org.apache.hadoop.hbase.ipc.RpcClient.java Source code

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/**
 *
 * 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.hbase.ipc;

import com.google.common.annotations.VisibleForTesting;
import com.google.protobuf.BlockingRpcChannel;
import com.google.protobuf.Descriptors.MethodDescriptor;
import com.google.protobuf.Message;
import com.google.protobuf.Message.Builder;
import com.google.protobuf.RpcController;
import com.google.protobuf.ServiceException;
import com.google.protobuf.TextFormat;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.CellScanner;
import org.apache.hadoop.hbase.DoNotRetryIOException;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.codec.Codec;
import org.apache.hadoop.hbase.codec.KeyValueCodec;
import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.protobuf.generated.AuthenticationProtos;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.CellBlockMeta;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.ConnectionHeader;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.ExceptionResponse;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.RequestHeader;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.ResponseHeader;
import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.UserInformation;
import org.apache.hadoop.hbase.protobuf.generated.TracingProtos.RPCTInfo;
import org.apache.hadoop.hbase.security.AuthMethod;
import org.apache.hadoop.hbase.security.HBaseSaslRpcClient;
import org.apache.hadoop.hbase.security.SaslUtil.QualityOfProtection;
import org.apache.hadoop.hbase.security.SecurityInfo;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.hbase.security.UserProvider;
import org.apache.hadoop.hbase.security.token.AuthenticationTokenSelector;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.ExceptionUtil;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.hbase.util.PoolMap;
import org.apache.hadoop.hbase.util.PoolMap.PoolType;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.ipc.RemoteException;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.TokenIdentifier;
import org.apache.hadoop.security.token.TokenSelector;
import org.htrace.Span;
import org.htrace.Trace;
import org.htrace.TraceScope;

import javax.net.SocketFactory;
import javax.security.sasl.SaslException;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InterruptedIOException;
import java.io.OutputStream;
import java.net.ConnectException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.security.PrivilegedExceptionAction;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Does RPC against a cluster.  Manages connections per regionserver in the cluster.
 * <p>See HBaseServer
 */
@SuppressWarnings("SynchronizationOnLocalVariableOrMethodParameter")
@InterfaceAudience.Private
public class RpcClient {
    // The LOG key is intentionally not from this package to avoid ipc logging at DEBUG (all under
    // o.a.h.hbase is set to DEBUG as default).
    public static final Log LOG = LogFactory.getLog("org.apache.hadoop.ipc.RpcClient");
    protected final PoolMap<ConnectionId, Connection> connections;

    protected final AtomicInteger callIdCnt = new AtomicInteger();
    protected final AtomicBoolean running = new AtomicBoolean(true); // if client runs
    final protected Configuration conf;
    protected final int minIdleTimeBeforeClose; // if the connection is iddle for more than this
                                                // time (in ms), it will be closed at any moment.
    final protected int maxRetries; //the max. no. of retries for socket connections
    final protected long failureSleep; // Time to sleep before retry on failure.
    protected final boolean tcpNoDelay; // if T then disable Nagle's Algorithm
    protected final boolean tcpKeepAlive; // if T then use keepalives
    protected final FailedServers failedServers;
    private final Codec codec;
    private final CompressionCodec compressor;
    private final IPCUtil ipcUtil;

    protected final SocketFactory socketFactory; // how to create sockets
    private final int connectTO;
    private final int readTO;
    private final int writeTO;
    protected String clusterId;
    protected final SocketAddress localAddr;

    private final boolean fallbackAllowed;
    private UserProvider userProvider;

    final private static String SOCKET_TIMEOUT_CONNECT = "hbase.ipc.client.socket.timeout.connect";
    final static int DEFAULT_SOCKET_TIMEOUT_CONNECT = 10000; // 10 seconds

    /**
     * How long we wait when we wait for an answer. It's not the operation time, it's the time
     *  we wait when we start to receive an answer, when the remote write starts to send the data.
     */
    final private static String SOCKET_TIMEOUT_READ = "hbase.ipc.client.socket.timeout.read";
    final static int DEFAULT_SOCKET_TIMEOUT_READ = 20000; // 20 seconds

    final private static String SOCKET_TIMEOUT_WRITE = "hbase.ipc.client.socket.timeout.write";
    final static int DEFAULT_SOCKET_TIMEOUT_WRITE = 60000; // 60 seconds

    // Used by the server, for compatibility with old clients.
    // The client in 0.99+ does not ping the server.
    final static int PING_CALL_ID = -1;

    public final static String FAILED_SERVER_EXPIRY_KEY = "hbase.ipc.client.failed.servers.expiry";
    public final static int FAILED_SERVER_EXPIRY_DEFAULT = 2000;

    public final static String IDLE_TIME = "hbase.ipc.client.connection.minIdleTimeBeforeClose";

    public static final String IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY = "hbase.ipc.client.fallback-to-simple-auth-allowed";
    public static final boolean IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT = false;

    public static final String ALLOWS_INTERRUPTS = "hbase.ipc.client.allowsInterrupt";

    /**
     * A class to manage a list of servers that failed recently.
     */
    static class FailedServers {
        private final LinkedList<Pair<Long, String>> failedServers = new LinkedList<Pair<Long, java.lang.String>>();
        private final int recheckServersTimeout;

        FailedServers(Configuration conf) {
            this.recheckServersTimeout = conf.getInt(FAILED_SERVER_EXPIRY_KEY, FAILED_SERVER_EXPIRY_DEFAULT);
        }

        /**
         * Add an address to the list of the failed servers list.
         */
        public synchronized void addToFailedServers(InetSocketAddress address) {
            final long expiry = EnvironmentEdgeManager.currentTimeMillis() + recheckServersTimeout;
            failedServers.addFirst(new Pair<Long, String>(expiry, address.toString()));
        }

        /**
         * Check if the server should be considered as bad. Clean the old entries of the list.
         *
         * @return true if the server is in the failed servers list
         */
        public synchronized boolean isFailedServer(final InetSocketAddress address) {
            if (failedServers.isEmpty()) {
                return false;
            }

            final String lookup = address.toString();
            final long now = EnvironmentEdgeManager.currentTimeMillis();

            // iterate, looking for the search entry and cleaning expired entries
            Iterator<Pair<Long, String>> it = failedServers.iterator();
            while (it.hasNext()) {
                Pair<Long, String> cur = it.next();
                if (cur.getFirst() < now) {
                    it.remove();
                } else {
                    if (lookup.equals(cur.getSecond())) {
                        return true;
                    }
                }
            }

            return false;
        }
    }

    /**
     * Indicates that we're trying to connect to a already known as dead server. We will want to
     *  retry: we're getting this because the region location was wrong, or because
     *  the server just died, in which case the retry loop will help us to wait for the
     *  regions to recover.
     */
    @SuppressWarnings("serial")
    @InterfaceAudience.Public
    @InterfaceStability.Evolving
    public static class FailedServerException extends HBaseIOException {
        public FailedServerException(String s) {
            super(s);
        }
    }

    /** A call waiting for a value. */
    protected class Call {
        final int id; // call id
        final Message param; // rpc request method param object
        /**
         * Optionally has cells when making call.  Optionally has cells set on response.  Used
         * passing cells to the rpc and receiving the response.
         */
        CellScanner cells;
        Message response; // value, null if error
        // The return type.  Used to create shell into which we deserialize the response if any.
        Message responseDefaultType;
        IOException error; // exception, null if value
        volatile boolean done; // true when call is done
        long startTime;
        final MethodDescriptor md;
        final int timeout; // timeout in millisecond for this call; 0 means infinite.

