Introduce support for dumping Rails process heap at the end of a benchmark run

app/controllers/admin/diagnostics_controller.rb

@@ -18,4 +18,20 @@ class Admin::DiagnosticsController < Admin::AdminController
       content_type: Mime::TEXT
 
   end
+
+  def dump_heap
+    begin
+      # ruby 2.1
+      GC.start(full_mark: true)
+      require 'objspace'
+
+      io = File.open("discourse-heap-#{SecureRandom.hex(3)}.json",'w')
+      ObjectSpace.dump_all(:output => io)
+      io.close
+
+      render text: "HEAP DUMP:\n#{io.path}", content_type: Mime::TEXT
+    rescue
+      render text: "HEAP DUMP:\nnot supported", content_type: Mime::TEXT
+    end
+  end
 end

config/boot.rb

@@ -1,3 +1,8 @@
+if ENV['DISCOURSE_DUMP_HEAP'] == "1"
+  require 'objspace'
+  ObjectSpace.trace_object_allocations_start
+end
+
 require 'rubygems'
 
 # Set up gems listed in the Gemfile.

config/routes.rb

@@ -181,6 +181,7 @@ Discourse::Application.routes.draw do
     end
 
     get "memory_stats"=> "diagnostics#memory_stats", constraints: AdminConstraint.new
+    get "dump_heap"=> "diagnostics#dump_heap", constraints: AdminConstraint.new
 
   end # admin namespace
 

script/bench.rb

@@ -10,6 +10,7 @@ require "fileutils"
 @best_of = 1
 @mem_stats = false
 @unicorn = false
+@dump_heap = false
 
 opts = OptionParser.new do |o|
   o.banner = "Usage: ruby bench.rb [options]"
@@ -26,6 +27,11 @@ opts = OptionParser.new do |o|
   o.on("-b", "--best_of [NUM]", "Number of times to run the bench taking best as result") do |i|
     @best_of = i.to_i
   end
+  o.on("-d", "--heap_dump") do
+    @dump_heap = true
+    # We need an env var for config/boot.rb to enable allocation tracing prior to framework init
+    ENV['DISCOURSE_DUMP_HEAP'] = "1"
+  end
   o.on("-m", "--memory_stats") do
     @mem_stats = true
   end
@@ -103,18 +109,18 @@ end
 ENV["RAILS_ENV"] = "profile"
 
 
-gc_env_vars = %w(RUBY_GC_HEAP_INIT_SLOTS RUBY_GC_HEAP_FREE_SLOTS RUBY_GC_HEAP_GROWTH_FACTOR RUBY_GC_HEAP_GROWTH_MAX_SLOTS RUBY_GC_MALLOC_LIMIT RUBY_GC_OLDMALLOC_LIMIT RUBY_GC_MALLOC_LIMIT_MAX RUBY_GC_OLDMALLOC_LIMIT_MAX RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR)
+discourse_env_vars = %w(DISCOURSE_DUMP_HEAP RUBY_GC_HEAP_INIT_SLOTS RUBY_GC_HEAP_FREE_SLOTS RUBY_GC_HEAP_GROWTH_FACTOR RUBY_GC_HEAP_GROWTH_MAX_SLOTS RUBY_GC_MALLOC_LIMIT RUBY_GC_OLDMALLOC_LIMIT RUBY_GC_MALLOC_LIMIT_MAX RUBY_GC_OLDMALLOC_LIMIT_MAX RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR)
 
 if @include_env
   puts "Running with tuned environment"
   ENV["RUBY_GC_MALLOC_LIMIT"] = "50_000_000"
-  gc_env_vars - %w(RUBY_GC_MALLOC_LIMIT).each do |v|
+  discourse_env_vars - %w(RUBY_GC_MALLOC_LIMIT).each do |v|
     ENV.delete v
   end
 else
   # clean env
   puts "Running with the following custom environment"
-  gc_env_vars.each do |w|
+  discourse_env_vars.each do |w|
     puts "#{w}: #{ENV[w]}"
   end
 end
@@ -256,6 +262,11 @@ begin
     puts open("http://127.0.0.1:#{@port}/admin/memory_stats#{append}").read
   end
 
+  if @dump_heap
+    puts
+    puts open("http://127.0.0.1:#{@port}/admin/dump_heap#{append}").read
+  end
+
   if @result_file
     File.open(@result_file,"wb") do |f|
       f.write(results)