/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.nifi.processors.standard;

import static org.apache.nifi.processors.standard.util.HTTPUtils.PROXY_HOST;
import static org.apache.nifi.processors.standard.util.HTTPUtils.PROXY_PORT;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.UnknownHostException;
import java.security.Principal;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.regex.Pattern;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLPeerUnverifiedException;
import javax.net.ssl.SSLSession;
import javax.security.auth.x500.X500Principal;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.core.Response.Status;
import org.apache.http.Header;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
import org.apache.http.NoHttpResponseException;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.HttpRequestRetryHandler;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpDelete;
import org.apache.http.client.methods.HttpHead;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.config.SocketConfig;
import org.apache.http.conn.ManagedHttpClientConnection;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.entity.ContentProducer;
import org.apache.http.entity.EntityTemplate;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.protocol.HttpContext;
import org.apache.http.protocol.HttpCoreContext;
import org.apache.http.util.EntityUtils;
import org.apache.http.util.VersionInfo;
import org.apache.nifi.annotation.behavior.InputRequirement;
import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
import org.apache.nifi.annotation.behavior.SupportsBatching;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.DeprecationNotice;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.annotation.lifecycle.OnScheduled;
import org.apache.nifi.annotation.lifecycle.OnStopped;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.ValidationContext;
import org.apache.nifi.components.ValidationResult;
import org.apache.nifi.expression.ExpressionLanguageScope;
import org.apache.nifi.flowfile.FlowFile;
import org.apache.nifi.flowfile.attributes.CoreAttributes;
import org.apache.nifi.flowfile.attributes.StandardFlowFileMediaType;
import org.apache.nifi.logging.ComponentLog;
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.DataUnit;
import org.apache.nifi.processor.FlowFileFilter;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.ProcessorInitializationContext;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.io.InputStreamCallback;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.processors.standard.util.HTTPUtils;
import org.apache.nifi.ssl.SSLContextService;
import org.apache.nifi.stream.io.GZIPOutputStream;
import org.apache.nifi.stream.io.LeakyBucketStreamThrottler;
import org.apache.nifi.stream.io.StreamThrottler;
import org.apache.nifi.stream.io.StreamUtils;
import org.apache.nifi.util.FlowFilePackager;
import org.apache.nifi.util.FlowFilePackagerV1;
import org.apache.nifi.util.FlowFilePackagerV2;
import org.apache.nifi.util.FlowFilePackagerV3;
import org.apache.nifi.util.FormatUtils;
import org.apache.nifi.util.StopWatch;
import org.apache.nifi.util.StringUtils;

@Deprecated
@DeprecationNotice(alternatives = {InvokeHTTP.class}, reason = "This processor is deprecated and may be removed in future releases.")
@SupportsBatching
@InputRequirement(Requirement.INPUT_REQUIRED)
@Tags({"http", "https", "remote", "copy", "archive"})
@CapabilityDescription("Please be aware this processor is deprecated and may be removed in the near future. Use InvokeHTTP instead. Performs an HTTP Post with the content of the FlowFile. "
        + "Uses a connection pool with max number of connections equal to "
        + "the number of possible endpoints multiplied by the Concurrent Tasks configuration.")
public class PostHTTP extends AbstractProcessor {

    public static final String CONTENT_TYPE_HEADER = "Content-Type";
    public static final String ACCEPT = "Accept";
    public static final String ACCEPT_ENCODING = "Accept-Encoding";
    public static final String DEFAULT_CONTENT_TYPE = "application/octet-stream";
    public static final String FLOWFILE_CONFIRMATION_HEADER = "x-prefer-acknowledge-uri";
    public static final String LOCATION_HEADER_NAME = "Location";
    public static final String LOCATION_URI_INTENT_NAME = "x-location-uri-intent";
    public static final String LOCATION_URI_INTENT_VALUE = "flowfile-hold";
    public static final String GZIPPED_HEADER = "flowfile-gzipped";
    public static final String CONTENT_ENCODING_HEADER = "Content-Encoding";
    public static final String CONTENT_ENCODING_GZIP_VALUE = "gzip";

    public static final String PROTOCOL_VERSION_HEADER = "x-nifi-transfer-protocol-version";
    public static final String TRANSACTION_ID_HEADER = "x-nifi-transaction-id";
    public static final String PROTOCOL_VERSION = "3";
    public static final String REMOTE_DN = "remote.dn";

    private static final String FLOW_FILE_CONNECTION_LOG = "Connection to URI {} will be using Content Type {} if sending data as FlowFile";