        protected Call(final MethodDescriptor md, Message param, final CellScanner cells,
                final Message responseDefaultType, int timeout) {
            this.param = param;
            this.md = md;
            this.cells = cells;
            this.startTime = EnvironmentEdgeManager.currentTimeMillis();
            this.responseDefaultType = responseDefaultType;
            this.id = callIdCnt.getAndIncrement();
            this.timeout = timeout;
        }

        /**
         * Check if the call did timeout. Set an exception (includes a notify) if it's the case.
         * @return true if the call is on timeout, false otherwise.
         */
        public boolean checkAndSetTimeout() {
            if (timeout == 0) {
                return false;
            }

            long waitTime = EnvironmentEdgeManager.currentTimeMillis() - getStartTime();
            if (waitTime >= timeout) {
                IOException ie = new CallTimeoutException(
                        "Call id=" + id + ", waitTime=" + waitTime + ", operationTimeout=" + timeout + " expired.");
                setException(ie); // includes a notify
                return true;
            } else {
                return false;
            }
        }

        public int remainingTime() {
            if (timeout == 0) {
                return Integer.MAX_VALUE;
            }

            int remaining = timeout - (int) (EnvironmentEdgeManager.currentTimeMillis() - getStartTime());
            return remaining > 0 ? remaining : 0;
        }

        @Override
        public String toString() {
            return "callId: " + this.id + " methodName: " + this.md.getName() + " param {"
                    + (this.param != null ? ProtobufUtil.getShortTextFormat(this.param) : "") + "}";
        }

        /** Indicate when the call is complete and the
         * value or error are available.  Notifies by default.  */
        protected synchronized void callComplete() {
            this.done = true;
            notify(); // notify caller
        }

        /** Set the exception when there is an error.
         * Notify the caller the call is done.
         *
         * @param error exception thrown by the call; either local or remote
         */
        public void setException(IOException error) {
            this.error = error;
            callComplete();
        }

        /**
         * Set the return value when there is no error.
         * Notify the caller the call is done.
         *
         * @param response return value of the call.
         * @param cells Can be null
         */
        public void setResponse(Message response, final CellScanner cells) {
            this.response = response;
            this.cells = cells;
            callComplete();
        }

        public long getStartTime() {
            return this.startTime;
        }
    }

    protected final static Map<AuthenticationProtos.TokenIdentifier.Kind, TokenSelector<? extends TokenIdentifier>> tokenHandlers = new HashMap<AuthenticationProtos.TokenIdentifier.Kind, TokenSelector<? extends TokenIdentifier>>();
    static {
        tokenHandlers.put(AuthenticationProtos.TokenIdentifier.Kind.HBASE_AUTH_TOKEN,
                new AuthenticationTokenSelector());
    }

    /**
     * Creates a connection. Can be overridden by a subclass for testing.
     * @param remoteId - the ConnectionId to use for the connection creation.
     */
    protected Connection createConnection(ConnectionId remoteId, final Codec codec,
            final CompressionCodec compressor) throws IOException {
        return new Connection(remoteId, codec, compressor);
    }

    /**
     * see {@link org.apache.hadoop.hbase.ipc.RpcClient.Connection.CallSender}
     */
    private static class CallFuture {
        final Call call;
        final int priority;
        final Span span;

        // We will use this to stop the writer
        final static CallFuture DEATH_PILL = new CallFuture(null, -1, null);

        CallFuture(Call call, int priority, Span span) {
            this.call = call;
            this.priority = priority;
            this.span = span;
        }
    }

    /** Thread that reads responses and notifies callers.  Each connection owns a
     * socket connected to a remote address.  Calls are multiplexed through this
     * socket: responses may be delivered out of order. */
    @SuppressWarnings("SynchronizeOnNonFinalField")
    protected class Connection extends Thread {
        private ConnectionHeader header; // connection header
        protected ConnectionId remoteId;
        protected Socket socket = null; // connected socket
        protected DataInputStream in;
        protected DataOutputStream out; // Warning: can be locked inside a class level lock.
        private InetSocketAddress server; // server ip:port
        private String serverPrincipal; // server's krb5 principal name
        private AuthMethod authMethod; // authentication method
        private boolean useSasl;
        private Token<? extends TokenIdentifier> token;
        private HBaseSaslRpcClient saslRpcClient;
        private int reloginMaxBackoff; // max pause before relogin on sasl failure
        private final Codec codec;
        private final CompressionCodec compressor;

        // currently active calls
        protected final ConcurrentSkipListMap<Integer, Call> calls = new ConcurrentSkipListMap<Integer, Call>();

        protected final AtomicBoolean shouldCloseConnection = new AtomicBoolean();
        protected final CallSender callSender;

        /**
         * If the client wants to interrupt its calls easily (i.e. call Thread#interrupt),
         *  it gets into a java issue: an interruption during a write closes the socket/channel.
         * A way to avoid this is to use a different thread for writing. This way, on interruptions,
         *  we either cancel the writes or ignore the answer if the write is already done, but we
         *  don't stop the write in the middle.
         * This adds a thread per region server in the client, so it's kept as an option.
         * <p>
         * The implementation is simple: the client threads adds their call to the queue, and then
         *  wait for an answer. The CallSender blocks on the queue, and writes the calls one
         *  after the other. On interruption, the client cancels its call. The CallSender checks that
         *  the call has not been canceled before writing it.
         * </p>
         * When the connection closes, all the calls not yet sent are dismissed. The client thread
         *  is notified with an appropriate exception, as if the call was already sent but the answer
         *  not yet received.
         * </p>
         */
        private class CallSender extends Thread implements Closeable {
            protected final BlockingQueue<CallFuture> callsToWrite;

            public CallFuture sendCall(Call call, int priority, Span span)
                    throws InterruptedException, IOException {
                CallFuture cts = new CallFuture(call, priority, span);
                callsToWrite.add(cts);
                checkIsOpen(); // We check after the put, to be sure that the call we added won't stay
                               //  in the list while the cleanup was already done.
                return cts;
            }

            public void close() {
                assert shouldCloseConnection.get();
                callsToWrite.offer(CallFuture.DEATH_PILL);
                // We don't care if we can't add the death pill to the queue: the writer
                //  won't be blocked in the 'take', as its queue is full.
            }

            CallSender(String name, Configuration conf) {
                int queueSize = conf.getInt("hbase.ipc.client.write.queueSize", 1000);
                callsToWrite = new ArrayBlockingQueue<CallFuture>(queueSize);
                setDaemon(true);
                setName(name + " - writer");
            }

            public void remove(CallFuture cts) {
                callsToWrite.remove(cts);
                calls.remove(cts.call.id);
            }

            /**
             * Reads the call from the queue, write them on the socket.
             */
            @Override
            public void run() {
                while (!shouldCloseConnection.get()) {
                    CallFuture cts = null;
                    try {
                        cts = callsToWrite.take();
                    } catch (InterruptedException e) {
                        markClosed(new InterruptedIOException());
                    }

                    if (cts == null || cts == CallFuture.DEATH_PILL) {
                        assert shouldCloseConnection.get();
                        break;
                    }

                    if (cts.call.done) {
                        continue;
                    }

                    if (cts.call.checkAndSetTimeout()) {
                        continue;
                    }

                    try {
                        Connection.this.tracedWriteRequest(cts.call, cts.priority, cts.span);
                    } catch (IOException e) {
                        LOG.warn("call write error for call #" + cts.call.id + ", message =" + e.getMessage());
                        cts.call.setException(e);
                        markClosed(e);
                    }
                }

                cleanup();
            }

            /**
             * Cleans the call not yet sent when we finish.
             */
            private void cleanup() {
                assert shouldCloseConnection.get();

