Refactor Router#find_routes to be lazier

[skipkayhil]

Motivation / Background

Previously, #find_routes would take all of the routes that match the current request and eagerly generate MatchData and path_parameters for each route.

Detail

This commit changes #find_routes to only perform the computation one route at a time, since the computation will never be needed for routes in the list after #serve returns.

This change improves the performance of RouteSet#call by ~10% when #find_routes finds two routes, and ~60% when #find_routes finds ten routes.

Additional information

Before:

Warming up --------------------------------------
  10 matching routes     1.182k i/100ms
   2 matching routes     1.967k i/100ms
   1 matching routes     2.221k i/100ms
Calculating -------------------------------------
  10 matching routes     11.846k (± 3.7%) i/s -     60.282k in   5.095922s
   2 matching routes     19.871k (± 3.5%) i/s -    100.317k in   5.054796s
   1 matching routes     21.904k (± 3.8%) i/s -    111.050k in   5.077449s

Comparison:
   1 matching routes:    21904.0 i/s
   2 matching routes:    19870.6 i/s - 1.10x  slower
  10 matching routes:    11845.9 i/s - 1.85x  slower

After:

Warming up --------------------------------------
  10 matching routes     1.888k i/100ms
   2 matching routes     2.215k i/100ms
   1 matching routes     2.312k i/100ms
Calculating -------------------------------------
  10 matching routes     18.623k (± 3.7%) i/s -     94.400k in   5.076043s
   2 matching routes     22.210k (± 3.6%) i/s -    112.965k in   5.092873s
   1 matching routes     22.953k (± 4.1%) i/s -    115.600k in   5.045017s

Comparison:
   1 matching routes:    22952.9 i/s
   2 matching routes:    22210.4 i/s - same-ish: difference falls within error
  10 matching routes:    18622.8 i/s - 1.23x  slower

Benchmark:

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "actionpack", path: "~/src/github.com/skipkayhil/rails"
  gem "benchmark-ips"
end

require "action_dispatch"

routes = ActionDispatch::Routing::RouteSet.new
routes.draw do
  get "/a", to: ->(e) { [200, {}, ["a"]] }

  2.times do |i|
    is = "b" + i.to_s
    get "/b", to: ->(e) { [200, {}, [is]] }
  end

  10.times do |i|
    is = "c" + i.to_s
    get "/c", to: ->(e) { [200, {}, [is]] }
  end
end

one_env = {
  "REQUEST_METHOD" => "GET",
  "SCRIPT_NAME" => "",
  "rack.input" => File.open("/dev/null"),
  "PATH_INFO" => "/a",
}.freeze

two_env = {
  "REQUEST_METHOD" => "GET",
  "SCRIPT_NAME" => "",
  "rack.input" => File.open("/dev/null"),
  "PATH_INFO" => "/b",
}.freeze

ten_env = {
  "REQUEST_METHOD" => "GET",
  "SCRIPT_NAME" => "",
  "rack.input" => File.open("/dev/null"),
  "PATH_INFO" => "/c",
}.freeze

raise unless routes.call(one_env.dup)[2] == ["a"]
raise unless routes.call(two_env.dup)[2] == ["b0"]
raise unless routes.call(ten_env.dup)[2] == ["c0"]

require "benchmark/ips"

Benchmark.ips do |x|
  x.report("10 matching routes") { routes.call(ten_env.dup) }
  x.report("2 matching routes") { routes.call(two_env.dup) }
  x.report("1 matching routes") { routes.call(one_env.dup) }
  x.compare!
end

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.