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From jia...@apache.org
Subject [12/50] [abbrv] hadoop git commit: YARN-5218. Initial core change for DNS for YARN. Contributed by Jonathan Maron
Date Tue, 18 Apr 2017 06:07:46 GMT
http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNS.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNS.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNS.java
new file mode 100644
index 0000000..52b3c37
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNS.java
@@ -0,0 +1,1534 @@
+/*
+ * 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.hadoop.registry.server.dns;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.filefilter.IOFileFilter;
+import org.apache.commons.net.util.Base64;
+import org.apache.commons.net.util.SubnetUtils;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.net.NetUtils;
+import org.apache.hadoop.registry.client.api.DNSOperations;
+import org.apache.hadoop.registry.client.types.ServiceRecord;
+import org.apache.hadoop.registry.client.types.yarn.YarnRegistryAttributes;
+import org.apache.hadoop.service.AbstractService;
+import org.apache.hadoop.util.concurrent.HadoopExecutors;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.xbill.DNS.CNAMERecord;
+import org.xbill.DNS.DClass;
+import org.xbill.DNS.DNSKEYRecord;
+import org.xbill.DNS.DNSSEC;
+import org.xbill.DNS.DSRecord;
+import org.xbill.DNS.ExtendedFlags;
+import org.xbill.DNS.Flags;
+import org.xbill.DNS.Header;
+import org.xbill.DNS.Message;
+import org.xbill.DNS.NSRecord;
+import org.xbill.DNS.Name;
+import org.xbill.DNS.NameTooLongException;
+import org.xbill.DNS.OPTRecord;
+import org.xbill.DNS.Opcode;
+import org.xbill.DNS.RRSIGRecord;
+import org.xbill.DNS.RRset;
+import org.xbill.DNS.Rcode;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.SOARecord;
+import org.xbill.DNS.Section;
+import org.xbill.DNS.SetResponse;
+import org.xbill.DNS.TSIG;
+import org.xbill.DNS.TSIGRecord;
+import org.xbill.DNS.TextParseException;
+import org.xbill.DNS.Type;
+import org.xbill.DNS.Zone;
+
+import java.io.DataOutputStream;
+import java.io.EOFException;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.DatagramChannel;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.RSAPrivateKeySpec;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import java.util.Collection;
+import java.util.Date;
+import java.util.Iterator;
+import java.util.Properties;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import static org.apache.hadoop.registry.client.api.RegistryConstants.*;
+
+/**
+ * A DNS service reflecting the state of the YARN registry.  Records are created
+ * based on service records available in the YARN ZK-based registry.
+ */
+public class RegistryDNS extends AbstractService implements DNSOperations,
+    ZoneSelector {
+
+  public static final String CONTAINER = "container";
+
+  static final int FLAG_DNSSECOK = 1;
+  static final int FLAG_SIGONLY = 2;
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(RegistryDNS.class);
+  public static final String IN_ADDR_ARPA = "in-addr.arpa.";
+  public static final String ZONE_SUFFIX = ".zone";
+
+  private ExecutorService executor;
+  private ReentrantReadWriteLock zoneLock = new ReentrantReadWriteLock();
+  private CloseableLock readLock = new CloseableLock(zoneLock.readLock());
+  private CloseableLock writeLock = new CloseableLock(zoneLock.writeLock());
+  private String domainName;
+  private long ttl = 0L;
+
+  private static final Pattern USER_NAME = Pattern.compile("/users/(\\w*)/?");
+  private Boolean dnssecEnabled;
+  private PrivateKey privateKey;
+
+  private ConcurrentMap<Name, DNSKEYRecord> dnsKeyRecs =
+      new ConcurrentHashMap<>();
+  private ConcurrentMap<Name, Zone> zones = new ConcurrentHashMap<>();
+  private Name bindHost;
+
+  /**
+   * Construct the service.
+   *
+   * @param name service name
+   */
+  public RegistryDNS(String name) {
+    super(name);
+    executor = HadoopExecutors.newCachedThreadPool(
+        new ThreadFactory() {
+          private AtomicInteger counter = new AtomicInteger(1);
+
+          @Override
+          public Thread newThread(Runnable r) {
+            return new Thread(r,
+                "RegistryDNS "
+                    + counter.getAndIncrement());
+          }
+        });
+  }
+
+  /**
+   * Initializes the registry.
+   *
+   * @param conf the hadoop configuration
+   * @throws Exception if there are tcp/udp issues
+   */
+  @Override
+  protected void serviceInit(Configuration conf) throws Exception {
+    super.serviceInit(conf);
+
+    // create the zone.  for now create a "dummy" SOA record
+    try {
+      setDomainName(conf);
+
+      int port = initializeZones(conf);
+
+      InetAddress addr = InetAddress.getLocalHost();
+
+      String bindAddress = conf.get(KEY_DNS_BIND_ADDRESS);
+      if (bindAddress != null) {
+        addr = InetAddress.getByName(bindAddress);
+      }
+      addNIOUDP(addr, port);
+      addNIOTCP(addr, port);
+
+    } catch (IOException e) {
+      LOG.error("Error initializing Registry DNS Server", e);
+      throw e;
+    }
+  }
+
+  /**
+   * Initializes the registry based on available parameters in the hadoop
+   * configuration.
+   *
+   * @param conf the hadoop configuration
+   * @return the listener port
+   * @throws IOException
+   */
+  int initializeZones(Configuration conf) throws IOException {
+    int port = conf.getInt(KEY_DNS_PORT, DEFAULT_DNS_PORT);
+    ttl = conf.getTimeDuration(KEY_DNS_TTL, 1L, TimeUnit.SECONDS);
+    RecordCreatorFactory.setTtl(ttl);
+
+    setDNSSECEnabled(conf);
+
+    initializeZonesFromFiles(conf);
+
+    Zone registryZone = configureZone(Name.fromString(domainName), conf);
+    zones.put(registryZone.getOrigin(), registryZone);
+
+    initializeReverseLookupZone(conf);
+
+    return port;
+  }
+
+  /**
+   * Signs zone records if necessary (DNSSEC enabled).  Zones may not have
+   * their NS and SOA records signed if they were initialized from master files.
+   */
+  private void signZones() throws IOException {
+    if (isDNSSECEnabled()) {
+      Collection<Zone> zoneCollection = zones.values();
+      for (Zone zone : zoneCollection) {
+        Iterator itor = zone.iterator();
+        while (itor.hasNext()) {
+          RRset rRset = (RRset) itor.next();
+          Iterator sigs = rRset.sigs();
+          if (!sigs.hasNext()) {
+            try {
+              signSiteRecord(zone, rRset.first());
+            } catch (DNSSEC.DNSSECException e) {
+              throw new IOException(e);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Initializes a zone by reading any zone file by the same name in the
+   * designated zone file directory.
+   *
+   * @param conf the Hadoop configuration object.
+   * @throws IOException
+   */
+  private void initializeZonesFromFiles(Configuration conf) throws IOException {
+    // should this be in HDFS?
+    String zonesDir = conf.get(KEY_DNS_ZONES_DIR);
+    if (zonesDir != null) {
+      Iterator<File> iterator = FileUtils.iterateFiles(new File(zonesDir),
+          new IOFileFilter() {
+            @Override
+            public boolean accept(
+                File file) {
+              return file.getName().endsWith(
+                  ZONE_SUFFIX);
+            }
+
+            @Override
+            public boolean accept(
+                File file,
+                String s) {
+              return s.endsWith(
+                  ZONE_SUFFIX);
+            }
+          }, null);
+      while (iterator.hasNext()) {
+        File file = iterator.next();
+        String name = file.getName();
+        name = name.substring(0, name.indexOf(ZONE_SUFFIX) + 1);
+        Zone zone = new SecureableZone(Name.fromString(name),
+            file.getAbsolutePath());
+        zones.putIfAbsent(zone.getOrigin(), zone);
+      }
+    }
+  }
+
+  /**
+   * Initializes the reverse lookup zone (mapping IP to name).