                IOException ie = new IOException("Connection to " + server + " is closing.");
                while (true) {
                    CallFuture cts = callsToWrite.poll();
                    if (cts == null) {
                        break;
                    }
                    if (cts.call != null && !cts.call.done) {
                        cts.call.setException(ie);
                    }
                }
            }
        }

        Connection(ConnectionId remoteId, final Codec codec, final CompressionCodec compressor) throws IOException {
            if (remoteId.getAddress().isUnresolved()) {
                throw new UnknownHostException("unknown host: " + remoteId.getAddress().getHostName());
            }
            this.server = remoteId.getAddress();
            this.codec = codec;
            this.compressor = compressor;

            UserGroupInformation ticket = remoteId.getTicket().getUGI();
            SecurityInfo securityInfo = SecurityInfo.getInfo(remoteId.getServiceName());
            this.useSasl = userProvider.isHBaseSecurityEnabled();
            if (useSasl && securityInfo != null) {
                AuthenticationProtos.TokenIdentifier.Kind tokenKind = securityInfo.getTokenKind();
                if (tokenKind != null) {
                    TokenSelector<? extends TokenIdentifier> tokenSelector = tokenHandlers.get(tokenKind);
                    if (tokenSelector != null) {
                        token = tokenSelector.selectToken(new Text(clusterId), ticket.getTokens());
                    } else if (LOG.isDebugEnabled()) {
                        LOG.debug("No token selector found for type " + tokenKind);
                    }
                }
                String serverKey = securityInfo.getServerPrincipal();
                if (serverKey == null) {
                    throw new IOException("Can't obtain server Kerberos config key from SecurityInfo");
                }
                serverPrincipal = SecurityUtil.getServerPrincipal(conf.get(serverKey),
                        server.getAddress().getCanonicalHostName().toLowerCase());
                if (LOG.isDebugEnabled()) {
                    LOG.debug("RPC Server Kerberos principal name for service=" + remoteId.getServiceName() + " is "
                            + serverPrincipal);
                }
            }

            if (!useSasl) {
                authMethod = AuthMethod.SIMPLE;
            } else if (token != null) {
                authMethod = AuthMethod.DIGEST;
            } else {
                authMethod = AuthMethod.KERBEROS;
            }

            if (LOG.isDebugEnabled()) {
                LOG.debug("Use " + authMethod + " authentication for service " + remoteId.serviceName + ", sasl="
                        + useSasl);
            }
            reloginMaxBackoff = conf.getInt("hbase.security.relogin.maxbackoff", 5000);
            this.remoteId = remoteId;

            ConnectionHeader.Builder builder = ConnectionHeader.newBuilder();
            builder.setServiceName(remoteId.getServiceName());
            UserInformation userInfoPB;
            if ((userInfoPB = getUserInfo(ticket)) != null) {
                builder.setUserInfo(userInfoPB);
            }
            if (this.codec != null) {
                builder.setCellBlockCodecClass(this.codec.getClass().getCanonicalName());
            }
            if (this.compressor != null) {
                builder.setCellBlockCompressorClass(this.compressor.getClass().getCanonicalName());
            }
            this.header = builder.build();

            this.setName("IPC Client (" + socketFactory.hashCode() + ") connection to "
                    + remoteId.getAddress().toString()
                    + ((ticket == null) ? " from an unknown user" : (" from " + ticket.getUserName())));
            this.setDaemon(true);

            if (conf.getBoolean(ALLOWS_INTERRUPTS, false)) {
                callSender = new CallSender(getName(), conf);
                callSender.start();
            } else {
                callSender = null;
            }
        }

        private UserInformation getUserInfo(UserGroupInformation ugi) {
            if (ugi == null || authMethod == AuthMethod.DIGEST) {
                // Don't send user for token auth
                return null;
            }
            UserInformation.Builder userInfoPB = UserInformation.newBuilder();
            if (authMethod == AuthMethod.KERBEROS) {
                // Send effective user for Kerberos auth
                userInfoPB.setEffectiveUser(ugi.getUserName());
            } else if (authMethod == AuthMethod.SIMPLE) {
                //Send both effective user and real user for simple auth
                userInfoPB.setEffectiveUser(ugi.getUserName());
                if (ugi.getRealUser() != null) {
                    userInfoPB.setRealUser(ugi.getRealUser().getUserName());
                }
            }
            return userInfoPB.build();
        }

        protected synchronized void setupConnection() throws IOException {
            short ioFailures = 0;
            short timeoutFailures = 0;
            while (true) {
                try {
                    this.socket = socketFactory.createSocket();
                    this.socket.setTcpNoDelay(tcpNoDelay);
                    this.socket.setKeepAlive(tcpKeepAlive);
                    if (localAddr != null) {
                        this.socket.bind(localAddr);
                    }
                    NetUtils.connect(this.socket, remoteId.getAddress(), connectTO);
                    this.socket.setSoTimeout(readTO);
                    return;
                } catch (SocketTimeoutException toe) {
                    /* The max number of retries is 45,
                     * which amounts to 20s*45 = 15 minutes retries.
                     */
                    handleConnectionFailure(timeoutFailures++, maxRetries, toe);
                } catch (IOException ie) {
                    handleConnectionFailure(ioFailures++, maxRetries, ie);
                }
            }
        }

        protected synchronized void closeConnection() {
            if (socket == null) {
                return;
            }

            // close the current connection
            try {
                if (socket.getOutputStream() != null) {
                    socket.getOutputStream().close();
                }
            } catch (IOException ignored) { // Can happen if the socket is already closed
            }
            try {
                if (socket.getInputStream() != null) {
                    socket.getInputStream().close();
                }
            } catch (IOException ignored) { // Can happen if the socket is already closed
            }
            try {
                if (socket.getChannel() != null) {
                    socket.getChannel().close();
                }
            } catch (IOException ignored) { // Can happen if the socket is already closed
            }
            try {
                socket.close();
            } catch (IOException e) {
                LOG.warn("Not able to close a socket", e);
            }

            // set socket to null so that the next call to setupIOstreams
            // can start the process of connect all over again.
            socket = null;
        }

        /**
         *  Handle connection failures
         *
         * If the current number of retries is equal to the max number of retries,
         * stop retrying and throw the exception; Otherwise backoff N seconds and
         * try connecting again.
         *
         * This Method is only called from inside setupIOstreams(), which is
         * synchronized. Hence the sleep is synchronized; the locks will be retained.
         *
         * @param curRetries current number of retries
         * @param maxRetries max number of retries allowed
         * @param ioe failure reason
         * @throws IOException if max number of retries is reached
         */
        private void handleConnectionFailure(int curRetries, int maxRetries, IOException ioe) throws IOException {
            closeConnection();

            // throw the exception if the maximum number of retries is reached
            if (curRetries >= maxRetries || ExceptionUtil.isInterrupt(ioe)) {
                throw ioe;
            }

            // otherwise back off and retry
            try {
                Thread.sleep(failureSleep);
            } catch (InterruptedException ie) {
                ExceptionUtil.rethrowIfInterrupt(ie);
            }

            LOG.info("Retrying connect to server: " + remoteId.getAddress() + " after sleeping " + failureSleep
                    + "ms. Already tried " + curRetries + " time(s).");
        }