    public static final PropertyDescriptor URL = new PropertyDescriptor.Builder()
            .name("URL")
            .description("The URL to POST to. The URL may be defined using the Attribute Expression Language. "
                    + "A separate connection pool will be created for each unique host:port combination.")
            .required(true)
            .addValidator(StandardValidators.createRegexMatchingValidator(Pattern.compile("https?\\://.*")))
            .addValidator(StandardValidators.URL_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.FLOWFILE_ATTRIBUTES)
            .build();
    public static final PropertyDescriptor SEND_AS_FLOWFILE = new PropertyDescriptor.Builder()
            .name("Send as FlowFile")
            .description("If true, will package the FlowFile's contents and attributes together and send the FlowFile Package; otherwise, will send only the FlowFile's content")
            .required(true)
            .allowableValues("true", "false")
            .defaultValue("false")
            .build();
    public static final PropertyDescriptor CONNECTION_TIMEOUT = new PropertyDescriptor.Builder()
            .name("Connection Timeout")
            .description("How long to wait when attempting to connect to the remote server before giving up")
            .required(true)
            .defaultValue("30 sec")
            .addValidator(StandardValidators.TIME_PERIOD_VALIDATOR)
            .build();
    public static final PropertyDescriptor DATA_TIMEOUT = new PropertyDescriptor.Builder()
            .name("Data Timeout")
            .description("How long to wait between receiving segments of data from the remote server before giving up and discarding the partial file")
            .required(true)
            .defaultValue("30 sec")
            .addValidator(StandardValidators.TIME_PERIOD_VALIDATOR)
            .build();
    public static final PropertyDescriptor USERNAME = new PropertyDescriptor.Builder()
            .name("Username")
            .description("Username required to access the URL")
            .required(false)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .build();
    public static final PropertyDescriptor PASSWORD = new PropertyDescriptor.Builder()
            .name("Password")
            .description("Password required to access the URL")
            .required(false)
            .sensitive(true)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .build();
    public static final PropertyDescriptor USER_AGENT = new PropertyDescriptor.Builder()
            .name("User Agent")
            .description("What to report as the User Agent when we connect to the remote server")
            .required(false)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .defaultValue(VersionInfo.getUserAgent("Apache-HttpClient", "org.apache.http.client", HttpClientBuilder.class))
            .build();
    public static final PropertyDescriptor COMPRESSION_LEVEL = new PropertyDescriptor.Builder()
            .name("Compression Level")
            .description("Determines the GZIP Compression Level to use when sending the file; the value must be in the range of 0-9. A value of 0 indicates that the file will not be GZIP'ed")
            .required(true)
            .addValidator(StandardValidators.createLongValidator(0, 9, true))
            .defaultValue("0")
            .build();
    public static final PropertyDescriptor ATTRIBUTES_AS_HEADERS_REGEX = new PropertyDescriptor.Builder()
            .name("Attributes to Send as HTTP Headers (Regex)")
            .description("Specifies the Regular Expression that determines the names of FlowFile attributes that should be sent as HTTP Headers")
            .addValidator(StandardValidators.REGULAR_EXPRESSION_VALIDATOR)
            .required(false)
            .build();
    public static final PropertyDescriptor MAX_DATA_RATE = new PropertyDescriptor.Builder()
            .name("Max Data to Post per Second")
            .description("The maximum amount of data to send per second; this allows the bandwidth to be throttled to a specified data rate; if not specified, the data rate is not throttled")
            .required(false)
            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
            .build();
    public static final PropertyDescriptor MAX_BATCH_SIZE = new PropertyDescriptor.Builder()
            .name("Max Batch Size")
            .description("If the Send as FlowFile property is true, specifies the max data size for a batch of FlowFiles to send in a single "
                    + "HTTP POST. If not specified, each FlowFile will be sent separately. If the Send as FlowFile property is false, this "
                    + "property is ignored")
            .required(false)
            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
            .defaultValue("100 MB")
            .build();
    public static final PropertyDescriptor CHUNKED_ENCODING = new PropertyDescriptor.Builder()
            .name("Use Chunked Encoding")
            .description("Specifies whether or not to use Chunked Encoding to send the data. This property is ignored in the event the contents are compressed "
                    + "or sent as FlowFiles.")
            .allowableValues("true", "false")
            .build();
    public static final PropertyDescriptor SSL_CONTEXT_SERVICE = new PropertyDescriptor.Builder()
            .name("SSL Context Service")
            .description("The Controller Service to use in order to obtain an SSL Context")
            .required(false)
            .identifiesControllerService(SSLContextService.class)
            .build();
    public static final PropertyDescriptor CONTENT_TYPE = new PropertyDescriptor.Builder()
            .name("Content-Type")
            .description("The Content-Type to specify for the content of the FlowFile being POSTed if " + SEND_AS_FLOWFILE.getName() + " is false. "
                    + "In the case of an empty value after evaluating an expression language expression, Content-Type defaults to " + DEFAULT_CONTENT_TYPE)
            .required(true)
            .expressionLanguageSupported(ExpressionLanguageScope.FLOWFILE_ATTRIBUTES)
            .defaultValue("${" + CoreAttributes.MIME_TYPE.key() + "}")
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .build();

    public static final Relationship REL_SUCCESS = new Relationship.Builder()
            .name("success")
            .description("Files that are successfully send will be transferred to success")
            .build();
    public static final Relationship REL_FAILURE = new Relationship.Builder()
            .name("failure")
            .description("Files that fail to send will transferred to failure")
            .build();

    private Set<Relationship> relationships;
    private List<PropertyDescriptor> properties;

    private final AtomicReference<StreamThrottler> throttlerRef = new AtomicReference<>();
    private final ConcurrentMap<String, DestinationAccepts> destinationAcceptsMap = new ConcurrentHashMap<>();
    private volatile PoolingHttpClientConnectionManager connManager;
    private volatile CloseableHttpClient client;
    private volatile RequestConfig requestConfig;