+   *
+   * @param conf the Hadoop configuration.
+   * @throws IOException
+   */
+  private void initializeReverseLookupZone(Configuration conf)
+      throws IOException {
+    Name reverseLookupZoneName = getReverseZoneName(conf);
+    Zone reverseLookupZone =
+        configureZone(reverseLookupZoneName, conf);
+    zones.put(reverseLookupZone.getOrigin(), reverseLookupZone);
+  }
+
+  /**
+   * Returns the list of reverse lookup zones.
+   *
+   * @param conf the hadoop configuration.
+   * @return the list of reverse zone names required based on the configuration
+   * properties.
+   */
+  protected Name getReverseZoneName(Configuration conf) {
+    Name name = null;
+    String zoneSubnet = getZoneSubnet(conf);
+    if (zoneSubnet == null) {
+      LOG.warn("Zone subnet is not configured.  Reverse lookups disabled");
+    } else {
+      // is there a netmask
+      String mask = conf.get(KEY_DNS_ZONE_MASK);
+      if (mask != null) {
+        // get the range of IPs
+        SubnetUtils utils = new SubnetUtils(zoneSubnet, mask);
+        name = getReverseZoneName(utils, zoneSubnet);
+      } else {
+        name = getReverseZoneName(zoneSubnet);
+      }
+    }
+    return name;
+  }
+
+  /**
+   * Return the subnet for the zone.  this should be a network address for the
+   * subnet (ends in ".0").
+   *
+   * @param conf the hadoop configuration.
+   * @return the zone subnet.
+   */
+  private String getZoneSubnet(Configuration conf) {
+    String subnet = conf.get(KEY_DNS_ZONE_SUBNET);
+    if (subnet != null) {
+      final String[] bytes = subnet.split("\\.");
+      if (bytes.length == 3) {
+        subnet += ".0";
+      }
+    }
+    return subnet;
+  }
+
+  /**
+   * Return the reverse zone name based on the address.
+   *
+   * @param networkAddress the network address.
+   * @return the reverse zone name.
+   */
+  private Name getReverseZoneName(String networkAddress) {
+    return getReverseZoneName(null, networkAddress);
+  }
+
+  /**
+   * Return the reverse zone name based on the address.
+   *
+   * @param utils          subnet utils
+   * @param networkAddress the network address.
+   * @return the reverse zone name.
+   */
+  private Name getReverseZoneName(SubnetUtils utils, String networkAddress) {
+    Name reverseZoneName = null;
+    boolean isLargeNetwork = false;
+    if (utils != null) {
+      isLargeNetwork = utils.getInfo().getAddressCount() > 256;
+    }
+    final String[] bytes = networkAddress.split("\\.");
+    if (bytes.length == 4) {
+      String reverseLookupZoneName = null;
+      if (isLargeNetwork) {
+        reverseLookupZoneName =
+            String.format("%s.%s.%s",
+                bytes[1],
+                bytes[0],
+                IN_ADDR_ARPA);
+      } else {
+        reverseLookupZoneName =
+            String.format("%s.%s.%s.%s",
+                bytes[2],
+                bytes[1],
+                bytes[0],
+                IN_ADDR_ARPA);
+      }
+      try {
+        reverseZoneName = Name.fromString(reverseLookupZoneName);
+      } catch (TextParseException e) {
+        LOG.warn("Unable to convert {} to DNS name", reverseLookupZoneName);
+      }
+    }
+    return reverseZoneName;
+  }
+
+  /**
+   * Create the zone and its related zone associated DNS records  (NS, SOA).
+   *
+   * @param zoneName domain name of the zone
+   * @param conf     configuration reference.
+   * @return the zone.
+   * @throws IOException
+   */
+  private Zone configureZone(Name zoneName, Configuration conf)
+      throws IOException {
+    bindHost = Name.fromString(
+        InetAddress.getLocalHost().getCanonicalHostName() + ".");
+    SOARecord soaRecord = new SOARecord(zoneName, DClass.IN, ttl,
+        bindHost,
+        bindHost, getSerial(), 86000, 7200,
+        1209600, 600);
+    NSRecord nsRecord = new NSRecord(zoneName, DClass.IN, ttl, bindHost);
+    Zone zone = zones.get(zoneName);
+    if (zone == null) {
+      zone = new SecureableZone(zoneName, new Record[] {soaRecord, nsRecord});
+    }
+
+    try {
+      enableDNSSECIfNecessary(zone, conf, soaRecord, nsRecord);
+    } catch (NoSuchAlgorithmException e) {
+      throw new IOException(e);
+    } catch (InvalidKeySpecException e) {
+      throw new IOException(e);
+    } catch (DNSSEC.DNSSECException e) {
+      throw new IOException(e);
+    }
+
+    return zone;
+  }
+
+  /**
+   * Return a serial number based on the current date and time.
+   *
+   * @return the serial number.
+   */
+  private long getSerial() {
+    Date curDate = new Date();
+    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMddHH");
+    String serial = simpleDateFormat.format(curDate);
+    return Long.parseLong(serial);
+  }
+
+  /**
+   * Set the value of the DNSSEC enabled property.
+   *
+   * @param conf the Hadoop configuration.
+   */
+  private void setDNSSECEnabled(Configuration conf) {
+    dnssecEnabled = conf.getBoolean(KEY_DNSSEC_ENABLED, false);
+  }
+
+  /**
+   * Is DNSSEC enabled?
+   *
+   * @return true if enabled, false otherwise.
+   */
+  private boolean isDNSSECEnabled() {
+    return dnssecEnabled;
+  }
+
+  /**
+   * Load the required public/private keys, create the zone DNSKEY record, and
+   * sign the zone level records.
+   *
+   * @param zone      the zone.
+   * @param conf      the configuration.
+   * @param soaRecord the SOA record.
+   * @param nsRecord  the NS record.
+   * @throws IOException
+   * @throws NoSuchAlgorithmException
+   * @throws InvalidKeySpecException
+   * @throws DNSSEC.DNSSECException
+   */
+  private void enableDNSSECIfNecessary(Zone zone, Configuration conf,
+      SOARecord soaRecord,
+      NSRecord nsRecord)
+      throws IOException, NoSuchAlgorithmException, InvalidKeySpecException,
+      DNSSEC.DNSSECException {
+    if (isDNSSECEnabled()) {
+      // read in the DNSKEY and create the DNSKEYRecord
+      // TODO:  reading these out of config seems wrong...
+      String publicKey = conf.get(KEY_DNSSEC_PUBLIC_KEY);
+      if (publicKey == null) {
+        throw new IOException("DNSSEC Key not configured");
+      }
+      //TODO - perhaps read in actual DNSKEY record structure?
+      Name zoneName = zone.getOrigin();
+      DNSKEYRecord dnskeyRecord = dnsKeyRecs.get(zoneName);
+      if (dnskeyRecord == null) {
+        byte[] key = Base64.decodeBase64(publicKey.getBytes("UTF-8"));
+        dnskeyRecord = new DNSKEYRecord(zoneName,
+            DClass.IN, ttl,
+            DNSKEYRecord.Flags.ZONE_KEY,
+            DNSKEYRecord.Protocol.DNSSEC,
+            DNSSEC.Algorithm.RSASHA256, key);
+        dnsKeyRecs.putIfAbsent(zoneName, dnskeyRecord);
+      }
+      LOG.info("Registering {}", dnskeyRecord);
+      try (CloseableLock lock = writeLock.lock()) {
+        zone.addRecord(dnskeyRecord);
+
+        String privateKeyFile = conf.get(KEY_DNSSEC_PRIVATE_KEY_FILE,
+            DEFAULT_DNSSEC_PRIVATE_KEY_FILE);
+
+        Properties props = new Properties();
+        try (
+            FileInputStream inputStream = new FileInputStream(privateKeyFile)) {
+          props.load(inputStream);
+        }
+
+        String privateModulus = props.getProperty("Modulus");
+        String privateExponent = props.getProperty("PrivateExponent");
+
+        RSAPrivateKeySpec privateSpec = new RSAPrivateKeySpec(
+            new BigInteger(1, Base64.decodeBase64(privateModulus)),
+            new BigInteger(1, Base64.decodeBase64(privateExponent)));
+
+        KeyFactory factory = KeyFactory.getInstance("RSA");
+        privateKey = factory.generatePrivate(privateSpec);
+
+        signSiteRecord(zone, dnskeyRecord);
+        signSiteRecord(zone, soaRecord);
+        signSiteRecord(zone, nsRecord);
+      }
+      // create required DS records
+
+      // domain
+//      DSRecord dsRecord = new DSRecord(zoneName, DClass.IN, ttl,
+//                                       DSRecord.Digest.SHA1, dnskeyRecord);
+//      zone.addRecord(dsRecord);
+//      signSiteRecord(zone, dsRecord);
+    }
+  }
+
+  /**
+   * Sign a DNS record.