        /**
         * @throws IOException if the connection is not open.
         */
        private void checkIsOpen() throws IOException {
            if (shouldCloseConnection.get()) {
                throw new IOException(getName() + " is closing");
            }
        }

        /* wait till someone signals us to start reading RPC response or
         * it is idle too long, it is marked as to be closed,
         * or the client is marked as not running.
         *
         * Return true if it is time to read a response; false otherwise.
         */
        protected synchronized boolean waitForWork() throws InterruptedException {
            // beware of the concurrent access to the calls list: we can add calls, but as well
            //  remove them.
            long waitUntil = EnvironmentEdgeManager.currentTimeMillis() + minIdleTimeBeforeClose;
            while (!shouldCloseConnection.get() && running.get()
                    && EnvironmentEdgeManager.currentTimeMillis() < waitUntil && calls.isEmpty()) {
                wait(Math.min(minIdleTimeBeforeClose, 1000));
            }

            if (shouldCloseConnection.get()) {
                return false;
            }

            if (!running.get()) {
                markClosed(new IOException("stopped with " + calls.size() + " pending request(s)"));
                return false;
            }

            if (!calls.isEmpty()) {
                // shouldCloseConnection can be set to true by a parallel thread here. The caller
                //  will need to check anyway.
                return true;
            }

            // Connection is idle.
            // We expect the number of calls to be zero here, but actually someone can
            //  adds a call at the any moment, as there is no synchronization between this task
            //  and adding new calls. It's not a big issue, but it will get an exception.
            markClosed(new IOException("idle connection closed with " + calls.size() + " pending request(s)"));

            return false;
        }

        public InetSocketAddress getRemoteAddress() {
            return remoteId.getAddress();
        }

        @Override
        public void run() {
            if (LOG.isDebugEnabled()) {
                LOG.debug(getName() + ": starting, connections " + connections.size());
            }

            try {
                while (waitForWork()) { // Wait here for work - read or close connection
                    readResponse();
                }
            } catch (Throwable t) {
                LOG.debug(getName() + ": unexpected exception receiving call responses", t);
                markClosed(new IOException("Unexpected exception receiving call responses", t));
            }

            close();

            if (LOG.isDebugEnabled())
                LOG.debug(getName() + ": stopped, connections " + connections.size());
        }

        private synchronized void disposeSasl() {
            if (saslRpcClient != null) {
                try {
                    saslRpcClient.dispose();
                    saslRpcClient = null;
                } catch (IOException ioe) {
                    LOG.error("Error disposing of SASL client", ioe);
                }
            }
        }

        private synchronized boolean shouldAuthenticateOverKrb() throws IOException {
            UserGroupInformation loginUser = UserGroupInformation.getLoginUser();
            UserGroupInformation currentUser = UserGroupInformation.getCurrentUser();
            UserGroupInformation realUser = currentUser.getRealUser();
            return authMethod == AuthMethod.KERBEROS && loginUser != null &&
            //Make sure user logged in using Kerberos either keytab or TGT
                    loginUser.hasKerberosCredentials() &&
                    // relogin only in case it is the login user (e.g. JT)
                    // or superuser (like oozie).
                    (loginUser.equals(currentUser) || loginUser.equals(realUser));
        }

        private synchronized boolean setupSaslConnection(final InputStream in2, final OutputStream out2)
                throws IOException {
            saslRpcClient = new HBaseSaslRpcClient(authMethod, token, serverPrincipal, fallbackAllowed,
                    conf.get("hbase.rpc.protection", QualityOfProtection.AUTHENTICATION.name().toLowerCase()));
            return saslRpcClient.saslConnect(in2, out2);
        }

        /**
         * If multiple clients with the same principal try to connect
         * to the same server at the same time, the server assumes a
         * replay attack is in progress. This is a feature of kerberos.
         * In order to work around this, what is done is that the client
         * backs off randomly and tries to initiate the connection
         * again.
         * The other problem is to do with ticket expiry. To handle that,
         * a relogin is attempted.
         * <p>
         * The retry logic is governed by the {@link #shouldAuthenticateOverKrb}
         * method. In case when the user doesn't have valid credentials, we don't
         * need to retry (from cache or ticket). In such cases, it is prudent to
         * throw a runtime exception when we receive a SaslException from the
         * underlying authentication implementation, so there is no retry from
         * other high level (for eg, HCM or HBaseAdmin).
         * </p>
         */
        private synchronized void handleSaslConnectionFailure(final int currRetries, final int maxRetries,
                final Exception ex, final Random rand, final UserGroupInformation user)
                throws IOException, InterruptedException {
            user.doAs(new PrivilegedExceptionAction<Object>() {
                public Object run() throws IOException, InterruptedException {
                    closeConnection();
                    if (shouldAuthenticateOverKrb()) {
                        if (currRetries < maxRetries) {
                            LOG.debug("Exception encountered while connecting to " + "the server : " + ex);
                            //try re-login
                            if (UserGroupInformation.isLoginKeytabBased()) {
                                UserGroupInformation.getLoginUser().reloginFromKeytab();
                            } else {
                                UserGroupInformation.getLoginUser().reloginFromTicketCache();
                            }
                            disposeSasl();
                            //have granularity of milliseconds
                            //we are sleeping with the Connection lock held but since this
                            //connection instance is being used for connecting to the server
                            //in question, it is okay
                            Thread.sleep((rand.nextInt(reloginMaxBackoff) + 1));
                            return null;
                        } else {
                            String msg = "Couldn't setup connection for "
                                    + UserGroupInformation.getLoginUser().getUserName() + " to " + serverPrincipal;
                            LOG.warn(msg);
                            throw (IOException) new IOException(msg).initCause(ex);
                        }
                    } else {
                        LOG.warn("Exception encountered while connecting to " + "the server : " + ex);
                    }
                    if (ex instanceof RemoteException) {
                        throw (RemoteException) ex;
                    }
                    if (ex instanceof SaslException) {
                        String msg = "SASL authentication failed."
                                + " The most likely cause is missing or invalid credentials."
                                + " Consider 'kinit'.";
                        LOG.fatal(msg, ex);
                        throw new RuntimeException(msg, ex);
                    }
                    throw new IOException(ex);
                }
            });
        }

        protected synchronized void setupIOstreams() throws IOException {
            if (socket != null) {
                // The connection is already available. Perfect.
                return;
            }

            if (shouldCloseConnection.get()) {
                throw new IOException("This connection is closing");
            }

            if (failedServers.isFailedServer(remoteId.getAddress())) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Not trying to connect to " + server + " this server is in the failed servers list");
                }
                IOException e = new FailedServerException("This server is in the failed servers list: " + server);
                markClosed(e);
                close();
                throw e;
            }

