# TargetHandler.java

    /*
     *  Copyright (c) 2009, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     *  Licensed under the Apache License, Version 2.0 (the "License");
     *  you may not use this file except in compliance with the License.
     *  You may obtain a copy of the License at
     *
     *        http://www.apache.org/licenses/LICENSE-2.0
     *
     *  Unless required by applicable law or agreed to in writing, software
     *  distributed under the License is distributed on an "AS IS" BASIS,
     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     *  See the License for the specific language governing permissions and
     *  limitations under the License.
     */

    package org.apache.synapse.transport.passthru;

    import org.apache.axis2.AxisFault;
    import org.apache.axis2.context.MessageContext;
    import org.apache.axis2.description.WSDL2Constants;
    import org.apache.axis2.engine.MessageReceiver;
    import org.apache.axis2.transport.base.MetricsCollector;
    import org.apache.axis2.transport.base.threads.WorkerPool;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.http.ConnectionClosedException;
    import org.apache.http.HttpException;
    import org.apache.http.HttpRequest;
    import org.apache.http.HttpResponse;
    import org.apache.http.HttpStatus;
    import org.apache.http.StatusLine;
    import org.apache.http.conn.routing.HttpRoute;
    import org.apache.http.impl.nio.DefaultNHttpClientConnection;
    import org.apache.http.nio.ContentDecoder;
    import org.apache.http.nio.ContentEncoder;
    import org.apache.http.nio.NHttpClientConnection;
    import org.apache.http.nio.NHttpClientEventHandler;
    import org.apache.http.nio.NHttpServerConnection;
    import org.apache.http.nio.reactor.IOSession;
    import org.apache.http.protocol.HttpContext;
    import org.apache.synapse.commons.CorrelationConstants;
    import org.apache.synapse.commons.logger.ContextAwareLogger;
    import org.apache.synapse.commons.util.MiscellaneousUtil;
    import org.apache.synapse.transport.http.conn.ClientConnFactory;
    import org.apache.synapse.transport.http.conn.LoggingNHttpClientConnection;
    import org.apache.synapse.transport.http.conn.ProxyTunnelHandler;
    import org.apache.synapse.transport.nhttp.NhttpConstants;
    import org.apache.synapse.transport.passthru.config.PassThroughConfiguration;
    import org.apache.synapse.transport.passthru.config.PassThroughCorrelationConfigDataHolder;
    import org.apache.synapse.transport.passthru.config.TargetConfiguration;
    import org.apache.synapse.transport.passthru.connections.HostConnections;
    import org.apache.synapse.transport.passthru.jmx.PassThroughTransportMetricsCollector;
    import org.apache.synapse.transport.passthru.util.PassThroughTransportUtils;

    import java.io.IOException;
    import java.net.SocketAddress;
    import java.nio.ByteBuffer;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;

    /**
     * This class is handling events from the transport -- > client.
     */
    public class TargetHandler implements NHttpClientEventHandler {
        private static Log log = LogFactory.getLog(TargetHandler.class);

        /** log for correlation.log */
        private static final Log correlationLog = LogFactory.getLog(PassThroughConstants.CORRELATION_LOGGER);
        private static final Log transportLatencyLog = LogFactory.getLog(PassThroughConstants.TRANSPORT_LATENCY_LOGGER);

        /** Delivery agent */
        private final DeliveryAgent deliveryAgent;

        /** Connection factory */
        private ClientConnFactory connFactory;

        /** Configuration used by the sender */
        private final TargetConfiguration targetConfiguration;

        /** Error handler for injecting faults */
        private final TargetErrorHandler targetErrorHandler;

        private PassThroughTransportMetricsCollector metrics = null;

        private static boolean isMessageSizeValidationEnabled = false;

        private static int validMaxMessageSize = Integer.MAX_VALUE;

        public static final String PROPERTY_FILE = "passthru-http.properties";
        public static final String MESSAGE_SIZE_VALIDATION = "message.size.validation.enabled";
        public static final String VALID_MAX_MESSAGE_SIZE = "valid.max.message.size.in.bytes";
        public static final String CONNECTION_POOL = "CONNECTION_POOL";

        private List<StreamInterceptor> streamInterceptors;
        private boolean interceptStream;
        private int noOfInterceptors;
        private static List<String> allowedResponseProperties = new ArrayList<>();

        private PassThroughConfiguration conf = PassThroughConfiguration.getInstance();

        public TargetHandler(DeliveryAgent deliveryAgent, ClientConnFactory connFactory,
                             TargetConfiguration configuration) {
            this(deliveryAgent, connFactory, configuration, new ArrayList<StreamInterceptor>());
        }

        public TargetHandler(DeliveryAgent deliveryAgent,
                             ClientConnFactory connFactory,
                             TargetConfiguration configuration,
                             List<StreamInterceptor> interceptors) {
            this.deliveryAgent = deliveryAgent;
            this.connFactory = connFactory;
            this.targetConfiguration = configuration;
            this.targetErrorHandler = new TargetErrorHandler(targetConfiguration);
            this.metrics = targetConfiguration.getMetrics();
            this.streamInterceptors = interceptors;
            this.interceptStream = !streamInterceptors.isEmpty();
            this.noOfInterceptors = streamInterceptors.size();

            Properties props = MiscellaneousUtil.loadProperties(PROPERTY_FILE);
            String validationProperty = MiscellaneousUtil.getProperty(props, MESSAGE_SIZE_VALIDATION, "false");
            String validMaxMessageSizeStr = MiscellaneousUtil
                    .getProperty(props, VALID_MAX_MESSAGE_SIZE, String.valueOf(Integer.MAX_VALUE));
            isMessageSizeValidationEnabled = Boolean.valueOf(validationProperty);
            try {
                validMaxMessageSize = Integer.valueOf(validMaxMessageSizeStr);
            } catch (NumberFormatException e) {
                log.warn("Invalid max message size configured for property \"valid.max.message.size.in.bytes\", "
                        + "setting the Integer MAX_VALUE as the valid maximum message size", e);
                validMaxMessageSize = Integer.MAX_VALUE;
            }

            PassThroughConfiguration conf = PassThroughConfiguration.getInstance();
            String properties = conf.getAllowedResponseProperties();
            if (properties != null) {
                String[] propertyList = properties.trim().split(",");
                for (String property : propertyList) {
                    allowedResponseProperties.add(property.trim());
                }
            }
        }

        public void connected(NHttpClientConnection conn, Object o) {
            long connectionCreationTimestamp = 0;
            if (transportLatencyLog.isDebugEnabled()) {
                connectionCreationTimestamp = System.currentTimeMillis();
            }
            assert o instanceof HostConnections : "Attachment should be a HostConnections";
            HostConnections pool = (HostConnections) o;
            conn.getContext().setAttribute(PassThroughConstants.CONNECTION_POOL, pool);
            RouteRequestMapping routeRequestMapping = pool.getRouteRequestMapping();
            HttpRoute route = routeRequestMapping.getRoute();

            // create the connection information and set it to request ready
            TargetContext.create(conn, ProtocolState.REQUEST_READY, targetConfiguration);

