Ubuntu 18.04 uses systemd to manage services.

There are basically two commands for listing all services and manipulating the state of a certain service: service and systemctl:

• service manages System V init scripts
• systemctl controls the state of the systemd system and service manager. It is backwards compatible to System V and includes the System V services

Therefore I prefer to use systemctl.

See which services are there

>systemctl list-units -a --type=service
  UNIT                                 LOAD     ...

Recently I made an upgrade from Bootstrap 3 to Bootstrap 4 in a bigger project. Here are some tips how to plan and perform such an upgrade. The effort will scale with the size of the project and its structure. If your stylesheets already follow strict rules, it may take less time to adapt them to the new version.

Preparation

There are several gems and libraries that works well with bootstrap or provide at least stylesheets/plugins to easily integrate the bootstrap theme. But very often they only work with specific version or are no long...

If you want Sidekiq to be able to talk to Redis on staging and production servers, you need to add the following to your configuration:

# config/initializers/sidekiq.rb
require 'sidekiq'

Sidekiq.configure_client do |config|
  config.redis = { url: REDIS_URL }
end

Sidekiq.configure_server do |config|
  config.redis = { url: REDIS_URL }
end

The following step may be skipped for new Sidekiq 6+, since it isn't recommended anymore to use a global redis client.

# config/initializers/redis.rb
require 'redis'
require_relativ...

Redis.current will be removed without replacement in redis-rb 5.0.
Version 4.6.0 adds deprecation warnings for Redis.current and Redis.current=:

`Redis.current=` is deprecated and will be removed in 5.0.

If your application still uses Redis.current, you can only fix it by no longer using it. Here is how.

Redis.new when you need it

You can easily instantiate a Redis client when you need it.

There is probably already a constant like REDIS_URL that you use to configure Sidekiq or similar. So just use that one.

``...

Ubuntu has decided to disable PDF processing because ImageMagick and the underlying Ghostscript had several security issues.

When your Ghostscript is up to date (and receiving updates regularly), you can safely reactivate PDF processing on your computer like this:

1. Open /etc/ImageMagick-6/policy.xml (requires sudo)
   • For older versions of Ubuntu (or possibly ImageMagick), the path is /etc/ImageMagick/policy.xml
2. Remove/Comment lines after <!-- disable ghostscript format types -->

If you need ...

Let's say you have a form that you render a few times but you would like to customize your submit section each time. You can achieve this by rendering your form partial as layout and passing in a block. Your template or partial then serves as the surrounding layout of the block that you pass in. You can then yield back the form to the block and access the form in your block.

-# record/_form.haml

= form_for record do |form|
  -# ...
  .form-actions
    yield(form)
  

In order to make your template record/_form.haml accept a...

There is a new card about how to do this with the new AWS Command Line Interface

At first you need the IAM Cli Tools.
-------------------------------------------------------------------------------------------------------------...

The linked GitHub repository is a bit like our "dev" cards deck, but groomed from a single person (Josh Branchaud). It includes an extensive list of over 900 TILs on many topics that might be interesting for most of us. (e.g. Ruby, Rails, Git, Unix..)

Ruby

Here is an excerpt of all the Ruby TILs that were new to me. I encourage you to take your time to skim over the original list as well!

• Assoc For Hashes
  • `Hash#ass...

If you are connected with a network that forbids e-mail traffic but allows SSH, you can tunnel your e-mail connection through a trusted, intermediary server:

 sudo ssh -i /home/local-user/.ssh/local-user.key -L 143:mail-server.tld:143 remote-user@trusted-server.tld

Explanation for the command above:

| sudo | Secure ports may only be forwarded by root |
| ssh -i /home/local-user/.ssh/local-user.key | Private half of your SSH key for the trusted server |
| -L 143:mail-server.tld:143 | Forward connections to port 143 on your mail s...

In Selenium features the server and client are running in separate processes. Therefore, when mocking time with a tool like Timecop, the browser controlled by Selenium will still see the unmocked system time.

timemachine.js allows you to mock the client's time by monkey-patching into Javascript core classes. We use timemachine.js in combination with the Timecop gem to synchronize the local browser time to the ...

If you get this warning on your local machine one of these steps might help:

Rebuilt the gem with the newer library

gem install --no-rdoc --no-ri nokogiri -- --with-xml2-include=/opt/local/include/libxml2 --with-xml2-lib=/opt/local/lib

If you still get the error, try to uninstall all nokogiri versions with

gem uninstall nokogiri

and install nokogiri again.

Fixing the issue on servers

However, on our servers this probably will not work. On the server, gems are stored in the ../shared/bundle/ruby/:version/gems dire...

When deploying code with Capistrano (depending on your configuration) at some point Capistrano tries to check out code from your repository. In order to do so, Capistrano connects to your repository server from the application server you're deploying to with SSH. For this connection you can use two SSH keys:

• the user's ~/.ssh/id_rsa [default]
• the very same key you used for connecting to the application server - forwarded automatically to the git repository.