            try {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Connecting to " + server);
                }
                short numRetries = 0;
                final short MAX_RETRIES = 5;
                Random rand = null;
                while (true) {
                    setupConnection();
                    InputStream inStream = NetUtils.getInputStream(socket);
                    // This creates a socket with a write timeout. This timeout cannot be changed.
                    OutputStream outStream = NetUtils.getOutputStream(socket, writeTO);
                    // Write out the preamble -- MAGIC, version, and auth to use.
                    writeConnectionHeaderPreamble(outStream);
                    if (useSasl) {
                        final InputStream in2 = inStream;
                        final OutputStream out2 = outStream;
                        UserGroupInformation ticket = remoteId.getTicket().getUGI();
                        if (authMethod == AuthMethod.KERBEROS) {
                            if (ticket != null && ticket.getRealUser() != null) {
                                ticket = ticket.getRealUser();
                            }
                        }
                        boolean continueSasl;
                        if (ticket == null)
                            throw new FatalConnectionException("ticket/user is null");
                        try {
                            continueSasl = ticket.doAs(new PrivilegedExceptionAction<Boolean>() {
                                @Override
                                public Boolean run() throws IOException {
                                    return setupSaslConnection(in2, out2);
                                }
                            });
                        } catch (Exception ex) {
                            ExceptionUtil.rethrowIfInterrupt(ex);
                            if (rand == null) {
                                rand = new Random();
                            }
                            handleSaslConnectionFailure(numRetries++, MAX_RETRIES, ex, rand, ticket);
                            continue;
                        }
                        if (continueSasl) {
                            // Sasl connect is successful. Let's set up Sasl i/o streams.
                            inStream = saslRpcClient.getInputStream(inStream);
                            outStream = saslRpcClient.getOutputStream(outStream);
                        } else {
                            // fall back to simple auth because server told us so.
                            authMethod = AuthMethod.SIMPLE;
                            useSasl = false;
                        }
                    }
                    this.in = new DataInputStream(new BufferedInputStream(inStream));
                    this.out = new DataOutputStream(new BufferedOutputStream(outStream));
                    // Now write out the connection header
                    writeConnectionHeader();

                    // start the receiver thread after the socket connection has been set up
                    start();
                    return;
                }
            } catch (Throwable t) {
                IOException e = ExceptionUtil.asInterrupt(t);
                if (e == null) {
                    failedServers.addToFailedServers(remoteId.address);
                    if (t instanceof LinkageError) {
                        // probably the hbase hadoop version does not match the running hadoop version
                        e = new DoNotRetryIOException(t);
                    } else if (t instanceof IOException) {
                        e = (IOException) t;
                    } else {
                        e = new IOException("Could not set up IO Streams to " + server, t);
                    }
                }
                markClosed(e);
                close();
                throw e;
            }
        }

        /**
         * Write the RPC header: <MAGIC WORD -- 'HBas'> <ONEBYTE_VERSION> <ONEBYTE_AUTH_TYPE>
         */
        private void writeConnectionHeaderPreamble(OutputStream outStream) throws IOException {
            // Assemble the preamble up in a buffer first and then send it.  Writing individual elements,
            // they are getting sent across piecemeal according to wireshark and then server is messing
            // up the reading on occasion (the passed in stream is not buffered yet).

            // Preamble is six bytes -- 'HBas' + VERSION + AUTH_CODE
            int rpcHeaderLen = HConstants.RPC_HEADER.array().length;
            byte[] preamble = new byte[rpcHeaderLen + 2];
            System.arraycopy(HConstants.RPC_HEADER.array(), 0, preamble, 0, rpcHeaderLen);
            preamble[rpcHeaderLen] = HConstants.RPC_CURRENT_VERSION;
            preamble[rpcHeaderLen + 1] = authMethod.code;
            outStream.write(preamble);
            outStream.flush();
        }

        /**
         * Write the connection header.
         */
        private synchronized void writeConnectionHeader() throws IOException {
            synchronized (this.out) {
                this.out.writeInt(this.header.getSerializedSize());
                this.header.writeTo(this.out);
                this.out.flush();
            }
        }

        /** Close the connection. */
        protected synchronized void close() {
            if (!shouldCloseConnection.get()) {
                LOG.error(getName() + ": the connection is not in the closed state");
                return;
            }

            // release the resources
            // first thing to do;take the connection out of the connection list
            synchronized (connections) {
                connections.removeValue(remoteId, this);
            }

            // close the streams and therefore the socket
            if (this.out != null) {
                synchronized (this.out) {
                    IOUtils.closeStream(out);
                    this.out = null;
                }
            }
            IOUtils.closeStream(in);
            this.in = null;
            disposeSasl();

            // log the info
            if (LOG.isDebugEnabled()) {
                LOG.debug(getName() + ": closing ipc connection to " + server);
            }

            cleanupCalls(true);

            if (LOG.isDebugEnabled()) {
                LOG.debug(getName() + ": ipc connection to " + server + " closed");
            }
        }

        protected void tracedWriteRequest(Call call, int priority, Span span) throws IOException {
            TraceScope ts = Trace.continueSpan(span);
            try {
                writeRequest(call, priority, span);
            } finally {
                ts.close();
            }
        }

        /**
         * Initiates a call by sending the parameter to the remote server.
         * Note: this is not called from the Connection thread, but by other
         * threads.
         * @see #readResponse()
         */
        private void writeRequest(Call call, final int priority, Span span) throws IOException {
            RequestHeader.Builder builder = RequestHeader.newBuilder();
            builder.setCallId(call.id);
            if (span != null) {
                builder.setTraceInfo(
                        RPCTInfo.newBuilder().setParentId(span.getSpanId()).setTraceId(span.getTraceId()));
            }
            builder.setMethodName(call.md.getName());
            builder.setRequestParam(call.param != null);
            ByteBuffer cellBlock = ipcUtil.buildCellBlock(this.codec, this.compressor, call.cells);
            if (cellBlock != null) {
                CellBlockMeta.Builder cellBlockBuilder = CellBlockMeta.newBuilder();
                cellBlockBuilder.setLength(cellBlock.limit());
                builder.setCellBlockMeta(cellBlockBuilder.build());
            }
            // Only pass priority if there one.  Let zero be same as no priority.
            if (priority != 0)
                builder.setPriority(priority);
            RequestHeader header = builder.build();

            setupIOstreams();

            // Now we're going to write the call. We take the lock, then check that the connection
            //  is still valid, and, if so we do the write to the socket. If the write fails, we don't
            //  know where we stand, we have to close the connection.
            checkIsOpen();
            IOException writeException = null;
            synchronized (this.out) {
                if (Thread.interrupted())
                    throw new InterruptedIOException();

                calls.put(call.id, call); // We put first as we don't want the connection to become idle.
                checkIsOpen(); // Now we're checking that it didn't became idle in between.

                try {
                    IPCUtil.write(this.out, header, call.param, cellBlock);
                } catch (IOException e) {
                    // We set the value inside the synchronized block, this way the next in line
                    //  won't even try to write
                    shouldCloseConnection.set(true);
                    writeException = e;
                }
            }

            // We added a call, and may be started the connection close. In both cases, we
            //  need to notify the reader.
            synchronized (this) {
                notifyAll();
            }

            // Now that we notified, we can rethrow the exception if any. Otherwise we're good.
            if (writeException != null)
                throw writeException;

            if (LOG.isDebugEnabled()) {
                LOG.debug(getName() + ": wrote request header " + TextFormat.shortDebugString(header));
            }
        }

        /* Receive a response.
         * Because only one receiver, so no synchronization on in.
         */
        protected void readResponse() {
            if (shouldCloseConnection.get())
                return;
            Call call = null;
            boolean expectedCall = false;
            try {
                // See HBaseServer.Call.setResponse for where we write out the response.
                // Total size of the response.  Unused.  But have to read it in anyways.
                int totalSize = in.readInt();