            // notify the pool about the new connection
            targetConfiguration.getConnections().addConnection(conn);

            // notify about the new connection
            deliveryAgent.connected(pool.getRouteRequestMapping(), conn);

            HttpContext context = conn.getContext();
            context.setAttribute(PassThroughConstants.REQ_DEPARTURE_TIME, System.currentTimeMillis());
            metrics.connected();

            if (route.isTunnelled()) {
                // Requires a proxy tunnel
                ProxyTunnelHandler tunnelHandler = new ProxyTunnelHandler(routeRequestMapping, connFactory);
                context.setAttribute(PassThroughConstants.TUNNEL_HANDLER, tunnelHandler);
            }
            if (transportLatencyLog.isDebugEnabled()) {
                transportLatencyLog.debug(context.getAttribute(CorrelationConstants.CORRELATION_ID) + "|" +
                        "Connection established at time stamp: " + connectionCreationTimestamp + " for route: " + route);
            }
        }

        public void requestReady(NHttpClientConnection conn) {
            HttpContext context = conn.getContext();
            ProtocolState connState = null;
            try {

                connState = TargetContext.getState(conn);

                if (connState == ProtocolState.REQUEST_DONE || connState == ProtocolState.RESPONSE_BODY) {
                    return;
                }

                if (connState != ProtocolState.REQUEST_READY) {
                    handleInvalidState(conn, "Request not started");
                    return;
                }

                ProxyTunnelHandler tunnelHandler = (ProxyTunnelHandler) context.getAttribute(PassThroughConstants.TUNNEL_HANDLER);
                if (tunnelHandler != null && !tunnelHandler.isCompleted()) {
                    Object targetHost = TargetContext.get(conn).getRequestMsgCtx().getProperty(PassThroughConstants.PROXY_PROFILE_TARGET_HOST);
                    context.setAttribute(PassThroughConstants.PROXY_PROFILE_TARGET_HOST, targetHost);
                    if (!tunnelHandler.isRequested()) {
                        HttpRequest request = tunnelHandler.generateRequest(context);
                        if (targetConfiguration.getProxyAuthenticator() != null) {
                            targetConfiguration.getProxyAuthenticator().authenticatePreemptively(request, context);
                        }
                        if (log.isDebugEnabled()) {
                            log.debug(conn + ": Sending CONNECT request to " + tunnelHandler.getProxy());
                        }
                        conn.submitRequest(request);
                        tunnelHandler.setRequested();
                    }
                    return;
                }

                TargetRequest request = TargetContext.getRequest(conn);
                if (request != null) {
                    TargetContext targetContext = TargetContext.get(conn);
                    targetContext.updateLastStateUpdatedTime();
                    request.start(conn);
                    targetConfiguration.getMetrics().incrementMessagesSent();
                }

                if (transportLatencyLog.isDebugEnabled()) {
                    String route = request == null ? "null" : request.getRoute().toString();
                    transportLatencyLog.debug(context.getAttribute(CorrelationConstants.CORRELATION_ID) + "|" +
                            "Request writing started at time stamp: " + System.currentTimeMillis() + " and route: " +
                            route);
                }
                context.setAttribute(PassThroughConstants.REQ_TO_BACKEND_WRITE_START_TIME, System.currentTimeMillis());
                context.setAttribute(PassThroughConstants.REQ_DEPARTURE_TIME, System.currentTimeMillis());
            } catch (IOException e) {
                logIOException(conn, e);
                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);

                MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
                if (requestMsgCtx != null) {
                    requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    targetErrorHandler.handleError(requestMsgCtx,
                            ErrorCodes.SND_IO_ERROR,
                            "Error in Sender",
                            null,
                            connState);
                }
            } catch (HttpException e) {
                log.error(e.getMessage(), e);
                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);

                MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
                if (requestMsgCtx != null) {
                    requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    targetErrorHandler.handleError(requestMsgCtx,
                            ErrorCodes.SND_HTTP_ERROR,
                            "Error in Sender",
                            null,
                            connState);
                }
            }
        }

        public void outputReady(NHttpClientConnection conn, ContentEncoder encoder) {
            ProtocolState connState = null;
            MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
            if (transportLatencyLog.isTraceEnabled()) {
                HttpContext context = conn.getContext();
                HostConnections pool = (HostConnections) context.getAttribute(CONNECTION_POOL);
                String route = pool == null ? "null" : pool.getRouteRequestMapping().toString();
                transportLatencyLog.trace(context.getAttribute(CorrelationConstants.CORRELATION_ID) + "|" +
                        "Writing request chunk to Backend at time stamp: " + System.currentTimeMillis() +
                        " and route: " + route);
            }
            try {
                connState = TargetContext.getState(conn);
                if (connState != ProtocolState.REQUEST_HEAD &&
                        connState != ProtocolState.REQUEST_DONE) {
                    handleInvalidState(conn, "Writing message body");
                    return;
                }

                TargetRequest request = TargetContext.getRequest(conn);
                if (request.hasEntityBody()) {
                    int bytesWritten = -1;
                    boolean interceptionEnabled = false;
                    Boolean[] interceptorResults = new Boolean[noOfInterceptors];
                    if (interceptStream) {
                        int index = 0;
                        for (StreamInterceptor interceptor : streamInterceptors) {
                            interceptorResults[index] = interceptor.interceptTargetRequest(
                                    (MessageContext) conn.getContext()
                                            .getAttribute(PassThroughConstants.REQUEST_MESSAGE_CONTEXT));
                            if (!interceptionEnabled && interceptorResults[index]) {
                                interceptionEnabled = true;
                            }
                            index++;
                        }
                        if (interceptionEnabled) {
                            ByteBuffer bytesSent = request.copyAndWrite(conn, encoder);
                            if (bytesSent != null) {
                                bytesWritten = bytesSent.remaining();
                                index = 0;
                                for (StreamInterceptor interceptor : streamInterceptors) {
                                    if (interceptorResults[index]) {
                                        interceptor.targetRequest(bytesSent.duplicate().asReadOnlyBuffer(),
                                                                  (MessageContext) conn.getContext().getAttribute(
                                                                          PassThroughConstants.REQUEST_MESSAGE_CONTEXT));
                                    }
                                    index++;
                                }
                            }
                        } else {
                            bytesWritten = request.write(conn, encoder);
                        }
                    } else {
                        bytesWritten = request.write(conn, encoder);
                    }
                    if (bytesWritten > 0) {
                        if (metrics.getLevel() == MetricsCollector.LEVEL_FULL) {
                            metrics.incrementBytesSent(requestMsgCtx, bytesWritten);
                        } else {
                            metrics.incrementBytesSent(bytesWritten);
                        }
                    }

                    if (encoder.isCompleted()) {
                        if (metrics.getLevel() == MetricsCollector.LEVEL_FULL) {
                            metrics.incrementMessagesSent(requestMsgCtx);
                        } else {
                            metrics.incrementMessagesSent();
                        }
                    }
                }
            } catch (IOException ex) {
                logIOException(conn, ex);
                TargetContext.updateState(conn, ProtocolState.CLOSING);
                targetConfiguration.getConnections().shutdownConnection(conn, true);

