Linked content

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...

Linked contentRepeats

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...
Linked contentAuto-destruct in 36 days

Updated: Showing a custom maintenance page while deploying

Added a section "manual mode" in case you don't have capistrano 2.

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]...


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


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](

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...


How to make your application assets cachable in Rails

Note: Modern Rails has two build pipelines, the asset pipeline (or "Sprockets") and Webpacker. The principles below apply for both, but the examples shown are for Sprockets.

Every page in your application uses many assets, such as images, javascripts and stylesheets. Without your intervention, the browser will request these assets again and again on every request. There is no magic in Rails that gives you automatic caching for assets. In fact, if you haven't been paying attention to this, your application is probabl...

Linked content

Workflow: How to use a key management service to encrypt passwords in the database

This is an extract from the linked article. It shows an approach on how to implement encrypted passwords with the AWS Key Management Service (KMS).

For most applications it's enough to use a hashed password with a salt (e.g. the gem devise defaults to this).

Upon password creation

  1. Generate hash as hash of password + salt.

  2. Encrypt the hash with a public key from KMS (you can store the public key in your server code).

  3. In your database sto...

Carrierwave: How to migrate to another folder structure

A flat folder structure can be cool if you have only a few folders but can be painful for huge amounts. We recently had this issue in a project with more than 100.000 attachments, where we used a structure like this /attachments/123456789/file.pdf.

Even the ls command lasted several minutes to show us the content of the attachments folder.

So we decided to use a more hierarchical structure with a limited maximum of folder per layer. As our attachment folder will grow very fast we choosed to use three layers, but that's up to you. Here...


HTML5: disabled vs. readonly form fields

Form fields can be rendered as noneditable by setting the disabled or the readonly attribute. Be aware of the differences:

disabled fields

  • don’t post to the server
  • don’t get focus
  • are skipped while tab navigation
  • available for button, fieldset, input, select, textarea, command, keygen, optgroup, option

Browser specific behavior:

  • IE 11: text inputs that are descendants of a disabled fieldset appear disabled but the user can still interact with them
  • Firefox: selecting text in a disabled text field is no...

Git: Advisory for cherry-picks to production branches

We often have a separate production branch that lags a bit behind the more cutting edge master branch. Sometimes you want to move some, but not all commits from master to production. This can be done with a git cherry-pick.

However, this may lead to considerable pain later, since git does not understand the commits are actually "the same". Hazards are unnecessary and hard to resolve conflicts as well as incorrect auto-merges.

In order to avoid this, always merge the production branch back to the master after the cherry-pick. ...


Decide whether cronjobs should run on one or all servers

Understanding your type of cronjob

Some cronjobs must only run on a single server. E.g. when you run nightly batch operations on the database, it should probably run on a single server. Running it on multiple servers would likely result in deadlocks or corrupt data.

Some cronjobs must always run on all servers. E.g. starting a sidekiq process on reboot.

Configuring whenever

If not configured otherwise, cronjobs defined in whenever's `s...

Vortrag: Content Security Policy: Eine Einführung


CSP hat zum Ziel einen Browser-seitigen Mechanismus zu schaffen um einige Angriffe auf Webseiten zu verhindern, hauptsächlich XSS-Angriffe.

Einschub: Was ist XSS?

XSS = Cross Site Scripting. Passiert wenn ein User ungefiltertes HTML in die Webseite einfügen kann.

<div class="comment">
  Danke für den interessanten Beitrag! <script>alert('you have been hacked')</script>

Rails löst das Problem weitgehend, aber

  • Programmierfehler weiter möglich
  • manchmal Sicherheitslücken in Gems oder Rails


Geordi 4 released

4.0.0 2020-07-30

Compatible changes

  • Improved documentation; README now includes command options.
  • Improvement #90: geordi console, geordi deploy, geordi rake and geordi shell now work correctly if the project hasn't been bundled before
  • Use binstubs if present – breaks Geordi execution when a binstub is not working

Breaking changes

  • Removed deprecated executables

How to create giant memory leaks in AngularJS (and other client-side JavaScript)

This guide shows how to create an AngularJS application that consumes more and more memory until, eventually, the browser process crashes on your users.

Although this guide has been written for Angular 1 originally, most of the advice is relevant for all client-side JavaScript code.

How to observe memory consumption

To inspect the amount of memory consumed by your Javascripts in Chrome:

  • Open an incognito window
  • Open the page you want to inspect
  • Press Shift + ESC to see a list of Chrome processes...

Concurrency issues with find-as-you-type boxes

Find-as-you-type boxes are usually built by observing changes in a text field, and querying the server via AJAX for search results or suggestions when the field has changed.

A common problem with this implementation is that there is no guarantee that AJAX responses are evaluated in the same order as the original requests. The effect for the user is that the search results are flashing back and forth while the user is typing the query, and when the user has stopped typing the last results don't always match the final query.

You won't notice...

Git: Merge a single commit from another branch

This is called "cherry-picking".

git cherry-pick commit-sha1

Note that since branches are nothing but commit pointers, cherry-picking the latest commit of a branch is as simple as

git cherry-pick my-feature-branch

Be aware that cherry-picking will make a copy of the picked commit, with its own hash. If you merge the branch later, the commit will appear in a history a second time (probably without a diff since there was nothing left to do).

Also see our advice for [cherry picking to production branches](https://makandraca...

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