                // Read the header
                ResponseHeader responseHeader = ResponseHeader.parseDelimitedFrom(in);
                int id = responseHeader.getCallId();
                if (LOG.isDebugEnabled()) {
                    LOG.debug(getName() + ": got response header " + TextFormat.shortDebugString(responseHeader)
                            + ", totalSize: " + totalSize + " bytes");
                }
                call = calls.remove(id); // call.done have to be set before leaving this method
                expectedCall = (call != null && !call.done);
                if (!expectedCall) {
                    // So we got a response for which we have no corresponding 'call' here on the client-side.
                    // We probably timed out waiting, cleaned up all references, and now the server decides
                    // to return a response.  There is nothing we can do w/ the response at this stage. Clean
                    // out the wire of the response so its out of the way and we can get other responses on
                    // this connection.
                    int readSoFar = IPCUtil.getTotalSizeWhenWrittenDelimited(responseHeader);
                    int whatIsLeftToRead = totalSize - readSoFar;
                    LOG.debug("Unknown callId: " + id + ", skipping over this response of " + whatIsLeftToRead
                            + " bytes");
                    IOUtils.skipFully(in, whatIsLeftToRead);
                }
                if (responseHeader.hasException()) {
                    ExceptionResponse exceptionResponse = responseHeader.getException();
                    RemoteException re = createRemoteException(exceptionResponse);
                    if (expectedCall)
                        call.setException(re);
                    if (isFatalConnectionException(exceptionResponse)) {
                        markClosed(re);
                    }
                } else {
                    Message value = null;
                    // Call may be null because it may have timeout and been cleaned up on this side already
                    if (expectedCall && call.responseDefaultType != null) {
                        Builder builder = call.responseDefaultType.newBuilderForType();
                        builder.mergeDelimitedFrom(in);
                        value = builder.build();
                    }
                    CellScanner cellBlockScanner = null;
                    if (responseHeader.hasCellBlockMeta()) {
                        int size = responseHeader.getCellBlockMeta().getLength();
                        byte[] cellBlock = new byte[size];
                        IOUtils.readFully(this.in, cellBlock, 0, cellBlock.length);
                        cellBlockScanner = ipcUtil.createCellScanner(this.codec, this.compressor, cellBlock);
                    }
                    // it's possible that this call may have been cleaned up due to a RPC
                    // timeout, so check if it still exists before setting the value.
                    if (expectedCall)
                        call.setResponse(value, cellBlockScanner);
                }
            } catch (IOException e) {
                if (expectedCall)
                    call.setException(e);
                if (e instanceof SocketTimeoutException) {
                    // Clean up open calls but don't treat this as a fatal condition,
                    // since we expect certain responses to not make it by the specified
                    // {@link ConnectionId#rpcTimeout}.
                } else {
                    // Treat this as a fatal condition and close this connection
                    markClosed(e);
                }
            } finally {
                cleanupCalls(false);
                if (expectedCall && !call.done) {
                    LOG.warn("Coding error: code should be true for callId=" + call.id + ", server="
                            + getRemoteAddress() + ", shouldCloseConnection=" + shouldCloseConnection.get());
                }
            }
        }

        /**
         * @param e
         * @return True if the exception is a fatal connection exception.
         */
        private boolean isFatalConnectionException(final ExceptionResponse e) {
            return e.getExceptionClassName().equals(FatalConnectionException.class.getName());
        }

        /**
         * @param e exception to be wrapped
         * @return RemoteException made from passed <code>e</code>
         */
        private RemoteException createRemoteException(final ExceptionResponse e) {
            String innerExceptionClassName = e.getExceptionClassName();
            boolean doNotRetry = e.getDoNotRetry();
            return e.hasHostname() ?
            // If a hostname then add it to the RemoteWithExtrasException
                    new RemoteWithExtrasException(innerExceptionClassName, e.getStackTrace(), e.getHostname(),
                            e.getPort(), doNotRetry)
                    : new RemoteWithExtrasException(innerExceptionClassName, e.getStackTrace(), doNotRetry);
        }

        protected synchronized void markClosed(IOException e) {
            if (e == null)
                throw new NullPointerException();

            if (shouldCloseConnection.compareAndSet(false, true)) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug(getName() + ": marking at should close, reason =" + e.getMessage());
                }
                if (callSender != null) {
                    callSender.close();
                }
                notifyAll();
            }
        }

        /**
         * Cleanup the calls older than a given timeout, in milli seconds.
         * @param allCalls true for all calls, false for only the calls in timeout
         */
        protected synchronized void cleanupCalls(boolean allCalls) {
            Iterator<Entry<Integer, Call>> itor = calls.entrySet().iterator();
            while (itor.hasNext()) {
                Call c = itor.next().getValue();
                if (c.done) {
                    // To catch the calls without timeout that were cancelled.
                    itor.remove();
                } else if (allCalls) {
                    long waitTime = EnvironmentEdgeManager.currentTimeMillis() - c.getStartTime();
                    IOException ie = new IOException("Connection to " + getRemoteAddress() + " is closing. Call id="
                            + c.id + ", waitTime=" + waitTime);
                    c.setException(ie);
                    itor.remove();
                } else if (c.checkAndSetTimeout()) {
                    itor.remove();
                } else {
                    // We expect the call to be ordered by timeout. It may not be the case, but stopping
                    //  at the first valid call allows to be sure that we still have something to do without
                    //  spending too much time by reading the full list.
                    break;
                }
            }
        }
    }

    /**
     * Client-side call timeout
     */
    @SuppressWarnings("serial")
    @InterfaceAudience.Public
    @InterfaceStability.Evolving
    public static class CallTimeoutException extends IOException {
        public CallTimeoutException(final String msg) {
            super(msg);
        }
    }

    /**
     * Construct an IPC cluster client whose values are of the {@link Message} class.
     * @param conf configuration
     * @param clusterId the cluster id
     * @param factory socket factory
     */
    RpcClient(Configuration conf, String clusterId, SocketFactory factory) {
        this(conf, clusterId, factory, null);
    }

    /**
     * Construct an IPC cluster client whose values are of the {@link Message} class.
     * @param conf configuration
     * @param clusterId the cluster id
     * @param factory socket factory
     * @param localAddr client socket bind address
     */
    RpcClient(Configuration conf, String clusterId, SocketFactory factory, SocketAddress localAddr) {
        this.minIdleTimeBeforeClose = conf.getInt(IDLE_TIME, 120000); // 2 minutes
        this.maxRetries = conf.getInt("hbase.ipc.client.connect.max.retries", 0);
        this.failureSleep = conf.getLong(HConstants.HBASE_CLIENT_PAUSE, HConstants.DEFAULT_HBASE_CLIENT_PAUSE);
        this.tcpNoDelay = conf.getBoolean("hbase.ipc.client.tcpnodelay", true);
        this.tcpKeepAlive = conf.getBoolean("hbase.ipc.client.tcpkeepalive", true);
        this.ipcUtil = new IPCUtil(conf);
        this.conf = conf;
        this.codec = getCodec();
        this.compressor = getCompressor(conf);
        this.socketFactory = factory;
        this.clusterId = clusterId != null ? clusterId : HConstants.CLUSTER_ID_DEFAULT;
        this.connections = new PoolMap<ConnectionId, Connection>(getPoolType(conf), getPoolSize(conf));
        this.failedServers = new FailedServers(conf);
        this.fallbackAllowed = conf.getBoolean(IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY,
                IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT);
        this.localAddr = localAddr;
        this.userProvider = UserProvider.instantiate(conf);
        this.connectTO = conf.getInt(SOCKET_TIMEOUT_CONNECT, DEFAULT_SOCKET_TIMEOUT_CONNECT);
        this.readTO = conf.getInt(SOCKET_TIMEOUT_READ, DEFAULT_SOCKET_TIMEOUT_READ);
        this.writeTO = conf.getInt(SOCKET_TIMEOUT_WRITE, DEFAULT_SOCKET_TIMEOUT_WRITE);