    // this is used when creating thet HttpContext, which is a thread local variable that is used by
    // HTTPClient to obtain an available, reusable connection
    private volatile Principal principal;

    @Override
    protected void init(final ProcessorInitializationContext context) {
        final Set<Relationship> relationships = new HashSet<>();
        relationships.add(REL_SUCCESS);
        relationships.add(REL_FAILURE);
        this.relationships = Collections.unmodifiableSet(relationships);

        final List<PropertyDescriptor> properties = new ArrayList<>();
        properties.add(URL);
        properties.add(MAX_BATCH_SIZE);
        properties.add(MAX_DATA_RATE);
        properties.add(SSL_CONTEXT_SERVICE);
        properties.add(USERNAME);
        properties.add(PASSWORD);
        properties.add(SEND_AS_FLOWFILE);
        properties.add(CHUNKED_ENCODING);
        properties.add(COMPRESSION_LEVEL);
        properties.add(CONNECTION_TIMEOUT);
        properties.add(DATA_TIMEOUT);
        properties.add(ATTRIBUTES_AS_HEADERS_REGEX);
        properties.add(USER_AGENT);
        properties.add(HTTPUtils.PROXY_CONFIGURATION_SERVICE);
        properties.add(PROXY_HOST);
        properties.add(PROXY_PORT);
        properties.add(CONTENT_TYPE);
        this.properties = Collections.unmodifiableList(properties);
    }

    @Override
    public Set<Relationship> getRelationships() {
        return relationships;
    }

    @Override
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return properties;
    }

    @Override
    protected Collection<ValidationResult> customValidate(final ValidationContext context) {
        final Collection<ValidationResult> results = new ArrayList<>();

        if (context.getProperty(URL).getValue().startsWith("https") && context.getProperty(SSL_CONTEXT_SERVICE).getValue() == null) {
            results.add(new ValidationResult.Builder()
                    .explanation("URL is set to HTTPS protocol but no SSLContext has been specified")
                    .valid(false).subject("SSL Context").build());
        }

        boolean sendAsFlowFile = context.getProperty(SEND_AS_FLOWFILE).asBoolean();
        int compressionLevel = context.getProperty(COMPRESSION_LEVEL).asInteger();
        boolean chunkedSet = context.getProperty(CHUNKED_ENCODING).isSet();

        if (compressionLevel == 0 && !sendAsFlowFile && !chunkedSet) {
            results.add(new ValidationResult.Builder().valid(false).subject(CHUNKED_ENCODING.getName())
                    .explanation("if compression level is 0 and not sending as a FlowFile, then the \'" + CHUNKED_ENCODING.getName() + "\' property must be set").build());
        }

        HTTPUtils.validateProxyProperties(context, results);

        return results;
    }

    @OnStopped
    public void onStopped() {
        destinationAcceptsMap.clear();

        try {
            connManager.shutdown();
            client.close();
        } catch (IOException e) {
            getLogger().error("Could not properly shutdown connections", e);
        }

        final StreamThrottler throttler = throttlerRef.getAndSet(null);
        if (throttler != null) {
            try {
                throttler.close();
            } catch (IOException e) {
                getLogger().error("Failed to close StreamThrottler", e);
            }
        }
    }

    @OnScheduled
    public void onScheduled(final ProcessContext context) {
        final Double bytesPerSecond = context.getProperty(MAX_DATA_RATE).asDataSize(DataUnit.B);
        this.throttlerRef.set(bytesPerSecond == null ? null : new LeakyBucketStreamThrottler(bytesPerSecond.intValue()));

        String hostname = "unknown";
        try {
            hostname = InetAddress.getLocalHost().getCanonicalHostName();
        } catch (UnknownHostException ignore) {}
        principal = new X500Principal("CN=" + hostname + ", OU=unknown, O=unknown, C=unknown");

        // setup the PoolingHttpClientConnectionManager
        final SSLContextService sslContextService = context.getProperty(SSL_CONTEXT_SERVICE).asControllerService(SSLContextService.class);
        if (sslContextService == null) {
            connManager = new PoolingHttpClientConnectionManager();

        } else {
            final SSLContext sslContext;
            try {
                sslContext = sslContextService.createContext();
            } catch (final Exception e) {
                throw new ProcessException(e);
            }

            final SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext);
            // Also use a plain socket factory for regular http connections (especially proxies)
            final Registry<ConnectionSocketFactory> socketFactoryRegistry =
                    RegistryBuilder.<ConnectionSocketFactory>create()
                            .register("https", sslsf)
                            .register("http", PlainConnectionSocketFactory.getSocketFactory())
                            .build();

            connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
        }

        // setup SocketConfig
        SocketConfig.Builder socketConfigBuilder = SocketConfig.custom();
        socketConfigBuilder.setSoTimeout(context.getProperty(CONNECTION_TIMEOUT).asTimePeriod(TimeUnit.MILLISECONDS).intValue());
        SocketConfig socketConfig = socketConfigBuilder.build();
        connManager.setDefaultSocketConfig(socketConfig);

