Switch from proc-wait3 to rusage gem.

proc-wait3 monkey patches `$?` which was causing
problems for poltergeist. rusage is lighter weight
and provides the bit of proc-wait3 we care about.

Author: myronmarston

Gemfile.lock

@@ -60,7 +60,6 @@ GEM
       http_parser.rb (~> 0.5.3)
       multi_json (~> 1.0)
     powerpack (0.0.8)
-    proc-wait3 (1.6.0)
     rack (1.5.2)
     rack-protection (1.5.0)
       rack
@@ -84,6 +83,7 @@ GEM
       powerpack (~> 0.0.6)
       rainbow (>= 1.1.4)
     rubyzip (0.9.9)
+    rusage (0.2.0)
     selenium-webdriver (2.35.1)
       childprocess (>= 0.2.5)
       multi_json (~> 1.0)
@@ -124,12 +124,12 @@ DEPENDENCIES
   launchy (~> 2.1.0)
   metriks (~> 0.9)
   poltergeist (~> 1.0.0)
-  proc-wait3 (~> 1.6)
   qless!
   rake (~> 10.0)
   rspec (~> 2.12)
   rspec-fire (~> 1.1)
   rubocop (~> 0.13.1)
+  rusage (~> 0.2.0)
   sentry-raven (~> 0.4)
   simplecov (~> 0.7.1)
   sinatra (~> 1.3.2)

benchmarks/current_memory_usage.rb

@@ -7,22 +7,22 @@
     n.times { Integer(`ps -o rss= -p #{Process.pid}`) * 1024 }
   end
 
-  x.report("proc-wait3") do
-    require 'proc/wait3'
-    n.times { Process.getrusage }
+  x.report("rusage") do
+    require 'rusage'
+    n.times { Process.rusage }
   end
 end
 
 =begin
 On my computer:
 
 Rehearsal ------------------------------------------------
-shelling out   0.100000   0.670000   3.750000 (  4.141153)
-proc-wait3     0.000000   0.000000   0.000000 (  0.002601)
---------------------------------------- total: 3.750000sec
+shelling out   0.090000   0.550000   3.650000 (  4.051986)
+rusage         0.010000   0.000000   0.010000 (  0.002501)
+--------------------------------------- total: 3.660000sec
 
                    user     system      total        real
-shelling out   0.090000   0.730000   3.760000 (  4.150078)
-proc-wait3     0.000000   0.000000   0.000000 (  0.003116)
+shelling out   0.100000   0.550000   3.660000 (  4.031830)
+rusage         0.010000   0.000000   0.010000 (  0.001669)
 =end
 

lib/qless/middleware/memory_usage_monitor.rb

@@ -28,12 +28,12 @@ def format_large_number(num)
       end
 
       begin
-        require 'proc/wait3'
+        require 'rusage'
         def self.current_usage
-          Process.getrusage.maxrss
+          Process.rusage.maxrss
         end
       rescue LoadError
-        warn "Could not load `proc-wait3` gem. Falling back to shelling out to get process memory usage, " +
+        warn "Could not load `rusage` gem. Falling back to shelling out to get process memory usage, " +
              "which is several orders of magnitude slower."
 
         def self.current_usage

qless.gemspec

@@ -50,5 +50,5 @@ language-specific extension will also remain up to date.
   s.add_development_dependency 'sentry-raven'  , '~> 0.4'
   s.add_development_dependency 'metriks'       , '~> 0.9'
   s.add_development_dependency 'rubocop'       , '~> 0.13.1'
-  s.add_development_dependency 'proc-wait3'    , '~> 1.6'
+  s.add_development_dependency 'rusage'        , '~> 0.2.0'
 end

spec/integration/middleware/memory_usage_monitor_spec.rb

@@ -92,19 +92,19 @@ def self.puts(msg)
         end
       end
 
-      context "when the proc-wait3 gem is available" do
+      context "when the rusage gem is available" do
         before do
           load "qless/middleware/memory_usage_monitor.rb"
 
-          unless Process.respond_to?(:getrusage)
-            pending "Could not load the proc-wait3 gem"
+          unless Process.respond_to?(:rusage)
+            pending "Could not load the rusage gem"
           end
         end
 
         include_examples "memory usage monitor"
       end
 
-      context "when the proc-wait3 gem is not available" do
+      context "when the rusage gem is not available" do
         before do
           MemoryUsageMonitor.stub(:warn)
           MemoryUsageMonitor.stub(:require).and_raise(LoadError)