I'm wondering what file I should use to ensure my initializing code will only be executed once when the application starts up. Is environment.rb the correct file to use or will it be invoked on every http request?
environment.rb is only loaded when the application is first started up. subsequent changes to the environment.rb file require a restart. What kind of code do you only want to execute once?
You might want to read through the Ruby on Rails guide for Configuring Rails Applications which talks about the different places to put initialization code.
Look at config/initializers for the recommended location custom startup code.
As far as possible leave environment.rb alone unless you're explicitly adding or changing items defined within the Rails::Initializer.run block.
If you want to manage custom settings across your various environments, e.g. you want production and development to have different settings for something, then the config/environments directory should be your first port of call.
Related
I started a rails app using the -O (--skip-activerecord) configuration, but now I want to add it back.
I added require "rails/all" to my application.rb file, and added in a database.yml file. Unfortunately, it's not picking up the database when I initialize the application.
I hacked together a module which will connect to the database if I call it, but there has to be a better, more railsy way. A rails app created without the -O option doesn't need any additional code to make the connection.
What else do I need to do to get rails to automatically connect to the database without explicitly making a connection?
Add this line to your config/application.rb. If you already have it commented, uncomment it.
require "active_record/railtie"
Add database.yml and restart the server
It turns out that ActiveRecord 4 doesn't actually make the db connection until you call something. So just adding back in require "rails/all" and adding a database.yml does work. Just don't test it in the console without calling a method like Model.last.
Here's the rails issue explaining the functionality: https://github.com/rails/rails/issues/12804#issuecomment-29885300
I read a post about the rails load_paths, here is the link.
But, I am still confused about the difference between the autoload_paths and eager_load_paths:
I have tested them in a newly created Rails 4 project. It seems that they run the same way, that auto-reload in the development mode but in the production mode.
Author of the linked article here. Here's an attempt to clear up the confusion, going off of #fkreusch's answer.
In Ruby you have to require every .rb file in order to have its code run. However, notice how in Rails you never specifically require any of your models, controllers, or other files in the app/ dir. Why is that? That's because in Rails app/* is in autoload_paths. This means that when you run your rails app in development (for example via rails console) — none of the models and controllers are actually required by ruby yet. Rails uses special magical feature of ruby to actually wait until the code mentions a constant, say Book, and only then it would run require 'book' which it finds in one of the autoload_paths. This gives you faster console and server startup in development, because nothing gets required when you start it, only when code actually needs it.
Now, this behavior is good for local development, but what about production? Imagine that in production your server does the same type of magical constant loading (autoloading). It's not the end of the world really, you start your server in production, and people start browsing your pages slightly slower, because some of the files will need to be autoloaded. Yes, it's slower for those few initial requests, while the server "warms up", but it's not that bad. Except, that's not the end of the story.
If you are running on ruby 1.9.x (if I recall correctly), then auto-requiring files like that is not thread safe. So if you are using a server like puma, you will run into problems. Even if you aren't using a multi-threaded server, you are still probably better off having your whole application get required "proactively", on startup. This means that in production, you want every model, every controller, etc all fully required as you start your app, and you don't mind the longer startup time. This is called eager loading. All ruby files get eagerly loaded, get it? But how can you do that, if your rails app doesn't have a single require statement? That's where eager_load_paths come in. Whatever you put in them, all the files in all the directories underneath those paths will be required at startup in production. Hope this clears it up.
It's important to note that eager_load_paths are not active in development environment, so whatever you put in them will not be eagerly required immediately in development, only in production.
It's also important to note that just putting something into autoload_paths will not make it eager-loaded in production. Unfortunately. You have to explicitly put it into eager_load_paths as well.
Another interesting quirk is that in every rails app, all directories under app/ are automatically in both autoload_paths and eager_load_paths, meaning that adding a directory there requires no further actions.
Basically, autoload_paths are paths Rails will use to try loading your classes automatically. E.g. when you call Book, if that class isn't loaded yet, it will go through the autoload_paths and look for it in those paths.
In production, it might be better to load those upfront to avoid autoload concurrent issues. For that, it provides the eager_load_paths. Paths in that list will be required upfront when your application starts.
Rails server seems to need restart when I change config/environment.rb.
Is there a way to reflect the change without restarting server?
A gem for it or something like that exists?
The environment.rb file is one of the main initialiser files for starting your app and can't really be reloaded on each request because reloading that is nearly the same as restarting the whole app. I'm guessing there are some variables in there that you want to change without restarting every time. Well instead of putting them in there, you could create a .rb file in the lib directory. That code gets run when the app is started and is useful for defining custom classes, etc.
To make it automatically reload it on each request you need to use eager_load_paths in your config/application.rb. This question specifies how to do that.
I have some iPhone client tests that run against my development rails server. The whole suite runs an order of magnitude faster if I turn on class caching in the Rails config. On the other hand, that slows down development when I'm not actually running the tests.
I want the test suite to hit an action at the beginning to turn on class caching and another action at the end to turn class caching off again.
Is this even possible? If so, how?
Not without some serious hacking. Rails goes to quite a lot of trouble to make sure your files are reloaded on every request (when cache_classes=false). The value of the cache_classes configuration variable is used by initializers in several places not the least of which being:
using require to load ruby files when cache_classes is true (meaning they are no longer reloadable)
setting up dispatcher callbacks to reaload the application on every request when cache_classes is false
You do have access to the value of the cache_classes variable, and you can even change it if you like:
Rails.configuration.cache_classes = true
But, this will have no effect on the running rails instance as the initializers where that value is used only run once when the rails app starts up.
What this means is this, unless you're prepared to invest some serious time and hacking effort you can't really avoid a restart of your server. So, what you need to look at is controlling this restart process via your test suite.
For example you can try to restart rails from within rails. This would allow you to define an action that your test suite can hit right before it begins executing (to restart the server in the right mode), and another action which the server can hit after all tests have finished, to restart everything with cache_classes set to what it used to be. You would control the value of cache classes via an environment variable like this post suggests.
It would still require a bit of work to set all of this up and get it to hang together, but this is probably your best bet if you want an 'auto-magical' solution.
I don't think doing what you suggest will work.
But I suggest you may be looking for the wrong solution.
If what you want is to access your development database from your iphone testing,
then why not add a new environment.
Add a new file config/environments/iphone_dev.rb
require File.dirname(__FILE__)+"/development.rb"
config.cache_classes = true
And in your database.yml (or mongoid.yml or whatever)
iphone_dev:
host: localhost
database: my_app_development
There is no reason the database cant be the same
Now just run rails server -eiphone_dev -p3001
You should have a server, almost the same as your dev server,
but running on a different port, with caching enabled.
I am working on an existing Rails 2.3.x application, So I was working on it and it was a messy code with great difficulty I was able to run the application. But now for every small change in one of my controller it is expecting me to restart my serer otherwise the changes are not reflecting back, Let's take an example scenario here, Let's just say in one of the before_filter method I just added a puts statement on top of the method and it was not printing in the log, after I restart the server it is printing, Can some one please let me know if I am missing something here.
What environment are you using?
The default environment is 'development', where the code is reloaded on each request. However, this behaviour can be overwritten in the config file.
To be sure that the code is reloaded, add this into your config/development.rb file:
# In the development environment your application's code is reloaded on
# every request. This slows down response time but is perfect for development
# since you don't have to restart the webserver when you make code changes.
config.cache_classes = false
If you are using config.threadsafe! It needs to be present before config.cache_classes=false as threadsafe makes cache_classes true again, following link would make it more clear. here
Maybe you have don't flush. The log system in Rails use a BufferedLogger. So need a flush to be print. Try a default logger.