                informWriterError(conn);

                if (requestMsgCtx != null) {
                    requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    targetErrorHandler.handleError(requestMsgCtx,
                            ErrorCodes.SND_HTTP_ERROR,
                            "Error in Sender",
                            null,
                            connState);
                }
            } catch (Exception e) {
                log.error("Error occurred while writing data to the target", e);
                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);

                informWriterError(conn);

                if (requestMsgCtx != null) {
                    requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    targetErrorHandler.handleError(requestMsgCtx,
                            ErrorCodes.SND_HTTP_ERROR,
                            "Error in Sender",
                            null,
                            connState);
                }
            }
        }

        public void responseReceived(NHttpClientConnection conn) {
            HttpContext context = conn.getContext();
            if (transportLatencyLog.isDebugEnabled()) {
                HostConnections pool = (HostConnections) context.getAttribute(CONNECTION_POOL);
                String route = pool == null ? "null" : pool.getRouteRequestMapping().toString();
                transportLatencyLog.debug(context.getAttribute(CorrelationConstants.CORRELATION_ID) + "|" +
                        "Received Response headers from Backend at time stamp: " + System.currentTimeMillis() +
                        " and route: " + route);
            }
            if (isMessageSizeValidationEnabled) {
                context.setAttribute(PassThroughConstants.MESSAGE_SIZE_VALIDATION_SUM, 0);
            }
            HttpResponse response = conn.getHttpResponse();
            ProtocolState connState;
            try {
                boolean isError = false;
                String method = null;
                ProxyTunnelHandler tunnelHandler = (ProxyTunnelHandler) context.getAttribute(PassThroughConstants.TUNNEL_HANDLER);
                if (tunnelHandler != null && !tunnelHandler.isCompleted()) {
                    method = "CONNECT";
                    context.removeAttribute(PassThroughConstants.TUNNEL_HANDLER);
                    tunnelHandler.handleResponse(response, conn);
                    if (tunnelHandler.isSuccessful()) {
                        log.debug(conn + ": Tunnel established");
                        conn.resetInput();
                        conn.requestOutput();
                        return;
                    } else {
                        // TLS tunnel has not been established, so mark connection as failed to prevent that it is
                        // returned back into pool
                        isError = true;
                        log.warn("Tunnel response failed");
                        // the reason for getting the targetRequest and calling the consumeError() on pipe. Instead of
                        // calling the informWriterError(NHTTPClientConnection) is, at this point the
                        // "writeCondition.await()" is already called but the corresponding pipe is not yet set as
                        // a writer in TargetContext
                        TargetRequest targetRequest = TargetContext.getRequest(conn);
                        if (targetRequest != null) {
                            targetRequest.getPipe().consumerError();
                        } else {
                            log.warn("Failed target response, but the target request is null");
                        }
                        TargetContext.updateState(conn, ProtocolState.REQUEST_DONE);
                    }
                }

                int statusCode = response.getStatusLine().getStatusCode();
                if (statusCode < HttpStatus.SC_OK) {
                    if (log.isDebugEnabled()) {
                        log.debug(conn + ": Received a 100 Continue response");
                    }
                    // Ignore 1xx response
                    return;
                }
                context.setAttribute(PassThroughConstants.RES_HEADER_ARRIVAL_TIME, System.currentTimeMillis());
                connState = TargetContext.getState(conn);
                //check correlation logs enabled
                if (PassThroughCorrelationConfigDataHolder.isEnable()
                        && TargetContext.isCorrelationIdAvailable(conn)) {
                    long startTime = (long) context.getAttribute(PassThroughConstants.REQ_TO_BACKEND_WRITE_START_TIME);
                    ContextAwareLogger.getLogger(context, correlationLog, false)
                            .info((System.currentTimeMillis() - startTime) + "|HTTP|"
                            + TargetContext.getRequest(conn).getUrl().toString() + "|BACKEND LATENCY");
                }
                if (connState != ProtocolState.REQUEST_DONE) {
                    isError = true;
                    MessageContext requestMsgContext = TargetContext.get(conn).getRequestMsgCtx();
                    if (conf.isConsumeAndDiscard()) {
                        log.warn("Response received before the request is sent to the backend completely , CORRELATION_ID = "
                                + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID) + ". Consuming the " +
                                "request message and discarding the data completely");
                    } else {
                        log.warn("Response received before the request is sent to the backend completely , CORRELATION_ID = "
                                + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID));
                    }
                    // State is not REQUEST_DONE. i.e the request is not completely written. But the response is started
                    // receiving, therefore informing a write error has occurred. So the thread which is
                    // waiting on writing the request out, will get notified. And we will proceed with the response
                    // regardless of the http status code. But mark target and source connections to be closed.
                    informWriterError(conn);
                    requestMsgContext.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    StatusLine errorStatus = response.getStatusLine();
                    if (errorStatus != null) {
                        TargetContext.updateState(conn, ProtocolState.REQUEST_DONE);
                        conn.resetOutput();
                        if (log.isDebugEnabled()) {
                            log.debug(conn + ": Received response with status code : " + response.getStatusLine()
                                    .getStatusCode() + " in invalid state : " + connState.name());
                        }
                        if (errorStatus.getStatusCode() < HttpStatus.SC_BAD_REQUEST) {
                            log.warn(conn + ": Received a response with status code : "
                                    + response.getStatusLine().getStatusCode() + " in state : " + connState.name()
                                    + " but request is not completely written to the backend, CORRELATION_ID = "
                                    + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID));
                        }
                        if (requestMsgContext != null) {
                            NHttpServerConnection sourceConn = (NHttpServerConnection) requestMsgContext.getProperty(
                                    PassThroughConstants.PASS_THROUGH_SOURCE_CONNECTION);
                            if (sourceConn != null) {
                                if (!conf.isConsumeAndDiscard()) {
                                    //Suspend input to avoid invoking input ready method and set this property here
                                    //to avoid invoking the input ready method, while response is mediating through the
                                    // mediation since we have set REQUEST_DONE state in SourceHandler responseReady method
                                    sourceConn.suspendInput();
                                    SourceContext sourceContext = (SourceContext)sourceConn.getContext().getAttribute(TargetContext.CONNECTION_INFORMATION);
                                    if (sourceContext != null) {
                                        sourceContext.setIsSourceRequestMarkedToBeDiscarded(true);
                                    }
                                }
                                SourceContext.get(sourceConn).setShutDown(true);
                            }
                        } else {
                            if (log.isDebugEnabled()) {
                                log.debug(conn + ": has not started any request");
                            }
                            if (statusCode == HttpStatus.SC_REQUEST_TIMEOUT) {
                                return; // ignoring the stale connection close
                            }
                        }
                    } else {
                        handleInvalidState(conn, "Receiving response");
                        return;
                    }
                }
                context.setAttribute(PassThroughConstants.RES_FROM_BACKEND_READ_START_TIME,System.currentTimeMillis());
                TargetRequest targetRequest = TargetContext.getRequest(conn);

                if (targetRequest != null) {
                    method = targetRequest.getMethod();
                }
                boolean canResponseHaveBody =
                        isResponseHaveBodyExpected(method, response);
                if (!canResponseHaveBody) {
                    if (log.isDebugEnabled()) {
                        log.debug(conn + ": Received no-content response " +
                                response.getStatusLine().getStatusCode());
                    }
                    conn.resetInput();
                }
                TargetResponse targetResponse = new TargetResponse(
                        targetConfiguration, response, conn, canResponseHaveBody, isError);
                TargetContext.setResponse(conn, targetResponse);
                targetResponse.start(conn);