        // the +1 here accommodates math error calculating excess connections in AbstractConnPool.getPoolEntryBlocking()
        connManager.setDefaultMaxPerRoute(context.getMaxConcurrentTasks() + 1);
        // max total connections will get set in onTrigger(), because a new route will require increasing this
        connManager.setMaxTotal(1);
        // enable inactivity check, to detect and close idle connections
        connManager.setValidateAfterInactivity(30_000);

        // setup the HttpClientBuilder
        final HttpClientBuilder clientBuilder = HttpClientBuilder.create();
        clientBuilder.setConnectionManager(connManager);
        clientBuilder.setUserAgent(context.getProperty(USER_AGENT).getValue());
        clientBuilder.addInterceptorFirst(new HttpResponseInterceptor() {
            @Override
            public void process(final HttpResponse response, final HttpContext httpContext) throws HttpException, IOException {
                final HttpCoreContext coreContext = HttpCoreContext.adapt(httpContext);
                final ManagedHttpClientConnection conn = coreContext.getConnection(ManagedHttpClientConnection.class);
                if (!conn.isOpen()) {
                    return;
                }

                final SSLSession sslSession = conn.getSSLSession();

                if (sslSession != null) {
                    final Certificate[] certChain = sslSession.getPeerCertificates();
                    if (certChain == null || certChain.length == 0) {
                        throw new SSLPeerUnverifiedException("No certificates found");
                    }

                    final X509Certificate cert = (X509Certificate) certChain[0];
                    httpContext.setAttribute(REMOTE_DN, cert.getSubjectDN().getName().trim());
                }
            }
        });

        HttpRequestRetryHandler retryHandler = (exception, attempt, httpContext) -> {
            if (attempt > 3 || !isScheduled()) {
                return false;
            }
            final HttpClientContext clientContext = HttpClientContext.adapt(httpContext);
            // A heavily loaded remote listener can manifest as NoHttpResponseExceptions here.
            // When this happens, take a 5 second snooze before retrying to give the remote a short break.
            if (exception instanceof NoHttpResponseException) {
                if (getLogger().isDebugEnabled()) {
                    getLogger().debug("Sleeping for 5 secs then retrying {} request for remote server {}",
                            clientContext.getRequest().getRequestLine().getMethod(), clientContext.getTargetHost());
                }
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    return false;
                }
                return true;
            }
            // do not retry more serious exceptions
            return false;
        };
        clientBuilder.setRetryHandler(retryHandler);
        clientBuilder.disableContentCompression();

        final String username = context.getProperty(USERNAME).getValue();
        final String password = context.getProperty(PASSWORD).getValue();
        // set the credentials if appropriate
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        clientBuilder.setDefaultCredentialsProvider(credentialsProvider);
        if (username != null) {
            credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
        }

        // Set the proxy if specified
        HTTPUtils.setProxy(context, clientBuilder, credentialsProvider);

        // complete the HTTPClient build
        client = clientBuilder.build();

        // setup RequestConfig
        final RequestConfig.Builder requestConfigBuilder = RequestConfig.custom();
        requestConfigBuilder.setConnectionRequestTimeout(context.getProperty(DATA_TIMEOUT).asTimePeriod(TimeUnit.MILLISECONDS).intValue());
        requestConfigBuilder.setConnectTimeout(context.getProperty(CONNECTION_TIMEOUT).asTimePeriod(TimeUnit.MILLISECONDS).intValue());
        requestConfigBuilder.setRedirectsEnabled(false);
        requestConfigBuilder.setSocketTimeout(context.getProperty(DATA_TIMEOUT).asTimePeriod(TimeUnit.MILLISECONDS).intValue());
        requestConfig = requestConfigBuilder.build();
    }

    private String getBaseUrl(final String url) {
        final int index = url.indexOf("/", 9);
        if (index < 0) {
            return url;
        }
        return url.substring(0, index);
    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) {
        FlowFile firstFlowFile = session.get();
        if (firstFlowFile == null) {
            return;
        }

        final ComponentLog logger = getLogger();
        final String url = context.getProperty(URL).evaluateAttributeExpressions(firstFlowFile).getValue();
        try {
            new java.net.URL(url);
        } catch (final MalformedURLException e) {
            logger.error("After substituting attribute values for {}, URL is {}; this is not a valid URL, so routing to failure",
                    firstFlowFile, url);
            firstFlowFile = session.penalize(firstFlowFile);
            session.transfer(firstFlowFile, REL_FAILURE);
            return;
        }

        final List<FlowFile> toSend = new ArrayList<>();
        toSend.add(firstFlowFile);

        final boolean sendAsFlowFile = context.getProperty(SEND_AS_FLOWFILE).asBoolean();
        final int compressionLevel = context.getProperty(COMPRESSION_LEVEL).asInteger();

        final StreamThrottler throttler = throttlerRef.get();

        final Double maxBatchBytes = context.getProperty(MAX_BATCH_SIZE).asDataSize(DataUnit.B);
        final AtomicLong bytesToSend = new AtomicLong(firstFlowFile.getSize());

        DestinationAccepts destinationAccepts = null;
        final String transactionId = UUID.randomUUID().toString();
        final HttpClientContext httpClientContext = HttpClientContext.create();
        httpClientContext.setUserToken(principal);

        // determine whether or not destination accepts flowfile/gzip
        final String baseUrl = getBaseUrl(url);
        destinationAccepts = destinationAcceptsMap.get(baseUrl);
        if (destinationAccepts == null) {
            try {
                destinationAccepts = getDestinationAcceptance(sendAsFlowFile, url, transactionId, httpClientContext);
                if (null == destinationAcceptsMap.putIfAbsent(baseUrl, destinationAccepts)) {
                    // url indicates a new route, so increase the max allowed open connections
                    connManager.setMaxTotal(connManager.getMaxTotal() + connManager.getDefaultMaxPerRoute());
                }
            } catch (final IOException e) {
                firstFlowFile = session.penalize(firstFlowFile);
                session.transfer(firstFlowFile, REL_FAILURE);
                logger.error("Unable to communicate with destination {} to determine whether or not it can accept flowfiles/gzip; routing {} to failure", url, firstFlowFile, e);
                return;
            }
        }

        // if we are sending as flowfile and the destination accepts V3 or V2 (streaming) format,
        // then we can get more flowfiles from the session up to MAX_BATCH_SIZE for the same URL
        if (sendAsFlowFile && (destinationAccepts.isFlowFileV3Accepted() || destinationAccepts.isFlowFileV2Accepted())) {
            toSend.addAll(session.get(new FlowFileFilter() {
                @Override
                public FlowFileFilterResult filter(FlowFile flowFile) {
                    // if over MAX_BATCH_SIZE, then stop adding files
                    if (bytesToSend.get() + flowFile.getSize() > maxBatchBytes) {
                        return FlowFileFilterResult.REJECT_AND_TERMINATE;
                    }
                    // check URL to see if this flowfile can be included in the batch
                    final String urlToCheck = context.getProperty(URL).evaluateAttributeExpressions(flowFile).getValue();
                    if (url.equals(urlToCheck)) {
                        bytesToSend.addAndGet(flowFile.getSize());
                        return FlowFileFilterResult.ACCEPT_AND_CONTINUE;
                    } else {
                        return FlowFileFilterResult.REJECT_AND_CONTINUE;
                    }
                }
            }));
        }

        final HttpPost post = new HttpPost(url);
        final DestinationAccepts accepts = destinationAccepts;
        final boolean isDestinationLegacyNiFi = accepts.getProtocolVersion() == null;

        final EntityTemplate entity = new EntityTemplate(new ContentProducer() {
            @Override
            public void writeTo(final OutputStream rawOut) throws IOException {
                final OutputStream throttled = throttler == null ? rawOut : throttler.newThrottledOutputStream(rawOut);
                OutputStream wrappedOut = new BufferedOutputStream(throttled);
                if (compressionLevel > 0 && accepts.isGzipAccepted()) {
                    wrappedOut = new GZIPOutputStream(wrappedOut, compressionLevel);
                }

                try (final OutputStream out = wrappedOut) {
                    final FlowFilePackager packager;
                    if (!sendAsFlowFile) {
                        packager = null;
                    } else if (accepts.isFlowFileV3Accepted()) {
                        packager = new FlowFilePackagerV3();
                    } else if (accepts.isFlowFileV2Accepted()) {
                        packager = new FlowFilePackagerV2();
                    } else if (accepts.isFlowFileV1Accepted()) {
                        packager = new FlowFilePackagerV1();
                    } else {
                        packager = null;
                    }

                    for (final FlowFile flowFile : toSend) {
                        session.read(flowFile, new InputStreamCallback() {
                            @Override
                            public void process(final InputStream rawIn) throws IOException {
                                try (final InputStream in = new BufferedInputStream(rawIn)) {

                                    // if none of the above conditions is met, we should never get here, because
                                    // we will have already verified that at least 1 of the FlowFile packaging
                                    // formats is acceptable if sending as FlowFile.
                                    if (packager == null) {
                                        StreamUtils.copy(in, out);
                                    } else {
                                        final Map<String, String> flowFileAttributes;
                                        if (isDestinationLegacyNiFi) {
                                            // Old versions of NiFi expect nf.file.name and nf.file.path to indicate filename & path;
                                            // in order to maintain backward compatibility, we copy the filename & path to those attribute keys.
                                            flowFileAttributes = new HashMap<>(flowFile.getAttributes());
                                            flowFileAttributes.put("nf.file.name", flowFile.getAttribute(CoreAttributes.FILENAME.key()));
                                            flowFileAttributes.put("nf.file.path", flowFile.getAttribute(CoreAttributes.PATH.key()));
                                        } else {
                                            flowFileAttributes = flowFile.getAttributes();
                                        }

                                        packager.packageFlowFile(in, out, flowFileAttributes, flowFile.getSize());
                                    }
                                }
                            }
                        });
                    }

                    out.flush();
                } catch (ProcessException pe) {
                    // Pull out IOExceptions so that HTTPClient can properly do what it needs to do
                    Throwable t = pe.getCause();
                    if (t != null && t instanceof IOException) {
                        IOException ioe = new IOException(t.getMessage());
                        ioe.setStackTrace(t.getStackTrace());
                        throw ioe;
                    }
                    throw pe;
                }
            }
        }) {

            @Override
            public long getContentLength() {
                if (compressionLevel == 0 && !sendAsFlowFile && !context.getProperty(CHUNKED_ENCODING).asBoolean()) {
                    return toSend.get(0).getSize();
                } else {
                    return -1;
                }
            }
        };

        final String flowFileDescription = toSend.size() <= 10 ? toSend.toString() : toSend.size() + " FlowFiles";

        if (context.getProperty(CHUNKED_ENCODING).isSet()) {
            entity.setChunked(context.getProperty(CHUNKED_ENCODING).asBoolean());
        }
        post.setEntity(entity);
        post.setConfig(requestConfig);

        final String contentType;
        if (sendAsFlowFile) {
            if (accepts.isFlowFileV3Accepted()) {
                contentType = StandardFlowFileMediaType.VERSION_3.getMediaType();
            } else if (accepts.isFlowFileV2Accepted()) {
                contentType = StandardFlowFileMediaType.VERSION_2.getMediaType();
            } else if (accepts.isFlowFileV1Accepted()) {
                contentType = StandardFlowFileMediaType.VERSION_1.getMediaType();
            } else {
                logger.error("Cannot send {} to {} because the destination does not accept FlowFiles and this processor is configured to deliver FlowFiles; routing to failure",
                        flowFileDescription, url);
                for (FlowFile flowFile : toSend) {
                    flowFile = session.penalize(flowFile);
                    session.transfer(flowFile, REL_FAILURE);
                }
                return;
            }
        } else {
            final String contentTypeValue = context.getProperty(CONTENT_TYPE).evaluateAttributeExpressions(toSend.get(0)).getValue();
            contentType = StringUtils.isBlank(contentTypeValue) ? DEFAULT_CONTENT_TYPE : contentTypeValue;
        }

        final String attributeHeaderRegex = context.getProperty(ATTRIBUTES_AS_HEADERS_REGEX).getValue();
        if (attributeHeaderRegex != null && !sendAsFlowFile && toSend.size() == 1) {
            final Pattern pattern = Pattern.compile(attributeHeaderRegex);

            final Map<String, String> attributes = toSend.get(0).getAttributes();
            for (final Map.Entry<String, String> entry : attributes.entrySet()) {
                final String key = entry.getKey();
                if (pattern.matcher(key).matches()) {
                    post.setHeader(entry.getKey(), entry.getValue());
                }
            }
        }

        post.setHeader(CONTENT_TYPE_HEADER, contentType);
        post.setHeader(FLOWFILE_CONFIRMATION_HEADER, "true");
        post.setHeader(PROTOCOL_VERSION_HEADER, PROTOCOL_VERSION);
        post.setHeader(TRANSACTION_ID_HEADER, transactionId);
        if (compressionLevel > 0 && accepts.isGzipAccepted()) {
            if (sendAsFlowFile) {
                post.setHeader(GZIPPED_HEADER, "true");
            } else {
                post.setHeader(CONTENT_ENCODING_HEADER, CONTENT_ENCODING_GZIP_VALUE);
            }
        }

        // Do the actual POST
        final String uploadDataRate;
        final long uploadMillis;
        CloseableHttpResponse response = null;
        try {
            final StopWatch stopWatch = new StopWatch(true);
            response = client.execute(post, httpClientContext);
            stopWatch.stop();
            uploadDataRate = stopWatch.calculateDataRate(bytesToSend.get());
            uploadMillis = stopWatch.getDuration(TimeUnit.MILLISECONDS);
        } catch (final IOException | ProcessException e) {
            logger.error("Failed to Post {} transferring to failure", flowFileDescription, e);
            for (FlowFile flowFile : toSend) {
                flowFile = session.penalize(flowFile);
                session.transfer(flowFile, REL_FAILURE);
            }
            return;
        } finally {
            if (response != null) {
                try {
                    // consume input stream entirely, ignoring its contents. If we
                    // don't do this, the Connection will not be returned to the pool
                    EntityUtils.consume(response.getEntity());
                } catch (final IOException ignore) {
                }
            }
        }

