Eagerly calculate and cache the name of Symbol objects in the path AST.
This drops about 26 string allocations per resource:
```ruby
require 'action_pack'
require 'action_dispatch'
require 'benchmark/ips'
route_set = ActionDispatch::Routing::RouteSet.new
routes = ActionDispatch::Routing::Mapper.new route_set
ObjectSpace::AllocationTracer.setup(%i{path line type})
result = ObjectSpace::AllocationTracer.trace do
500.times do
routes.resources :foo
end
end
sorted = ObjectSpace::AllocationTracer.allocated_count_table.sort_by(&:last)
sorted.each do |k,v|
next if v == 0
p k => v
end
__END__
Before:
{:T_SYMBOL=>11}
{:T_REGEXP=>17}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_OBJECT=>99009}
{:T_DATA=>116084}
{:T_HASH=>122015}
{:T_STRING=>172647}
{:T_IMEMO=>371132}
{:T_ARRAY=>433056}
After:
{:T_SYMBOL=>11}
{:T_REGEXP=>17}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_OBJECT=>99009}
{:T_DATA=>100088}
{:T_HASH=>122015}
{:T_STRING=>159637}
{:T_IMEMO=>363134}
{:T_ARRAY=>433056}
```
Rather than building a regexp for every route, lets use the strategy
pattern to select among objects that can match HTTP verbs. This commit
introduces strategy objects for each verb that has a predicate method on
the request object like `get?`, `post?`, etc.
When we build the route object, look up the strategy for the verbs the
user specified. If we can't find it, fall back on string matching.
Using a strategy / null object pattern (the `All` VerbMatcher is our
"null" object in this case) we can:
1) Remove conditionals
2) Drop boot time allocations
2) Drop run time allocations
3) Improve runtime performance
Here is our boot time allocation benchmark:
```ruby
require 'action_pack'
require 'action_dispatch'
route_set = ActionDispatch::Routing::RouteSet.new
routes = ActionDispatch::Routing::Mapper.new route_set
result = ObjectSpace::AllocationTracer.trace do
500.times do
routes.resources :foo
end
end
sorted = ObjectSpace::AllocationTracer.allocated_count_table.sort_by(&:last)
sorted.each do |k,v|
next if v == 0
p k => v
end
__END__
Before:
$ be ruby -rallocation_tracer route_test.rb
{:T_SYMBOL=>11}
{:T_REGEXP=>4017}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_DATA=>84092}
{:T_OBJECT=>99009}
{:T_HASH=>122015}
{:T_STRING=>216652}
{:T_IMEMO=>355137}
{:T_ARRAY=>441057}
After:
$ be ruby -rallocation_tracer route_test.rb
{:T_SYMBOL=>11}
{:T_REGEXP=>17}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_DATA=>84092}
{:T_OBJECT=>99009}
{:T_HASH=>122015}
{:T_STRING=>172647}
{:T_IMEMO=>355136}
{:T_ARRAY=>433056}
```
This benchmark adds 500 resources. Each resource has 8 routes, so it
adds 4000 routes. You can see from the results that this patch
eliminates 4000 Regexp allocations, ~44000 String allocations, and ~8000
Array allocations. With that, we can figure out that the previous code
would allocate 1 regexp, 11 strings, and 2 arrays per route *more* than
this patch in order to handle verb matching.
Next lets look at runtime allocations:
```ruby
require 'action_pack'
require 'action_dispatch'
require 'benchmark/ips'
route_set = ActionDispatch::Routing::RouteSet.new
routes = ActionDispatch::Routing::Mapper.new route_set
routes.resources :foo
route = route_set.routes.first
request = ActionDispatch::Request.new("REQUEST_METHOD" => "GET")
result = ObjectSpace::AllocationTracer.trace do
500.times do
route.matches? request
end
end
sorted = ObjectSpace::AllocationTracer.allocated_count_table.sort_by(&:last)
sorted.each do |k,v|
next if v == 0
p k => v
end
__END__
Before:
$ be ruby -rallocation_tracer route_test.rb
{:T_MATCH=>500}
{:T_STRING=>501}
{:T_IMEMO=>1501}
After:
$ be ruby -rallocation_tracer route_test.rb
{:T_IMEMO=>1001}
```
This benchmark runs 500 calls against the `matches?` method on the route
object. We check this method in the case that there are two methods
that match the same path, but they are differentiated by the verb (or
other conditionals). For example `POST /users` vs `GET /users`, same
path, different action.
