Re: [RFC/PATCH] Add Rack::Builder#warmup method for app preloading.

[James Tucker <jftucker@gmail.com>]

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Yeah, Builder#call leads to mistakes all the time and then people claiming
performance sucks. I don't think the simple use case there ever helped.

I'll keep this starred for my next round of merges. Probably not before 1.6.


On Wed, Oct 2, 2013 at 4:55 PM, Konstantin Haase <k.haase@finn.de> wrote:

> "Could you rebase and add some tests." /trololo
>
> I generally like the idea. I think we might have to remove Builder#call,
> though, just to avoid concurrency issues and double firing warmup blocks.
>
> Konstantin
>
> On Oct 3, 2013, at 1:10 AM, ruby@tmm1.net wrote:
>
> > From: Aman Gupta <aman@tmm1.net>
> >
> > This new `warmup` method takes a block which is invoked after the app
> > is built. The block can be used to make mock requests that ensure
> > all application dependencies are loaded before the app starts
> > serving traffic.
> >
> > With complex frameworks like Rails, many dependencies are auto-loaded
> > and data like mime-type and i18n is not loaded into memory by default.
> This
> > often means the first few requests handled by an application are quite
> > slow.
> >
> > With this patch, config.ru can simply make requests via warmup to
> > exercise the app before it is used:
> >
> >  $ tail -4 config.ru
> >  warmup do |app|
> >    client = Rack::MockRequest.new(app)
> >    client.get('/')
> >  end
> > ---
> > lib/rack/builder.rb  | 19 +++++++++++++++++--
> > test/spec_builder.rb | 11 +++++++++++
> > 2 files changed, 28 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/rack/builder.rb b/lib/rack/builder.rb
> > index 66dc7bd..fa3a1ea 100644
> > --- a/lib/rack/builder.rb
> > +++ b/lib/rack/builder.rb
> > @@ -51,7 +51,7 @@ module Rack
> >     end
> >
> >     def initialize(default_app = nil,&block)
> > -      @use, @map, @run = [], nil, default_app
> > +      @use, @map, @run, @warmup = [], nil, default_app, nil
> >       instance_eval(&block) if block_given?
> >     end
> >
> > @@ -104,6 +104,19 @@ module Rack
> >       @run = app
> >     end
> >
> > +    # Takes a lambda or block that is used to warm-up the application.
> > +    #
> > +    #   warmup do |app|
> > +    #     client = Rack::MockRequest.new(app)
> > +    #     client.get('/')
> > +    #   end
> > +    #
> > +    #   use SomeMiddleware
> > +    #   run MyApp
> > +    def warmup(prc=nil, &block)
> > +      @warmup = prc || block
> > +    end
> > +
> >     # Creates a route within the application.
> >     #
> >     #   Rack::Builder.app do
> > @@ -131,7 +144,9 @@ module Rack
> >     def to_app
> >       app = @map ? generate_map(@run, @map) : @run
> >       fail "missing run or map statement" unless app
> > -      @use.reverse.inject(app) { |a,e| e[a] }
> > +      app = @use.reverse.inject(app) { |a,e| e[a] }
> > +      @warmup.call(app) if @warmup
> > +      app
> >     end
> >
> >     def call(env)
> > diff --git a/test/spec_builder.rb b/test/spec_builder.rb
> > index 0774f59..20ea668 100644
> > --- a/test/spec_builder.rb
> > +++ b/test/spec_builder.rb
> > @@ -130,6 +130,17 @@ describe Rack::Builder do
> >     Rack::MockRequest.new(app).get("/foo").should.be.server_error
> >   end
> >
> > +  it "yields the generated app to a block for warmup" do
> > +    warmed_up_app = nil
> > +
> > +    app = Rack::Builder.new do
> > +      warmup { |a| warmed_up_app = a }
> > +      run lambda { |env| [200, {}, []] }
> > +    end.to_app
> > +
> > +    warmed_up_app.should.equal app
> > +  end
> > +
> >   should "initialize apps once" do
> >     app = builder do
> >       class AppClass
> > --
> > 1.8.3.4
> >
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> >
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