+   *
+   * @param zone   the zone reference
+   * @param record the record to sign.
+   * @throws DNSSEC.DNSSECException
+   */
+  private void signSiteRecord(Zone zone, Record record)
+      throws DNSSEC.DNSSECException {
+    RRset rrset = zone.findExactMatch(record.getName(),
+        record.getType());
+    Calendar cal = Calendar.getInstance();
+    Date inception = cal.getTime();
+    cal.add(Calendar.YEAR, 1);
+    Date expiration = cal.getTime();
+    RRSIGRecord rrsigRecord =
+        DNSSEC.sign(rrset, dnsKeyRecs.get(zone.getOrigin()),
+            privateKey, inception, expiration);
+    LOG.info("Adding {}", record);
+    rrset.addRR(rrsigRecord);
+  }
+
+  /**
+   * Sets the zone/domain name.  The name will be read from the configuration
+   * and the code will ensure the name is absolute.
+   *
+   * @param conf the configuration.
+   * @throws IOException
+   */
+  void setDomainName(Configuration conf) throws IOException {
+    domainName = conf.get(KEY_DNS_DOMAIN);
+    if (domainName == null) {
+      throw new IOException("No DNS domain name specified");
+    }
+    if (!domainName.endsWith(".")) {
+      domainName += ".";
+    }
+  }
+
+  /**
+   * Stops the registry.
+   *
+   * @throws Exception if the service stop generates an issue.
+   */
+  @Override
+  protected void serviceStop() throws Exception {
+    stopExecutor();
+    super.serviceStop();
+  }
+
+  /**
+   * Shuts down the leveraged executor service.
+   */
+  protected synchronized void stopExecutor() {
+    if (executor != null) {
+      executor.shutdownNow();
+    }
+  }
+
+  /**
+   * Creates a DNS error response.
+   *
+   * @param in the byte array detailing the error.
+   * @return the error message, in bytes
+   */
+  public byte[] formErrorMessage(byte[] in) {
+    Header header;
+    try {
+      header = new Header(in);
+    } catch (IOException e) {
+      return null;
+    }
+    return buildErrorMessage(header, Rcode.FORMERR, null);
+  }
+
+  /**
+   * Process a TCP request.
+   *
+   * @param ch the socket channel for the request.
+   * @throws IOException if the tcp processing generates an issue.
+   */
+  public void nioTCPClient(SocketChannel ch) throws IOException {
+    try {
+      // query sizes are small, so the following two lines should work
+      // in all instances
+      ByteBuffer buf = ByteBuffer.allocate(1024);
+      ch.read(buf);
+      buf.flip();
+      int messageLength = getMessgeLength(buf);
+
+      byte[] in = new byte[messageLength];
+
+      buf.get(in, 0, messageLength);
+
+      Message query;
+      byte[] response = null;
+      try {
+        query = new Message(in);
+        response = generateReply(query, ch.socket());
+        if (response == null) {
+          return;
+        }
+      } catch (IOException e) {
+        response = formErrorMessage(in);
+      }
+
+      ByteBuffer out = ByteBuffer.allocate(response.length + 2);
+      out.putShort(0, (short) (response.length & 0xffff));
+      out.put(response);
+
+      ch.write(out);
+    } catch (IOException e) {
+      throw NetUtils.wrapException(ch.socket().getInetAddress().getHostName(),
+          ch.socket().getPort(),
+          ch.socket().getLocalAddress().getHostName(),
+          ch.socket().getLocalPort(), e);
+    } finally {
+      IOUtils.closeStream(ch);
+    }
+
+  }
+
+  /**
+   * Calculate the inbound message length, which is related in the message as an
+   * unsigned short value.
+   *
+   * @param buf the byte buffer containing the message.
+   * @return the message length
+   * @throws EOFException
+   */
+  private int getMessgeLength(ByteBuffer buf) throws EOFException {
+    int ch1 = buf.get();
+    int ch2 = buf.get();
+    if ((ch1 | ch2) < 0) {
+      throw new EOFException();
+    }
+    return (ch1 << 8) + (ch2 & 0xff);
+  }
+
+  /**
+   * Monitor the TCP socket for inbound requests.
+   *
+   * @param serverSocketChannel the server socket channel
+   * @param addr                the local inet address
+   * @param port                the listener (local) port
+   * @throws Exception if the tcp processing fails.
+   */
+  public void serveNIOTCP(ServerSocketChannel serverSocketChannel,
+      InetAddress addr, int port) throws Exception {
+    try {
+
+      while (true) {
+        final SocketChannel socketChannel = serverSocketChannel.accept();
+        if (socketChannel != null) {
+          executor.submit(new Callable<Boolean>() {
+            @Override
+            public Boolean call() throws Exception {
+              nioTCPClient(socketChannel);
+              return true;
+            }
+          });
+
+        }
+      }
+    } catch (IOException e) {
+      throw NetUtils.wrapException(addr.getHostName(), port,
+          addr.getHostName(), port, e);
+    }
+  }
+
+  /**
+   * Open the TCP listener.
+   *
+   * @param addr the host address.
+   * @param port the host port.
+   * @return the created server socket channel.
+   * @throws IOException
+   */
+  private ServerSocketChannel openTCPChannel(InetAddress addr, int port)
+      throws IOException {
+    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
+    try {
+      serverSocketChannel.socket().bind(new InetSocketAddress(addr, port));
+      serverSocketChannel.configureBlocking(false);
+    } catch (IOException e) {
+      throw NetUtils.wrapException(null, 0,
+          InetAddress.getLocalHost().getHostName(),
+          port, e);
+    }
+    return serverSocketChannel;
+  }
+
+  /**
+   * Create the thread (Callable) monitoring the TCP listener.
+   *
+   * @param addr host address.
+   * @param port host port.
+   * @throws Exception if the tcp listener generates an error.
+   */
+  public void addNIOTCP(final InetAddress addr, final int port)
+      throws Exception {
+    final ServerSocketChannel tcpChannel = openTCPChannel(addr, port);
+    executor.submit(new Callable<Boolean>() {
+      @Override
+      public Boolean call() throws Exception {
+        try {
+          serveNIOTCP(tcpChannel, addr, port);
+        } catch (Exception e) {
+          LOG.error("Error initializing DNS TCP listener", e);
+          throw e;
+        }
+
+        return true;
+      }
+
+    });
+  }
+
+  /**
+   * Create the thread monitoring the socket for inbound UDP requests.
+   *
+   * @param addr host address.
+   * @param port host port.
+   * @throws Exception if the UDP listener creation generates an error.
+   */
+  public void addNIOUDP(final InetAddress addr, final int port)
+      throws Exception {
+    final DatagramChannel udpChannel = openUDPChannel(addr, port);
+    executor.submit(new Callable<Boolean>() {
+      @Override
+      public Boolean call() throws Exception {
+        try {
+          serveNIOUDP(udpChannel, addr, port);
+        } catch (Exception e) {
+          LOG.error("Error initializing DNS UDP listener", e);
+          throw e;
+        }
+        return true;
+      }
+    });
+  }
+
+  /**
+   * Process an inbound UDP request.