                MessageContext requestMsgContext = TargetContext.get(conn).getRequestMsgCtx();

                if (statusCode == HttpStatus.SC_ACCEPTED && handle202(requestMsgContext)) {
                    return;
                }
                if (targetResponse.isForceShutdownConnectionOnComplete() && conf.isConsumeAndDiscardBySecondaryWorkerPool()
                        && conf.isConsumeAndDiscard()) {
                    NHttpServerConnection sourceConn = (NHttpServerConnection) requestMsgContext.getProperty(
                            PassThroughConstants.PASS_THROUGH_SOURCE_CONNECTION);
                    MessageDiscardWorker messageDiscardWorker = new MessageDiscardWorker(requestMsgContext,
                            targetResponse, targetConfiguration, conn);
                    conn.getContext().setAttribute(PassThroughConstants.MESSAGE_DISCARD_WORKER_REFERENCE
                            , messageDiscardWorker);
                    if (sourceConn != null) {
                        sourceConn.getContext().setAttribute(PassThroughConstants.MESSAGE_DISCARD_WORKER_REFERENCE
                                , messageDiscardWorker);
                    }
                    targetConfiguration.getSecondaryWorkerPool().execute(messageDiscardWorker);
                    return;
                }

                WorkerPool workerPool = targetConfiguration.getWorkerPool();
                ClientWorker clientWorker = new ClientWorker(targetConfiguration, requestMsgContext, targetResponse,
                        allowedResponseProperties);
                conn.getContext().setAttribute(PassThroughConstants.CLIENT_WORKER_REFERENCE, clientWorker);
                workerPool.execute(clientWorker);

                targetConfiguration.getMetrics().incrementMessagesReceived();

                NHttpServerConnection sourceConn = (NHttpServerConnection) requestMsgContext.getProperty(
                        PassThroughConstants.PASS_THROUGH_SOURCE_CONNECTION);
                if (sourceConn != null) {
                    PassThroughTransportUtils.setSourceConnectionContextAttributes(sourceConn, conn);
                }

            } catch (Exception ex) {
                log.error("Exception occurred while processing response", ex);

                informReaderError(conn);

                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);
            }
        }

        private boolean handle202(MessageContext requestMsgContext) throws AxisFault {
            if (requestMsgContext.isPropertyTrue(NhttpConstants.IGNORE_SC_ACCEPTED)) {
                // We should not further process this 202 response - Ignore it
                return true;
            }

            MessageReceiver mr = requestMsgContext.getAxisOperation().getMessageReceiver();
            MessageContext responseMsgCtx = requestMsgContext.getOperationContext().
                            getMessageContext(WSDL2Constants.MESSAGE_LABEL_IN);
            if (responseMsgCtx == null || requestMsgContext.getOptions().isUseSeparateListener()) {
                // Most probably a response from a dual channel invocation
                // Inject directly into the SynapseCallbackReceiver
                requestMsgContext.setProperty(NhttpConstants.HTTP_202_RECEIVED, "true");
                mr.receive(requestMsgContext);
                return true;
            }

            return false;
        }

        /**
         * Closes the target side HTTP connection.
         *
         * @param conn HTTP client connection reference
         */
        private void dropTargetConnection(NHttpClientConnection conn) {
            try {
                TargetContext.updateState(conn, ProtocolState.CLOSED);
                conn.close();
            } catch (Exception ex) {
                log.error(ex.getMessage(), ex);
                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);
            }
        }

        public void inputReady(NHttpClientConnection conn, ContentDecoder decoder) {
            ProtocolState connState;
            MessageContext msgCtx = TargetContext.get(conn).getRequestMsgCtx();
            if (transportLatencyLog.isTraceEnabled()) {
                HttpContext context = conn.getContext();
                HostConnections pool = (HostConnections) context.getAttribute(CONNECTION_POOL);
                String route = pool == null ? "null" : pool.getRouteRequestMapping().toString();
                transportLatencyLog.trace(context.getAttribute(CorrelationConstants.CORRELATION_ID) + "|" +
                        "Response chunk received from Backend at time stamp: " + System.currentTimeMillis() +
                        " and route: " + route);
            }
            try {
                connState = TargetContext.getState(conn);
                if (connState.compareTo(ProtocolState.RESPONSE_HEAD) < 0) {
                    return;
                }
                if (connState != ProtocolState.RESPONSE_HEAD &&
                        connState != ProtocolState.RESPONSE_BODY) {
                    handleInvalidState(conn, "Response received");
                    return;
                }

                TargetContext.updateState(conn, ProtocolState.RESPONSE_BODY);

                TargetResponse response = TargetContext.getResponse(conn);
                int statusCode = -1;

                if (response != null) {
                    statusCode = conn.getHttpResponse().getStatusLine().getStatusCode();
                    int responseRead = -1;
                    boolean interceptionEnabled = false;
                    Boolean[] interceptorResults = new Boolean[noOfInterceptors];
                    if (conn.getContext().getAttribute(PassThroughConstants.RESPONSE_MESSAGE_CONTEXT) != null
                            && interceptStream) {
                        int index = 0;
                        for (StreamInterceptor interceptor : streamInterceptors) {
                            interceptorResults[index] = interceptor.interceptTargetResponse(
                                    (MessageContext) conn.getContext()
                                            .getAttribute(PassThroughConstants.RESPONSE_MESSAGE_CONTEXT));
                            if (!interceptionEnabled && interceptorResults[index]) {
                                interceptionEnabled = true;
                            }
                            index++;
                        }
                        if (interceptionEnabled) {
                            ByteBuffer bytesRead = response.copyAndRead(conn, decoder);
                            if (bytesRead != null) {
                                responseRead = bytesRead.remaining();
                                boolean proceed;
                                index = 0;
                                for (StreamInterceptor interceptor : streamInterceptors) {
                                    if (interceptorResults[index]) {
                                        proceed = interceptor.targetResponse(bytesRead.duplicate().asReadOnlyBuffer(),
                                                                             (MessageContext) conn.getContext()
                                                                                     .getAttribute(
                                                                                             PassThroughConstants.RESPONSE_MESSAGE_CONTEXT));
                                        if (!proceed) {
                                            log.info("Dropping target connection since request is blocked by : "
                                                             + interceptor.getClass().getName());
                                            dropTargetConnection(conn);
                                            response.getPipe().forceProducerComplete(decoder);
                                            break;
                                        }
                                    }
                                    index++;
                                }
                            }
                        } else {
                            responseRead = response.read(conn, decoder);
                        }
                    } else {
                        responseRead = response.read(conn, decoder);
                    }
              if (isMessageSizeValidationEnabled) {
                  HttpContext httpContext = conn.getContext();
                  //this is introduced as some transports which extends passthrough target handler which have overloaded
                  //method responseReceived()
                  if (httpContext.getAttribute(PassThroughConstants.MESSAGE_SIZE_VALIDATION_SUM) == null) {
                      httpContext.setAttribute(PassThroughConstants.MESSAGE_SIZE_VALIDATION_SUM, 0);
                  }
                  int messageSizeSum = (int) httpContext.getAttribute(PassThroughConstants.MESSAGE_SIZE_VALIDATION_SUM);

