feat: Support waiting indefinitely for initialization

README.md

@@ -38,7 +38,7 @@ This matrix mirrors the [feature matrix of the OpenFeature SDK for Ruby](https:/
 | ✅      | Logging                         | The provider logs through the logger of the `LaunchDarkly::Config` it is given.                                                                                                                                           |
 | ✅      | Domains                         | Domains bind clients to providers in the OpenFeature SDK; a separate provider instance may be registered per domain.                                                                                                      |
 | ✅      | Eventing                        | LaunchDarkly data source status changes are emitted as `PROVIDER_READY`, `PROVIDER_STALE`, and `PROVIDER_ERROR`. Flag changes are emitted as `PROVIDER_CONFIGURATION_CHANGED` with the changed flag key.                  |
-| ✅      | Initialization                  | `init` reports whether the LaunchDarkly client became ready within the configured wait time; a failure results in the `ERROR` state so that cached or fallback flag data is still evaluated.                              |
+| ✅      | Initialization                  | `init` reports whether the LaunchDarkly client became ready within the configured wait time, and waits without a deadline when that wait time is `nil`; a failure results in the `ERROR` state so that cached or fallback flag data is still evaluated. |
 | ✅      | Shutdown                        | `shutdown` closes the LaunchDarkly client. A closed client cannot be restarted, so a new provider instance is required afterward.                                                                                        |
 | ✅      | Tracking                        | `track` sends a LaunchDarkly custom event for the evaluation context, with the tracking event value and remaining details attached.                                                                                       |
 | ✅      | Transaction Context Propagation | Provided by the OpenFeature SDK, which merges the transaction context into the evaluation context before the provider is called; no provider support is required.                                                         |

lib/ldclient-openfeature/impl/event_listeners.rb

@@ -25,14 +25,14 @@ def initialize(provider)
         def update(status)
           case status.state
           when ::LaunchDarkly::Interfaces::DataSource::Status::VALID
-            @provider.emit_event(::OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+            @provider.emit_status_event(::OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
           when ::LaunchDarkly::Interfaces::DataSource::Status::INTERRUPTED
-            @provider.emit_event(
+            @provider.emit_status_event(
               ::OpenFeature::SDK::ProviderEvent::PROVIDER_STALE,
               message: message(status, "the data source has been interrupted")
             )
           when ::LaunchDarkly::Interfaces::DataSource::Status::OFF
-            @provider.emit_event(
+            @provider.emit_status_event(
               ::OpenFeature::SDK::ProviderEvent::PROVIDER_ERROR,
               error_code: ::OpenFeature::SDK::Provider::ErrorCode::GENERAL,
               message: message(status, "the data source has been permanently shut down")
@@ -54,6 +54,31 @@ def update(status)
         end
       end
 
+      #
+      # Reports the first data source state which decides the outcome of the client's initial connection attempt.
+      #
+      class DataSourceOutcomeListener
+        #
+        # @param outcome [Queue]
+        #
+        def initialize(outcome)
+          @outcome = outcome
+        end
+
+        #
+        # @param status [LaunchDarkly::Interfaces::DataSource::Status]
+        #
+        # @return [void]
+        #
+        def update(status)
+          case status.state
+          when ::LaunchDarkly::Interfaces::DataSource::Status::VALID,
+            ::LaunchDarkly::Interfaces::DataSource::Status::OFF
+            @outcome.push(status.state)
+          end
+        end
+      end
+
       #
       # Translates LaunchDarkly flag change events into OpenFeature configuration changed events.
       #

lib/ldclient-openfeature/provider.rb

@@ -33,43 +33,94 @@ class Provider
       #
       # @param sdk_key [String]
       # @param config [LaunchDarkly::Config]
-      # @param wait_for_seconds [Float]
+      # @param wait_for_seconds [Float, nil] the number of seconds to wait for the client to become ready, or nil to
+      #   wait for it without a deadline
       #
       def initialize(sdk_key, config = LaunchDarkly::Config.default, wait_for_seconds = 5)
-        @client = LaunchDarkly::LDClient.new(sdk_key, config.with_wrapper_information(WRAPPER_NAME, VERSION), wait_for_seconds)
+        @client = LaunchDarkly::LDClient.new(sdk_key, config.with_wrapper_information(WRAPPER_NAME, VERSION), wait_for_seconds.nil? ? 0 : wait_for_seconds)
 
