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When upgrading/downgrading RubyGems and Bundler on a server, you must clear bundled gems

On application servers, gems are usually bundled into the project directory, at a location shared across deployments.

This is usually shared/bundle inside your project's root directory, e.g. /var/www/your-project/shared/bundle/.
If you can't find that, take a look at current/.bundle/config and look for BUNDLE_PATH.

When you are changing the version of RubyGems or Bundler on a system where gems are installed this way, you must wipe that bundle directory in addition to the user and system gems or gems that are already ins…

Capistrano: Finding out who deployed which revision of your application and when

Capistrano automatically logs each (successful) deployment into a file on your application servers.

It is located at the root of your server's project folder, i.e. the parent of releases and current, like so:

/var/www/your-project$ ls
current
log
releases
repo
revisions.log  <---  here
shared

Each line in that file contains the deployed branch, commit, release ID, and username (was read from the deploying user's machine):

```
$ tail -n3 revisions.log
Branch master (at da45511bea63002ac2ff002d1692e09d0dd7cb88) deployed as rel…

Repeats

Unpoly: Automatically show the full better_errors page when Rails raises an error

When an AJAX request raises an exception on the server, Rails will show a minimal error page with only basic information. Because all Unpoly updates work using AJAX requests, you won't get the more detailled better_errors page with the interactive REPL.

Below is an event listener that automatically repeats the request as a full-page load if your development error shows an error page. This means you get…

Repeats

Use Time.current / Date.current / DateTime.current on projects that have a time zone

Basically, you now need to know if your project uses a "real" time zone or :local, and if config.active_record.time_zone_aware_attributes is set to false or not.

  • With time zones configured, always use .current for Time, Date, and DateTime.

    ActiveRecord attributes will be time-zoned, and .current values will be converted properly when written to the database.
    Do not use Time.now and friends. Timezone-less objects will not be converted properly when written to the database.

  • With no/local time zone use Time.now, `…

Repeats

Working with or without time zones in Rails applications

Rails supports time zones, but there are several pitfalls. Most importantly because Time.now and Time.current are completely different things and code from gems might use one or the other.

Especially configuring an application that cares only about one time zone is a bit tricky.

The following was tested on Rails 5.1 but should apply to Rails 4.2 as well.

Using only local time

Your life will be easier if your application does not need to support time zones. Disable them like this:

```
config.time_zone = 'Berlin' # Your local time…

Repeats

Webpack(er): A primer

webpack is a very powerful asset bundler written in node.js to bundle (ES6) JavaScript modules, stylesheets, images, and other assets for consumption in browsers.

Webpacker is a wrapper around webpack that handles integration with Rails.

This is a short introduction.

Installation

If you haven't already, you need to install node.js and Yarn.

Then, put

```ruby
gem 'webpacker', '~> 4.x' # check if 4.x is still cu…

Deal with certain travis CI failures

Travis changed their default distribution from Ubuntu 14.04 (trusty) to 16.04 (precise). This might break your test setup for new builds.

You can solve this issue by freezing your test distribution in the .travis.yml to Ubuntu 14.04 until you have the time to solve all the issues you will have in 16.04:


dist: trusty

Error details

Here are few indicators that you ran into this issue:

Connection to the PostgreSQL database does not work anymore

Your travis-ci builds might have started failing on the usual

```
psql -c…

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…

Repeats

no passenger served applications running error when deploying via capistrano

When deploying with capistrano it's possible you get this "error" message:

*** [err :: example.com] There are no Phusion Passenger-served applications running whose paths begin with '/var/www/example.com'.
*** [err :: example.com] 

This is just because there were no running passenger process for this application on the server which could be restarted. It's not a real error. The application process will start if the first request for this app hits the appserver.

The output appears as err because it's printed to stderr.

Dep…

Linked contentDeprecated

Execution of shell code in Ruby scripts

Deprecated ways to execute shell code in Ruby

This is just a reference for legacy code. For new code, always use capture3.

%x{ } or backticks – quick and easy

Returns the standard output of running the given command in a subshell. This is an alias for `…`, and you can use string interpolation.

