Debugging SPF records
While debugging a SPF record I found spf-record.de 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 vamsoft.com has a very good interface to test new SPF policies.
List of Helpful RubyMine Shortcuts
Navigation
CTRL + SHIFT + ALT + N
-
Search for any symbol in your application, like CSS classes, Ruby classes, methods, helpers etc.
CTRL + SHIFT + N
-
Search for filename in your application (also dependencies)
CTRL + E
-
Open a list of recently opened files
ALT + POS1
-
Open a the navigation bar as a context menu. Allows you to quickly navigate between files.
CTRL + G
-
Go to line
Actions
:...
Gatekeeping: Guide for gatekeeper
If you're responsible for gatekeeping in a projects, here is a guide, what to do.
In order to reduce the number of rejects we get from clients, we want to review all code written before it goes to the staging server.
Note: This process is tailored to our specific needs and tools at makandra. While it will certainly not apply to all (especially larger teams), we think it is a helpful starting point.
First, read the [Gatekeeping for developers](https://makandracards.com/makandra/6579-gatekeeping-guide-for...
How to use Active Job to decouple your background processing from a gem
In a web application you sometimes have tasks that can not be processed during a request but need to go to the background.
There are several gems that help to you do that, like Sidekiq or Resque.
With newer Rails you can also use ActiveJob as interface for a background processing library. See here for a list of supported queueing adapters.
For ...
SameSite cookies
TL;DR Most web applications do not require action on this. SameSite=None
(old browser default) will continue to work, and SameSite=Lax
(new Chrome default, gradually rolled out) is an even better default for cookies. Set SameSite=Strict
only for extra security in special cases (see below). If your application is rendered in an iframe (e.g. a video player or some news stream), you need to configure its relevant cookies as SameSite=None
.
The SameSite
cookie attribute targets **c...
Building web applications: Beyond the happy path
When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.
Different screen sizes and browsers
Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?
- Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
- Use @media queries to build a responsive design
- If you do not suppo...
Gatekeeping: Guide for developer
If your project manager wants to do gatekeeping on a project, as a developer you need to follow the following guidelines (e.g. by using something like this issue checklist template).
In order to reduce the number of rejects we get from clients, we want to review all code written before it goes to the staging server.
Note
This process is tailored to our specific needs and tools at makandra. While it will certainly not apply to all (especially larger teams), we think it...
How to use html_safe correctly
By default, Rails views escape HTML in any strings you insert. If you want to insert HTML verbatim, you need to call #html_safe
. However, #html_safe
does not "unescape" a string. It merely marks a string as safe for unescaped insertion.
How html_safe works
Calling html_safe
on a String
returns a new object that looks and acts like a String
, but actually is a ActiveSupport::SafeBuffer
:
"foo".length
# => 3
"foo".class
# => String
"foo".html_safe.length
# => 3
"foo".html_safe.class
# => ActiveSupport::S...
Integrating or upgrading makandra-rubocop
Introduction
Most of the time it is a tedious task to apply a code style guide to an existing code base as there are likely to be a lot of conflicts. At makandra we are using makandra-rubocop to have code style checks. Here is some advice on how to add makandra-rubocop efficiently.
Note
RubyMine by default has a Rubocop inspection with rules that we don't always agree with. We recommend replacing this with makandra-rubocop or disabling the inspection.
...
How to write complex migrations in Rails
Rails gives you migrations to change your database schema with simple commands like add_column
or update
.
Unfortunately these commands are simply not expressive enough to handle complex cases.
This card outlines three different techniques you can use to describe nontrivial migrations in Rails / ActiveRecord.
Note that the techniques below should serve you well for tables with many thousand rows. Once your database tables grows to millions of rows, migration performance becomes an iss...
Heads up: network requests `Kernel#open` are not mocked with VCR
We usually rely on VCR and WebMock to prevent any real network connection when running our unit tests.
This is not entirely true: They are both limited to a set of HTTP libraries listed below (as of 2022). Direct calls to Kernel#open
or OpenURI#open_uri
are not mocked and will trigger real network requests even in tests. This might bite you e.g. in [older versions of CarrierWave](https://github.com/carrierwaveuploader/carrierwave/blob/0.11-stable/lib/carrierwave/upl...
VCR: Alternative way of mocking remote APIs
If you need to test interaction with a remote API, check out the VCR gem as an alternative to Webmock or stubbing hell.
The idea behind VCR is that is performs real HTTP requests and logs the interaction in a .yml file. When you run the test again, requests and responses are stubbed from the log and the test can run offline.
It's a great way to mock network requests to an external service without going through the pain of log...
How to set up database_cleaner for Rails with Cucumber and RSpec
Add gem 'database_cleaner'
to your Gemfile. Then:
Cucumber & Rails 3+
# features/support/database_cleaner.rb
DatabaseCleaner.clean_with(:deletion) # clean once, now
DatabaseCleaner.strategy = :transaction
Cucumber::Rails::Database.javascript_strategy = :deletion
Cucumber & Rails 2
The latest available cucumber-rails
for Rails 2 automatically uses database_cleaner
when cucumber/rails/active_record
is required -- but only if transactional fixtures are off. To have database_cleaner
work correctly:
- Add the ...
