Does Rails have to lazy load everything? Or does it? - ruby-on-rails

When I notice things like: 0.15s in my specs for a simple method like:
class String
def to_slug
(self.dup).gsub(/["']/, '').gsub(/#/, 'at').gsub(/&/, 'and').parameterize
end
end
I start to ask myself what is going on, so after benching the method without parameterize I decided this was a problem inside of parameterize and not necessarily with the method itself but, well, with the way it's loaded, it seems to me like it's lazily loaded when Monkey Patches like that should be eager loaded, it is causing latency where it should not exist IMO. So my questions are, does Rails really lazily load the file that contains parameterize and is there way to convince Rails to eager load patches to String and other stdlib's.

Calling config.threadsafe! in your config/environments/test.rb should force all code to be loaded at boot time. Note that this will set cache_classes to true, so don't use it in development environment or you will lose code reloading.
Another way would be to change config.eager_load_paths to include the directory you want to load.
Resources:
Aaron Patterson explains config.threadsafe! in his article Removing config.threadsafe!.
The Rails guide on configuration has a lot of information on each option.

Related

Accessing models and modules in a Rails 7 initializer

This issue relates to a need to set a Rails config variable as the application boots, and the value of that variable needs to come from data in the database (which are then modified). So, I have an initializer with something like this:
require "#{Rails.root}/lib/modules/facet_altering.rb"
include FacetAltering
Rails.application.config.reject_subjects = FacetAltering.reject
The reject method is potentially slow and calls the Subject model (which includes some concerns).
If I try to require subject.rb, application_rb and the relevant concerns from app/models then I progress a bit further, but eventually get stuck on uninitialized constant Subject::MySpecialConcern.
There might be some better way to set the reject_subjects value; I'd prefer not to run FacetAltering.reject each time the value of reject_subjects is used, though this might be an easy 'fix' if no other solution arises (at the cost of slowing things down). Or, is there another way to access these classes as the application boots?
Edit: Following on from the comment below, this is in config/application.rb:
%W[#{Rails.root}/lib/modules #{Rails.root}/test/mailers/previews].each do |path|
config.eager_load_paths << path
end
This post offered a useful clue:
Rails Model no longer available in initializer after upgrade to Rails 7.0
So, putting my code in config/application.rb as follows did the trick:
config.after_initialize do
Rails.application.config.reject_subjects = FacetAltering.reject
end
Now to find the answer to RuntimeError: Foreign key violations found in your fixture data. Ensure you aren't referring to labels that don't exist on associations. and I might be able to complete this Rails 6 -> 7 upgrade!

Losing namespace information in a rails namespaced model

When you create a namespaced model with rails scaffolding, you get two files. For example, this scaffold:
rails generate model Staff::Location name:string address:string
Generates these files:
/app/models/staff.rb
module Staff
def self.table_name_prefix
"staff_"
end
...
/app/models/staff/location.rb
class Staff::Location < ActiveRecord::Base
...
I am running into problems when in development mode where rails unloads the Staff module and never reloads it. This causes several annoying bugs such as Location not able to access it's table due to the missing table_name_prefix. The problem seems to crop up when I don't access the models directly, such as through a polymorphic relationship.
I can't seem to get the module loaded on a consistent basis. Is this the best practice way to do namespaced models? If it is, what am I missing?
Although I wasn't able to reproduce the problem in Rails 3.2.2, I've run into something like this before. The generic way to hack around this problem in development mode is through an ActionDispatch callback. Add this to config/environments/development.rb:
MyApp::Application.configure do
ActionDispatch::Callbacks.before do
load Rails.root.join('app', 'models', 'staff.rb')
end
end
Anything you do in that block will be executed before each request, so make sure you're only doing it in development mode.† Otherwise, you're going to suffer a performance hit in production.
I logged a message inside the staff.rb file and within the Staff module itself, and both messages appeared in the log for each request.
† I tried using the to_prepare callback, since that seems to be the documented way to execute code before each request only when cache_classes is false. But that only seemed to execute after restarting the application. There's at least one other open Stack Overflow question regarding this, although he's using a slightly different syntax than I used. If you can get to_prepare to work, I'd suggest that instead of before.
About a year later, I have finally found the answer to this question. This answer is specifically for rails 3.1. I am not sure if it is a problem in rails 3.2.
The problem occurs when setting up a model. If scaffolding is used, no helper file is generated. This would normally be in /app/helpers/staff/location_helper.rb. There are two ways to setup this file:
module Staff::LocationHelper
...
end
module Staff
module LocationHelper
...
end
end
In rails 3.1, specifically for helpers, you must use the first solution. You do not have to use it for other modules that use a namespace in other parts of the rails project. In fact, some structures in ruby require the second solution.
If you use the second solution when declaring a helper, in certain cases the Staff module in the helper file will override the module in /app/models/staff.rb. It will silently replace it with the empty Staff module in the file. This does not happen 100% of the time because helpers are not always loaded.