+   *
+   * @param channel the UDP datagram channel.
+   * @param addr    local host address.
+   * @param port    local port.
+   * @throws IOException if the UDP processing fails.
+   */
+  private void serveNIOUDP(DatagramChannel channel,
+      InetAddress addr, int port) throws Exception {
+    SocketAddress remoteAddress = null;
+    try {
+
+      ByteBuffer input = ByteBuffer.allocate(4096);
+      ByteBuffer output = ByteBuffer.allocate(4096);
+      byte[] in = null;
+
+      while (true) {
+        input.clear();
+        try {
+          remoteAddress = channel.receive(input);
+        } catch (IOException e) {
+          LOG.debug("Error during message receipt", e);
+          continue;
+        }
+        Message query;
+        byte[] response = null;
+        try {
+          int position = input.position();
+          in = new byte[position];
+          input.flip();
+          input.get(in);
+          query = new Message(in);
+          LOG.info("{}:  received query {}", remoteAddress,
+              query.getQuestion());
+          response = generateReply(query, null);
+          if (response == null) {
+            continue;
+          }
+        } catch (IOException e) {
+          response = formErrorMessage(in);
+        }
+        output.clear();
+        output.put(response);
+        output.flip();
+
+        LOG.info("{}:  sending response", remoteAddress);
+        channel.send(output, remoteAddress);
+      }
+    } catch (Exception e) {
+      if (e instanceof IOException && remoteAddress != null) {
+        throw NetUtils.wrapException(addr.getHostName(),
+            port,
+            ((InetSocketAddress) remoteAddress).getHostName(),
+            ((InetSocketAddress) remoteAddress).getPort(),
+            (IOException) e);
+      } else {
+        throw e;
+      }
+    }
+  }
+
+  /**
+   * Create and UDP listener socket.
+   *
+   * @param addr host address.
+   * @param port host port.
+   * @return
+   * @throws IOException if listener creation fails.
+   */
+  private DatagramChannel openUDPChannel(InetAddress addr, int port)
+      throws IOException {
+    DatagramChannel channel = DatagramChannel.open();
+    try {
+      channel.socket().bind(new InetSocketAddress(addr, port));
+    } catch (IOException e) {
+      throw NetUtils.wrapException(null, 0,
+          InetAddress.getLocalHost().getHostName(),
+          port, e);
+    }
+    return channel;
+  }
+
+  /**
+   * Create an error message.
+   *
+   * @param header   the response header.
+   * @param rcode    the response code.
+   * @param question the question record.
+   * @return  the error message.
+   */
+  byte[] buildErrorMessage(Header header, int rcode, Record question) {
+    Message response = new Message();
+    response.setHeader(header);
+    for (int i = 0; i < 4; i++) {
+      response.removeAllRecords(i);
+    }
+    if (rcode == Rcode.SERVFAIL) {
+      response.addRecord(question, Section.QUESTION);
+    }
+    header.setRcode(rcode);
+    return response.toWire();
+  }
+
+  /**
+   * Generate an error message based on inbound query.
+   *
+   * @param query the query.
+   * @param rcode the response code for the specific error.
+   * @return the error message.
+   */
+  public byte[] errorMessage(Message query, int rcode) {
+    return buildErrorMessage(query.getHeader(), rcode,
+        query.getQuestion());
+  }
+
+  /**
+   * Generate the response for the inbound DNS query.
+   *
+   * @param query the query.
+   * @param s     the socket associated with the query.
+   * @return the response, in bytes.
+   * @throws IOException if reply generation fails.
+   */
+  byte[] generateReply(Message query, Socket s)
+      throws IOException {
+    Header header;
+    boolean badversion;
+    int maxLength;
+    int flags = 0;
+
+    OPTRecord queryOPT = query.getOPT();
+    maxLength = getMaxLength(s, queryOPT);
+
+    header = query.getHeader();
+    if (header.getFlag(Flags.QR)) {
+      LOG.debug("returning null");
+      return null;
+    }
+    if (header.getRcode() != Rcode.NOERROR) {
+      return errorMessage(query, Rcode.FORMERR);
+    }
+    if (header.getOpcode() != Opcode.QUERY) {
+      return errorMessage(query, Rcode.NOTIMP);
+    }
+
+    Record queryRecord = query.getQuestion();
+
+    if (queryOPT != null && (queryOPT.getFlags() & ExtendedFlags.DO) != 0) {
+      flags = FLAG_DNSSECOK;
+    }
+
+    Message response = new Message(query.getHeader().getID());
+    response.getHeader().setFlag(Flags.QR);
+    if (query.getHeader().getFlag(Flags.RD)) {
+      response.getHeader().setFlag(Flags.RD);
+    }
+    response.addRecord(queryRecord, Section.QUESTION);
+
+    Name name = queryRecord.getName();
+    int type = queryRecord.getType();
+    int dclass = queryRecord.getDClass();
+
+    TSIGRecord queryTSIG = query.getTSIG();
+    if (type == Type.AXFR && s != null) {
+      return doAXFR(name, query, null, queryTSIG, s);
+    }
+    if (!Type.isRR(type) && type != Type.ANY) {
+      return errorMessage(query, Rcode.NOTIMP);
+    }
+
+    LOG.debug("calling addAnswer");
+    byte rcode = addAnswer(response, name, type, dclass, 0, flags);
+    if (rcode != Rcode.NOERROR && rcode != Rcode.NXDOMAIN) {
+      return errorMessage(query, rcode);
+    }
+
+    addAdditional(response, flags);
+
+    if (queryOPT != null) {
+      int optflags = (flags == FLAG_DNSSECOK) ? ExtendedFlags.DO : 0;
+      OPTRecord opt = new OPTRecord((short) 4096, rcode >>> 16, (byte) 0,
+          optflags);
+      response.addRecord(opt, Section.ADDITIONAL);
+    }
+
+    return response.toWire(maxLength);
+  }
+
+  /**
+   * Create a query to forward to the primary DNS server (if configured).
+   * NOTE:  Experimental
+   *
+   * @param query the inbound query.
+   * @return the query to forward to the primary server.
+   * @throws NameTooLongException
+   * @throws TextParseException if query creation fails.
+   */
+  private Message createPrimaryQuery(Message query)
+      throws NameTooLongException, TextParseException {
+    Name name = query.getQuestion().getName();
+    if (name.labels() > 0 && name.labels() <= 2) {
+      // short relative or absolute name.  this code may not be necessary -
+      // OS resolution utilities probably append the search paths defined
+      // in resolv.conf prior to the lookup
+      int id = query.getHeader().getID();
+      String queryName = name.getLabelString(0);
+      Name qualifiedName = Name.concatenate(Name.fromString(queryName),
+          Name.fromString(domainName));
+      LOG.info("Received query {}.  Forwarding query {}", name, qualifiedName);
+      Record question = Record.newRecord(qualifiedName,
+          query.getQuestion().getType(),
+          query.getQuestion().getDClass());
+      query = Message.newQuery(question);
+      query.getHeader().setID(id);
+    }
+    return query;
+  }
+
+  /**
+   * Calculate the max length for a response.
+   *
+   * @param s        the request socket.
+   * @param queryOPT describes Extended DNS (EDNS) properties of a Message.
+   * @return  the length of the response.
+   */
+  private int getMaxLength(Socket s, OPTRecord queryOPT) {
+    int maxLength;
+    if (s != null) {
+      maxLength = 65535;
+    } else if (queryOPT != null) {
+      maxLength = Math.max(queryOPT.getPayloadSize(), 512);
+    } else {
+      maxLength = 512;
+    }
+    return maxLength;
+  }
+
+  /**
+   * Add additional information to a DNS response section if a glue name is
+   * specified.
+   *
+   * @param response the response message.
+   * @param section  the section of the response (e.g. ANSWER, AUTHORITY)
+   * @param flags the flags.