        // If we get a 'SEE OTHER' status code and an HTTP header that indicates that the intent
        // of the Location URI is a flowfile hold, we will store this holdUri. This prevents us
        // from posting to some other webservice and then attempting to delete some resource to which
        // we are redirected
        final int responseCode = response.getStatusLine().getStatusCode();
        final String responseReason = response.getStatusLine().getReasonPhrase();
        String holdUri = null;
        if (responseCode == HttpServletResponse.SC_SEE_OTHER) {
            final Header locationUriHeader = response.getFirstHeader(LOCATION_URI_INTENT_NAME);
            if (locationUriHeader != null) {
                if (LOCATION_URI_INTENT_VALUE.equals(locationUriHeader.getValue())) {
                    final Header holdUriHeader = response.getFirstHeader(LOCATION_HEADER_NAME);
                    if (holdUriHeader != null) {
                        holdUri = holdUriHeader.getValue();
                    }
                }
            }

            if (holdUri == null) {
                logger.error("Failed to Post {} to {}: sent content and received status code {}:{} but no Hold URI",
                        flowFileDescription, url, responseCode, responseReason);
                for (FlowFile flowFile : toSend) {
                    flowFile = session.penalize(flowFile);
                    session.transfer(flowFile, REL_FAILURE);
                }
                return;
            }
        }

        if (holdUri == null) {
            if (responseCode == HttpServletResponse.SC_SERVICE_UNAVAILABLE) {
                logger.error("Failed to Post {} to {}: response code was {}:{}", flowFileDescription, url, responseCode, responseReason);
                for (FlowFile flowFile : toSend) {
                    flowFile = session.penalize(flowFile);
                    session.transfer(flowFile, REL_FAILURE);
                }
                return;
            }

            if (responseCode >= 300) {
                logger.error("Failed to Post {} to {}: response code was {}:{}", flowFileDescription, url, responseCode, responseReason);
                for (FlowFile flowFile : toSend) {
                    flowFile = session.penalize(flowFile);
                    session.transfer(flowFile, REL_FAILURE);
                }
                return;
            }

            logger.info("Successfully Posted {} to {} in {} at a rate of {}",
                    flowFileDescription, url, FormatUtils.formatMinutesSeconds(uploadMillis, TimeUnit.MILLISECONDS), uploadDataRate);

            for (final FlowFile flowFile : toSend) {
                session.getProvenanceReporter().send(flowFile, url, "Remote DN=" + httpClientContext.getAttribute(REMOTE_DN), uploadMillis, true);
                session.transfer(flowFile, REL_SUCCESS);
            }
            return;
        }

        //
        // the response indicated a Hold URI; delete the Hold.
        //
        // determine the full URI of the Flow File's Hold; Unfortunately, the responses that are returned have
        // changed over the past, so we have to take into account a few different possibilities.
        String fullHoldUri = holdUri;
        if (holdUri.startsWith("/contentListener")) {
            // If the Hold URI that we get starts with /contentListener, it may not really be /contentListener,
            // as this really indicates that it should be whatever we posted to -- if posting directly to the
            // ListenHTTP component, it will be /contentListener, but if posting to a proxy/load balancer, we may
            // be posting to some other URL.
            fullHoldUri = url + holdUri.substring(16);
        } else if (holdUri.startsWith("/")) {
            // URL indicates the full path but not hostname or port; use the same hostname & port that we posted
            // to but use the full path indicated by the response.
            int firstSlash = url.indexOf("/", 8);
            if (firstSlash < 0) {
                firstSlash = url.length();
            }
            final String beforeSlash = url.substring(0, firstSlash);
            fullHoldUri = beforeSlash + holdUri;
        } else if (!holdUri.startsWith("http")) {
            // Absolute URL
            fullHoldUri = url + (url.endsWith("/") ? "" : "/") + holdUri;
        }

        final HttpDelete delete = new HttpDelete(fullHoldUri);
        delete.setHeader(TRANSACTION_ID_HEADER, transactionId);
        delete.setConfig(requestConfig);

        HttpResponse holdResponse = null;
        try {
            holdResponse = client.execute(delete, httpClientContext);
            final int holdStatusCode = holdResponse.getStatusLine().getStatusCode();
            final String holdReason = holdResponse.getStatusLine().getReasonPhrase();
            if (holdStatusCode >= 300) {
                logger.error("Failed to delete Hold that destination placed on {}: got response code {}:{}; routing to failure",
                        flowFileDescription, holdStatusCode, holdReason);

                for (FlowFile flowFile : toSend) {
                    flowFile = session.penalize(flowFile);
                    session.transfer(flowFile, REL_FAILURE);
                }
                return;
            }

            logger.info("Successfully Posted {} to {} in {} at a rate of {}",
                    flowFileDescription, url, FormatUtils.formatMinutesSeconds(uploadMillis, TimeUnit.MILLISECONDS), uploadDataRate);

            for (final FlowFile flowFile : toSend) {
                session.getProvenanceReporter().send(flowFile, url, "Remote DN=" + httpClientContext.getAttribute(REMOTE_DN), uploadMillis, true);
                session.transfer(flowFile, REL_SUCCESS);
            }
            return;

