Cloud Sync

lib/flipper/adapters/sync.rb

@@ -12,6 +12,9 @@ class Sync
       # Public: The name of the adapter.
       attr_reader :name
 
+      # Public: The synchronizer that will keep the local and remote in sync.
+      attr_reader :synchronizer
+
       # Public: Build a new sync instance.
       #
       # local - The local flipper adapter that should serve reads.

lib/flipper/adapters/sync/interval_synchronizer.rb

@@ -12,6 +12,10 @@ def self.now_ms
           Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
         end
 
+        # Public: The number of milliseconds between invocations of the
+        # wrapped synchronizer.
+        attr_reader :interval
+
         # Public: Initializes a new interval synchronizer.
         #
         # synchronizer - The Synchronizer to call when the interval has passed.

lib/flipper/cloud/configuration.rb

@@ -1,4 +1,6 @@
 require "flipper/adapters/http"
+require "flipper/adapters/memory"
+require "flipper/adapters/sync"
 require "flipper/instrumenters/noop"
 
 module Flipper
@@ -36,19 +38,34 @@ class Configuration
       #  configuration.instrumenter = ActiveSupport::Notifications
       attr_accessor :instrumenter
 
+      # Public: Local adapter that all reads should go to in order to ensure
+      # latency is low and resiliency is high. This adapter is automatically
+      # kept in sync with cloud.
+      #
+      #  # for example, to use active record you could do:
+      #  configuration = Flipper::Cloud::Configuration.new
+      #  configuration.local_adapter = Flipper::Adapters::ActiveRecord.new
+      attr_accessor :local_adapter
+
+      # Public: Number of milliseconds between attempts to bring the local in
+      # sync with cloud (default: 10_000 aka 10 seconds).
+      attr_accessor :sync_interval
+
       def initialize(options = {})
         @token = options.fetch(:token)
         @instrumenter = options.fetch(:instrumenter, Instrumenters::Noop)
         @read_timeout = options.fetch(:read_timeout, 5)
         @open_timeout = options.fetch(:open_timeout, 5)
+        @sync_interval = options.fetch(:sync_interval, 10_000)
+        @local_adapter = options.fetch(:local_adapter) { Adapters::Memory.new }
         @debug_output = options[:debug_output]
         @adapter_block = ->(adapter) { adapter }
 
         self.url = options.fetch(:url, DEFAULT_URL)
       end
 
       # Public: Read or customize the http adapter. Calling without a block will
-      # perform a read. Calling with a block yields the http_adapter
+      # perform a read. Calling with a block yields the cloud adapter
       # for customization.
       #
       #   # for example, to instrument the http calls, you can wrap the http
@@ -62,23 +79,34 @@ def adapter(&block)
         if block_given?
           @adapter_block = block
         else
-          @adapter_block.call(http_adapter)
+          @adapter_block.call sync_adapter
         end
       end
 
-      # Public: Set url and uri for the http adapter.
+      # Public: Set url for the http adapter.
       attr_writer :url
 
       private
 
+      def sync_adapter
+        sync_options = {
+          instrumenter: instrumenter,
+          interval: sync_interval,
+        }
+        Flipper::Adapters::Sync.new(local_adapter, http_adapter, sync_options)
+      end
+
       def http_adapter
-        Flipper::Adapters::Http.new(url: @url,
-                                    read_timeout: @read_timeout,
-                                    open_timeout: @open_timeout,
-                                    debug_output: @debug_output,
-                                    headers: {
-                                      "Feature-Flipper-Token" => @token,
-                                    })
+        http_options = {
+          url: @url,
+          read_timeout: @read_timeout,
+          open_timeout: @open_timeout,
+          debug_output: @debug_output,
+          headers: {
+            "Feature-Flipper-Token" => @token,
+          },
+        }
+        Flipper::Adapters::Http.new(http_options)
       end
     end
   end

spec/flipper/cloud/configuration_spec.rb

@@ -28,17 +28,36 @@
     expect(instance.open_timeout).to eq(5)
   end
 
+  it "can set sync_interval" do
+    instance = described_class.new(required_options.merge(sync_interval: 1_000))
+    expect(instance.sync_interval).to eq(1_000)
+  end
+
+  it "passes sync_interval into sync adapter" do
+    # The initial sync of http to local invokes this web request.
+    stub_request(:get, /featureflipper\.com/).to_return(status: 200, body: "{}")
+
+    instance = described_class.new(required_options.merge(sync_interval: 1_000))
+    expect(instance.adapter.synchronizer.interval).to be(1_000)
+  end
+
   it "can set debug_output" do
     instance = described_class.new(required_options.merge(debug_output: STDOUT))
     expect(instance.debug_output).to eq(STDOUT)
   end
 
   it "defaults adapter block" do
+    # The initial sync of http to local invokes this web request.
+    stub_request(:get, /featureflipper\.com/).to_return(status: 200, body: "{}")
+
     instance = described_class.new(required_options)
-    expect(instance.adapter).to be_instance_of(Flipper::Adapters::Http)
+    expect(instance.adapter).to be_instance_of(Flipper::Adapters::Sync)
   end
 
   it "can override adapter block" do
+    # The initial sync of http to local invokes this web request.
+    stub_request(:get, /featureflipper\.com/).to_return(status: 200, body: "{}")
+
     instance = described_class.new(required_options)
     instance.adapter do |adapter|
       Flipper::Adapters::Instrumented.new(adapter)

spec/flipper/cloud_spec.rb

@@ -1,15 +1,21 @@
 require 'helper'
 require 'flipper/cloud'
 require 'flipper/adapters/instrumented'
+require 'flipper/instrumenters/memory'
 
 RSpec.describe Flipper::Cloud do
+  before do
+    stub_request(:get, /featureflipper\.com/).to_return(status: 200, body: "{}")
+  end
+
   context "initialize with token" do
     let(:token) { 'asdf' }
 
     before do
       @instance = described_class.new(token)
       memoized_adapter = @instance.adapter
-      @http_adapter = memoized_adapter.adapter
+      sync_adapter = memoized_adapter.adapter
+      @http_adapter = sync_adapter.instance_variable_get('@remote')
       @http_client = @http_adapter.instance_variable_get('@client')
     end
 
@@ -40,9 +46,12 @@
 
   context 'initialize with token and options' do
     before do
+      stub_request(:get, /fakeflipper\.com/).to_return(status: 200, body: "{}")
+
       @instance = described_class.new('asdf', url: 'https://www.fakeflipper.com/sadpanda')
       memoized_adapter = @instance.adapter
-      @http_adapter = memoized_adapter.adapter
+      sync_adapter = memoized_adapter.adapter
+      @http_adapter = sync_adapter.instance_variable_get('@remote')
       @http_client = @http_adapter.instance_variable_get('@client')
     end
 
@@ -55,7 +64,7 @@
   end
 
   it 'can set instrumenter' do
-    instrumenter = Object.new
+    instrumenter = Flipper::Instrumenters::Memory.new
     instance = described_class.new('asdf', instrumenter: instrumenter)
     expect(instance.instrumenter).to be(instrumenter)
   end