How can I keep my initializer configuration from being lost in development mode?

I'm working on a Rails app that uses an engine. I'm using an initializer to configure one of my engine's controllers so that it will trigger an action in the host app. The code looks something like this:
# config/initializers/my_engine.rb
MyEngine::SomeController.after_filter proc {
# Do something in the host app
}, :only => :update
This works fine in production, but in development mode, the proc is only called on the first request. This is because the classes are getting reloaded and this configuration is lost, because it was stored in a class variable. (For example, MyEngine::SomeController is reloaded from the file it's in, and since the after_filter isn't declared there, it isn't added back on.)
Some Rails background
In development mode, Rails uses the following load strategy:
Code in the app directory is reloaded on each request, on the assumption that you're actively changing it.
Code in the lib directory, along with config/initializer files, are loaded once, when the application boots.
Initializer files are generally used for configuring gems. In the past, gems have mostly had code in the lib directory, so running their configuration once was sufficient.
How engines change things
However, Rails engines have code in the app directory: controllers, models, etc. These files are reloaded in development mode on each request. Therefore, configuration like my example above is lost.
Enter to_prepare
Rails provides config.to_prepare specifically to solve this problem: it run once in production, and on every request in development.
For example, we have this in application.rb, which works fine:
config.to_prepare do
# set up class variables (after_filters, etc)
end
However, if I have to put all my engines' configuration in application.rb, this defeats the point of config/initializers in keeping things organized.
So, for any configuration of classes in my engines' app directories, I want to put that code in files under config/initializers.
Here are my questions.
I'm unclear how to get config into scope in an initializer file. I'm thinking it would be Rails.application.config. Is that right?
Can I add add multiple to_prepare blocks? I'm afraid that calling it multiple times will overwrite previous blocks.
Update
As #Frederick Cheung mentioned, Rails.application.config.to_prepare does work in config/initializer files, and one can use as many of these as needed in the various files; each call appends its block to an array, so nothing is overwritten.
So the solution to this problem is:
# config/initializers/my_engine.rb
Rails.application.config.to_prepare do
MyEngine::SomeController.after_filter proc {
# Do something in the host app
}, :only => :update
end
One thing that still seems odd: I expected the to_prepare block to be called on every request in development mode, but instead it seems to be called randomly every 3rd request or so. I added block:
Rails.application.config.to_prepare do
Rails.logger.info "Running the prepare block!"
end
... restarted my app, and refreshed the page nine times. I only saw the message on the 1st, 5th, 7th and 9th requests. I'm not sure what explains this behavior, but it does explain why my code without the to_prepare worked intermittently in development.
You can add as many to_prepare blocks as you want - when you do config.to_prepare, Rails is doing (in configuration.rb in railties)
def to_prepare(&blk)
to_prepare_blocks << blk if blk
end
and then iterates over those blocks handing them over to ActionDispatch::Reloader, where to_prepare is implemented using ActiveSupport::Callbacks (i.e. the same thing that is used for before_save and so on). Multiple to_prepare blocks are fine.
Currently it looks like Rails iterates over to_prepare_blocks after reading application initialisers so adding to Rails.application.configuration.to_prepare should work. You may prefer to use ActionDispatch::Reloader.to_prepare.
There's nothing to stop you from doing initializer code in a file that lives in app/models.
for example
class MyClass
def self.run_me_when_the_class_is_loaded
end
end
MyClass.run_me_when_the_class_is_loaded
MyClass.run_me... will run when the class is loaded .... which is what we want, right?
Not sure if its the Rails way.... but its extremely straightforward, and does not depend on the shifting winds of Rails.