        // login the server principal (if using secure Hadoop)
        if (LOG.isDebugEnabled()) {
            LOG.debug("Codec=" + this.codec + ", compressor=" + this.compressor + ", tcpKeepAlive="
                    + this.tcpKeepAlive + ", tcpNoDelay=" + this.tcpNoDelay + ", connectTO=" + this.connectTO
                    + ", readTO=" + this.readTO + ", writeTO=" + this.writeTO + ", minIdleTimeBeforeClose="
                    + this.minIdleTimeBeforeClose + ", maxRetries=" + this.maxRetries + ", fallbackAllowed="
                    + this.fallbackAllowed + ", bind address="
                    + (this.localAddr != null ? this.localAddr : "null"));
        }
    }

    /**
     * Construct an IPC client for the cluster <code>clusterId</code> with the default SocketFactory
     * @param conf configuration
     * @param clusterId the cluster id
     */
    public RpcClient(Configuration conf, String clusterId) {
        this(conf, clusterId, NetUtils.getDefaultSocketFactory(conf), null);
    }

    /**
     * Construct an IPC client for the cluster <code>clusterId</code> with the default SocketFactory
     * @param conf configuration
     * @param clusterId the cluster id
     * @param localAddr client socket bind address.
     */
    public RpcClient(Configuration conf, String clusterId, SocketAddress localAddr) {
        this(conf, clusterId, NetUtils.getDefaultSocketFactory(conf), localAddr);
    }

    /**
     * Encapsulate the ugly casting and RuntimeException conversion in private method.
     * @return Codec to use on this client.
     */
    Codec getCodec() {
        // For NO CODEC, "hbase.client.rpc.codec" must be configured with empty string AND
        // "hbase.client.default.rpc.codec" also -- because default is to do cell block encoding.
        String className = conf.get(HConstants.RPC_CODEC_CONF_KEY, getDefaultCodec(this.conf));
        if (className == null || className.length() == 0)
            return null;
        try {
            return (Codec) Class.forName(className).newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Failed getting codec " + className, e);
        }
    }

    @VisibleForTesting
    public static String getDefaultCodec(final Configuration c) {
        // If "hbase.client.default.rpc.codec" is empty string -- you can't set it to null because
        // Configuration will complain -- then no default codec (and we'll pb everything).  Else
        // default is KeyValueCodec
        return c.get("hbase.client.default.rpc.codec", KeyValueCodec.class.getCanonicalName());
    }

    /**
     * Encapsulate the ugly casting and RuntimeException conversion in private method.
     * @param conf configuration
     * @return The compressor to use on this client.
     */
    private static CompressionCodec getCompressor(final Configuration conf) {
        String className = conf.get("hbase.client.rpc.compressor", null);
        if (className == null || className.isEmpty())
            return null;
        try {
            return (CompressionCodec) Class.forName(className).newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Failed getting compressor " + className, e);
        }
    }

    /**
     * Return the pool type specified in the configuration, which must be set to
     * either {@link PoolType#RoundRobin} or {@link PoolType#ThreadLocal},
     * otherwise default to the former.
     *
     * For applications with many user threads, use a small round-robin pool. For
     * applications with few user threads, you may want to try using a
     * thread-local pool. In any case, the number of {@link RpcClient} instances
     * should not exceed the operating system's hard limit on the number of
     * connections.
     *
     * @param config configuration
     * @return either a {@link PoolType#RoundRobin} or
     *         {@link PoolType#ThreadLocal}
     */
    protected static PoolType getPoolType(Configuration config) {
        return PoolType.valueOf(config.get(HConstants.HBASE_CLIENT_IPC_POOL_TYPE), PoolType.RoundRobin,
                PoolType.ThreadLocal);
    }

    /**
     * Return the pool size specified in the configuration, which is applicable only if
     * the pool type is {@link PoolType#RoundRobin}.
     *
     * @param config configuration
     * @return the maximum pool size
     */
    protected static int getPoolSize(Configuration config) {
        return config.getInt(HConstants.HBASE_CLIENT_IPC_POOL_SIZE, 1);
    }

    /** Stop all threads related to this client.  No further calls may be made
     * using this client. */
    public void stop() {
        if (LOG.isDebugEnabled())
            LOG.debug("Stopping rpc client");
        if (!running.compareAndSet(true, false))
            return;

        // wake up all connections
        synchronized (connections) {
            for (Connection conn : connections.values()) {
                conn.interrupt();
            }
        }

        // wait until all connections are closed
        while (!connections.isEmpty()) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                LOG.info("Interrupted while stopping the client. We still have " + connections.size()
                        + " connections.");
                Thread.currentThread().interrupt();
                return;
            }
        }
    }

    Pair<Message, CellScanner> call(MethodDescriptor md, Message param, CellScanner cells, Message returnType,
            User ticket, InetSocketAddress addr, int rpcTimeout) throws InterruptedException, IOException {
        return call(md, param, cells, returnType, ticket, addr, rpcTimeout, HConstants.NORMAL_QOS);
    }

    /** Make a call, passing <code>param</code>, to the IPC server running at
     * <code>address</code> which is servicing the <code>protocol</code> protocol,
     * with the <code>ticket</code> credentials, returning the value.
     * Throws exceptions if there are network problems or if the remote code
     * threw an exception.
     * @param ticket Be careful which ticket you pass. A new user will mean a new Connection.
     *          {@link UserProvider#getCurrent()} makes a new instance of User each time so will be a
     *          new Connection each time.
     * @return A pair with the Message response and the Cell data (if any).
     * @throws InterruptedException
     * @throws IOException
     */
    Pair<Message, CellScanner> call(MethodDescriptor md, Message param, CellScanner cells, Message returnType,
            User ticket, InetSocketAddress addr, int callTimeout, int priority)
            throws IOException, InterruptedException {
        Call call = new Call(md, param, cells, returnType, callTimeout);
        Connection connection = getConnection(ticket, call, addr, this.codec, this.compressor);

        CallFuture cts = null;
        if (connection.callSender != null) {
            cts = connection.callSender.sendCall(call, priority, Trace.currentSpan());
        } else {
            connection.tracedWriteRequest(call, priority, Trace.currentSpan());
        }

        while (!call.done) {
            if (call.checkAndSetTimeout()) {
                if (cts != null)
                    connection.callSender.remove(cts);
                break;
            }
            if (connection.shouldCloseConnection.get()) {
                throw new IOException(
                        "Call id=" + call.id + " on server " + addr + " aborted: connection is closing");
            }
            try {
                synchronized (call) {
                    call.wait(Math.min(call.remainingTime(), 1000) + 1);
                }
            } catch (InterruptedException e) {
                call.setException(new InterruptedIOException());
                if (cts != null)
                    connection.callSender.remove(cts);
                throw e;
            }
        }

        if (call.error != null) {
            if (call.error instanceof RemoteException) {
                call.error.fillInStackTrace();
                throw call.error;
            }
            // local exception
            throw wrapException(addr, call.error);
        }

        return new Pair<Message, CellScanner>(call.response, call.cells);
    }

    /**
     * Take an IOException and the address we were trying to connect to
     * and return an IOException with the input exception as the cause.
     * The new exception provides the stack trace of the place where
     * the exception is thrown and some extra diagnostics information.
     * If the exception is ConnectException or SocketTimeoutException,
     * return a new one of the same type; Otherwise return an IOException.
     *
     * @param addr target address
     * @param exception the relevant exception
     * @return an exception to throw
     */
    protected IOException wrapException(InetSocketAddress addr, IOException exception) {
        if (exception instanceof ConnectException) {
            //connection refused; include the host:port in the error
            return (ConnectException) new ConnectException(
                    "Call to " + addr + " failed on connection exception: " + exception).initCause(exception);
        } else if (exception instanceof SocketTimeoutException) {
            return (SocketTimeoutException) new SocketTimeoutException(
                    "Call to " + addr + " failed because " + exception).initCause(exception);
        } else {
            return (IOException) new IOException("Call to " + addr + " failed on local exception: " + exception)
                    .initCause(exception);
        }
    }