                  messageSizeSum += responseRead;

                  if (messageSizeSum > validMaxMessageSize) {
                      log.warn("Payload exceeds valid payload size range, hence discontinuing chunk stream at "
                              + messageSizeSum + " bytes to prevent OOM for"
                              + " URI : " + msgCtx.getProperty(PassThroughConstants.TRANSPORT_IN_URL)
                              + ", Method : " + msgCtx.getProperty(PassThroughConstants.HTTP_METHOD)
                              + ", Correlation ID: " + msgCtx.getProperty(CorrelationConstants.CORRELATION_ID)
                      );
                      dropTargetConnection(conn);
                      response.getPipe().forceProducerComplete(decoder);
                  }
                  httpContext.setAttribute(PassThroughConstants.MESSAGE_SIZE_VALIDATION_SUM, messageSizeSum);
              }

              if (metrics.getLevel() == MetricsCollector.LEVEL_FULL) {
                        metrics.incrementBytesReceived(msgCtx, responseRead);
                    } else {
                        metrics.incrementBytesReceived(responseRead);
                    }
                }
                if (decoder.isCompleted()) {
                    if (metrics.getLevel() == MetricsCollector.LEVEL_FULL) {
                        metrics.incrementMessagesReceived(msgCtx);
                        metrics.notifyReceivedMessageSize(
                                msgCtx, conn.getMetrics().getReceivedBytesCount());
                        metrics.notifySentMessageSize(msgCtx, conn.getMetrics().getSentBytesCount());
                        if(statusCode != -1) {
                            metrics.reportResponseCode(msgCtx, statusCode);
                        }
                    } else {
                        metrics.incrementMessagesReceived();
                        metrics.notifyReceivedMessageSize(
                                conn.getMetrics().getReceivedBytesCount());
                        metrics.notifySentMessageSize(conn.getMetrics().getSentBytesCount());
                    }
                    MessageContext requestMsgContext = TargetContext.get(conn).getRequestMsgCtx();
                    NHttpServerConnection sourceConn =
                            (NHttpServerConnection) requestMsgContext.getProperty(PassThroughConstants.PASS_THROUGH_SOURCE_CONNECTION);
                    if (sourceConn != null) {
                        if (conn.getContext().getAttribute(PassThroughConstants.RES_FROM_BACKEND_READ_END_TIME) != null) {
                            sourceConn.getContext().setAttribute(
                                    PassThroughConstants.RES_FROM_BACKEND_READ_END_TIME,
                                    conn.getContext().getAttribute(PassThroughConstants.RES_FROM_BACKEND_READ_END_TIME)
                            );
                            conn.getContext().removeAttribute(PassThroughConstants.RES_FROM_BACKEND_READ_END_TIME);

                        }
                        sourceConn.getContext().setAttribute(
                                PassThroughConstants.RES_ARRIVAL_TIME,
                                conn.getContext().getAttribute(PassThroughConstants.RES_ARRIVAL_TIME)
                        );
                        conn.getContext().removeAttribute(PassThroughConstants.RES_ARRIVAL_TIME);
                    }
                }
            } catch (IOException e) {
                logException(conn, e);
                logIOException(conn, e);
                informReaderError(conn);

                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);
            } catch (Exception ex) {
                log.error("Exception occurred while reading request body", ex);

                informReaderError(conn);

                TargetContext.updateState(conn, ProtocolState.CLOSED);
                targetConfiguration.getConnections().shutdownConnection(conn, true);
            }
        }

        private void logException(NHttpClientConnection conn, Exception e) {
            ProtocolState state = TargetContext.getState(conn);
            if (state != null) {
                MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
                Map<String, String> logDetails = getLoggingInfo(conn, state, requestMsgCtx, e);
                log.warn("ERROR_CODE = " + logDetails.get("error_code") + ", STATE_DESCRIPTION = Exception occurred "
                        + logDetails.get("state_description") + ", INTERNAL_STATE = " + state + ", DIRECTION = "
                        + logDetails.get("direction") + ", " + "CAUSE_OF_ERROR = " + logDetails.get("cause_of_error")
                        + ", TARGET_HOST = " + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port")
                        + ", TARGET_CONTEXT = " + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                        + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                        .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                        + ", CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                        + ", CONNECTION = " + conn);
            }
        }

        public void closed(NHttpClientConnection conn) {
            ProtocolState state = TargetContext.getState(conn);
            MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
            Map<String, String> logDetails = getLoggingInfo(conn, state, requestMsgCtx);

            boolean isFault = false;
            if (log.isDebugEnabled()) {
                log.debug("Connection closed by target host while in state " + state.name() + ". Response code : " + conn.getStatus());
            }
            if (state == ProtocolState.RESPONSE_DONE || state == ProtocolState.REQUEST_READY) {
                if (log.isDebugEnabled()) {
                    log.debug("Keep-Alive Connection closed " + getConnectionLoggingInfo(conn));
                }
            } else if (state == ProtocolState.REQUEST_HEAD || state == ProtocolState.REQUEST_BODY) {
                informWriterError(conn);
                log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_CLOSED + ", STATE_DESCRIPTION = Connection closed by "
                        + "target host " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                        + ", DIRECTION = " + logDetails.get("direction") + ", "
                        + "CAUSE_OF_ERROR = Connection between the Server and the BackEnd has been closed, TARGET_HOST = "
                        + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                        + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method") + ", TRIGGER_TYPE = "
                        + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails.get("trigger_name")
                        + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                        + ", CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                        + ", CONNECTION = " + conn);
                isFault = true;
            } else if (state == ProtocolState.RESPONSE_HEAD || state == ProtocolState.RESPONSE_BODY) {
                informReaderError(conn);
                log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_CLOSED + ", STATE_DESCRIPTION = Connection closed by "
                        + "target host " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                        + ", DIRECTION = " + logDetails.get("direction") + ", "
                        + "CAUSE_OF_ERROR = Connection between the Server and the BackEnd has been closed, TARGET_HOST = "
                        + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                        + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method") + ", TRIGGER_TYPE = "
                        + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails.get("trigger_name")
                        + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                        + ", CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                        + ", CONNECTION = " + conn);
                isFault = true;
            } else if (state == ProtocolState.REQUEST_DONE) {
                log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_CLOSED + ", STATE_DESCRIPTION = Connection closed by "
                        + "target host " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                        + ", DIRECTION = " + logDetails.get("direction") + ", "
                        + "CAUSE_OF_ERROR = Connection between the Server and the BackEnd has been closed, TARGET_HOST = "
                        + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                        + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method") + ", TRIGGER_TYPE = "
                        + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails.get("trigger_name")
                        + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                        + ", CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                        + ", CONNECTION = " + conn);
                isFault = true;
            }

            if (isFault) {
                if (requestMsgCtx != null) {
                    requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                            PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                    targetErrorHandler.handleError(requestMsgCtx,
                            ErrorCodes.CONNECTION_CLOSED,
                            "Error in Sender",
                            null,
                            state);
                }
            }

            metrics.disconnected();