If you prefer the second way, add this to deploy.rb:

ssh_options[:forwar...

If you're experiencing problems with your Google Chrome installation after an update, it might help downgrading Chrome to check if the problem disappears. Keep in mind though that running outdated software, especially web browsers, is in most cases not a good idea. Please verify periodically if you still need to run the old version or if an even more recently updated version fixes the problems introduced in your version.

Here's how to get old versions of Chrome for your Ubuntu installation:

First, go to [UbuntuUpdates](https://www.ubuntuup...

This is a personal post-mortem analysis of a project that was mainly build to provide a REST API to mobile clients.

For the API backend we used the following components:

• Active Model Serializer (AMS) to serializer our Active Record models to JSON.
• JSON Schema to test the responses of our server.
• SwaggerUI to document the API.

It worked

The concept worked really good. Here are two points that were extraordinary compared to normal Rails project with many UI components:

• Having a Rails application, that has no UI components (only...

Debugging your integration tests, that run a headless Chrome inside a docker image, is tricky.

In many cases you can connect your Chrome to a remote docker container like docker-selenium, which should be the preferred way when you try to inspect a page within your integration test.

Otherwise you might be able to start your docker container with --net=host and access your local chromedriver in the host address space host.docker.internal.

If both options above don't work for you here is a...

If you want to see how long your database queries actually take, you need to disable MySQL's query cache. This can be done globally by logging into a database console, run

SET GLOBAL query_cache_type=OFF;

and restart your rails server.

You can also disable the cache on a per query basis by saying

SELECT SQL_NO_CACHE * FROM ...

You also probably want to disable Rails internal (per-request) cache. For this, wrap your code with a call to ActiveRecord::Base.uncached. For example, as an around_filter:

d...

Capistrano 3 has a doctor task that will print information about

• Environment: Ruby, Rubygems and Bundler versions
• List of Capistrano gems and whether an update is available
• All config variables and their values
• Capistrano server config

$ bundle exec cap staging doctor

If your Webpack build is slow, you can use the Speed Measure Plugin for Webpack to figure out where time is being spent.
Note that at time of writing, Webpack 5 seems unsupported. It works on Webpack 4, though.

Wire it into your application as described in the library's documentation:

1. Hook into your environment file, e.g. config/webpack/development.js and instead of exporting your Webpack config,...

Building application assets with esbuild is the new way to do it, and it's great, especially in combination with Sprockets (or Propshaft on Rails 7).
You might be missing some convenience features, though.

Here we cover one specific issue:
Once you have started your development Rails server and esbuild with the --watch option (if you used jsbundling-rails to set up, you probably use bin/dev), esbuild will recompile your assets upon change, but build errors will only be printed to the terminal. Your application won't complain about them ...

If you use a newer SSH key generated with the ED25519 algorithm instead of RSA (see Create a new SSH key pair), the deployment with Capistrano may fail with the following message:

The deploy has failed with an error: unsupported key type `ssh-ed25519'
net-ssh requires the following gems for ed25519 support:
 * ed25519 (>= 1.2, < 2.0)
 * bcrypt_pbkdf (>= 1.0, < 2.0)
See https://github.com/net-ssh/net-ssh/issues/565 for more information
Gem::LoadError : "ed25519 i...

When you have a complex recipe setup with multistage deployment you may run into this error:

`role_list_from': unknown role `something' (ArgumentError)

Consider this task definition:

namespace :foo do
  task :bar, :roles => :something do
    # do crazy stuff
  end
end

Whenever we call foo.bar in our recipe, Capistrano will fail if you deploy to a stage where none of the servers has the role the error complains about, "something" in this case.

However, you can [hack around it](http://groups.google.com/group/ca...

Using Ruby 1.8.7 you will not be able to use the maximum versions Rubygems 1.8.30 and Bundler 1.17.3 with https://rubygems.org/ anymore. This is a result of a server certificate on December 5th, 2020. The resulting errors will look like following:

• TypeError: can't modify frozen object
• Could not verify the SSL certificate for https://rubygems.org/*
• Bundler::Fetcher::CertificateFailureError: Could not verify the SSL certificate for https://index.rubygems.org/versions.
• `Error fetching data: hostname was not m...

When making cross-domain AJAX requests with jQuery (using CORS or xdomain or similar), you will run into issues with HTTP headers:

• jQuery will not set the X-Requested-With header. On your server, requests will not look like AJAX requests (request.xhr? will be false).
• jquery-ujs will not set CSRF headers.

This is by design and improves secu...

Web forms can be made much more usable with a few HTML attributes. Short summary:

• type: Tells browsers about the input data type. Mobile browsers will select a virtual keyboard based on this value. Some browsers will add simple validation, e.g. for type email.
• inputmode: Direct hint about the virtual keyboard to use. Inferred from type, but can be very handy when ...