    /**
     * Interrupt the connections to the given ip:port server. This should be called if the server
     *  is known as actually dead. This will not prevent current operation to be retried, and,
     *  depending on their own behavior, they may retry on the same server. This can be a feature,
     *  for example at startup. In any case, they're likely to get connection refused (if the
     *  process died) or no route to host: i.e. their next retries should be faster and with a
     *  safe exception.
     */
    public void cancelConnections(String hostname, int port) {
        synchronized (connections) {
            for (Connection connection : connections.values()) {
                if (connection.isAlive() && connection.getRemoteAddress().getPort() == port
                        && connection.getRemoteAddress().getHostName().equals(hostname)) {
                    LOG.info("The server on " + hostname + ":" + port + " is dead - stopping the connection "
                            + connection.remoteId);
                    connection.interrupt(); // We're interrupting a Reader. It means we want it to finish.
                                            // This will close the connection as well.
                }
            }
        }
    }

    /**
     *  Get a connection from the pool, or create a new one and add it to the
     * pool. Connections to a given host/port are reused.
     */
    protected Connection getConnection(User ticket, Call call, InetSocketAddress addr, final Codec codec,
            final CompressionCodec compressor) throws IOException {
        if (!running.get())
            throw new StoppedRpcClientException();
        Connection connection;
        ConnectionId remoteId = new ConnectionId(ticket, call.md.getService().getName(), addr);
        synchronized (connections) {
            connection = connections.get(remoteId);
            if (connection == null) {
                connection = createConnection(remoteId, this.codec, this.compressor);
                connections.put(remoteId, connection);
            }
        }

        return connection;
    }

    /**
     * This class holds the address and the user ticket, etc. The client connections
     * to servers are uniquely identified by <remoteAddress, ticket, serviceName, rpcTimeout>
     */
    protected static class ConnectionId {
        final InetSocketAddress address;
        final User ticket;
        private static final int PRIME = 16777619;
        final String serviceName;

        ConnectionId(User ticket, String serviceName, InetSocketAddress address) {
            this.address = address;
            this.ticket = ticket;
            this.serviceName = serviceName;
        }

        String getServiceName() {
            return this.serviceName;
        }

        InetSocketAddress getAddress() {
            return address;
        }

        User getTicket() {
            return ticket;
        }

        @Override
        public String toString() {
            return this.address.toString() + "/" + this.serviceName + "/" + this.ticket;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj instanceof ConnectionId) {
                ConnectionId id = (ConnectionId) obj;
                return address.equals(id.address)
                        && ((ticket != null && ticket.equals(id.ticket)) || (ticket == id.ticket))
                        && this.serviceName == id.serviceName;
            }
            return false;
        }

        @Override // simply use the default Object#hashcode() ?
        public int hashCode() {
            int hashcode = (address.hashCode()
                    + PRIME * (PRIME * this.serviceName.hashCode() ^ (ticket == null ? 0 : ticket.hashCode())));
            return hashcode;
        }
    }

    /**
     * Make a blocking call. Throws exceptions if there are network problems or if the remote code
     * threw an exception.
     * @param ticket Be careful which ticket you pass. A new user will mean a new Connection.
     *          {@link UserProvider#getCurrent()} makes a new instance of User each time so will be a
     *          new Connection each time.
     * @return A pair with the Message response and the Cell data (if any).
     */
    Message callBlockingMethod(MethodDescriptor md, PayloadCarryingRpcController pcrc, Message param,
            Message returnType, final User ticket, final InetSocketAddress isa) throws ServiceException {
        long startTime = 0;
        if (LOG.isTraceEnabled()) {
            startTime = EnvironmentEdgeManager.currentTimeMillis();
        }
        int callTimeout = 0;
        CellScanner cells = null;
        if (pcrc != null) {
            callTimeout = pcrc.getCallTimeout();
            cells = pcrc.cellScanner();
            // Clear it here so we don't by mistake try and these cells processing results.
            pcrc.setCellScanner(null);
        }
        Pair<Message, CellScanner> val;
        try {
            val = call(md, param, cells, returnType, ticket, isa, callTimeout,
                    pcrc != null ? pcrc.getPriority() : HConstants.NORMAL_QOS);
            if (pcrc != null) {
                // Shove the results into controller so can be carried across the proxy/pb service void.
                if (val.getSecond() != null)
                    pcrc.setCellScanner(val.getSecond());
            } else if (val.getSecond() != null) {
                throw new ServiceException("Client dropping data on the floor!");
            }

            if (LOG.isTraceEnabled()) {
                long callTime = EnvironmentEdgeManager.currentTimeMillis() - startTime;
                LOG.trace("Call: " + md.getName() + ", callTime: " + callTime + "ms");
            }
            return val.getFirst();
        } catch (Throwable e) {
            throw new ServiceException(e);
        }
    }

    /**
     * Creates a "channel" that can be used by a blocking protobuf service.  Useful setting up
     * protobuf blocking stubs.
     * @return A blocking rpc channel that goes via this rpc client instance.
     */
    public BlockingRpcChannel createBlockingRpcChannel(final ServerName sn, final User ticket,
            int defaultOperationTimeout) {
        return new BlockingRpcChannelImplementation(this, sn, ticket, defaultOperationTimeout);
    }

    /**
     * Blocking rpc channel that goes via hbase rpc.
     */
    @VisibleForTesting
    public static class BlockingRpcChannelImplementation implements BlockingRpcChannel {
        private final InetSocketAddress isa;
        private final RpcClient rpcClient;
        private final User ticket;
        private final int defaultOperationTimeout;

        /**
         * @param defaultOperationTimeout - the default timeout when no timeout is given
         *                                   by the caller.
         */
        protected BlockingRpcChannelImplementation(final RpcClient rpcClient, final ServerName sn,
                final User ticket, int defaultOperationTimeout) {
            this.isa = new InetSocketAddress(sn.getHostname(), sn.getPort());
            this.rpcClient = rpcClient;
            this.ticket = ticket;
            this.defaultOperationTimeout = defaultOperationTimeout;
        }

        @Override
        public Message callBlockingMethod(MethodDescriptor md, RpcController controller, Message param,
                Message returnType) throws ServiceException {
            PayloadCarryingRpcController pcrc;
            if (controller != null) {
                pcrc = (PayloadCarryingRpcController) controller;
                if (!pcrc.hasCallTimeout()) {
                    pcrc.setCallTimeout(defaultOperationTimeout);
                }
            } else {
                pcrc = new PayloadCarryingRpcController();
                pcrc.setCallTimeout(defaultOperationTimeout);
            }

            return this.rpcClient.callBlockingMethod(md, pcrc, param, returnType, this.ticket, this.isa);
        }
    }
}