+        @wait_for_seconds = wait_for_seconds
+        @status_lock = Mutex.new
+        @status_event = nil
+        @initialization_complete = false
         @logger = config.logger
         @context_converter = Impl::EvaluationContextConverter.new(config.logger)
         @details_converter = Impl::ResolutionDetailsConverter.new
 
         @metadata = ::OpenFeature::SDK::Provider::ProviderMetadata.new(name: "launchdarkly-openfeature-server").freeze
 
-        @client.data_source_status_provider.add_listener(Impl::DataSourceStatusListener.new(self))
-        @client.flag_tracker.add_listener(Impl::FlagChangeListener.new(self))
+        @status_listener = Impl::DataSourceStatusListener.new(self)
+        @flag_change_listener = Impl::FlagChangeListener.new(self)
+
+        @client.data_source_status_provider.add_listener(@status_listener)
+        @client.flag_tracker.add_listener(@flag_change_listener)
       end
 
       #
-      # Called by the OpenFeature SDK when this provider is set. The LaunchDarkly client has already been given the
-      # opportunity to initialize, so this only reports whether that succeeded.
+      # Called by the OpenFeature SDK when this provider is set.
+      #
+      # A wait time has already been applied by the LaunchDarkly client constructor, so this reports whether that
+      # succeeded. A nil wait time asks for no deadline, so this waits for the data source to become valid or to fail
+      # permanently.
       #
       # @param _evaluation_context [::OpenFeature::SDK::EvaluationContext, nil]
       #
       # @return [void]
       #
       def init(_evaluation_context = nil)
-        return if @client.initialized?
+        wait_for_data_source_outcome if @wait_for_seconds.nil?
+
+        initialized = @client.initialized?
+
+        @status_lock.synchronize do
+          # The OpenFeature SDK emits its own event for the outcome of initialization, so the status is recorded
+          # here without emitting an event.
+          @status_event = if initialized
+                            ::OpenFeature::SDK::ProviderEvent::PROVIDER_READY
+                          else
+                            ::OpenFeature::SDK::ProviderEvent::PROVIDER_ERROR
+                          end
+          @initialization_complete = true
+        end
+
+        return if initialized
 
         state = @client.data_source_status_provider.status.state
         raise "the LaunchDarkly client was unable to initialize; the data source state is #{state}"
       end
 
+      #
+      # Emit a provider event for a data source state change.
+      #
+      # A state which does not change the provider status is not emitted, and neither is the change which completes
+      # initialization, because the OpenFeature SDK emits its own event for that one. Changes after initialization has
+      # completed, including after it has failed, are emitted.
+      #
+      # @param event [String]
+      # @param details [Hash]
+      #
+      # @return [void]
+      #
+      def emit_status_event(event, **details)
+        @status_lock.synchronize do
+          return if event == @status_event
+
+          @status_event = event
+          return unless @initialization_complete
+        end
+
+        emit_event(event, **details)
+      end
+
       #
       # Called by the OpenFeature SDK when this provider is replaced or the SDK is shut down. The LaunchDarkly client
       # cannot be restarted, so a new provider instance is required afterward.
       #
       # @return [void]
       #
       def shutdown
+        @client.data_source_status_provider.remove_listener(@status_listener)
+        @client.flag_tracker.remove_listener(@flag_change_listener)
         @client.close
       end
 
@@ -170,6 +221,27 @@ def track(tracking_event_name, evaluation_context: nil, tracking_event_details:
         @details_converter.to_resolution_details(evaluation_detail)
       end
 
