/**
* 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.ipc;
import java.net.Socket;
import java.net.InetSocketAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.net.ConnectException;
import java.io.IOException;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FilterInputStream;
import java.io.InputStream;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import javax.net.SocketFactory;
import org.apache.commons.logging.*;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableUtils;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.util.ReflectionUtils;
/** A client for an IPC service. IPC calls take a single {@link Writable} as a
* parameter, and return a {@link Writable} as their value. A service runs on
* a port and is defined by a parameter class and a value class.
*
* @see Server
*/
public class Client {
public static final Log LOG =
LogFactory.getLog(Client.class);
private Hashtable<ConnectionId, Connection> connections =
new Hashtable<ConnectionId, Connection>();
private Class<? extends Writable> valueClass; // class of call values
private int counter; // counter for call ids
private AtomicBoolean running = new AtomicBoolean(true); // if client runs
final private Configuration conf;
final private int maxIdleTime; //connections will be culled if it was idle for
//maxIdleTime msecs
final private int maxRetries; //the max. no. of retries for socket connections
private boolean tcpNoDelay; // if T then disable Nagle's Algorithm
private int pingInterval; // how often sends ping to the server in msecs
private SocketFactory socketFactory; // how to create sockets
private int refCount = 1;
final private static String PING_INTERVAL_NAME = "ipc.ping.interval";
final static int DEFAULT_PING_INTERVAL = 60000; // 1 min
final static int PING_CALL_ID = -1;
/**
* set the ping interval value in configuration
*
* @param conf Configuration
* @param pingInterval the ping interval
*/
final public static void setPingInterval(Configuration conf, int pingInterval) {
conf.setInt(PING_INTERVAL_NAME, pingInterval);
}
/**
* Get the ping interval from configuration;
* If not set in the configuration, return the default value.
*
* @param conf Configuration
* @return the ping interval
*/
final static int getPingInterval(Configuration conf) {
return conf.getInt(PING_INTERVAL_NAME, DEFAULT_PING_INTERVAL);
}
/**
* Increment this client's reference count
*
*/
synchronized void incCount() {
refCount++;
}
/**
* Decrement this client's reference count
*
*/
synchronized void decCount() {
refCount--;
}
/**
* Return if this client has no reference
*
* @return true if this client has no reference; false otherwise
*/
synchronized boolean isZeroReference() {
return refCount==0;
}
/** A call waiting for a value. */
private class Call {
int id; // call id
Writable param; // parameter
Writable value; // value, null if error
IOException error; // exception, null if value
boolean done; // true when call is done
protected Call(Writable param) {
this.param = param;
synchronized (Client.this) {
this.id = counter++;
}
}
/** 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 synchronized 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 value return value of the call.
*/
public synchronized void setValue(Writable value) {
this.value = value;
callComplete();
}
}
/** 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. */
private class Connection extends Thread {
private InetSocketAddress server; // server ip:port
private ConnectionHeader header; // connection header
private ConnectionId remoteId; // connection id
private Socket socket = null; // connected socket
private DataInputStream in;
private DataOutputStream out;
// currently active calls
private Hashtable<Integer, Call> calls = new Hashtable<Integer, Call>();
private AtomicLong lastActivity = new AtomicLong();// last I/O activity time
private AtomicBoolean shouldCloseConnection = new AtomicBoolean(); // indicate if the connection is closed
private IOException closeException; // close reason
public Connection(ConnectionId remoteId) throws IOException {
this.remoteId = remoteId;
this.server = remoteId.getAddress();
if (server.isUnresolved()) {
throw new UnknownHostException("unknown host: " +
remoteId.getAddress().getHostName());
}
UserGroupInformation ticket = remoteId.getTicket();
Class<?> protocol = remoteId.getProtocol();
header =
new ConnectionHeader(protocol == null ? null : protocol.getName(), ticket);
this.setName("IPC Client (" + socketFactory.hashCode() +") connection to " +
remoteId.getAddress().toString() +
" from " + ((ticket==null)?"an unknown user":ticket.getUserName()));
this.setDaemon(true);
}
/** Update lastActivity with the current time. */
private void touch() {
lastActivity.set(System.currentTimeMillis());
}
/**
* Add a call to this connection's call queue and notify
* a listener; synchronized.