Your browser might silently change setTimeout(f, 0) to setTimeout(f, 4)
When you're nesting setTimeout(f, 0)
calls, your browser will silently increase the delay to 5 milliseconds after the fourth level of nesting.
This is called "timeout clamping" and defined in the HTML spec:
If nesting level is greater than 5, and timeout is less than 4, then set timeout to 4.
Timeouts are clamped harder in background tabs
On a similar note, all major browsers have implemented throttling rules for setInterval
and setTimeout
calls from tabs...
RSpec: Composing a custom matcher from existing matchers
When you find similar groups of expect
calls in your tests, you can improve readability by extracting the group into its own matcher. RSpec makes this easy by allowing matchers to call other matchers.
Example
The following test checks that two variables foo
and bar
(1) have no lowercase characters and (2) end with an exclamation mark:
expect(foo).to_not match(/[a-z]/)
expect(foo).to end_with('!')
expect(bar).to_not match(/[a-z]/)
expect(bar).to end_with('!')
We can extract the repeated matcher chains into a custom m...
How to: Use git bisect to find bugs and regressions
Git allows you to do a binary search across commits to hunt down the commit that introduced a bug.
Given you are currently on your branch's HEAD that is not working as expected, an example workflow could be:
git bisect start # Start bisecting
git bisect bad # Tag the revision you are currently on (HEAD) as bad. You could also pass a commit's SHA1 like below:
git bisect good abcdef12345678 # Give the SHA1 of any commit that was working as it should
# shorthand:
git bisect start <bad ref> <good ref>
Git will fetch a comm...
How to: Benchmark an Active Record query with a Ruby script
Recently I needed to benchmark an Active Record query for performance measurements. I wrote a small script that runs each query to benchmark 100 times and calculates the 95th percentile.
Note: The script requires sudo permissions to drop RAM cache of PostgreSQL. Due to the number of iterations it was impractical to enter my user password that often. And I temporary edited my /etc/sudoers
to not ask for the sudo password with johndoe ALL=(ALL) NOPASSWD: ALL
.
# Run this script with e.g. `rails ru...
PostgreSQL: Be careful when creating records with specific ids
In tests, it is sometimes useful to create records with specific ids. On PostgreSQL this can cause problems:
Usually, PostgreSQL uses an "autoincrement" sequences to provide sequential ids for new database rows. However, these sequences will not increment if you insert a record "by hand". This will cause an error:
record = Record.create!
record.id # => 100, next automatic id will be 101
Record.create!(id: record.id + 1) # okay, but next automatic id will still be 101
Record.create! ...
Spreewald development steps
Our gem spreewald supports a few helpers for development. In case you notice errors in your Cucumber tests, you might want to use one of them to better understand the underlying background of the failure. The following content is also part of the spreewald's README, but is duplicated to this card to allow repeating.
Then console
Pauses test execution and opens an IRB shell with current cont...
Using the ActiveSupport::BroadcastLogger
The ActiveSupport::BroadcastLogger allows you to log to multiple sinks. You know this behavior from from the rails server
command, that both logs to standard out and the log/development.log
file.
Here is an example from the ActiveSupport::BroadcastLogger
API:
stdout_logger = ActiveSupport::Logger.new(STDOUT)
file_logger = ActiveSupport::Logger.new("development.log")
broadcast = ActiveSupport::BroadcastLogger.new(stdout_logger, file_logger)
broadcast.i...
RSpec: Running examples by name (or running a single shared example)
When an Rspec example fails, I usually investigate by running that example again using rspec <file:line>
. However, this does not work with shared examples, since Rspec doesn't know in which context the shared example should be run.
But there is a different way: You can run the shared example using the -e
, --example
option. It takes a string value and runs all scenarios containing that substring in their full description.
This allows you to run a single uniquely named example, all examples with
similar names, all the examples in a u...
A simple example with a GIN index in Rails for optimizing a ILIKE query
You can improve your LIKE
/ ILIKE
search queries in PostgreSQL by adding a GIN index with an operate class ("opclass") to split the words into trigrams to the required columns.
Example
class AddSearchTextIndexToUsers < ActiveRecord::Migration[7.1]
def change
enable_extension 'pg_trgm'
add_index :users, :search_tex...
Custom error pages in Rails
Static error pages
To add a few basic styles to the default error pages in Rails, just edit the default templates in public
, e.g. public/404.html
.
A limitation to these default templates is that they're just static files. You cannot use Haml, Rails helpers or your application layout here. If you need Rails to render your error pages, you need the approach below.
Dynamic error pages
- Register your own app as the applicatio...
Always convert and strip user-provided images to sRGB
Debugging image color profiles is hard. You can't trust your eyes in this matter, as the image rendering depends on multiple factors. At least the operation system, browser or image viewer software and monitor influence the resulting image colors on your screen.
When we offer our users the possibility to upload images, they will most likely contain tons of EXIF metadata and sometimes exotic color profiles like eciRGB. We want to get rid of the metadata, as it might contain sensitiv...