+   */
+  private void addAdditional2(Message response, int section, int flags) {
+    Record[] records = response.getSectionArray(section);
+    for (int i = 0; i < records.length; i++) {
+      Record r = records[i];
+      Name glueName = r.getAdditionalName();
+      if (glueName != null) {
+        addGlue(response, glueName, flags);
+      }
+    }
+  }
+
+  /**
+   * Process any additional records indicated for both the ANSWER and AUTHORITY
+   * sections of the response.
+   *
+   * @param response the response message.
+   * @param flags the flags.
+   */
+  private void addAdditional(Message response, int flags) {
+    addAdditional2(response, Section.ANSWER, flags);
+    addAdditional2(response, Section.AUTHORITY, flags);
+  }
+
+  /**
+   * Add the specific record indicated by the "glue", or the mapping to a
+   * specific host.
+   *
+   * @param response the response message.
+   * @param name     the name of the glue record.
+   * @param flags    the flags.
+   */
+  private void addGlue(Message response, Name name, int flags) {
+    RRset a = findExactMatch(name, Type.A);
+    if (a == null) {
+      return;
+    }
+    addRRset(name, response, a, Section.ADDITIONAL, flags);
+  }
+
+  /**
+   * Find the record set that matches the requested name and type.
+   *
+   * @param name the requested name.
+   * @param type the record type.
+   * @return the set of records with the given name and type.
+   */
+  public RRset findExactMatch(Name name, int type) {
+    try (CloseableLock lock = readLock.lock()) {
+      Zone zone = findBestZone(name);
+      if (zone != null) {
+        return zone.findExactMatch(name, type);
+      }
+    }
+
+    return null;
+  }
+
+  /**
+   * Find the zone that correlates to the provided name.
+   *
+   * @param name the name to be matched to a zone.
+   * @return the zone.
+   */
+  @Override public Zone findBestZone(Name name) {
+    Zone foundzone = null;
+    foundzone = zones.get(name);
+    if (foundzone != null) {
+      return foundzone;
+    }
+    int labels = name.labels();
+    for (int i = 1; i < labels; i++) {
+      Name tname = new Name(name, i);
+      foundzone = zones.get(tname);
+      if (foundzone != null) {
+        return foundzone;
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Add the answer section to the response.
+   *
+   * @param response   the response message.
+   * @param name       the name of the answer record.
+   * @param type       the type of record.
+   * @param dclass     the DNS class.
+   * @param iterations iteration count.
+   * @param flags
+   * @return the response code.
+   */
+  byte addAnswer(Message response, Name name, int type, int dclass,
+      int iterations, int flags) {
+    SetResponse sr = null;
+    byte rcode = Rcode.NOERROR;
+
+    if (iterations > 6) {
+      return Rcode.NOERROR;
+    }
+
+    if (type == Type.SIG || type == Type.RRSIG) {
+      type = Type.ANY;
+      flags |= FLAG_SIGONLY;
+    }
+
+    Zone zone = findBestZone(name);
+
+    LOG.debug("finding record");
+    try (CloseableLock lock = readLock.lock()) {
+      if (zone != null) {
+        sr = zone.findRecords(name, type);
+      } else {
+        rcode = Rcode.NOTAUTH;
+      }
+    }
+    LOG.info("found record? {}", sr != null && sr.isSuccessful());
+
+    if (sr != null) {
+      if (sr.isCNAME()) {
+        CNAMERecord cname = sr.getCNAME();
+        RRset rrset = zone.findExactMatch(cname.getName(), Type.CNAME);
+        addRRset(name, response, rrset, Section.ANSWER, flags);
+        if (iterations == 0) {
+          response.getHeader().setFlag(Flags.AA);
+        }
+        rcode = addAnswer(response, cname.getTarget(),
+            type, dclass, iterations + 1, flags);
+      }
+      if (sr.isNXDOMAIN()) {
+        response.getHeader().setRcode(Rcode.NXDOMAIN);
+        if (isDNSSECEnabled()) {
+          try {
+            addNXT(response, flags);
+          } catch (Exception e) {
+            LOG.warn("Unable to add NXTRecord to AUTHORITY Section", e);
+          }
+        }
+        addSOA(response, zone, flags);
+        if (iterations == 0) {
+          response.getHeader().setFlag(Flags.AA);
+        }
+        rcode = Rcode.NXDOMAIN;
+      } else if (sr.isNXRRSET()) {
+        LOG.info("No data found the given name {} and type {}", name, type);
+        addSOA(response, zone, flags);
+        if (iterations == 0) {
+          response.getHeader().setFlag(Flags.AA);
+        }
+      } else if (sr.isSuccessful()) {
+        RRset[] rrsets = sr.answers();
+        LOG.info("found answers {}", rrsets);
+        for (int i = 0; i < rrsets.length; i++) {
+          addRRset(name, response, rrsets[i],
+              Section.ANSWER, flags);
+        }
+        addNS(response, zone, flags);
+        if (iterations == 0) {
+          response.getHeader().setFlag(Flags.AA);
+        }
+      }
+    } else {
+      if (zone != null) {
+        Name defaultDomain = null;
+        try {
+          defaultDomain = Name.fromString(domainName);
+          zone = zones.get(defaultDomain);
+          addNS(response, zone, flags);
+          if (iterations == 0) {
+            response.getHeader().setFlag(Flags.AA);
+          }
+        } catch (TextParseException e) {
+          LOG.warn("Unable to obtain default zone for unknown name response",
+              e);
+        }
+      }
+    }
+    return rcode;
+  }
+
+  /**
+   * Add the SOA record (describes the properties of the zone) to the authority
+   * section of the response.
+   *
+   * @param response the response message.
+   * @param zone     the DNS zone.
+   */
+  private void addSOA(Message response, Zone zone, int flags) {
+    RRset soa = zone.findExactMatch(zone.getOrigin(), Type.SOA);
+    addRRset(soa.getName(), response, soa,
+        Section.AUTHORITY, flags);
+  }
+
+  /**
+   * Add the NXT record to the authority
+   * section of the response.
+   *
+   * @param response the response message.
+   */
+  private void addNXT(Message response, int flags)
+      throws DNSSEC.DNSSECException, IOException {
+    Record nxtRecord = getNXTRecord(
+        response.getSectionArray(Section.QUESTION)[0]);
+    Zone zone = findBestZone(nxtRecord.getName());
+    addRecordCommand.exec(zone, nxtRecord);
+    RRset nxtRR = zone.findExactMatch(nxtRecord.getName(), Type.NXT);
+    addRRset(nxtRecord.getName(), response, nxtRR, Section.AUTHORITY, flags);
+
+    removeRecordCommand.exec(zone, nxtRecord);
+  }
+
+  /**
+   * Return an NXT record required to validate negative responses.  If there is
+   * an issue returning the NXT record, a SOA record will be returned.
+   *
+   * @param query the query record.
+   * @return an NXT record.
+   */
+  private Record getNXTRecord(Record query) {
+    Record response = null;
+    SecureableZone zone = (SecureableZone) findBestZone(query.getName());
+    if (zone != null) {
+      response = zone.getNXTRecord(query, zone);
+      if (response == null) {
+        response = zone.getSOA();
+      }
+    }
+
+    return response;
+  }
+
+  /**
+   * Add the name server info to the authority section.
+   *
+   * @param response the response message.
+   * @param zone     the DNS zone.
+   * @param flags    the flags.
+   */
+  private void addNS(Message response, Zone zone, int flags) {
+    RRset nsRecords = zone.getNS();
+    addRRset(nsRecords.getName(), response, nsRecords,
+        Section.AUTHORITY, flags);
+  }
+
+  /**
+   * Add the provided record set to the response section specified.
+   *
+   * @param name     the name associated with the record set.
+   * @param response the response message.
+   * @param rrset    the record set.
+   * @param section  the response section to which the record set will be added.
+   * @param flags    the flags.
