Optimize JSON encoding

- Add 'oj' gem.
- Introduce optional 'use_optimized_json_encoder' config property.
- If 'use_optimized_json_encoder' is true, use Oj (optimized for Rails)
  and omit 'as_json' calls for all Presenters.

Gemfile

@@ -25,6 +25,7 @@ gem 'net-ssh'
 gem 'netaddr', '>= 2.0.4'
 gem 'newrelic_rpm'
 gem 'nokogiri', '>=1.10.5'
+gem 'oj'
 gem 'palm_civet'
 gem 'posix-spawn', '~> 0.3.15'
 gem 'protobuf', '3.6.12'

Gemfile.lock

@@ -308,6 +308,7 @@ GEM
       racc (~> 1.4)
     nokogiri (1.12.3-x86_64-linux)
       racc (~> 1.4)
+    oj (3.13.2)
     os (1.0.1)
     palm_civet (1.1.0)
     parallel (1.20.1)
@@ -553,6 +554,7 @@ DEPENDENCIES
   netaddr (>= 2.0.4)
   newrelic_rpm
   nokogiri (>= 1.10.5)
+  oj
   palm_civet
   parallel_tests
   pg

config/initializers/json.rb

@@ -1,7 +1,15 @@
 require 'active_support/json/encoding'
 
 module CCInitializers
-  def self.json(_cc_config)
+  def self.json(cc_config)
+    if cc_config[:use_optimized_json_encoder]
+      MultiJson.use(:oj)
+      Oj::Rails.optimize # Use optimized encoders instead of as_json() methods for available classes.
+      Oj.default_options = {
+        bigdecimal_load: :bigdecimal,
+      }
+    end
+
     ActiveSupport.json_encoder = Class.new do
       attr_reader :options
 
@@ -10,10 +18,16 @@ def initialize(options=nil)
       end
 
       def encode(value)
+        if MultiJson.default_adapter == :oj && value.is_a?(VCAP::CloudController::Presenters::V3::BasePresenter)
+          v = value.to_hash
+        else
+          v = value.as_json(options.dup)
+        end
+
         if Rails.env.test?
-          MultiJson.dump(value.as_json(options.dup))
+          MultiJson.dump(v)
         else
-          MultiJson.dump(value.as_json(options.dup), options.merge(pretty: true))
+          MultiJson.dump(v, options.merge(pretty: true))
         end
       end
     end

lib/cloud_controller/config_schemas/base/api_schema.rb

@@ -351,6 +351,8 @@ class ApiSchema < VCAP::Config
               write_key: String,
               dataset: String,
             },
+
+            optional(:use_optimized_json_encoder) => bool,
           }
         end
         # rubocop:enable Metrics/BlockLength

lib/cloud_controller/http_response_error.rb

@@ -10,6 +10,9 @@ def initialize(message, method, response)
 
     begin
       source = MultiJson.load(response.body)
+    rescue ArgumentError
+      # Either Oj should raise Oj::ParseError instead of ArgumentError, or MultiJson should also wrap
+      # ArgumentError into MultiJson::Adapters::Oj::ParseError
     rescue MultiJson::ParseError
       source = response.body
     end