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Terminator: do not broadcast to other windows

Terminator has a cool feature that allows you to split your terminal into many panels and type in all of them at the same time. It's called broadcasting and can be enabled by pressing Alt+a (and disabled by Alt+o).

However, in some circumstances it will also be broadcasted to other running instances of Terminator. This probably is not what you want and could be very dangerous (e.g. if you're logged in to a production server in a terminal that is on another workspace).

To prevent the broadcast from affecting other windows, go to `Prefer...

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How to let passenger restart after deployment with capistrano

Phusion Passenger changed the way how it gets restarted several times. Through the project's history, these all were valid:

  • touch tmp/restart.txt
  • sudo passenger-config restart-app /path/to/app
  • passenger-config restart-app /path/to/app

You should not need to know which one to use. Instead, the capistrano-passenger gem will choose the appropriate restart mechanism automatically based on your installed the passenger version.


  1. Add to your Gemfile:

    gem 'capistr...
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Passive event listeners may speed up your scroll and touch events

Scroll and touch event listeners tend to be computationally expensive as they are triggered very often. Every time the event is fired, the browser needs to wait for the event to be processed before continuing - the event could prevent the default behavior.
Luckily there is a concept called passive event listeners which is supported by all modern browsers.

Below are the key parts quoted from WICG's explainer on passive event listeners. See [this demo video](


How to negate scope conditions in Rails

Rails does not offer a "vanilla" way of negating an ActiveRecord scope. Here are two ways to do it yourself without too much effort.


class User
  scope :admins, -> { where(role: ['admin', 'superuser'] }
  # ...

Now what if we want a scope of users that are not admins? While you could declare a second scope like scope :non_admins, -> { where(role: ['guest', 'editor']) }, there are ways to use the opposite of the admins scope.

Option A: Subquery

You could just use a subquery. Doing that with scopes is easy...


CarrierWave: How to remove GIF animation

When accepting GIF images, you will also accept animated GIFs. Resizing them can be a time-consuming task and will block a Rails worker until the image is processed.

Save yourself that trouble, and simply tell ImageMagick to drop any frames but the first one.

Add the following to your uploader class:

process :remove_animation


def remove_animation
  if content_type == 'image/gif'
    manipulate! { |image| image.collapse! }

You may also define that process for specific versions only (e....

Migrate gem tests from Travis CI to Github Actions with gemika

We currently test most of our gems on Travis CI, but want to migrate those tests to Github Actions. This is a step-by-step guide on how to do this.

Note that this guide requires the gem to use gemika.

  1. Go to a new "ci" branch:
    git checkout -b ci
  2. Update gemika to version >= 0.5.0.
  3. Have gemika generate a Github Actions workflow definition by running
    mkdir -p .github/workflows; bundle exec rake gemika:generate_github_actions_workflow > .github/workflows/test.yml



Debugging SPF records

While debugging a SPF record I found to be very helpful.

  • it lists all IPs that are covered by the SPF record
  • shows syntax errors
  • helps you debugging errors like DNS lookup limit reached
  • it also lets you test a new SPF strings before applying it. This can save you time as you don't have to loop with operations

Also the advanced check at has a very good interface to test new SPF policies.

PostgreSQL: Importing dumps created with newer versions

When importing a dump created on a server that has a more recent pg_dump version you might get an error like

$ geordi dump staging -l
# Sourcing dump into the project_development db
pg_restore: [archiver] unsupported version (1.14) in file header
x An error occured loading staging.dump

On my machine I had psql version 10.14 which was the most recent package from the standard repository. The server, however, had pg_dump version 12.4.

The issue could be fixed by [installing postgres 12 from the PostgreSQL APT-Repositories]...

Rails: How to restore a postgres dump from the past

It sometimes happen that a database dump, that would want to insert into your development database, does not match the current schema of the database. This often happens when you have an old dump, but your current setup is up to date with the the master.

Hint: In most cases it is sufficient to delete and recreate the local database in order to import the dump. If any problems occur, proceed as follows:

1. Figure out the original migration status of the dumpfile

  • Convert your dump to plaintext: psql some.dump > some.dump.plain
  • ...

Keeping web applications fast

Our applications not only need to be functional, they need to be fast.

But, to quote Donald Knuth,

premature optimization is the root of all evil (or at least most of it) in programming

The reasoning is that you should not waste your time optimizing code where it does not even matter. However, I believe there are some kinds of optimizations you should do right away, because

  • they are either obvious and easy
  • or they are very hard to do optimize later

This is an attempt to list some of those things:

On the server


Security issues with hash conditions in Rails 2 and Rails 3

Find conditions for scopes can be given either as an array (:conditions => ['state = ?', 'draft']) or a hash (:conditions => { 'state' => 'draft' }). The later is nicer to read, but has horrible security implications in some versions of Ruby on Rails.

Affected versions

Version Affected? Remedy
2.3.18 yes Use chain_safely workaround
3.0.20 no ...
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QueryDiet 0.7.0 released

We released a new version of our gem QueryDiet.

0.7.0 2020-09-24

Compatible changes

  • Added: CSP support for query diet widget (#23)
  • Added the CHANGELOG file.

You can pass whether to use a nonce for style and script tags.
Note that the key must be a symbol like in the example below, otherwise it defaults to false.

<%= query_diet_widget(nonce: true) if Rails.env.development? %>

In your content security policy initializer of...

How to implement simple queue limiting/throttling for Sidekiq

The sidekiq-rate-limiter gem allows rate-limiting Sidekiq jobs and works like a charm. However, it needs to be integrated on a per-worker basis.

If you want to limit a whole queue instead, and if your requirements are simple enough, you can do it via a Sidekiq middleware yourself.

Here is an example that limits concurrency of the "mailers" queue to 1. It uses a database mutex via the [with_advisory_lock](

Rails: How to list all validations on a model or an attribute

If a model inherits from others or uses many concerns / traits, it might be hard to see in the code which validators it has.
But fortunately there's a method for that:

irb(main):002:0> pp UserGroup.validators
  @delimiter=[true, false],
  @options={:in=>[true, false], :allow_nil=>false}>,
  @delimiter=[true, false],
  @options={:in=>[true, false], ...

Always, always declare your associations with symbols

Never ever declare your associations with a string, especially when doing metaprogramming. A common mistake is something like

class Page < ActiveRecord::Base
  %w[main sub].each do |type|
    belongs_to "#{type}_title"

class Page < ActiveRecord::Base
  %w[main sub].each do |type|
    belongs_to :"#{type}_title"

Always convert to a symbol, otherwise you'll have [all](/makandra/4177-bugfix-rails-does-not-find-an-association-when-it-is-named-w...


Don't assign time values to date attributes

Do not pass times to date attributes. Always convert times to dates when your application uses time zones.


A time-zoned Time attribute on a Rails record is converted to UTC using to_s(:db) to be stored, and converted back into the correct time zone when the record is loaded from the database. So when you are not on UTC, time objects will be converted as follows.

>> Time.current
=> Fri, 15 Mar 2013 11:56:03 CET +01:00
>> Time.current.to_s(:db)
=> "2013-03-15 10:56:03" # This is now UTC


That will...

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What edge_rider offers you

edge_rider is Power tools for ActiveRecord relations (scopes). Please note that some of the functions edge_rider provides have native implementations in newer rails versions.

Useful in applications


Edge Rider gives your relations a method #traverse_association which returns a new relation by "pivoting" around a named association. You can traverse multiple associations in a single call. E.g. to turn a relation of posts into a relation of all posts o...

How to include Sidekiq job IDs in Rails logs

When logging in Rails, you can use the log_tags configuration option to add extra information to each line, like :request_id or :subdomain. However, those are only valid inside a request context and have no effect when your application is logging from inside a Sidekiq process.
This includes custom as well as any framework logs, like query logging from ActiveRecord.

Since Sidekiq Workers run inside threads of a single process, running multiple jobs in...

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