JavaScript Start-up Performance
As web developers, we know how easy it is to end up with web page bloat. But loading a webpage is much more than shipping bytes down the wire. Once the browser has downloaded our page’s scripts it then has to parse, interpret & run them. In this post, we’ll dive into this phase for JavaScript, why it might be slowing down your app’s start-up & how you can fix it.
The article author also tested 6000+ production sites for load times. Apps became interactive in 8 seconds on desktop (using cable) and 16 seconds on mobile (Moto G4 over 3G).
Never use SET GLOBAL sql_slave_skip_counter with a value higher than 1
If you have a replication error with MySQL and you know the "error" is okay (e.g. you've executed the same statement at the same time on 2 masters which sync each other), you can skip this error and continue with the replication without having to set up the slave from the ground up.
stop slave;
set global sql_slave_skip_counter = 1;
start slave;
But what if you have multiple errors which you want to skip? (e.g. you've executed multiple statement at the same time on 2 masters which sync each other)
Still do not use a value highe...
Error "undefined method last_comment"
This error message may occur when rspec gets loaded by rake, e.g. when you migrate the test database.
NoMethodError: undefined method 'last_comment' for #<Rake::Application:0x0055a617d37ad0>
Rake 11 removes a method that rspec-core < 3.4.4 depends on. To fix, lock Rake to < 11 in your Gemfile:
gem 'rake', '< 11', # Removes a method that rspec-core < 3.4 depends on
Geordi hints
Reminder of what you can do with Geordi.
Note: If you alias Geordi to something short like g, running commands gets much faster!
Note: You only need to type the first letters of a command to run it, e.g. geordi dep will run the deploy command.
geordi deploy
Guided deployment, including push, merge, switch branches. Does nothing without confirmation.
geordi capistrano
Run something for all Capistrano environments, e.g. geordi cap deploy
geordi setup -t -d staging
When you just clon...
JSONP for Rails
The rack-contrib gem brings a JSONP middleware that just works™. Whenever a JSON request has a callback parameter, it will wrap the application's JSON response appropriately.
The project is a bit dated, but the JSONP middleware is ok.
[jruby] TruffleRuby Status, start of 2017
TruffleRuby is an experimental Ruby implementation that tries to achieve ~10x performance over MRI.
This has been on our radar for a while. They seem to have made significant progress running Rails, reducing start-up time and becoming runtime-independent of the JVM.
Also see [Running Optcarrot, a Ruby NES emulator, at 150 fps with the GUI!](https://eregon.me/blog/2016/11/28/optcarrot.htm...
How to tackle complex refactorings in big projects
Sometimes huge refactorings or refactoring of core concepts of your application are necessary for being able to meet new requirements or to keep your application maintainable on the long run. Here are some thoughts about how to approach such challenges.
Break it down
Try to break your refactoring down in different parts. Try to make tests green for each part of your refactoring as soon as possible and only move to the next big part if your tests are fixed. It's not a good idea to work for weeks or months and wait for all puzzle pieces ...
JavaScript: Don't throw synchronous exceptions from functions that return a Promise
TLDR: A function is hard to use when it sometimes returns a promise and sometimes throws an exception. When writing an async function, prefer to signal failure by returning a rejected promise.
The full story
When your function returns a promise ("async function"), try not to throw synchronous exceptions when encountering fatal errors.
So avoid this:
function foo(x) {
if (!x) {
throw "No x given"
} else
return new Promise(funct...
An Introduction to Sending HTML Email for Web Developers
A comprehensive introduction to sending HTML emails.
Intro:
HTML email: Two words that, when combined, brings tears to a developer’s eyes. If you’re a web developer, it’s inevitable that coding an email will be a task that gets dropped in your lap at some time in your career, whether you like it or not. Coding HTML email is old school. Think back to 1999, when we called ourselves “webmasters” and used Frontpage, WYSIWYG editors and tables to mark up our websites.
Table of Contents
- Introduction To Sending Email Link
- Email List B...
CarrierWave: When your uploader generates filenames dynamically, use model.save! instead of uploader.recreate_versions!
If your Carrierwave uploader dynamically generates the filename (e.g. by incorporating a user's name), you must call model.save! after recreating versions.
uploader.recreate_versions! does not update the model with the stored filename.
Howto use ActiveRecord preload with plain SQL inner joins
Like you know from "How to tell ActiveRecord how to preload associations (either JOINs or separate queries)", you can tell ActiveRecord explicitly if it should use a LEFT OUTER JOIN or a separate query to preload associations.
Here is some special case, where a simple includes is not possible. For the diagram below we want to sort the rides by the translated name of the departure_place and the arrival_place:
 and open VNC for Firefox.
Features:
- It does not freeze your server like when you're using a debugger. (Compared to the
Then consolestep) - It enables interacting with the server. (Compared to taking screenshots in Capybara)
- It is a faster alternat...
Howto: Free disk space when /boot is full
Easy mode
This method will remove automatically installed packages that no other packages depend on any more. This, of course, includes obsolete kernel versions, with the explicit exception of the currently running kernel, the kernel version that was installed on the system before that and, of course, the latest updated version of the kernel. However, it will also remove any and all other packages that have been marked as installed automatically but have no other packages depending on them. This could lead to unexpected removal of packag...
