feat: Add postfork method to re-initialize after forking (#319)

Author: keelerm84

contract-tests/service.rb

@@ -41,6 +41,7 @@
       'context-comparison',
       'polling-gzip',
       'inline-context-all',
+      'instance-id',
       'anonymous-redaction',
       'evaluation-hooks',
       'omit-anonymous-contexts',

lib/ldclient-rb/config.rb

@@ -81,6 +81,7 @@ def initialize(opts = {})
       @hooks = (opts[:hooks] || []).keep_if { |hook| hook.is_a? Interfaces::Hooks::Hook }
       @omit_anonymous_contexts = opts.has_key?(:omit_anonymous_contexts) && opts[:omit_anonymous_contexts]
       @data_source_update_sink = nil
+      @instance_id = nil
     end
 
     #
@@ -97,6 +98,18 @@ def initialize(opts = {})
     #
     attr_accessor :data_source_update_sink
 
+
+    #
+    # Returns the unique identifier for this instance of the SDK.
+    #
+    # This property should only be set by the SDK. Long term access of this
+    # property is not supported; it is temporarily being exposed to maintain
+    # backwards compatibility while the SDK structure is updated.
+    #
+    # @private
+    #
+    attr_accessor :instance_id
+
     #
     # The base URL for the LaunchDarkly server. This is configurable mainly for testing
     # purposes; most users should use the default value.

lib/ldclient-rb/impl/util.rb

@@ -11,6 +11,9 @@ def self.current_time_millis
 
       def self.default_http_headers(sdk_key, config)
         ret = { "Authorization" => sdk_key, "User-Agent" => "RubyClient/" + LaunchDarkly::VERSION }
+
+        ret["X-LaunchDarkly-Instance-Id"] = config.instance_id unless config.instance_id.nil?
+
         if config.wrapper_name
           ret["X-LaunchDarkly-Wrapper"] = config.wrapper_name +
             (config.wrapper_version ? "/" + config.wrapper_version : "")

lib/ldclient-rb/ldclient.rb

@@ -13,6 +13,7 @@
 require "digest/sha1"
 require "forwardable"
 require "logger"
+require "securerandom"
 require "benchmark"
 require "json"
 require "openssl"
@@ -56,25 +57,57 @@ def initialize(sdk_key, config = Config.default, wait_for_sec = 5)
       end
 
       @sdk_key = sdk_key
-      @hooks = Concurrent::Array.new(config.hooks)
+      config.instance_id = SecureRandom.uuid
+      @config = config
+
+      start_up(wait_for_sec)
+    end
+
+    #
+    # Re-initializes an existing client after a process fork.
+    #
+    # The SDK relies on multiple background threads to operate correctly. When a process forks, `these threads are not
+    # available to the child <https://apidock.com/ruby/Process/fork/class>`.
+    #
+    # As a result, the SDK will not function correctly in the child process until it is re-initialized.
+    #
+    # This method is effectively equivalent to instantiating a new client. Future iterations of the SDK will provide
+    # increasingly efficient re-initializing improvements.
+    #
+    # Note that any configuration provided to the SDK will need to survive the forking process independently. For this
+    # reason, it is recommended that any listener or hook integrations be added postfork unless you are certain it can
+    # survive the forking process.
+    #
+    # @param wait_for_sec [Float] maximum time (in seconds) to wait for initialization
+    #
+    def postfork(wait_for_sec = 5)
+      @data_source = nil
+      @event_processor = nil
+      @big_segment_store_manager = nil
+
+      start_up(wait_for_sec)
+    end
+
+    private def start_up(wait_for_sec)
+      @hooks = Concurrent::Array.new(@config.hooks)
 
       @shared_executor = Concurrent::SingleThreadExecutor.new
 
-      data_store_broadcaster = LaunchDarkly::Impl::Broadcaster.new(@shared_executor, config.logger)
+      data_store_broadcaster = LaunchDarkly::Impl::Broadcaster.new(@shared_executor, @config.logger)
       store_sink = LaunchDarkly::Impl::DataStore::UpdateSink.new(data_store_broadcaster)
 
