Ever needed to use a global variable in Rails? Ugh, that's the worst. If you
need global state, you've probably reached for
Thread.current. Like this:
def self.foo Thread.current[:foo] ||= 0 end def self.foo=(value) Thread.current[:foo] = value end
Ugh! I hate it. But you gotta do what you gotta do...
Everyone's worrying about concurrency these days. So people are using those
fancy threaded web servers, like Thin or Puma. But if you use
and you use one of those servers, watch out! Values can stick around longer
than you'd expect, and this can cause bugs. For example, if we had this in
def index Thread.current[:counter] ||= 0 Thread.current[:counter] += 1 render :text => Thread.current[:counter] end
If we ran this on MRI with Webrick, you'd get
1 as output, every time. But if
you run it with Thin, you get
Add this line to your application's Gemfile:
And change the code to this:
def index RequestStore.store[:foo] ||= 0 RequestStore.store[:foo] += 1 render :text => RequestStore.store[:foo] end
Yep, everywhere you used
Thread.current just change it to
RequestStore.store. Now no matter what server you use, you'll get
time: the storage is local to that request.
fetch method returns the stored value if it already exists. If no stored value exists, it uses the provided block to add a new stored value.
top_posts = RequestStore.fetch(:top_posts) do # code to obtain the top posts end
Rails 2 compatibility
The gem includes a Railtie that will configure everything properly for Rails 3+ apps, but if your app is tied to an older (2.x) version, you will have to manually add the middleware yourself. Typically this should just be a matter of adding:
into your config/environment.rb.
No Rails? No Problem!
A Railtie is added that configures the Middleware for you, but if you're not using Rails, no biggie! Just use the Middleware yourself, however you need. You'll probably have to shove this somewhere:
No Rails + Rack::Test
In order to have
RequestStore storage cleared between requests, add it to the
# spec_helper.rb def app Rack::Builder.new do use RequestStore::Middleware run MyApp end end
Using with Sidekiq
This gem uses a Rack middleware to clear the store object after every request, but that doesn't translate well to background processing with Sidekiq.
A companion library, request_store-sidekiq creates a Sidekiq middleware that will ensure the store is cleared after each job is processed, for security and consistency with how this is done in Rack.
spec.add_dependency 'request_store', '~> 1.0'
This means your project is compatible with request_store 1.0 up until 2.0. You can also set a higher minimum version:
spec.add_dependency 'request_store', '~> 1.1'
- Fork it
- Create your feature branch (
git checkout -b my-new-feature)
- Commit your changes (
git commit -am 'Add some feature')
- Push to the branch (
git push origin my-new-feature)
- Create new Pull Request
Don't forget to run the tests with