private Sink<Message, NotUsed> createSink(final Integer version, final String connectionCorrelationId, final AuthorizationContext connectionAuthContext, final DittoHeaders additionalHeaders, final ProtocolAdapter adapter) { return Flow.<Message>create() .filter(Message::isText) .map(Message::asTextMessage) .map(textMsg -> { if (textMsg.isStrict()) { return Source.single(textMsg.getStrictText()); } else { return textMsg.getStreamedText(); } }) .flatMapConcat(textMsg -> textMsg.<String>fold("", (str1, str2) -> str1 + str2)) .via(Flow.fromFunction(result -> { LogUtil.logWithCorrelationId(LOGGER, connectionCorrelationId, logger -> logger.debug("Received incoming WebSocket message: {}", result)); return result; })) .withAttributes(Attributes.createLogLevels(Logging.DebugLevel(), Logging.DebugLevel(), Logging.WarningLevel())) .filter(strictText -> processProtocolMessage(connectionAuthContext, connectionCorrelationId, strictText)) .map(buildSignal(version, connectionCorrelationId, connectionAuthContext, additionalHeaders, adapter)) .to(Sink.actorSubscriber( CommandSubscriber.props(streamingActor, subscriberBackpressureQueueSize, eventStream))); }