Improve performance of Marshaler::Base#find_template

[Nash Bridges]

Hello guys!

According to https://github.com/cognitect/transit-ruby/blob/master/CONTRIBUTING.md I'm posting this pull request here.

In our Rails application we see Marshaler::Base#find_template as a hotspot.

The problem is that the method looks up all the inheritance chain for an encoded object:

def find_handler(obj)
  obj.class.ancestors.each do |a|
    if handler = @handlers[a]
      return handler
    end
  end
  nil
end

Here's Hash `ancestors` in Rails

[4] pry(main)> {}.class.ancestors
=> [ActiveSupport::ToJsonWithActiveSupportEncoder,
 Hash,
 JSON::Ext::Generator::GeneratorMethods::Hash,
 Enumerable,
 ActiveSupport::ToJsonWithActiveSupportEncoder,
 Object,
 PP::ObjectMixin,
 JSON::Ext::Generator::GeneratorMethods::Object,
 ActiveSupport::Tryable,
 ActiveSupport::Dependencies::Loadable,
 Kernel,
 BasicObject]

Here's String `ancestors`:

[5] pry(main)> "".class.ancestors
=> [ActiveSupport::ToJsonWithActiveSupportEncoder,
 String,
 JSON::Ext::Generator::GeneratorMethods::String,
 Comparable,
 ActiveSupport::ToJsonWithActiveSupportEncoder,
 Object,
 PP::ObjectMixin,
 JSON::Ext::Generator::GeneratorMethods::Object,
 ActiveSupport::Tryable,
 ActiveSupport::Dependencies::Loadable,
 Kernel,
 BasicObject]

Basically all core objects are prepended with ToJsonWithActiveSupportEncoder.

That makes Ruby to spend two loop iterations on each encoded key or value to get a handler for Array, Hash or String.

Performance implications are quite severe if encoded object is big enough:

# benchmark.rb

require "bundler/setup"


$LOAD_PATH << File.expand_path("../../lib", __FILE__)


require "transit"


require "active_support"
require "active_support/core_ext"


require "benchmark"


example = Array.new(1_000) do
  {
    ids: [1, 2, 3, 4],
    translations: {
      can: {
        be: {
          nested: "value"
        }
      }
    }
  }
end


module Transit
  module Marshaler
    class OrigJson < Json
      def find_handler(obj)
        obj.class.ancestors.each do |a|
          if handler = @handlers[a]
            return handler
          end
        end
        nil
      end
    end


    class PerfJson < Json
      def find_handler(obj)
        handler = @handlers[obj.class]
        return handler if handler


        obj.class.ancestors.each do |a|
          if handler = @handlers[a]
            return handler
          end
        end
        nil
      end
    end
  end


  class OrigWriter < Writer
    def initialize(format, io, opts = {})
      @marshaler = Marshaler::OrigJson.new(io, {:handlers => {},
                                              :oj_opts => {:indent => -1}}.merge(opts))
    end
  end


  class PerfWriter < Writer
    def initialize(format, io, opts = {})
      @marshaler = Marshaler::PerfJson.new(io, {:handlers => {},
                                              :oj_opts => {:indent => -1}}.merge(opts))
    end
  end
end


original_writer = Transit::OrigWriter.new(:json, StringIO.new)
perf_writer = Transit::PerfWriter.new(:json, StringIO.new)


n = 100


Benchmark.benchmark do |bm|
  puts "original"
  3.times do
    bm.report do
      n.times do
        original_writer.write(example)
      end
    end
  end


  puts
  puts "perf"
  3.times do
    bm.report do
      n.times do
        perf_writer.write(example)
      end
    end
  end
end


#original
   #4.490000   0.000000   4.490000 (  4.505609)
   #4.510000   0.010000   4.520000 (  4.522835)
   #4.500000   0.010000   4.510000 (  4.515551)


#perf
   #2.950000   0.010000   2.960000 (  2.955664)
   #2.920000   0.000000   2.920000 (  2.934824)
   #2.940000   0.010000   2.950000 (  2.951365)

Please, review and accept the attached patch.

[Nash Bridges]

I realized that I should've been posted this to issues. Sorry for the noise.

https://github.com/cognitect/transit-ruby/issues/23

середа, 5 вересня 2018 р. 22:14:36 UTC+3 користувач Nash Bridges написав: