushing and pulling or frequently need to SSH to a dev server, you’ve probably felt the pain of waiting for SSH to connect so you can get back to doing work.

Deployment Script Spring Cleaning - GitHub

As we get ready to upgrade our servers I thought it’d be a good time to upgrade our deployment process. Currently pushing out a new version of GitHub takes upwards of 15 minutes. Ouch. My goal: one minute deploys (excluding server restart time).

Juggernaut

The Juggernaut plugin for Ruby on Rails aims to revolutionize your Rails app by letting the server initiate a connection and push data to the client. In other words your app can have a real time connection to the server with the advantage of instant updates.

Sailing down the Hudson with RVM - GIANT ROBOTS SMASHING INTO OTHER GIANT ROBOTS

We recently decided our CI server needed an overhaul. I really enjoyed Integrity as a build server, but after trying out Hudson it’s hard to say I want to go back. Hudson has several huge advantages.

Spreewald: Content-Disposition not set when testing a download's filename

Precondition

  • You are not using javascript tests
  • The file is served from a public folder (not via controller)

Problem description

If you deliver files from a public folder it might be that the Content-Disposition header is not set. That's why the following spreewald step might raise an error:

Then I should get a download with filename "..."
expected: /filename="some.pdf"$/
     got: nil (using =~) (RSpec::Expectations::ExpectationNotMetError)

Solution

One solution...

Good real world example for form models / presenters in Rails

We have often felt the pain where our models need to serve too many masters. E.g. we are adding a lot of logic and callbacks for a particular form screen, but then the model becomes a pain in tests, where all those callbacks just get in the way. Or we have different forms for the same model but they need to behave very differently (e.g. admin user form vs. public sign up form).

There are many approaches that promise help. They have many names: DCI, presenters, exhibits, form models, view models, etc.

Unfortunately most of these approaches ...

Drag'n'drop in trees: I went to town

For my Gem Session project Holly I ran the Ironman of drag'n'drop implementations:

  • Dragging in nested lists
  • User-definable order of items
  • Complicated item elements with super-custom CSS and other Javascript functionality
  • Items that can be both leaves and containers of other items
  • has_ancestry on the server side

Things I learned:

  • Be ready to write a lot of CSS. You need to indicate what is being dragged, where it will be dropped, if it is dropped above, below o...

MySQL shell: Vertical vs horizontal layout

When talking to your MySQL server via a mysql shell, you can terminate queries by ; or \G -- the latter gives you a vertical output.

You know this:

mysql> SELECT * FROM users;
+----+---------+---------------------+-----------------+
| id | name    | email               | greeting        |
+----+---------+---------------------+-----------------+
|  1 | Alice   | alice@example.com   | Hello world!    |
|  2 | Bob     | bob@example.com     | Hello universe! |
|  3 | Charlie | charlie@example.com | Hi mom!    ...

Distribute files from a private bucket on AWS S3

Given you store files on Amazon S3 and you need to stream those files out to people while you don't want them to be able to distribute the content simply by sharing the S3 URL.

You could either mark the bucket as private and fetch the appropriate files from S3 to your application server and stream them to the client finally. While this is possible, I'd recommend to use what AWS calls "Query String Authentication".

If you're using Paperclip you can chose between two sto...

Enable NewRelic monitoring [for Rails] on specific hosts only

If you need to enable NewRelic monitoring on certain machines within the same Rails environment, a simple solution is to utilize the respective hostnames of you machines.

For example, if you have 8 application servers (e.g. app1.example.com, app2.example.com, ...) and want to enable NewRelic on app1 and app2 only, utilize those steps to do so:

  1. Put the attached file into your config directory (config/custom_new_relic_configuration.rb).
  2. Specify on which hosts NewRelic should be enabled (see NEWRELIC_HOSTS constant and list ...

Restangular: How to remove an element from a collection without breaking restangular

So you have a restangular collection and you want to remove an element from it, after you've successfully deleted it from the server.

The README suggests to say something like $scope.users = _.without($scope.users, user). While that works at first glance (the element is no longer in your collection), it will break horribly when you want to use restangular's attributes on that collection.

This...