Example:

name = 'ls'
result = `which #{name}`

It does not escape anything you inject in the string.

If you want to find out if the call was …

Repeats

Webpack(er): Analyze the size of your JavaScript components

We're always striving towards keeping our website's JavaScript as small as possible.

If you're using webpack(er), you can use the webpack-bundle-analyzer plugin to get a good overview, which of your JavaScript modules take up how much space, and where you can optimize.

To use it, add it via npm or yarn

yarn add webpack-bundle-analyzer

Then add this to your environment.js:

```
// Uncomment this code to show statistics of bundle sizes. Generated file will automatically o…

SameSite Cookies

The SameSite cookie attribute was first drafted in 2016. It defines under which circumstances a cookie should be sent to the server, putting cookies into three different classes:

SameSite variants

SameSite=None

Send the cookie whenever a request is made to the cookie domain. A cookie without the SameSite attribute will currently be handled as if it was sent with SameSite=None.

Note: Googl…

Repeats

Self-expiring URLs with Apache

When delivering non-public uploaded files (images, documents etc), one has to decide whether and how to do authorization. The usual approaches are:

  • Using send_file with a regular controller. This is secure, but potentially slow, especially for large collections of images.
  • Using unguessable URLs. This is fast (because Apache can deliver assets without going through Rails), but less secure.

When going with the "unguessable URL" approach, it is possible to somewhat increase security by using expiring URLs. The idea is to encode the expi…

How to test Autoprefixer and CSSnext in PostCSS

PostCSS is a tool for transforming styles with JS plugins. In Webpacker you can configure the plugins and their settings via the postcss.config.js file.

module.exports = {
  plugins: [
    require('postcss-import'),
    require('postcss-flexbugs-fixes'),
    require('postcss-preset-env')({
      autoprefixer: {
        flexbox: 'no-2009'
      },
      stage: 3
    })
  ]
}

Note: Stage 3 means you can use all CSS features that are listed as "This idea is becoming part of the web". Do not use …

Repeats

RestClient / Net::HTTP: How to communicate with self-signed or misconfigured HTTPS endpoints

Occasionally, you have to talk to APIs via HTTPS that use a custom certificate or a misconfigured certificate chain (like missing an intermediate certificate).

Using RestClient will then raise RestClient::SSLCertificateNotVerified errors, or when using plain Net::HTTP:

OpenSSL::SSL::SSLError: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

Here is how to fix that in your application.

Important: Do not disable certificate checks for production. The interwebs are full of people say…

Migration from the Asset Pipeline to Webpacker

This is a short overview of things that are required to upgrade a project from the Asset Pipeline to Webpacker. Expect this upgrade to take a few days even the diff is quite small afterwards.

Preparations

1. Find all libraries that are bundled with the asset pipeline. You can check the application.js and the application.css for require and import statements. The source of a library is most often a gem or a vendor directory.
2. Find an working example for each library in the application and write it down.
3. Find out the ver…

Repeats

How to search through logs on staging or production environments

We generally use multiple application servers (at least two) and you have to search on all of them if you don't know which one handled the request you are looking for.

Rails application logs usually live in /var/www/<project-environment-name>/shared/log.
Web server logs usually live in /var/www/<project-environment-name>/log.

Searching through single logs with grep / zgrep

You can use grep in this directory to only search the latest logs or zgrep to also search older (already zipped) logs. zgrep is used just like grep a…

During deployment: "You are trying to install in deployment mode after changing your Gemfile"

While deploying an Ruby update to an old application these days, we encountered the following misleading error:

*** [err :: some-host.makandra.de] You are trying to install in deployment mode after changing
*** [err :: some-host.makandra.de] your Gemfile. Run `bundle install` elsewhere and add the
*** [err :: some-host.makandra.de] updated Gemfile.lock to version control.
*** [err :: some-host.makandra.de] 
*** [err :: some-host.makandra.de] You have deleted from the Gemfile:
*** [err :: some-host.makandra.de] *

We found out a newe…

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