            TargetContext.updateState(conn, ProtocolState.CLOSED);

            if (conf.isTLSGracefulConnectionTerminationEnabled()) {
                targetConfiguration.getConnections().closeConnection(conn, isFault);
            } else {
                targetConfiguration.getConnections().shutdownConnection(conn, isFault);
            }

        }

        private void logIOException(NHttpClientConnection conn, IOException e) {
            String message = getErrorMessage("I/O error : " + e.getMessage(), conn);

            if (e.getMessage() != null && (e instanceof ConnectionClosedException
                    || e.getMessage().toLowerCase().contains("connection reset")
                    || e.getMessage().toLowerCase().contains("forcibly closed"))) {
                if (log.isDebugEnabled()) {
                    log.debug(conn + ": I/O error (Probably the keep-alive connection "
                            + "was closed):" + e.getMessage()
                            + "CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID));
                }
            } else if (e.getMessage() != null) {
                String msg = e.getMessage().toLowerCase();
                if (msg.indexOf("broken") != -1) {
                    log.warn("I/O error (Probably the connection "
                            + "was closed by the remote party):" + e.getMessage() + "CORRELATION_ID = "
                            + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID));
                } else {
                    log.error("I/O error: " + e.getMessage()
                            + "CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID), e);
                }
            } else {
                log.error(message, e);
            }
        }

        public void timeout(NHttpClientConnection conn) {
            ProtocolState state = TargetContext.getState(conn);
            MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
            Map<String, String> logDetails = getLoggingInfo(conn, state, requestMsgCtx);
            Object clientWorker = conn.getContext().getAttribute(
                    PassThroughConstants.CLIENT_WORKER_REFERENCE);
            Object messageDiscardWorker = conn.getContext().getAttribute(
                    PassThroughConstants.MESSAGE_DISCARD_WORKER_REFERENCE);

            if (log.isDebugEnabled()) {
                log.debug(getErrorMessage("Connection timeout", conn) + " "+ getConnectionLoggingInfo(conn));
            }
            if (state != null &&
                    (state == ProtocolState.REQUEST_READY || state == ProtocolState.RESPONSE_DONE)) {
                if (log.isDebugEnabled()) {
                    log.debug(getErrorMessage("Keep-alive connection timed out", conn) + " " +
                              getConnectionLoggingInfo(conn));
                }
            } else if (state != null ) {
                if (state == ProtocolState.REQUEST_BODY) {
                    metrics.incrementTimeoutsSending();
                    informWriterError(conn);
                    log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_TIMEOUT + ", STATE_DESCRIPTION = Socket Timeout "
                            + "occurred " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                            + ", DIRECTION = " + logDetails.get("direction") + ", "
                            + "CAUSE_OF_ERROR = Connection between the WSO2 Server and the BackEnd timeouts, TARGET_HOST = "
                            + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                            + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn) + ", "
                            + "CONNECTION = " + conn + ", SOCKET_TIMEOUT = " + conn.getSocketTimeout() + ", CORRELATION_ID"
                            + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + workerPoolExhaustedErrorMessage(clientWorker, messageDiscardWorker));
                }

                if (state == ProtocolState.RESPONSE_BODY || state == ProtocolState.REQUEST_HEAD) {
                    metrics.incrementTimeoutsReceiving();
                    informReaderError(conn);
                    log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_TIMEOUT + ", STATE_DESCRIPTION = Socket Timeout "
                            + "occurred " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                            + ", DIRECTION = " + logDetails.get("direction") + ", "
                            + "CAUSE_OF_ERROR = Connection between the WSO2 Server and the BackEnd timeouts, TARGET_HOST = "
                            + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                            + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn) + ", "
                            + "CONNECTION = " + conn + ", SOCKET_TIMEOUT = " + conn.getSocketTimeout() + ", "
                            + "CORRELATION_ID = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + workerPoolExhaustedErrorMessage(clientWorker, messageDiscardWorker));
                }

                if (state.compareTo(ProtocolState.REQUEST_DONE) <= 0) {
                    log.warn("ERROR_CODE = " + ErrorCodes.CONNECTION_TIMEOUT + ", STATE_DESCRIPTION = Socket Timeout "
                            + "occurred " + logDetails.get("state_description") + ", INTERNAL_STATE = " + state
                            + ", DIRECTION = " + logDetails.get("direction") + ", "
                            + "CAUSE_OF_ERROR = Connection between the WSO2 Server and the BackEnd timeouts, TARGET_HOST = "
                            + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port") + ", TARGET_CONTEXT = "
                            + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn) + ", "
                            + "CONNECTION = " + conn + ", SOCKET_TIMEOUT = " + conn.getSocketTimeout() + ", CORRELATION_ID"
                            + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + workerPoolExhaustedErrorMessage(clientWorker, messageDiscardWorker));

                    if (PassThroughCorrelationConfigDataHolder.isEnable()) {
                        logHttpRequestErrorInCorrelationLog(conn, "Timeout in " + state);
                    }
                    if (requestMsgCtx != null) {
                        requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                                PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                        targetErrorHandler.handleError(requestMsgCtx,
                                ErrorCodes.CONNECTION_TIMEOUT,
                                "Error in Sender",
                                null,
                                state);
                    }
                }
            }

            TargetContext.updateState(conn, ProtocolState.CLOSED);

            if (conf.isTLSGracefulConnectionTerminationEnabled()) {
                targetConfiguration.getConnections().closeConnection(conn, true);
            } else {
                targetConfiguration.getConnections().shutdownConnection(conn, true);
            }
        }

        private String workerPoolExhaustedErrorMessage(Object clientWorker
                , Object messageDiscardWorker) {
            String workerPoolExhaustedMessage = "";
            if (messageDiscardWorker != null
                    && WorkerState.CREATED == ((MessageDiscardWorker) messageDiscardWorker).getWorkerState()) {
                workerPoolExhaustedMessage = ", Could not get a secondary worker thread to discard the request content. "
                        + "The secondary worker pool is exhausted.";
                return workerPoolExhaustedMessage;
            } else if (messageDiscardWorker != null
                    && WorkerState.RUNNING == ((MessageDiscardWorker) messageDiscardWorker).getWorkerState()) {
                workerPoolExhaustedMessage = ", The secondary worker thread which was discarding the request content"
                        + " has been released.";
                return workerPoolExhaustedMessage;
            } else if (messageDiscardWorker != null
                    && WorkerState.FINISHED == ((MessageDiscardWorker) messageDiscardWorker).getWorkerState()) {
                if (clientWorker != null
                        && WorkerState.CREATED == ((ClientWorker)clientWorker).getWorkerState()) {
                    workerPoolExhaustedMessage = ", Could not get a  PassThroughMessageProcessor thread to process the "
                            + "response message. The primary worker pool is exhausted.";
                    return workerPoolExhaustedMessage;
                }
            } else if (clientWorker != null && WorkerState.CREATED == ((ClientWorker)clientWorker).getWorkerState()) {
                workerPoolExhaustedMessage = ", Could not get a  PassThroughMessageProcessor thread to process the "
                        + "response message. The primary worker pool is exhausted.";
                return workerPoolExhaustedMessage;
            }
            return workerPoolExhaustedMessage;
        }

        private boolean isResponseHaveBodyExpected(
                final String method, final HttpResponse response) {

            if ("HEAD".equalsIgnoreCase(method)) {
                return false;
            }

            int status = response.getStatusLine().getStatusCode();
            return status >= HttpStatus.SC_OK
                && status != HttpStatus.SC_NO_CONTENT
                && status != HttpStatus.SC_NOT_MODIFIED
                && status != HttpStatus.SC_RESET_CONTENT;
        }