       # We need to wrap the feature store object with a FeatureStoreClientWrapper in order to add
       # some necessary logic around updates. Unfortunately, we have code elsewhere that accesses
       # the feature store through the Config object, so we need to make a new Config that uses
       # the wrapped store.
-      @store = Impl::FeatureStoreClientWrapper.new(config.feature_store, store_sink, config.logger)
-      updated_config = config.clone
+      @store = Impl::FeatureStoreClientWrapper.new(@config.feature_store, store_sink, @config.logger)
+      updated_config = @config.clone
       updated_config.instance_variable_set(:@feature_store, @store)
       @config = updated_config
 
       @data_store_status_provider = LaunchDarkly::Impl::DataStore::StatusProvider.new(@store, store_sink)
 
-      @big_segment_store_manager = Impl::BigSegmentStoreManager.new(config.big_segments, @config.logger)
+      @big_segment_store_manager = Impl::BigSegmentStoreManager.new(@config.big_segments, @config.logger)
       @big_segment_store_status_provider = @big_segment_store_manager.status_provider
 
       get_flag = lambda { |key| @store.get(FEATURES, key) }
@@ -83,15 +116,15 @@ def initialize(sdk_key, config = Config.default, wait_for_sec = 5)
       @evaluator = LaunchDarkly::Impl::Evaluator.new(get_flag, get_segment, get_big_segments_membership, @config.logger)
 
       if !@config.offline? && @config.send_events && !@config.diagnostic_opt_out?
-        diagnostic_accumulator = Impl::DiagnosticAccumulator.new(Impl::DiagnosticAccumulator.create_diagnostic_id(sdk_key))
+        diagnostic_accumulator = Impl::DiagnosticAccumulator.new(Impl::DiagnosticAccumulator.create_diagnostic_id(@sdk_key))
       else
         diagnostic_accumulator = nil
       end
 
       if @config.offline? || !@config.send_events
         @event_processor = NullEventProcessor.new
       else
-        @event_processor = EventProcessor.new(sdk_key, config, nil, diagnostic_accumulator)
+        @event_processor = EventProcessor.new(@sdk_key, @config, nil, diagnostic_accumulator)
       end
 
       if @config.use_ldd?
@@ -115,9 +148,9 @@ def initialize(sdk_key, config = Config.default, wait_for_sec = 5)
         # Currently, data source factories take two parameters unless they need to be aware of diagnostic_accumulator, in
         # which case they take three parameters. This will be changed in the future to use a less awkware mechanism.
         if data_source_or_factory.arity == 3
-          @data_source = data_source_or_factory.call(sdk_key, @config, diagnostic_accumulator)
+          @data_source = data_source_or_factory.call(@sdk_key, @config, diagnostic_accumulator)
         else
-          @data_source = data_source_or_factory.call(sdk_key, @config)
+          @data_source = data_source_or_factory.call(@sdk_key, @config)
         end
       else
         @data_source = data_source_or_factory

spec/impl/event_sender_spec.rb

@@ -29,6 +29,7 @@ def with_sender_and_server(config_options = {})
       it "sends analytics event data without compression enabled" do
         with_sender_and_server(compress_events: false) do |es, server|
           server.setup_ok_response("/bulk", "")
+          es.instance_variable_get(:@config).instance_id = 'instance-id'
 
           result = es.send_event_data(fake_data, "", false)
 
@@ -43,6 +44,7 @@ def with_sender_and_server(config_options = {})
             "content-type" => [ "application/json" ],
             "user-agent" => [ "RubyClient/" + LaunchDarkly::VERSION ],
             "x-launchdarkly-event-schema" => [ "4" ],
+            "x-launchdarkly-instance-id" => [ "instance-id" ],
             "connection" => [ "Keep-Alive" ],
           })
           expect(req.header['x-launchdarkly-payload-id']).not_to eq []

spec/requestor_spec.rb

@@ -19,6 +19,7 @@ def with_requestor(base_uri, opts = {})
       it "uses expected URI and headers" do
         with_server do |server|
           with_requestor(server.base_uri.to_s) do |requestor|
+            requestor.instance_variable_get(:@config).instance_id = 'instance-id'
             server.setup_ok_response("/", "{}")
             requestor.request_all_data
             expect(server.requests.count).to eq 1
@@ -27,6 +28,7 @@ def with_requestor(base_uri, opts = {})
               "authorization" => [ sdk_key ],
               "user-agent" => [ "RubyClient/" + VERSION ],
               "x-launchdarkly-tags" => [ "application-id/id application-version/version" ],
+              "x-launchdarkly-instance-id" => [ "instance-id" ],
             })
           end
         end