Add ActorLimit adapter

lib/flipper.rb

@@ -175,10 +175,11 @@ def groups_registry=(registry)
 require 'flipper/actor'
 require 'flipper/adapter'
 require 'flipper/adapters/wrapper'
+require 'flipper/adapters/actor_limit'
+require 'flipper/adapters/instrumented'
 require 'flipper/adapters/memoizable'
 require 'flipper/adapters/memory'
 require 'flipper/adapters/strict'
-require 'flipper/adapters/instrumented'
 require 'flipper/adapter_builder'
 require 'flipper/configuration'
 require 'flipper/dsl'

lib/flipper/adapters/actor_limit.rb

@@ -0,0 +1,28 @@
+module Flipper
+  module Adapters
+    class ActorLimit < Wrapper
+      LimitExceeded = Class.new(Flipper::Error)
+
+      attr_reader :limit
+
+      def initialize(adapter, limit = 100)
+        super(adapter)
+        @limit = limit
+      end
+
+      def enable(feature, gate, resource)
+        if gate.is_a?(Flipper::Gates::Actor) && over_limit?(feature)
+          raise LimitExceeded, "Actor limit of #{@limit} exceeded for feature #{feature.key}. See https://www.flippercloud.io/docs/features/actors#limitations"
+        else
+          super
+        end
+      end
+
+      private
+
+      def over_limit?(feature)
+        feature.actors_value.size >= @limit
+      end
+    end
+  end
+end

lib/flipper/engine.rb

@@ -25,6 +25,7 @@ def self.default_strict_value
         log: ENV.fetch('FLIPPER_LOG', 'true').casecmp('true').zero?,
         cloud_path: "_flipper",
         strict: default_strict_value,
+        actor_limit: ENV["FLIPPER_ACTOR_LIMIT"]&.to_i || 100,
         test_help: Flipper::Typecast.to_boolean(ENV["FLIPPER_TEST_HELP"] || Rails.env.test?),
       )
     end
@@ -65,13 +66,12 @@ def self.default_strict_value
       end
     end
 
-    initializer "flipper.strict", after: :load_config_initializers do |app|
+    initializer "flipper.adapters", after: :load_config_initializers do |app|
       flipper = app.config.flipper
 
-      if flipper.strict
-        Flipper.configure do |config|
-          config.use Flipper::Adapters::Strict, flipper.strict
-        end
+      Flipper.configure do |config|
+        config.use Flipper::Adapters::Strict, flipper.strict if flipper.strict
+        config.use Flipper::Adapters::ActorLimit, flipper.actor_limit if flipper.actor_limit
       end
     end
 

spec/flipper/adapters/actor_limit_spec.rb

@@ -0,0 +1,20 @@
+require "flipper/adapters/actor_limit"
+
+RSpec.describe Flipper::Adapters::ActorLimit do
+  it_should_behave_like 'a flipper adapter' do
+    let(:limit) { 5 }
+    let(:adapter) { Flipper::Adapters::ActorLimit.new(Flipper::Adapters::Memory.new, limit) }
+
+    subject { adapter }
+
+    describe '#enable' do
+      it "fails when limit exceeded" do
+        5.times { |i| feature.enable Flipper::Actor.new("User;#{i}") }
+
+        expect {
+          feature.enable Flipper::Actor.new("User;6")
+        }.to raise_error(Flipper::Adapters::ActorLimit::LimitExceeded)
+      end
+    end
+  end
+end

spec/flipper/engine_spec.rb

@@ -53,7 +53,7 @@
       ENV['FLIPPER_STRICT'] = 'false'
       subject
       expect(config.strict).to eq(false)
-      expect(adapter).to be_instance_of(Flipper::Adapters::Memory)
+      expect(adapter).not_to be_instance_of(Flipper::Adapters::Strict)
     end
 
     [true, :raise, :warn].each do |value|
@@ -69,7 +69,7 @@
       initializer { config.strict = false }
       subject
       expect(config.strict).to eq(false)
-      expect(adapter).to be_instance_of(Flipper::Adapters::Memory)
+      expect(adapter).not_to be_instance_of(Flipper::Adapters::Strict)
     end
 
     it "defaults to strict=:warn in RAILS_ENV=development" do
@@ -85,7 +85,7 @@
         expect(Rails.env).to eq(env)
         subject
         expect(config.strict).to eq(false)
-        expect(adapter).to be_instance_of(Flipper::Adapters::Memory)
+        expect(adapter).not_to be_instance_of(Flipper::Adapters::Strict)
       end
     end
 
@@ -336,6 +336,33 @@
     expect(ActiveRecord::Base.ancestors).to include(Flipper::Model::ActiveRecord)
   end
 
+  describe "config.actor_limit" do
+    let(:adapter) do
+      application.initialize!
+      Flipper.adapter.adapter.adapter
+    end
+
+    it "defaults to 100" do
+      expect(adapter).to be_instance_of(Flipper::Adapters::ActorLimit)
+      expect(adapter.limit).to eq(100)
+    end
+
+    it "can be set from FLIPPER_ACTOR_LIMIT env" do
+      ENV["FLIPPER_ACTOR_LIMIT"] = "500"
+      expect(adapter.limit).to eq(500)
+    end
+
+    it "can be set from an initializer" do
+      initializer { config.actor_limit = 99 }
+      expect(adapter.limit).to eq(99)
+    end
+
+    it "can be disabled from an initializer" do
+      initializer { config.actor_limit = false }
+      expect(adapter).not_to be_instance_of(Flipper::Adapters::ActorLimit)
+    end
+  end
+
   # Add app initializer in the same order as config/initializers/*
   def initializer(&block)
     application.initializer 'spec', before: :load_config_initializers do

test/adapters/actor_limit_test.rb

@@ -0,0 +1,20 @@
+require "test_helper"
+require "flipper/test/shared_adapter_test"
+require "flipper/adapters/actor_limit"
+
+class Flipper::Adapters::ActorLimitTest < MiniTest::Test
+  prepend Flipper::Test::SharedAdapterTests
+
+  def setup
+    @memory = Flipper::Adapters::Memory.new
+    @adapter = Flipper::Adapters::ActorLimit.new(@memory, 5)
+  end
+
+  def test_enable_fails_when_limit_exceeded
+    5.times { |i| @feature.enable Flipper::Actor.new("User;#{i}") }
+
+    assert_raises Flipper::Adapters::ActorLimit::LimitExceeded do
+      @feature.enable Flipper::Actor.new("User;6")
+    end
+  end
+end