Explain to me how config works in Rails

I have a Rails 3 application, call it "MyApp". In my config\environments\production.rb file I see such things as
MyApp::Application.configure do
config.log_level = :info
config.logger = Logger.new(config.paths.log.first, 'daily')
...or...
config.logger = Logger.new(Rails.root.join("log",Rails.env + ".log"),3,20*1024*1024)
So, questions are focusing on terminology and wtf they mean... (or point me to some site ,I have looked but not found, to explain how this works.)
MyApp is a module?
MyApp::Application is a ...? What, a module too?
MyApp::Application.configure is a method?
config is a variable? How do I see it in console?
config.logger is a ???
config.paths.log.first is a ...??
--in console I can see "MyApp::Application.configure.config.paths.log.first" but don't know what that means or how to extract info from it!?!
Is this too much for one question? :)
I have looked at the tutorial http://guides.rubyonrails.org/configuring.html but it jumps right into what things do.
A six sided question! Oh my. Let's ahem roll.1 Here's hoping I receive 6 times the upvotes for it then? :)
1. MyApp is a module?
Yes, it's a module. It acts as a "container" for all things pertaining to your application. For instance you could define a class like this:
module MyApp
class MyFunClass
def my_fun_method
end
end
end
Then if someone else has a MyFunClass, it won't interfere with your MyFunClass. It's just a nice way of separating out the code.
2. MyApp::Application is a ...? What, a module too?
MyApp::Application is actually a class, which inherits from Rails::Application. This does a quite a lot of things, including setting up the Rails.application object which is actually an instance of MyApp::Application that you can do all sorts of fun things on like making requests to your application (in a rails console or rails c session). This code for instance would make a dummy request to the root path of your application, returning a 3-sized Array which is just a plain Rack response:
Rails.application.call(Rack::MockRequest.env_for("/"))
You can also get the routes for your application by calling this:
Rails.application.routes
The main purpose of defining MyApp::Application is not these fun things that you'll probably never use, but rather so that you can define application-specific configuration inside config/application.rb. Things like what parameters are filtered, the time zone of the application or what directories should be autoloaded. These are all covered in the Configuration Guide for Rails.
3. MyApp::Application.configure is a method?
Indeed it is a method, and it allows you to add further configuration options to your application's configuration after config/application.rb has been loaded. You've probably seen this used in config/environments/development.rb or one of the other two files in that directory, but basically they all use the same options as shown in that Configuration Guide linked to earlier.
4. config is a variable? How do I see it in console?
The config "variable" is actually a method defined within the code used for Rails::Application and returns quite simply a configuration object which stores the configuration for the application.
To access it in the console, just use Rails.application.config. This will return quite a large Rails::Application::Configuration object for your viewing pleasure.
5. config.logger is a ???
The method you're referring to, I assume, comes from this line in config/environments/production.rb:
# Use a different logger for distributed setups
# config.logger = SyslogLogger.new
The method in this example is not config.logger, but rather config.logger=, which is referred to as a "setter" method in Ruby-land. The one without the equal sign is referred to as a "getter". This method sets up an alternative logger for the production environment in Rails, which then can be accessed by using Rails.logger within the console or the application itself.
This is useful if you want to output something to the logs, as you can simply call this code:
Rails.logger.info("DEBUG INFO GOES HERE")
6. config.paths.log.first is a ...?? --in console I can see "MyApp::Application.configure.config.paths.log.first" but don't know what that means or how to extract info from it!?!
Within a Rails application, you can modify the locations of certain directories. And so, this config.paths method is a way of keeping track of where these directories map to. In my entire Rails life I have never had to use or modify this variable and that can mean either one of two things:
It's not used often by Rails programmers, or;
I don't live a very varied life.
Interpret it as you will. My main point is that you're probably never going to use it either.
I hope these help you understand Rails a little more!
1 Terrible dice joke.
MyApp is a module, it's a namespace including an app you'll launch, see next line
MyApp::Application is a Class and you're running it's instances when running a Rails app
MyApp::Application.configure is a method. It passes all instructions to the class. See Ref.
config is a method or an instance variable (when set) which belongs through inheritance to Rails::Application::Configuration. See Ref.
You can see it in console doing: MyApp::Application.config
config.logger doesn't exist until you define it, so it's a Logger instance. See Ref.
config.paths.log is a Rails::Paths::Path
you can access it in console using: MyApp::Application.config.paths.log

Exclude Sub Directory on Class Eager Load

I am facing an issue where my Rails application is set to cache classes when run in the staging or production environment. While load_paths only contains 'app/models', it appears that the initialization steps recursively caches everything in 'app/models'.
# Eager load application classes
def load_application_classes
if configuration.cache_classes
configuration.eager_load_paths.each do |load_path|
matcher = /\A#{Regexp.escape(load_path)}(.*)\.rb\Z/
Dir.glob("#{load_path}/**/*.rb").sort.each do |file|
require_dependency file.sub(matcher, '\1')
end
end
end
end
The problem in this is that we have a sub directory within 'app/models' that contains files with require statements that reference a concurrent JRuby environment. Since Rails knows nothing of this environment our application breaks on load.
As it stands, here are the proposed solutions...unfortunately only #1 is ideal.
1) The simplest solution would be to exclude the culprit sub directory, but have not found anything how to accomplish this.
2) Monkey patch the load_application_classes method to skip the specific sub directory.
3) Move the sub directory out from under 'app/models'. Feels a bit hackish and would require quite a few code changes.
Thoughts?
As a temporary measure you could go with a version of option 2 and override the definition of load_application_classes, replacing it with an empty implementation. That would force you to explicitly require the classes you need but it would give you complete control over what gets loaded and would be a completely transparent solution.
It sounds like your application is sufficiently sophisticated that it's growing beyond the Rails framework. I know that this doesn't directly answer your question so appologies in advance but you may want to consider looking at an alternative Ruby framework like Merb. Rails is great but sooner or later you bump into edge of the framework - sounds like that's where you are now.
We made the switch to Merb last year and haven't regreated it.
Chris

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