* Returns false if called during shutdown.
* @param call to add
* @return true if the call was added.
*/
private synchronized boolean addCall(Call call) {
if (shouldCloseConnection.get())
return false;
calls.put(call.id, call);
notify();
return true;
}
/** This class sends a ping to the remote side when timeout on
* reading. If no failure is detected, it retries until at least
* a byte is read.
*/
private class PingInputStream extends FilterInputStream {
/* constructor */
protected PingInputStream(InputStream in) {
super(in);
}
/* Process timeout exception
* if the connection is not going to be closed, send a ping.
* otherwise, throw the timeout exception.
*/
private void handleTimeout(SocketTimeoutException e) throws IOException {
if (shouldCloseConnection.get() || !running.get()) {
throw e;
} else {
sendPing();
}
}
/** Read a byte from the stream.
* Send a ping if timeout on read. Retries if no failure is detected
* until a byte is read.
* @throws IOException for any IO problem other than socket timeout
*/
public int read() throws IOException {
do {
try {
return super.read();
} catch (SocketTimeoutException e) {
handleTimeout(e);
}
} while (true);
}
/** Read bytes into a buffer starting from offset <code>off</code>
* Send a ping if timeout on read. Retries if no failure is detected
* until a byte is read.
*
* @return the total number of bytes read; -1 if the connection is closed.
*/
public int read(byte[] buf, int off, int len) throws IOException {
do {
try {
return super.read(buf, off, len);
} catch (SocketTimeoutException e) {
handleTimeout(e);
}
} while (true);
}
}
/** Connect to the server and set up the I/O streams. It then sends
* a header to the server and starts
* the connection thread that waits for responses.
*/
private synchronized void setupIOstreams() {
if (socket != null || shouldCloseConnection.get()) {
return;
}
short ioFailures = 0;
short timeoutFailures = 0;
try {
if (LOG.isDebugEnabled()) {
LOG.debug("Connecting to "+server);
}
while (true) {
try {
this.socket = socketFactory.createSocket();
this.socket.setTcpNoDelay(tcpNoDelay);
// connection time out is 20s
NetUtils.connect(this.socket, remoteId.getAddress(), 20000);
this.socket.setSoTimeout(pingInterval);
break;
} catch (SocketTimeoutException toe) {
/* The max number of retries is 45,
* which amounts to 20s*45 = 15 minutes retries.
*/
handleConnectionFailure(timeoutFailures++, 45, toe);
} catch (IOException ie) {
handleConnectionFailure(ioFailures++, maxRetries, ie);
}
}
this.in = new DataInputStream(new BufferedInputStream
(new PingInputStream(NetUtils.getInputStream(socket))));
this.out = new DataOutputStream
(new BufferedOutputStream(NetUtils.getOutputStream(socket)));
writeHeader();
// update last activity time
touch();
// start the receiver thread after the socket connection has been set up
start();
} catch (IOException e) {
markClosed(e);
close();
}
}
/* 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 1 second 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 {
// close the current connection
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;
// throw the exception if the maximum number of retries is reached
if (curRetries >= maxRetries) {
throw ioe;
}
// otherwise back off and retry
try {
Thread.sleep(1000);
} catch (InterruptedException ignored) {}
LOG.info("Retrying connect to server: " + server +
". Already tried " + curRetries + " time(s).");
}
/* Write the header for each connection
* Out is not synchronized because only the first thread does this.
*/
private void writeHeader() throws IOException {
// Write out the header and version
out.write(Server.HEADER.array());
out.write(Server.CURRENT_VERSION);
// Write out the ConnectionHeader
DataOutputBuffer buf = new DataOutputBuffer();
header.write(buf);
// Write out the payload length
int bufLen = buf.getLength();
out.writeInt(bufLen);
out.write(buf.getData(), 0, bufLen);
}
/* 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.
