Auto Detect Heroku Dyno Size

If you're on Heroku and you're not manually setting your RAM size, we'll now automagically set the RAM value to the right number. This is an experimental feature.

README.md

@@ -49,7 +49,7 @@ PumaAutoTune.config do |config|
 end
 ```
 
-The default is `512` which matches the amount of ram available on a Heroku dyno. There are a few other advanced config options:
+We will attempt to detect your RAM size if you are running on Heroku. If we cannot, the default is `512` mb. There are a few other advanced config options:
 
 ```ruby
 PumaAutoTune.config do |config|

bin/heroku_ulimit_to_ram

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+limit=$(ulimit -u)
+
+case $limit in
+256)
+  ram=512
+  ;;
+512)
+  ram=1024
+  ;;
+32768)
+  ram=8192
+  ;;
+*)
+  echo 'nope';
+  exit 1;
+  ;;
+esac
+
+echo $ram

lib/puma_auto_tune.rb

@@ -14,8 +14,19 @@ module PumaAutoTune
 
   extend self
 
+  def self.default_ram
+    result = `bin/heroku_ulimit_to_ram`
+    default = if $?.success?
+      Integer(result)
+    else
+      512
+    end
+    puts "Default RAM set to #{default}"
+    default
+  end
+
   attr_accessor :ram, :max_worker_limit, :frequency, :reap_duration
-  self.ram                = 512  # mb
+  self.ram                = self.default_ram  # mb
   self.max_worker_limit   = INFINITY
   self.frequency          = 10 # seconds
   self.reap_duration      = 90 # seconds