+   */
+  private void addRRset(Name name, Message response, RRset rrset, int section,
+      int flags) {
+    for (int s = 1; s <= section; s++) {
+      if (response.findRRset(name, rrset.getType(), s)) {
+        return;
+      }
+    }
+    if ((flags & FLAG_SIGONLY) == 0) {
+      Iterator it = rrset.rrs();
+      while (it.hasNext()) {
+        Record r = (Record) it.next();
+        if (r.getName().isWild() && !name.isWild()) {
+          r = r.withName(name);
+        }
+        response.addRecord(r, section);
+      }
+    }
+    if ((flags & (FLAG_SIGONLY | FLAG_DNSSECOK)) != 0) {
+      Iterator it = rrset.sigs();
+      while (it.hasNext()) {
+        Record r = (Record) it.next();
+        if (r.getName().isWild() && !name.isWild()) {
+          r = r.withName(name);
+        }
+        response.addRecord(r, section);
+      }
+    }
+  }
+
+  /**
+   * Perform a zone transfer.
+   *
+   * @param name  the zone name.
+   * @param query the query.
+   * @param tsig  the query signature.
+   * @param qtsig the signature record.
+   * @param s     the connection socket.
+   * @return      an error message if there is no matching zone
+   * or null due to error.
+   */
+  byte[] doAXFR(Name name, Message query, TSIG tsig, TSIGRecord qtsig,
+      Socket s) {
+    boolean first = true;
+    Zone zone = findBestZone(name);
+    if (zone == null) {
+      return errorMessage(query, Rcode.REFUSED);
+    }
+    Iterator it = zone.AXFR();
+    try {
+      DataOutputStream dataOut;
+      dataOut = new DataOutputStream(s.getOutputStream());
+      int id = query.getHeader().getID();
+      while (it.hasNext()) {
+        RRset rrset = (RRset) it.next();
+        Message response = new Message(id);
+        Header header = response.getHeader();
+        header.setFlag(Flags.QR);
+        header.setFlag(Flags.AA);
+        addRRset(rrset.getName(), response, rrset,
+            Section.ANSWER, FLAG_DNSSECOK);
+        if (tsig != null) {
+          tsig.applyStream(response, qtsig, first);
+          qtsig = response.getTSIG();
+        }
+        first = false;
+        byte[] out = response.toWire();
+        dataOut.writeShort(out.length);
+        dataOut.write(out);
+      }
+    } catch (IOException ex) {
+      System.out.println("AXFR failed");
+    }
+    try {
+      s.close();
+    } catch (IOException ex) {
+    }
+    return null;
+  }
+
+  /**
+   * Perform the registry operation (register or delete).  This method will take
+   * the provided service record and either add or remove the DNS records
+   * indicated.
+   *
+   * @param path    the ZK path for the service record.
+   * @param record  the service record.
+   * @param command the registry command (REGISTER or DELETE).
+   * @throws IOException if the is an error performing registry operation.
+   */
+  private void op(String path, ServiceRecord record, RegistryCommand command)
+      throws IOException {
+    ServiceRecordProcessor processor;
+    try {
+      if (record.get(YarnRegistryAttributes.YARN_PERSISTENCE)
+          .equals(CONTAINER)) {
+        // container registration.  the logic to identify and create the
+        // container entry needs to be enhanced/more accurate and associate to
+        // correct host
+        processor =
+            new ContainerServiceRecordProcessor(record, path, domainName, this);
+      } else {
+        processor =
+            new ApplicationServiceRecordProcessor(record, path, domainName,
+                this);
+      }
+      processor.manageDNSRecords(command);
+    } catch (Exception e) {
+      throw new IOException(e);
+    }
+
+  }
+
+  /**
+   * Return the username found in the ZK path.
+   *
+   * @param path the ZK path.
+   * @return the user name.
+   */
+  private String getUsername(String path) {
+    String user = "anonymous";
+    Matcher matcher = USER_NAME.matcher(path);
+    if (matcher.find()) {
+      user = matcher.group(1);
+    }
+    return user;
+  }
+
+  /**
+   * Register DNS records based on the provided service record.
+   *
+   * @param path   the ZK path of the service record.
+   * @param record record providing DNS registration info.
+   * @throws IOException if registration causes an error.
+   */
+  @Override
+  public void register(String path, ServiceRecord record) throws IOException {
+    op(path, record, addRecordCommand);
+  }
+
+  /**
+   * Delete the DNS records generated by the provided service record.
+   *
+   * @param path   the ZK path for the given record.
+   * @param record the service record
+   * @throws IOException if deletion causes and error.
+   */
+  @Override
+  public void delete(String path, ServiceRecord record) throws IOException {
+    op(path, record, removeRecordCommand);
+  }
+
+  /**
+   * An interface representing a registry associated function/command (see
+   * command pattern).
+   */
+  interface RegistryCommand {
+    void exec(Zone zone, Record record) throws IOException;
+
+    String getLogDescription();
+  }
+
+  /**
+   * The "add record" command.
+   */
+  private final RegistryCommand addRecordCommand = new RegistryCommand() {
+    @Override
+    public void exec(Zone zone, Record record) throws IOException {
+      if (zone != null) {
+        try (CloseableLock lock = writeLock.lock()) {
+          zone.addRecord(record);
+          LOG.info("Registered {}", record);
+          if (isDNSSECEnabled()) {
+            Calendar cal = Calendar.getInstance();
+            Date inception = cal.getTime();
+            cal.add(Calendar.YEAR, 1);
+            Date expiration = cal.getTime();
+            RRset rRset =
+                zone.findExactMatch(record.getName(), record.getType());
+            try {
+              DNSKEYRecord dnskeyRecord = dnsKeyRecs.get(zone.getOrigin());
+              RRSIGRecord rrsigRecord =
+                  DNSSEC.sign(rRset, dnskeyRecord, privateKey,
+                      inception, expiration);
+              LOG.info("Adding {}", rrsigRecord);
+              rRset.addRR(rrsigRecord);
+
+              //addDSRecord(zone, record.getName(), record.getDClass(),
+              //  record.getTTL(), inception, expiration);
+
+            } catch (DNSSEC.DNSSECException e) {
+              throw new IOException(e);
+            }
+          }
+        }
+      } else {
+        LOG.warn("Unable to find zone matching record {}", record);
+      }
+    }
+
+    /**
+     * Add a DS record associated with the input name.
+     * @param zone  the zone.
+     * @param name  the record name.
+     * @param dClass the DNS class.
+     * @param dsTtl the ttl value.
+     * @param inception  the time of inception of the record.
+     * @param expiration  the expiry time of the record.
+     * @throws DNSSEC.DNSSECException if the addition of DS record fails.
+     */
+    private void addDSRecord(Zone zone,
+        Name name, int dClass, long dsTtl,
+        Date inception,
+        Date expiration) throws DNSSEC.DNSSECException {
+      RRset rRset;
+      RRSIGRecord rrsigRecord;
+
+      DNSKEYRecord dnskeyRecord = dnsKeyRecs.get(zone.getOrigin());
+      DSRecord dsRecord = new DSRecord(name, dClass,
+          dsTtl, DSRecord.Digest.SHA1,
+          dnskeyRecord);
+      zone.addRecord(dsRecord);
+      LOG.info("Adding {}", dsRecord);
+      rRset = zone.findExactMatch(dsRecord.getName(), dsRecord.getType());
+
+      rrsigRecord = DNSSEC.sign(rRset, dnskeyRecord, privateKey,
+          inception, expiration);
+      rRset.addRR(rrsigRecord);
+    }
+
+    @Override
+    public String getLogDescription() {
+      return "Registering ";
+    }
+  };
+
+  /**
+   * The "remove record" command.
+   */
+  private final RegistryCommand removeRecordCommand = new RegistryCommand() {
+    @Override
+    public void exec(Zone zone, Record record) throws IOException {
+      zone.removeRecord(record);
+      LOG.info("Removed {}", record);
+      if (isDNSSECEnabled()) {
+        RRset rRset = zone.findExactMatch(record.getName(), Type.DS);
+        if (rRset != null) {
+          zone.removeRecord(rRset.first());
+        }
+      }
+    }
+
+    @Override
+    public String getLogDescription() {
+      return "Deleting ";
+    }
+  };
+
+  /**
+   * An implementation allowing for obtaining and releasing a lock.