        } catch (final IOException e) {
            logger.warn("Failed to delete Hold that destination placed on, routing to failure", flowFileDescription, e);
            for (FlowFile flowFile : toSend) {
                flowFile = session.penalize(flowFile);
                session.transfer(flowFile, REL_FAILURE);
            }
        } finally {
            if (null != holdResponse) {
                try {
                    // consume input stream entirely, ignoring its contents. If we
                    // don't do this, the Connection will not be returned to the pool
                    EntityUtils.consume(holdResponse.getEntity());
                } catch (IOException ignore) {}
            }
        }
    }

    private DestinationAccepts getDestinationAcceptance(final boolean sendAsFlowFile, final String uri, final String transactionId, final HttpContext httpContext) throws IOException {
        final HttpHead head = new HttpHead(uri);
        head.setConfig(requestConfig);
        if (sendAsFlowFile) {
            head.addHeader(TRANSACTION_ID_HEADER, transactionId);
        }

        final HttpResponse response = client.execute(head, httpContext);

        // we assume that the destination can support FlowFile v1 always when the processor is also configured to send as a FlowFile
        // otherwise, we do not bother to make any determinations concerning this compatibility
        final boolean acceptsFlowFileV1 = sendAsFlowFile;
        boolean acceptsFlowFileV2 = false;
        boolean acceptsFlowFileV3 = false;
        boolean acceptsGzip = false;
        Integer protocolVersion = null;

        final int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode == Status.METHOD_NOT_ALLOWED.getStatusCode()) {
            return new DestinationAccepts(acceptsFlowFileV3, acceptsFlowFileV2, acceptsFlowFileV1, false, null);
        } else if (statusCode == Status.OK.getStatusCode()) {
            Header[] headers = response.getHeaders(ACCEPT);
            // If configured to send as a flowfile, determine the capabilities of the endpoint
            if (sendAsFlowFile) {
                if (headers != null) {
                    for (final Header header : headers) {
                        for (final String accepted : header.getValue().split(",")) {
                            final String trimmed = accepted.trim();
                            if (trimmed.equals(StandardFlowFileMediaType.VERSION_3.getMediaType())) {
                                acceptsFlowFileV3 = true;
                            } else if (trimmed.equals(StandardFlowFileMediaType.VERSION_2.getMediaType())) {
                                acceptsFlowFileV2 = true;
                            }
                        }
                    }
                }

                final Header destinationVersion = response.getFirstHeader(PROTOCOL_VERSION_HEADER);
                if (destinationVersion != null) {
                    try {
                        protocolVersion = Integer.valueOf(destinationVersion.getValue());
                    } catch (final NumberFormatException e) {
                        // nothing to do here really.... it's an invalid value, so treat the same as if not specified
                    }
                }

                if (getLogger().isDebugEnabled()) {
                    if (acceptsFlowFileV3) {
                        getLogger().debug(FLOW_FILE_CONNECTION_LOG, uri, StandardFlowFileMediaType.VERSION_3.getMediaType());
                    } else if (acceptsFlowFileV2) {
                        getLogger().debug(FLOW_FILE_CONNECTION_LOG, uri, StandardFlowFileMediaType.VERSION_2.getMediaType());
                    } else if (acceptsFlowFileV1) {
                        getLogger().debug(FLOW_FILE_CONNECTION_LOG, uri, StandardFlowFileMediaType.VERSION_1.getMediaType());
                    }
                }
            }

            headers = response.getHeaders(ACCEPT_ENCODING);
            if (headers != null) {
                for (final Header header : headers) {
                    for (final String accepted : header.getValue().split(",")) {
                        if (accepted.equalsIgnoreCase("gzip")) {
                            acceptsGzip = true;
                        }
                    }
                }
            }

            if (getLogger().isDebugEnabled()) {
                if (acceptsGzip) {
                    getLogger().debug("Connection to URI " + uri + " indicates that inline GZIP compression is supported");
                } else {
                    getLogger().debug("Connection to URI " + uri + " indicates that it does NOT support inline GZIP compression");
                }
            }

            return new DestinationAccepts(acceptsFlowFileV3, acceptsFlowFileV2, acceptsFlowFileV1, acceptsGzip, protocolVersion);
        } else {
            getLogger().warn("Unable to communicate with destination; when attempting to perform an HTTP HEAD, got unexpected response code of "
                    + statusCode + ": " + response.getStatusLine().getReasonPhrase());
            return new DestinationAccepts(false, false, false, false, null);
        }
    }

    private static class DestinationAccepts {

        private final boolean flowFileV1;
        private final boolean flowFileV2;
        private final boolean flowFileV3;
        private final boolean gzip;
        private final Integer protocolVersion;

        public DestinationAccepts(final boolean flowFileV3, final boolean flowFileV2, final boolean flowFileV1, final boolean gzip, final Integer protocolVersion) {
            this.flowFileV3 = flowFileV3;
            this.flowFileV2 = flowFileV2;
            this.flowFileV1 = flowFileV1;
            this.gzip = gzip;
            this.protocolVersion = protocolVersion;
        }

        public boolean isFlowFileV3Accepted() {
            return flowFileV3;
        }

        public boolean isFlowFileV2Accepted() {
            return flowFileV2;
        }

        public boolean isFlowFileV1Accepted() {
            return flowFileV1;
        }

        public boolean isGzipAccepted() {
            return gzip;
        }

        public Integer getProtocolVersion() {
            return protocolVersion;
        }
    }
}