Previously, we were using regexps to match against the verb. You can
see that doing the regexp match would allocate 1 match object and 1
string object each time it was called. This patch eliminates those
allocations.
Next lets look at runtime performance.
```ruby
require 'action_pack'
require 'action_dispatch'
require 'benchmark/ips'
route_set = ActionDispatch::Routing::RouteSet.new
routes = ActionDispatch::Routing::Mapper.new route_set
routes.resources :foo
route = route_set.routes.first
match = ActionDispatch::Request.new("REQUEST_METHOD" => "GET")
no_match = ActionDispatch::Request.new("REQUEST_METHOD" => "POST")
Benchmark.ips do |x|
x.report("match") do
route.matches? match
end
x.report("no match") do
route.matches? no_match
end
end
__END__
Before:
$ be ruby -rallocation_tracer runtime.rb
Calculating -------------------------------------
match 17.145k i/100ms
no match 24.244k i/100ms
-------------------------------------------------
match 259.708k (± 4.3%) i/s - 1.303M
no match 453.376k (± 5.9%) i/s - 2.279M
After:
$ be ruby -rallocation_tracer runtime.rb
Calculating -------------------------------------
match 23.958k i/100ms
no match 29.402k i/100ms
-------------------------------------------------
match 465.063k (± 3.8%) i/s - 2.324M
no match 691.956k (± 4.5%) i/s - 3.469M
```
This tests tries to see how many times it can match a request per
second. Switching to method calls and string comparison makes the
successful match case about 79% faster, and the unsuccessful case about
52% faster.
That was fun!
verb matching is very common (all routes besides rack app endpoints
require one). We will extract verb matching for now, and use a more
efficient method of matching (then regexp) later
This commit introduces a functional Path AST visitor and implements
`each` on the AST in terms of the functional visitor. The functional
visitor doesn't maintain state, so we only need to allocate one of them.
Given this benchmark route file:
```ruby
require 'action_pack'
require 'action_dispatch'
route_set = ActionDispatch::Routing::RouteSet.new
routes = ActionDispatch::Routing::Mapper.new route_set
ObjectSpace::AllocationTracer.setup(%i{path line type})
result = ObjectSpace::AllocationTracer.trace do
500.times{|i|
routes.resource :omglol
}
end
result.find_all { |k,v| k.first =~ /git\/rails/ }.sort_by { |k,v|
v.first
}.each { |k,v|
p k => v
}
```
node.rb line 17 was in our top 3 allocation spot:
```
{["/Users/aaron/git/rails/actionpack/lib/action_dispatch/journey/nodes/node.rb", 17, :T_OBJECT]=>[31526, 0, 28329, 0, 2, 1123160]}
{["/Users/aaron/git/rails/actionpack/lib/action_dispatch/routing/mapper.rb", 2080, :T_IMEMO]=>[34002, 0, 30563, 0, 2, 1211480]}
{["/Users/aaron/git/rails/actionpack/lib/action_dispatch/routing/mapper.rb", 2071, :T_IMEMO]=>[121934, 1, 109608, 0, 7, 4344400]}
```
This commit eliminates allocations at that place.
I would like to change the signature of the Route constructor. Since
the mapping object has all the data required to construct a Route
object, move the allocation to a factory method.
We should build the routes using the user facing API which is `Mapper`.
This frees up the library internals to change as we see fit. IOW we
shouldn't be testing internals.
This is part of a larger refactoring on controller tests. We needed to
move these methods here so that we could get rid of the `|| key ==
:action || key == :controller` in `assign_parameters`. We know this is
ugly and intend to fix it but for now `generate_extras` needs to be used
in the two methods to access the path and the query_string_keys.
We're adding `:controller` and `:action` to the `query_string_keys`
because we always need a controller and action. If someone passed
`action` or `controller` in in there test they are unambigious - we
know they have to go into the query params.
if `to` was initialized, this method would return, so we can eliminate
the to ||= in the conditional. Finally, let's return a nil in the else
block so that it's explicit that this method can return nil
We don't need a method for something like this. I want to pull this up
the stack as well and move the module + :controller ArgumentError up the
stack as well
the same value that is extracted from the options hash earlier is
returned, so we don't need to pass it in in the first place. The caller
already has the data, so stop passing it around.
