Poll cold start fix

lib/flipper/adapters/poll.rb

@@ -18,6 +18,14 @@ def initialize(poller, adapter)
  @adapter = adapter
  @poller = poller
  @last_synced_at = 0
+
+ # If the adapter is empty, we need to sync before starting the poller.
+ # Yes, this will block the main thread, but that's better than thinking
+ # nothing is enabled.
+ if adapter.features.empty?
+ @poller.sync
+ end
+
  @poller.start
  end
 

spec/flipper/adapters/poll_spec.rb

@@ -0,0 +1,41 @@
+require 'flipper/adapters/poll'
+
+RSpec.describe Flipper::Adapters::Poll do
+ let(:remote_adapter) {
+ adapter = Flipper::Adapters::Memory.new(threadsafe: true)
+ flipper = Flipper.new(adapter)
+ flipper.enable(:search)
+ flipper.enable(:analytics)
+ adapter
+ }
+ let(:local_adapter) { Flipper::Adapters::Memory.new(threadsafe: true) }
+ let(:poller) {
+ Flipper::Poller.get("for_spec", {
+ start_automatically: false,
+ remote_adapter: remote_adapter,
+ })
+ }
+
+ it "syncs in main thread if local adapter is empty" do
+ instance = described_class.new(poller, local_adapter)
+ instance.features # call something to force sync
+ expect(local_adapter.features).to eq(remote_adapter.features)
+ end
+
+ it "does not sync in main thread if local adapter is not empty" do
+ # make local not empty by importing remote
+ flipper = Flipper.new(local_adapter)
+ flipper.import(remote_adapter)
+
+ # make a fake poller to verify calls
+ poller = double("Poller", last_synced_at: Concurrent::AtomicFixnum.new(0))
+ expect(poller).to receive(:start).twice
+ expect(poller).not_to receive(:sync)
+
+ # create new instance and call something to force sync
+ instance = described_class.new(poller, local_adapter)
+ instance.features # call something to force sync
+
+ expect(local_adapter.features).to eq(remote_adapter.features)
+ end
+end