+      #
+      # Block until the data source reports an outcome for the client's first connection attempt.
+      #
+      # @return [void]
+      #
+      private def wait_for_data_source_outcome
+        outcome = Queue.new
+        listener = Impl::DataSourceOutcomeListener.new(outcome)
+        status_provider = @client.data_source_status_provider
+        status_provider.add_listener(listener)
+
+        begin
+          return if @client.initialized?
+          return if status_provider.status.state == ::LaunchDarkly::Interfaces::DataSource::Status::OFF
+
+          outcome.pop
+        ensure
+          status_provider.remove_listener(listener)
+        end
+      end
+
       #
       # @param default_value [any]
       #

spec/impl/data_source_outcome_listener_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+RSpec.describe LaunchDarkly::OpenFeature::Impl::DataSourceOutcomeListener do
+  let(:outcome) { Queue.new }
+  let(:listener) { described_class.new(outcome) }
+
+  def status(state)
+    LaunchDarkly::Interfaces::DataSource::Status.new(state, Time.now, nil)
+  end
+
+  it "reports a valid data source" do
+    listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::VALID))
+
+    expect(outcome.pop).to eq(LaunchDarkly::Interfaces::DataSource::Status::VALID)
+  end
+
+  it "reports a shut down data source" do
+    listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::OFF))
+
+    expect(outcome.pop).to eq(LaunchDarkly::Interfaces::DataSource::Status::OFF)
+  end
+
+  it "does not report a state which leaves the outcome undecided" do
+    listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::INITIALIZING))
+    listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::INTERRUPTED))
+
+    expect(outcome).to be_empty
+  end
+end

spec/impl/data_source_status_listener_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 RSpec.describe LaunchDarkly::OpenFeature::Impl::DataSourceStatusListener do
-  let(:provider) { double(emit_event: nil) }
+  let(:provider) { double(emit_status_event: nil) }
   let(:listener) { described_class.new(provider) }
 
   def status(state, error = nil)
@@ -11,13 +11,13 @@ def status(state, error = nil)
   it "a valid data source is ready" do
     listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::VALID))
 
-    expect(provider).to have_received(:emit_event).with(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+    expect(provider).to have_received(:emit_status_event).with(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
   end
 
   it "an interrupted data source is stale" do
     listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::INTERRUPTED))
 
-    expect(provider).to have_received(:emit_event)
+    expect(provider).to have_received(:emit_status_event)
       .with(OpenFeature::SDK::ProviderEvent::PROVIDER_STALE, hash_including(:message))
   end
 
@@ -28,7 +28,7 @@ def status(state, error = nil)
 
     listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::OFF, error))
 
-    expect(provider).to have_received(:emit_event).with(
+    expect(provider).to have_received(:emit_status_event).with(
       OpenFeature::SDK::ProviderEvent::PROVIDER_ERROR,
       hash_including(error_code: OpenFeature::SDK::Provider::ErrorCode::GENERAL, message: /401/)
     )
@@ -37,6 +37,6 @@ def status(state, error = nil)
   it "an initializing data source does not emit an event" do
     listener.update(status(LaunchDarkly::Interfaces::DataSource::Status::INITIALIZING))
 
-    expect(provider).not_to have_received(:emit_event)
+    expect(provider).not_to have_received(:emit_status_event)
   end
 end

spec/provider_spec.rb

@@ -10,6 +10,10 @@
   let(:config) { LaunchDarkly::Config.new(data_source: td, send_events: false) }
   let(:provider) { described_class.new("example-key", config) }
 
+  def data_source_status(state, error = nil)
+    LaunchDarkly::Interfaces::DataSource::Status.new(state, Time.now, error)
+  end
+
   it "metadata is set correctly" do
     expect(provider.metadata.name).to eq("launchdarkly-openfeature-server")
   end
@@ -48,18 +52,98 @@
   end
 
   it "init raises when the client failed to initialize" do
-    status = LaunchDarkly::Interfaces::DataSource::Status.new(LaunchDarkly::Interfaces::DataSource::Status::OFF, Time.now, nil)
-    status_provider = double(status: status)
+    status_provider = double(status: data_source_status(LaunchDarkly::Interfaces::DataSource::Status::OFF))
     allow(provider.client).to receive_messages(initialized?: false, data_source_status_provider: status_provider)
 
     expect { provider.init(evaluation_context) }.to raise_error(/unable to initialize/)
   end
 