Ruby: Writing specs for (partially) memoized code
When you're writing specs for ActiveRecord models that use memoization, a simple #reload will not do:
it 'updates on changes' do
subject.seat_counts = [5]
subject.seat_total.should == 5
# seat_total is either memoized itself, or using some
# private memoized method
subject.seat_counts = [5, 1]
subject.seat_total.reload.should == 6 # => Still 5
end
You might be tempted to manually unmemoize any memoized internal method to get #seat_total to update, but that has two disadvant...
Copy to clipboard without flash (clipboard.js)
We used zeroclipboard.js in some of our projects but now we switched to clipboard.js because it does not rely on flash. Flash support of the major browsers has ended.
Some more advantages of clipboard.js:
- it consists only of a single javascript file, so it does not trigger additional requests with rails
- it automagically provides user feedback by selecting the text it has copied
- it provides callbacks for success and error which make it easier to add custom behaviour after copying to the clipboar...
mceachen/closure_tree: Easily and efficiently make your ActiveRecord models support hierarchies
Closure_tree lets your ActiveRecord models act as nodes in a tree data structure.
This promises a few improvements over the battle-tested ancestry gem, such as:
- Better performance
- Pre-ordered trees (painful to do with ancestry)
- Holds a mutex during tree manipulations (an issue with ancestry, where concurrent updates can cause deadlocks and corrupt data).
It has some more moving parts than ancestry though (see below).
Implementation
--------------...
Rails: Talking to the database without instantiating ActiveRecord objects
Instantiating ActiveRecord objects comes expensive. To speed up things, you can choose a more direct way to talk to your database: the ActiveRecord::ConnectionAdapters::DatabaseStatements module.
Using the module and its methods is not suggested in the usual in-app workflow, as validations, callbacks, custom getters/setters etc. are ignored. However, for database-centered stuff like migrations, these fill the gap between writing pure SQL and full...
Nested ActiveRecord transaction pitfalls
When working with custom transactions and use ActiveRecord::Rollback you may encounter unexpected behaviour if you try to roll back your changes.
tl;dr
When using nested transactions, ActiveRecord::Rollback might not do what you expect, since it will only roll back the inner, but not the outer transaction.
You can fix this behavior by using transaction(joinable: false) but this leads to a bunch of different problems.
When you don't need an explicit ActiveRecord::Rollback, don't worry about any of this and just use a plan `tran...
Repeatedly execute a bash command and observe its output
You can have a command repeatedly executed and the output displayed. This is useful e.g. for monitoring file system changes with ls, but has many more applications.
The update frequency is controlled by the -n argument (default: 2s), which is locale-specific; i.e. you might need to use a comma as delimiter.
> watch -n 1.5 ls
Git: Show commits that have touched specific text in a file
If you want to find the commits that touched a specific text in a file, use
git log -S 'text in the code' -- path/to/file
If you use tig you may run a similar command to get a navigatable list of affected files:
tig -S'text in the code'
Example
Here is an example, where the move of the convert_number_column_value(value) method in active record is traced (simplified output):
git log -n 1 --pretty=oneline -S 'convert_number_column_value(value)' -- activerecord/lib/active_record/base.rb
ceb33f84933639d3b6...
Creating icon fonts with Icomoon
Icomoon.io offers a free app to build custom icon webfonts. It offers downloads as webfont set (.eot, .ttf, .woff, .woff2) or as icon set of SVG and/or PNG and many more file types, or even SVG sprites.
From my experience, the frontend developer should create the font, and not the designer. There are many tweaks required during font development, and routing changes over the designer imposes just too much overhead.
On rare occasions, webfonts may be blocked by an entreprise's security policy. Be sure webfonts can be u...
Beware of rails' reverse_order!
#reverse_order does not work with complex sorting constraints and may even silently create malformed SQL for rails < 5.
Take a look at this query which orders by the maximum of two columns:
Page.order('GREATEST(pages.published_from_de, pages.published_from_en) DESC').to_sql
# => SELECT "pages".* FROM "pages" ORDER BY GREATEST(pages.published_from_de, pages.published_from_en) DESC
Rails 4
Rails 4 will not immediately raise but creates malformed SQL when trying to use reverse_order on this query:
Pageorder('GRE...
Different ways to set attributes in ActiveRecord
Rails 5 / 6 / 7
| Method | Uses Default Accessor | Saves to Database | Runs Validations | Runs Callbacks | Updates updated_at/updated_on | Respects Readonly |
|---|---|---|---|---|---|---|
attribute= |
Yes | No | n/a | n/a | n/a | n/a |
attributes= |
Yes | No ... |
Master the chrome history and autocomplete
1. Sometimes you have search entries in the autocomplete of the address bar, which are higher weighted than your bookmarks. Pressing SHIFT + DEL while searching removes them from the history immediately.
2. Sometimes you have search entries in the autocomplete of the address bar, which are all higher weighted than your recently visited sites. Add a search for your history, so you can get recent results first.
...