+   */
+  public static class CloseableLock implements AutoCloseable {
+    private Lock lock;
+
+    public CloseableLock(Lock lock) {
+      this.lock = lock;
+    }
+
+    public CloseableLock lock() {
+      lock.lock();
+      return this;
+    }
+
+    @Override
+    public void close() {
+      lock.unlock();
+    }
+  }
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNSServer.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNSServer.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNSServer.java
new file mode 100644
index 0000000..faa5fe1
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNSServer.java
@@ -0,0 +1,290 @@
+/*
+ * 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.hadoop.registry.server.dns;
+
+import com.google.common.base.Preconditions;
+import org.apache.commons.cli.BasicParser;
+import org.apache.commons.cli.CommandLine;
+import org.apache.commons.cli.CommandLineParser;
+import org.apache.commons.cli.Options;
+import org.apache.commons.cli.ParseException;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.PathNotFoundException;
+import org.apache.hadoop.registry.client.api.DNSOperationsFactory;
+import org.apache.hadoop.registry.client.api.RegistryConstants;
+import org.apache.hadoop.registry.client.binding.RegistryPathUtils;
+import org.apache.hadoop.registry.client.binding.RegistryUtils;
+import org.apache.hadoop.registry.client.impl.zk.PathListener;
+import org.apache.hadoop.registry.client.impl.zk.RegistryOperationsService;
+import org.apache.hadoop.registry.client.types.RegistryPathStatus;
+import org.apache.hadoop.registry.client.types.ServiceRecord;
+import org.apache.hadoop.service.CompositeService;
+import org.apache.hadoop.util.ExitUtil;
+import org.apache.hadoop.util.GenericOptionsParser;
+import org.apache.hadoop.util.ShutdownHookManager;
+import org.apache.hadoop.util.StringUtils;
+import org.apache.hadoop.yarn.YarnUncaughtExceptionHandler;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * A server/service that starts and manages the lifecycle of a DNS registry
+ * instance.
+ */
+public class RegistryDNSServer extends CompositeService {
+
+
+  public static final int SHUTDOWN_HOOK_PRIORITY = 30;
+  private RegistryDNS registryDNS;
+  private RegistryOperationsService registryOperations;
+  private static final Logger LOG =
+      LoggerFactory.getLogger(RegistryDNS.class);
+  private ConcurrentMap<String, ServiceRecord> pathToRecordMap;
+
+  /**
+   * Creates the DNS server.
+   * @param name the server name.
+   */
+  public RegistryDNSServer(String name) {
+    super(name);
+  }
+
+  /**
+   * Initializes the DNS server.
+   * @param conf the hadoop configuration instance.
+   * @throws Exception if service initialization fails.
+   */
+  @Override
+  protected void serviceInit(Configuration conf) throws Exception {
+
+    pathToRecordMap = new ConcurrentHashMap<>();
+
+    registryOperations = new RegistryOperationsService("RegistryDNSOperations");
+    addService(registryOperations);
+
+    // probably need to populate with existing apps?
+    registryDNS = (RegistryDNS) DNSOperationsFactory.createInstance(conf);
+    addService(registryDNS);
+
+    super.serviceInit(conf);
+  }
+
+  /**
+   * Starts the server.
+   * @throws Exception if service start fails.
+   */
+  @Override
+  protected void serviceStart() throws Exception {
+    super.serviceStart();
+    manageRegistryDNS();
+  }
+
+  /**
+   * Performs operations required to setup the DNS registry instance (e.g. sets
+   * up a path listener to react to service record creation/deletion and invoke
+   * the appropriate registry method).
+   */
+  private void manageRegistryDNS() {
+
+    try {
+      registryOperations.monitorRegistryEntries();
+      registryOperations.registerPathListener(new PathListener() {
+        private String registryRoot = getConfig().
+            get(RegistryConstants.KEY_REGISTRY_ZK_ROOT,
+                RegistryConstants.DEFAULT_ZK_REGISTRY_ROOT);
+
+        @Override
+        public void nodeAdded(String path) throws IOException {
+          // get a listing of service records
+          String relativePath = getPathRelativeToRegistryRoot(path);
+          String child = RegistryPathUtils.lastPathEntry(path);
+          Map<String, RegistryPathStatus> map = new HashMap<>();
+          map.put(child, registryOperations.stat(relativePath));
+          Map<String, ServiceRecord> records =
+              RegistryUtils.extractServiceRecords(registryOperations,
+                                                  getAdjustedParentPath(path),
+                                                  map);
+          processServiceRecords(records, register);
+          pathToRecordMap.putAll(records);
+        }
+
+        private String getAdjustedParentPath(String path) {
+          Preconditions.checkNotNull(path);
+          String adjustedPath = null;
+          adjustedPath = getPathRelativeToRegistryRoot(path);
+          try {
+            return RegistryPathUtils.parentOf(adjustedPath);
+          } catch (PathNotFoundException e) {
+            // attempt to use passed in path
+            return path;
+          }
+        }
+
+        private String getPathRelativeToRegistryRoot(String path) {
+          String adjustedPath;
+          if (path.equals(registryRoot)) {
+            adjustedPath = "/";
+          } else {
+            adjustedPath = path.substring(registryRoot.length());
+          }
+          return adjustedPath;
+        }
+
+        @Override
+        public void nodeRemoved(String path) throws IOException {
+          ServiceRecord record = pathToRecordMap.remove(path.substring(
+              registryRoot.length()));
+          processServiceRecord(path, record, delete);
+        }
+
+      });
+
+      // create listener for record deletions
+
+    } catch (Exception e) {
+      LOG.warn("Unable to monitor the registry.  DNS support disabled.", e);
+    }
+  }
+
+  /**
+   * A registry management command interface.
+   */
+  interface ManagementCommand {
+    void exec(String path, ServiceRecord record) throws IOException;
+  }
+
+  /**
+   * Performs registry service record registration.
+   */
+  private final ManagementCommand register = new ManagementCommand() {
+    @Override
+    public void exec(String path, ServiceRecord record) throws IOException {
+      if (record != null) {
+        LOG.info("Registering DNS records for {}", path);
+        registryDNS.register(path, record);
+      }
+    }
+  };
+
+  /**
+   * Performs registry service record deletion.
+   */
+  private ManagementCommand delete = new ManagementCommand() {
+    @Override
+    public void exec(String path, ServiceRecord record) throws IOException {
+      if (record != null) {
+        LOG.info("Deleting DNS records for {}", path);
+        registryDNS.delete(path, record);
+      }
+    }
+  };
+
+  /**
+   * iterates thru the supplied service records, executing the provided registry
+   * command.
+   * @param records the service records.
+   * @param command the registry command.
+   * @throws IOException
+   */
+  private void processServiceRecords(Map<String, ServiceRecord> records,
+                                     ManagementCommand command)
+      throws IOException {
+    for (Map.Entry<String, ServiceRecord> entry : records.entrySet()) {
+      processServiceRecord(entry.getKey(), entry.getValue(), command);
+    }
+  }
+
+  /**
+   * Process the service record, parsing the information and creating the
+   * required DNS records.
+   * @param path  the service record path.
+   * @param record  the record.
+   * @param command  the registry command to execute.
+   * @throws IOException
+   */
+  private void processServiceRecord(String path, ServiceRecord record,
+                                     ManagementCommand command)
+      throws IOException {
+    command.exec(path, record);
+  }
+
+  /**
+   * Launch the server.
+   * @param args command line args.