        /**
         * Include remote host and port information to an error message
         *
         * @param message the initial message
         * @param conn    the connection encountering the error
         * @return the updated error message
         */
        private String getErrorMessage(String message, NHttpClientConnection conn) {
            if (conn != null && conn instanceof DefaultNHttpClientConnection) {
                DefaultNHttpClientConnection c = ((DefaultNHttpClientConnection) conn);

                if (c.getRemoteAddress() != null) {
                    return message + " For : " + c.getRemoteAddress().getHostAddress() + ":" +
                            c.getRemotePort();
                }
            }
            return message;
        }

        private void handleInvalidState(NHttpClientConnection conn, String action) {
            ProtocolState state = TargetContext.getState(conn);

            if (log.isWarnEnabled()) {
                log.warn(conn + ": " + action + " while the handler is in an inconsistent state " +
                    TargetContext.getState(conn));
            }
            MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
            TargetContext.updateState(conn, ProtocolState.CLOSED);
            targetConfiguration.getConnections().shutdownConnection(conn, true);
            if (requestMsgCtx != null) {
                requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                        PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                targetErrorHandler.handleError(requestMsgCtx,
                        ErrorCodes.SND_INVALID_STATE,
                        "Error in Sender",
                        null,
                        state);
            }
        }

        private void informReaderError(NHttpClientConnection conn) {
            Pipe reader = TargetContext.get(conn).getReader();

            metrics.incrementFaultsReceiving();

            if (reader != null) {
                reader.producerError();
            }
        }

        private void informWriterError(NHttpClientConnection conn) {
            Pipe writer = TargetContext.get(conn).getWriter();

            metrics.incrementFaultsReceiving();

            if (writer != null) {
                writer.consumerError();
            }
        }

        public void endOfInput(NHttpClientConnection conn) throws IOException {
            conn.close();
        }

        public void exception(NHttpClientConnection conn, Exception ex) {
            ProtocolState state = TargetContext.getState(conn);
            MessageContext requestMsgCtx = TargetContext.get(conn).getRequestMsgCtx();
            try {
                Map<String, String> logDetails = getLoggingInfo(conn, state, requestMsgCtx, ex);
                if (state == ProtocolState.REQUEST_HEAD || state == ProtocolState.REQUEST_BODY) {
                    informWriterError(conn);
                    log.warn("ERROR_CODE = " + logDetails.get("error_code") + ", STATE_DESCRIPTION = Exception occurred "
                            + logDetails.get("state_description") + ", INTERNAL_STATE = " + state + ", DIRECTION = "
                            + logDetails.get("direction") + ", " + "CAUSE_OF_ERROR = " + logDetails.get("cause_of_error")
                            + ", TARGET_HOST = " + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port")
                            + ", TARGET_CONTEXT = " + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                            + ", CORRELATION_ID" + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + ", CONNECTION = " + conn);
                } else if (state == ProtocolState.RESPONSE_HEAD || state == ProtocolState.RESPONSE_BODY) {
                    informReaderError(conn);
                    log.warn("ERROR_CODE = " + logDetails.get("error_code") + ", STATE_DESCRIPTION = Exception occurred "
                            + logDetails.get("state_description") + ", INTERNAL_STATE = " + state + ", DIRECTION = "
                            + logDetails.get("direction") + ", " + "CAUSE_OF_ERROR = " + logDetails.get("cause_of_error")
                            + ", TARGET_HOST = " + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port")
                            + ", TARGET_CONTEXT = " + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                            + ", CORRELATION_ID" + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + ", CONNECTION = " + conn);
                } else if (state == ProtocolState.REQUEST_DONE) {
                    log.warn("ERROR_CODE = " + logDetails.get("error_code") + ", STATE_DESCRIPTION = Exception occurred "
                            + logDetails.get("state_description") + ", INTERNAL_STATE = " + state + ", DIRECTION = "
                            + logDetails.get("direction") + ", " + "CAUSE_OF_ERROR = " + logDetails.get("cause_of_error")
                            + ", TARGET_HOST = " + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port")
                            + ", TARGET_CONTEXT = " + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                            + ", CORRELATION_ID" + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + ", CONNECTION = " + conn);
                } else if (state == ProtocolState.REQUEST_READY) {
                    log.warn("ERROR_CODE = " + logDetails.get("error_code") + ", STATE_DESCRIPTION = Exception occurred "
                            + logDetails.get("state_description") + ", INTERNAL_STATE = " + state + ", DIRECTION = "
                            + logDetails.get("direction") + ", " + "CAUSE_OF_ERROR = " + logDetails.get("cause_of_error")
                            + ", TARGET_HOST = " + logDetails.get("host") + ", TARGET_PORT = " + logDetails.get("port")
                            + ", TARGET_CONTEXT = " + logDetails.get("url") + ", " + "HTTP_METHOD = " + logDetails.get("method")
                            + ", TRIGGER_TYPE = " + logDetails.get("trigger_type") + ", TRIGGER_NAME = " + logDetails
                            .get("trigger_name") + ", REMOTE_ADDRESS = " + getBackEndConnectionInfo(conn)
                            + ", CORRELATION_ID" + " = " + conn.getContext().getAttribute(CorrelationConstants.CORRELATION_ID)
                            + ", CONNECTION = " + conn);
                }
            } finally {
                if (ex instanceof IOException) {

                    logIOException(conn, (IOException) ex);
                    if (PassThroughCorrelationConfigDataHolder.isEnable()){
                        logHttpRequestErrorInCorrelationLog(conn, "IO Exception in " + state.name());
                    }
                    if (state != ProtocolState.RESPONSE_DONE && requestMsgCtx != null) {
                        requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                                PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                        targetErrorHandler.handleError(requestMsgCtx,
                                ErrorCodes.SND_IO_ERROR,
                                "Error in Sender",
                                ex,
                                state);
                    }

