From aaa88a7dacd1ccb6b1f53f4ae6c42861b61fe574 Mon Sep 17 00:00:00 2001
From: Leigh Caplan <lcaplan@onehub.com>
Date: Sat, 16 Aug 2014 22:36:00 -0700
Subject: [PATCH 1/4] Support non-contiguous user ids and different groups per
 feature.

---
 lib/rollout.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/rollout.rb b/lib/rollout.rb
index 37eb03e..2c3f288 100644
--- a/lib/rollout.rb
+++ b/lib/rollout.rb
@@ -89,6 +89,6 @@ def user_within_active_percentage?(feature, user)
       percentage = percentage(feature)
       return false if percentage.nil?
 
-      user.id % 10 < percentage.to_i / 10
+      (user.id.hash + feature.hash) % 100 < percentage.to_i
     end
 end

From 392cf1e78de0fb39a273cc3e3a89a78c67a70a69 Mon Sep 17 00:00:00 2001
From: Leigh Caplan <lcaplan@onehub.com>
Date: Sun, 17 Aug 2014 12:00:38 -0700
Subject: [PATCH 2/4] Better, repeatable hashing.

---
 lib/rollout.rb | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/rollout.rb b/lib/rollout.rb
index 2c3f288..7f5f922 100644
--- a/lib/rollout.rb
+++ b/lib/rollout.rb
@@ -89,6 +89,17 @@ def user_within_active_percentage?(feature, user)
       percentage = percentage(feature)
       return false if percentage.nil?
 
-      (user.id.hash + feature.hash) % 100 < percentage.to_i
+      (integer_hash(user.id) + integer_hash(feature)) % 100 < percentage.to_i
+    end
+
+    def integer_hash(obj)
+      str = obj.to_s
+
+      hash = Digest::SHA1.hexdigest(str)
+
+      # only take 20 digits
+      hash = hash[0..19]
+
+      hash.to_i(16)
     end
 end

From d26f2d7f84e87ac82c383f25a84cbae0e3c74672 Mon Sep 17 00:00:00 2001
From: Leigh Caplan <lcaplan@onehub.com>
Date: Sun, 17 Aug 2014 12:04:11 -0700
Subject: [PATCH 3/4] Nicer hash wrappers.

---
 lib/rollout.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/rollout.rb b/lib/rollout.rb
index 7f5f922..e483b92 100644
--- a/lib/rollout.rb
+++ b/lib/rollout.rb
@@ -89,7 +89,11 @@ def user_within_active_percentage?(feature, user)
       percentage = percentage(feature)
       return false if percentage.nil?
 
-      (integer_hash(user.id) + integer_hash(feature)) % 100 < percentage.to_i
+      combined_hash(user.id, feature) % 100 < percentage.to_i
+    end
+
+    def combined_hash(*objects)
+      objects.inject(0) { |m,o| m + integer_hash(o) }
     end
 
     def integer_hash(obj)

From b522931c37ec270743180415a982c7cc4d8b06e0 Mon Sep 17 00:00:00 2001
From: Leigh Caplan <lcaplan@onehub.com>
Date: Mon, 18 Aug 2014 10:05:09 -0700
Subject: [PATCH 4/4] Use CRC32

---
 lib/rollout.rb | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/lib/rollout.rb b/lib/rollout.rb
index e483b92..f1c901d 100644
--- a/lib/rollout.rb
+++ b/lib/rollout.rb
@@ -1,3 +1,5 @@
+require 'zlib'
+
 class Rollout
   
   attr_accessor :redis, :groups
@@ -97,13 +99,6 @@ def combined_hash(*objects)
     end
 
     def integer_hash(obj)
-      str = obj.to_s
-
-      hash = Digest::SHA1.hexdigest(str)
-
-      # only take 20 digits
-      hash = hash[0..19]
-
-      hash.to_i(16)
+      Zlib.crc32 obj.to_s
     end
 end