Merge pull request #203 from enova/redis-persist

Persistence within Redis directly

Author: andrew

README.mdown

@@ -191,11 +191,11 @@ end
 
 ### Experiment Persistence
 
-Split comes with two built-in persistence adapters for storing users and the alternatives they've been given for each experiment.
+Split comes with three built-in persistence adapters for storing users and the alternatives they've been given for each experiment.
 
 By default Split will store the tests for each user in the session.
 
-You can optionally configure Split to use a cookie or any custom adapter of your choosing.
+You can optionally configure Split to use a cookie, Redis, or any custom adapter of your choosing.
 
 #### Cookies
 
@@ -207,6 +207,22 @@ end
 
 __Note:__ Using cookies depends on `ActionDispatch::Cookies` or any identical API
 
+#### Redis
+
+Using Redis will allow ab_users to persist across sessions or machines.
+
+```ruby
+Split.configure do |config|
+  config.persistence = Split::Persistence::RedisAdapter.with_config(:lookup_by => proc { |context| context.current_user_id }
+  # Equivalent
+  # config.persistence = Split::Persistence::RedisAdapter.with_config(:lookup_by => :current_user_id }
+end
+```
+
+Options:
+* `lookup_by`: method to invoke per request for uniquely identifying ab_users (mandatory configuration)
+* `namespace`: separate namespace to store these persisted values (default "persistence")
+
 #### Custom Adapter
 
 Your custom adapter needs to implement the same API as existing adapters.

lib/split/persistence.rb

@@ -1,4 +1,4 @@
-%w[session_adapter cookie_adapter].each do |f|
+%w[session_adapter cookie_adapter redis_adapter].each do |f|
   require "split/persistence/#{f}"
 end
 
@@ -25,4 +25,4 @@ def self.persistence_config
       Split.configuration.persistence
     end
   end
-end
+end

lib/split/persistence/redis_adapter.rb

@@ -0,0 +1,52 @@
+module Split
+  module Persistence
+    class RedisAdapter
+      DEFAULT_CONFIG = {:namespace => 'persistence'}.freeze
+
+      attr_reader :redis_key
+
+      def initialize(context)
+        if lookup_by = self.class.config[:lookup_by]
+          if lookup_by.respond_to?(:call)
+            key_frag = lookup_by.call(context)
+          else
+            key_frag = context.send(lookup_by)
+          end
+          @redis_key = "#{self.class.config[:namespace]}:#{key_frag}"
+        else
+          raise "Please configure lookup_by"
+        end
+      end
+
+      def [](field)
+        Split.redis.hget(redis_key, field)
+      end
+
+      def []=(field, value)
+        Split.redis.hset(redis_key, field, value)
+      end
+
+      def delete(field)
+        Split.redis.hdel(redis_key, field)
+      end
+
+      def keys
+        Split.redis.hkeys(redis_key)
+      end
+
+      def self.with_config(options={})
+        self.config.merge!(options)
+        self
+      end
+
+      def self.config
+        @config ||= DEFAULT_CONFIG.dup
+      end
+
+      def self.reset_config!
+        @config = DEFAULT_CONFIG.dup
+      end
+
+    end
+  end
+end

spec/persistence/redis_adapter_spec.rb

@@ -0,0 +1,81 @@
+require "spec_helper"
+
+describe Split::Persistence::RedisAdapter do
+
+  let(:context) { double(:lookup => 'blah') }
+
+  subject { Split::Persistence::RedisAdapter.new(context) }
+
+  describe '#redis_key' do
+    before { Split::Persistence::RedisAdapter.reset_config! }
+
+    context 'default' do
+      it 'should raise error with prompt to set lookup_by' do
+        expect{Split::Persistence::RedisAdapter.new(context)
+              }.to raise_error
+      end
+    end
+
+    context 'config with lookup_by = proc { "block" }' do
+      before { Split::Persistence::RedisAdapter.with_config(:lookup_by => proc{'block'}) }
+
+      it 'should be "persistence:block"' do
+        subject.redis_key.should == 'persistence:block'
+      end
+    end
+
+    context 'config with lookup_by = proc { |context| context.test }' do
+      before { Split::Persistence::RedisAdapter.with_config(:lookup_by => proc{'block'}) }
+      let(:context) { double(:test => 'block') }
+
+      it 'should be "persistence:block"' do
+        subject.redis_key.should == 'persistence:block'
+      end
+    end
+
+    context 'config with lookup_by = "method_name"' do
+      before { Split::Persistence::RedisAdapter.with_config(:lookup_by => 'method_name') }
+      let(:context) { double(:method_name => 'val') }
+
+      it 'should be "persistence:bar"' do
+        subject.redis_key.should == 'persistence:val'
+      end
+    end
+
+    context 'config with namespace and lookup_by' do
+      before { Split::Persistence::RedisAdapter.with_config(:lookup_by => proc{'frag'}, :namespace => 'namer') }
+
+      it 'should be "namer"' do
+        subject.redis_key.should == 'namer:frag'
+      end
+    end
+  end
+
+  context 'functional tests' do
+    before { Split::Persistence::RedisAdapter.with_config(:lookup_by => 'lookup') }
+
+    describe "#[] and #[]=" do
+      it "should set and return the value for given key" do
+        subject["my_key"] = "my_value"
+        subject["my_key"].should eq("my_value")
+      end
+    end
+
+    describe "#delete" do
+      it "should delete the given key" do
+        subject["my_key"] = "my_value"
+        subject.delete("my_key")
+        subject["my_key"].should be_nil
+      end
+    end
+
+    describe "#keys" do
+      it "should return an array of the user's stored keys" do
+        subject["my_key"] = "my_value"
+        subject["my_second_key"] = "my_second_value"
+        subject.keys.should =~ ["my_key", "my_second_key"]
+      end
+    end
+
+  end
+end