+   * @return
+   */
+  static RegistryDNSServer launchDNSServer(String[] args) {
+    RegistryDNSServer dnsServer = null;
+
+    Thread
+        .setDefaultUncaughtExceptionHandler(new YarnUncaughtExceptionHandler());
+    StringUtils.startupShutdownMessage(RegistryDNSServer.class, args,
+                                       LOG);
+    try {
+      dnsServer = new RegistryDNSServer("RegistryDNSServer");
+      ShutdownHookManager.get().addShutdownHook(
+          new CompositeService.CompositeServiceShutdownHook(dnsServer),
+          SHUTDOWN_HOOK_PRIORITY);
+      YarnConfiguration conf = new YarnConfiguration();
+      processCommandLine(args, conf);
+      new GenericOptionsParser(conf, args);
+      dnsServer.init(conf);
+      dnsServer.start();
+    } catch (Throwable t) {
+      LOG.error("Error starting Registry DNS Server", t);
+      ExitUtil.terminate(-1, "Error starting Registry DNS Server");
+    }
+    return dnsServer;
+  }
+
+  /**
+   * Process input command line arguments.
+   * @param args the command line argument array.
+   * @param conf  the configuration.
+   */
+  private static void processCommandLine(String[] args,
+                                         YarnConfiguration conf) {
+    Options options = new Options();
+    options.addOption("p", "port", true,
+                      "the server listening port (override)");
+
+    CommandLineParser parser = new BasicParser();
+    try {
+      CommandLine cmd = parser.parse(options, args);
+      if (cmd.hasOption("p")) {
+        conf.set(RegistryConstants.KEY_DNS_PORT, cmd.getOptionValue("p"));
+      }
+    } catch (ParseException e) {
+      LOG.error("Error parsing the command line options", e);
+    }
+  }
+
+  /**
+   * Lanches the server instance.
+   * @param args the command line args.
+   */
+  public static void main(String[] args) {
+    launchDNSServer(args);
+  }
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/SecureableZone.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/SecureableZone.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/SecureableZone.java
new file mode 100644
index 0000000..4b0a852
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/SecureableZone.java
@@ -0,0 +1,151 @@
+/*
+ * 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.hadoop.registry.server.dns;
+
+import org.xbill.DNS.DClass;
+import org.xbill.DNS.NXTRecord;
+import org.xbill.DNS.Name;
+import org.xbill.DNS.RRset;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.SetResponse;
+import org.xbill.DNS.Type;
+import org.xbill.DNS.Zone;
+import org.xbill.DNS.ZoneTransferException;
+import org.xbill.DNS.ZoneTransferIn;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * A zone implementation geared to support some DNSSEC functionality.
+ */
+public class SecureableZone extends Zone {
+  private List<Record> records;
+
+  /**
+   * Creates a Zone by doing the specified zone transfer.
+   * @param xfrin The incoming zone transfer to execute.
+   * @throws IOException if there is an error.
+   * @throws ZoneTransferException if there is an error.
+   */
+  public SecureableZone(ZoneTransferIn xfrin)
+      throws IOException, ZoneTransferException {
+    super(xfrin);
+  }
+
+  /**
+   * Creates a Zone by performing a zone transfer to the specified host.
+   * @param zone  zone name.
+   * @param dclass the dclass
+   * @param remote  the remote host.
+   * @throws IOException if there is an error.
+   * @throws ZoneTransferException if there is an error.
+   */
+  public SecureableZone(Name zone, int dclass, String remote)
+      throws IOException, ZoneTransferException {
+    super(zone, dclass, remote);
+  }
+
+  /**
+   * Creates a Zone from the records in the specified master file.
+   * @param zone The name of the zone.
+   * @param file The master file to read from.
+   * @throws IOException if there is an error.
+   */
+  public SecureableZone(Name zone, String file) throws IOException {
+    super(zone, file);
+  }
+
+  /**
+   * Creates a Zone from an array of records.
+   * @param zone The name of the zone.
+   * @param records The records to add to the zone.
+   * @throws IOException if there is an error.
+   */
+  public SecureableZone(Name zone, Record[] records)
+      throws IOException {
+    super(zone, records);
+  }
+
+  /**
+   * Adds a Record to the Zone.
+   * @param r The record to be added
+   * @see Record
+   */
+  @Override public void addRecord(Record r) {
+    if (records == null) {
+      records = new ArrayList<Record>();
+    }
+    super.addRecord(r);
+    records.add(r);
+  }
+
+  /**
+   * Removes a record from the Zone.
+   * @param r The record to be removed
+   * @see Record
+   */
+  @Override public void removeRecord(Record r) {
+    if (records == null) {
+      records = new ArrayList<Record>();
+    }
+    super.removeRecord(r);
+    records.remove(r);
+  }
+
+  /**
+   * Return a NXT record appropriate for the query.
+   * @param queryRecord the query record.
+   * @param zone the zone to search.
+   * @return  the NXT record describing the insertion point.
+   */
+  @SuppressWarnings({"unchecked"})
+  public Record getNXTRecord(Record queryRecord, Zone zone) {
+    Collections.sort(records);
+
+    int index = Collections.binarySearch(records, queryRecord,
+        new Comparator<Record>() {
+          @Override public int compare(Record r1, Record r2) {
+            return r1.compareTo(r2);
+          }
+        });
+    if (index >= 0) {
+      return null;
+    }
+    index = -index - 1;
+    if (index >= records.size()) {
+      index = records.size() - 1;
+    }
+    Record base = records.get(index);
+    SetResponse sr = zone.findRecords(base.getName(), Type.ANY);
+    BitSet bitMap = new BitSet();
+    bitMap.set(Type.NXT);
+    RRset[] rRsets = sr.answers();
+    for (RRset rRset : rRsets) {
+      int typeCode = rRset.getType();
+      if (typeCode > 0 && typeCode < 128) {
+        bitMap.set(typeCode);
+      }
+    }
+    return new NXTRecord(base.getName(), DClass.IN, zone.getSOA().getMinimum(),
+        queryRecord.getName(), bitMap);
+  }
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ServiceRecordProcessor.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ServiceRecordProcessor.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ServiceRecordProcessor.java
new file mode 100644
index 0000000..b67cc7d
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ServiceRecordProcessor.java
@@ -0,0 +1,53 @@
+/*
+ * 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.hadoop.registry.server.dns;
+
+import org.apache.hadoop.registry.client.types.ServiceRecord;
+
+import java.io.IOException;
+
+/**
+ *  Manage the processing of service records in order to create DNS records.
+ */
+public interface ServiceRecordProcessor {
+  /**
+   * Initialize the mapping between DNS record type and record information
+   * for the given service record.
+   * @param serviceRecord  the registry service record.
+   * @throws Exception if encountering an error.
+   */
+  void initTypeToInfoMapping(ServiceRecord serviceRecord)
+      throws Exception;
+
+  /**
+   * Return the DNS record types valid for this processor.
+   * @return  the array of DNS record types.
+   */
+  int[] getRecordTypes();
+
+  /**
+   * Manage the creation and registration of DNS records generated by parsing
+   * a service record.
+   * @param command  the DNS registration command object (e.g. add_record,
+   *                 remove record)
+   * @throws IOException if the creation or registration generates an issue.
+   */
+  void manageDNSRecords(RegistryDNS.RegistryCommand command)
+      throws IOException;
+
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ZoneSelector.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ZoneSelector.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ZoneSelector.java
new file mode 100644
index 0000000..5043b85
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/ZoneSelector.java
@@ -0,0 +1,33 @@
+/*
+ * 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.hadoop.registry.server.dns;
+
+import org.xbill.DNS.Name;
+import org.xbill.DNS.Zone;
+
+/**
+ * A selector that returns the zone associated with a provided name.
+ */
+public interface ZoneSelector {
+  /**
+   * Finds the best matching zone given the provided name.
+   * @param name the record name for which a zone is requested.
+   * @return the matching zone.
+   */
+  Zone findBestZone(Name name);
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/a1ce97eb/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/package-info.java
----------------------------------------------------------------------
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/package-info.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/package-info.java
new file mode 100644
index 0000000..00d8c9db
--- /dev/null
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-registry/src/main/java/org/apache/hadoop/registry/server/dns/package-info.java
@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+/**
+ * DNS Server classes.
+ * <p>
+ *   These classes are leveraged to create a DNS server that can provide the
+ *   facilities necessary for YARN application and/or service discovery.
+ * </p>
+ */
+package org.apache.hadoop.registry.server.dns;


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