-  it "shutdown closes the client" do
-    allow(provider.client).to receive(:close)
+  it "init without a deadline waits for the data source to become valid" do
+    indefinite_provider = described_class.new("example-key", config, nil)
+
+    expect { indefinite_provider.init(evaluation_context) }.not_to raise_error
+    expect(indefinite_provider.client.initialized?).to be(true)
+  end
+
+  it "init without a deadline waits for a data source outcome which arrives later" do
+    indefinite_provider = described_class.new("example-key", config, nil)
+    listeners = []
+    status_provider = double(status: data_source_status(LaunchDarkly::Interfaces::DataSource::Status::INITIALIZING))
+    allow(status_provider).to receive(:add_listener) { |listener| listeners << listener }
+    allow(status_provider).to receive(:remove_listener)
+    allow(indefinite_provider.client).to receive_messages(initialized?: false, data_source_status_provider: status_provider)
+
+    reporter = Thread.new do
+      sleep(0.01) while listeners.empty?
+      listeners.each { |listener| listener.update(data_source_status(LaunchDarkly::Interfaces::DataSource::Status::OFF)) }
+    end
+
+    expect { indefinite_provider.init(evaluation_context) }.to raise_error(/unable to initialize/)
+
+    reporter.join
+  end
+
+  it "init with a wait time of zero does not wait" do
+    zero_wait_provider = described_class.new("example-key", config, 0)
+    status_provider = double(status: data_source_status(LaunchDarkly::Interfaces::DataSource::Status::INITIALIZING))
+    allow(status_provider).to receive(:add_listener)
+    allow(zero_wait_provider.client).to receive_messages(initialized?: false, data_source_status_provider: status_provider)
+
+    expect { zero_wait_provider.init(evaluation_context) }.to raise_error(/unable to initialize/)
+    expect(status_provider).not_to have_received(:add_listener)
+  end
+
+  it "init with a wait time does not wait again" do
+    wait_provider = described_class.new("example-key", config, 5)
+    status_provider = double(status: data_source_status(LaunchDarkly::Interfaces::DataSource::Status::INITIALIZING))
+    allow(status_provider).to receive(:add_listener)
+    allow(wait_provider.client).to receive_messages(initialized?: false, data_source_status_provider: status_provider)
+
+    expect { wait_provider.init(evaluation_context) }.to raise_error(/unable to initialize/)
+    expect(status_provider).not_to have_received(:add_listener)
+  end
+
+  it "a status change before initialization completes is not emitted" do
+    allow(provider).to receive(:emit_event)
+
+    provider.emit_status_event(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+
+    expect(provider).not_to have_received(:emit_event)
+  end
+
+  it "a status change after initialization failed is emitted" do
+    status_provider = double(status: data_source_status(LaunchDarkly::Interfaces::DataSource::Status::OFF))
+    allow(provider.client).to receive_messages(initialized?: false, data_source_status_provider: status_provider)
+    expect { provider.init(evaluation_context) }.to raise_error(/unable to initialize/)
+    allow(provider).to receive(:emit_event)
+
+    provider.emit_status_event(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+
+    expect(provider).to have_received(:emit_event).with(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+  end
+
+  it "a status which does not change is not emitted" do
+    provider.init(evaluation_context)
+    allow(provider).to receive(:emit_event)
+
+    provider.emit_status_event(OpenFeature::SDK::ProviderEvent::PROVIDER_READY)
+    provider.emit_status_event(OpenFeature::SDK::ProviderEvent::PROVIDER_STALE, message: "interrupted")
+    provider.emit_status_event(OpenFeature::SDK::ProviderEvent::PROVIDER_STALE, message: "interrupted again")
+
+    expect(provider).to have_received(:emit_event).once
+    expect(provider).to have_received(:emit_event)
+      .with(OpenFeature::SDK::ProviderEvent::PROVIDER_STALE, hash_including(:message))
+  end
+
+  it "shutdown unsubscribes the listeners and closes the client" do
+    status_provider = double(remove_listener: nil)
+    flag_tracker = double(remove_listener: nil)
+    allow(provider.client).to receive_messages(close: nil, data_source_status_provider: status_provider, flag_tracker: flag_tracker)
 
     provider.shutdown
 
+    expect(status_provider).to have_received(:remove_listener).with(instance_of(LaunchDarkly::OpenFeature::Impl::DataSourceStatusListener))
+    expect(flag_tracker).to have_received(:remove_listener).with(instance_of(LaunchDarkly::OpenFeature::Impl::FlagChangeListener))
     expect(provider.client).to have_received(:close)
   end