                    TargetContext.updateState(conn, ProtocolState.CLOSING);
                } else if (ex instanceof HttpException) {
                    String message = getErrorMessage("HTTP protocol violation : " + ex.getMessage(), conn);
                    log.error(message, ex);
                    if (PassThroughCorrelationConfigDataHolder.isEnable()){
                        logHttpRequestErrorInCorrelationLog(conn, "HTTP Exception in " + state.name());
                    }
                    if (state != ProtocolState.RESPONSE_DONE && requestMsgCtx != null) {
                        requestMsgCtx.setProperty(PassThroughConstants.INTERNAL_EXCEPTION_ORIGIN,
                                PassThroughConstants.INTERNAL_ORIGIN_ERROR_HANDLER);
                        targetErrorHandler.handleError(requestMsgCtx,
                                ErrorCodes.PROTOCOL_VIOLATION,
                                "Error in Sender",
                                null,
                                state);
                    }

                    TargetContext.updateState(conn, ProtocolState.CLOSED);
                } else {
                    if (null != ex && null != ex.getMessage()) {
                        log.error("Unexpected error: " + ex.getMessage(), ex);
                    } else {
                        log.error("Unexpected error.");
                    }
                    if (PassThroughCorrelationConfigDataHolder.isEnable()) {
                        logHttpRequestErrorInCorrelationLog(conn, "Unexpected error");
                    }
                    TargetContext.updateState(conn, ProtocolState.CLOSED);
                }

                targetConfiguration.getConnections().shutdownConnection(conn, true);
            }

        }

        public void setConnFactory(ClientConnFactory connFactory) {
            this.connFactory = connFactory;
        }

        public TargetConfiguration getTargetConfiguration() {
            return targetConfiguration;
        }

        private String getConnectionLoggingInfo(NHttpClientConnection conn) {
            if (conn instanceof LoggingNHttpClientConnection) {
                IOSession ioSession = ((LoggingNHttpClientConnection) conn).getIOSession();
                if (ioSession != null) {
                    return " Remote Address : " + ioSession.getRemoteAddress();
                }
            }
            return "";
        }

        private String getBackEndConnectionInfo(NHttpClientConnection conn) {
            if (conn instanceof LoggingNHttpClientConnection) {
                IOSession ioSession = ((LoggingNHttpClientConnection) conn).getIOSession();
                if (ioSession != null) {
                    SocketAddress socketAddress = ioSession.getRemoteAddress();
                    if (socketAddress != null) {
                        return socketAddress.toString();
                    }
                }
            }
            return "";
        }

        private Map<String, String> getLoggingInfo(NHttpClientConnection conn, ProtocolState state,
                                                   MessageContext requestMsgCtx) {
            return getLoggingInfo(conn, state, requestMsgCtx, null);
        }

        private Map<String, String> getLoggingInfo(NHttpClientConnection conn, ProtocolState state,
                                                   MessageContext requestMsgCtx, Exception ex) {
            HashMap<String, String> logDetails = new HashMap<>();
            TargetContext targetContext = TargetContext.get(conn);
            if (targetContext != null) {
                String url = "", method = "";
                if (targetContext.getRequest() != null) {
                    url = targetContext.getRequest().getUrl().toString();
                    method = targetContext.getRequest().getMethod();
                } else {
                    HttpRequest httpRequest = conn.getHttpRequest();
                    if (httpRequest != null) {
                        url = httpRequest.getRequestLine().getUri();
                        method = httpRequest.getRequestLine().getMethod();
                    }
                }
                logDetails.put("url", url);
                logDetails.put("method", method);
            }

            if (conn != null && conn instanceof DefaultNHttpClientConnection) {
                DefaultNHttpClientConnection connection = ((DefaultNHttpClientConnection) conn);
                if (connection.getRemoteAddress() != null) {
                    logDetails.put("host", connection.getRemoteAddress().getHostAddress());
                    logDetails.put("port", Integer.toString(connection.getRemotePort()));
                }
            }

            if (state != null) {
                if (state.compareTo(ProtocolState.REQUEST_DONE) <= 0) {
                    logDetails.put("direction", "REQUEST");
                } else {
                    logDetails.put("direction", "RESPONSE");
                }
                if (state == ProtocolState.REQUEST_BODY || state == ProtocolState.REQUEST_HEAD) {
                    logDetails.put("state_description", "after Server written the request headers but prior to write the "
                            + "request body to the backend");
                } else if (state == ProtocolState.RESPONSE_BODY || state == ProtocolState.RESPONSE_HEAD) {
                    logDetails.put("state_description",
                            "after Server read the response headers but prior to reading the response body from the "
                                    + "backend");
                } else if (state == ProtocolState.REQUEST_DONE) {
                    logDetails.put("state_description",
                            "after Server written the request headers and the request body to the backend");
                } else if (state == ProtocolState.REQUEST_READY) {
                    logDetails.put("state_description",
                            "when Server establishing a connection to the backend");
                }
            }

            if (requestMsgCtx != null) {
                Object triggerName = requestMsgCtx.getProperty(PassThroughConstants.INTERNAL_TRIGGER_NAME);
                Object triggerType = requestMsgCtx.getProperty(PassThroughConstants.INTERNAL_TRIGGER_TYPE);
                if (triggerType != null) {
                    logDetails.put("trigger_type", triggerType.toString());
                }
                if (triggerName != null) {
                    logDetails.put("trigger_name", triggerName.toString());
                }
            }

            if (ex != null) {
                if (ex instanceof IOException) {
                    logDetails.put("error_code", Integer.toString(ErrorCodes.SND_IO_ERROR));
                    logDetails.put("cause_of_error", "I/O exception : " + ex.getMessage());
                } else if (ex instanceof HttpException) {
                    logDetails.put("error_code", Integer.toString(ErrorCodes.PROTOCOL_VIOLATION));
                    logDetails.put("cause_of_error", "HTTP Protocol violation : " + ex.getMessage());
                } else {
                    logDetails.put("cause_of_error", "Unexpected error : " + ex.getMessage());
                }

            }
            return logDetails;
        }

        private void logHttpRequestErrorInCorrelationLog(NHttpClientConnection conn, String state) {

            TargetContext targetContext = TargetContext.get(conn);
            if (targetContext != null && TargetContext.isCorrelationIdAvailable(conn)) {
                String url = "", method = "";
                if (targetContext.getRequest() != null) {
                    url = targetContext.getRequest().getUrl().toString();
                    method = targetContext.getRequest().getMethod();
                } else {
                    HttpRequest httpRequest = conn.getHttpRequest();
                    if (httpRequest != null) {
                        url = httpRequest.getRequestLine().getUri();
                        method = httpRequest.getRequestLine().getMethod();
                    }
                }
                if ((method.length() != 0) && (url.length() != 0)) {
                    Object requestStartTime =
                            conn.getContext().getAttribute(PassThroughConstants.REQ_TO_BACKEND_WRITE_START_TIME);
                    long startTime = 0;
                    if (requestStartTime != null) {
                        startTime = (long) requestStartTime;
                    }
                    ContextAwareLogger.getLogger(conn.getContext(), correlationLog, false)
                            .info((System.currentTimeMillis() - startTime) + "|HTTP|"
                                    + conn.getContext().getAttribute("http.connection") + "|" + method + "|" + url
                                    + "|" + state);
                }
            }
        }
    }