*/
private synchronized boolean waitForWork() {
if (calls.isEmpty() && !shouldCloseConnection.get() && running.get()) {
long timeout = maxIdleTime-
(System.currentTimeMillis()-lastActivity.get());
if (timeout>0) {
try {
wait(timeout);
} catch (InterruptedException e) {}
}
}
if (!calls.isEmpty() && !shouldCloseConnection.get() && running.get()) {
return true;
} else if (shouldCloseConnection.get()) {
return false;
} else if (calls.isEmpty()) { // idle connection closed or stopped
markClosed(null);
return false;
} else { // get stopped but there are still pending requests
markClosed((IOException)new IOException().initCause(
new InterruptedException()));
return false;
}
}
public InetSocketAddress getRemoteAddress() {
return server;
}
/* Send a ping to the server if the time elapsed
* since last I/O activity is equal to or greater than the ping interval
*/
private synchronized void sendPing() throws IOException {
long curTime = System.currentTimeMillis();
if ( curTime - lastActivity.get() >= pingInterval) {
lastActivity.set(curTime);
synchronized (out) {
out.writeInt(PING_CALL_ID);
out.flush();
}
}
}
public void run() {
if (LOG.isDebugEnabled())
LOG.debug(getName() + ": starting, having connections "
+ connections.size());
while (waitForWork()) {//wait here for work - read or close connection
receiveResponse();
}
close();
if (LOG.isDebugEnabled())
LOG.debug(getName() + ": stopped, remaining connections "
+ connections.size());
}
/** Initiates a call by sending the parameter to the remote server.
* Note: this is not called from the Connection thread, but by other
* threads.
*/
public void sendParam(Call call) {
if (shouldCloseConnection.get()) {
return;
}
DataOutputBuffer d=null;
try {
synchronized (this.out) {
if (LOG.isDebugEnabled())
LOG.debug(getName() + " sending #" + call.id);
//for serializing the
//data to be written
d = new DataOutputBuffer();
d.writeInt(call.id);
call.param.write(d);
byte[] data = d.getData();
int dataLength = d.getLength();
out.writeInt(dataLength); //first put the data length
out.write(data, 0, dataLength);//write the data
out.flush();
}
} catch(IOException e) {
markClosed(e);
} finally {
//the buffer is just an in-memory buffer, but it is still polite to
// close early
IOUtils.closeStream(d);
}
}
/* Receive a response.
* Because only one receiver, so no synchronization on in.
*/
private void receiveResponse() {
if (shouldCloseConnection.get()) {
return;
}
touch();
try {
int id = in.readInt(); // try to read an id
if (LOG.isDebugEnabled())
LOG.debug(getName() + " got value #" + id);
Call call = calls.get(id);
int state = in.readInt(); // read call status
if (state == Status.SUCCESS.state) {
Writable value = ReflectionUtils.newInstance(valueClass, conf);
value.readFields(in); // read value
call.setValue(value);
calls.remove(id);
} else if (state == Status.ERROR.state) {
call.setException(new RemoteException(WritableUtils.readString(in),
WritableUtils.readString(in)));
} else if (state == Status.FATAL.state) {
// Close the connection
markClosed(new RemoteException(WritableUtils.readString(in),
WritableUtils.readString(in)));
}
} catch (IOException e) {
markClosed(e);
}
}
private synchronized void markClosed(IOException e) {
if (shouldCloseConnection.compareAndSet(false, true)) {
closeException = e;
notifyAll();
}
}
/** Close the connection. */
private synchronized void close() {
if (!shouldCloseConnection.get()) {
LOG.error("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) {
if (connections.get(remoteId) == this) {
connections.remove(remoteId);
}
}
// close the streams and therefore the socket
IOUtils.closeStream(out);
IOUtils.closeStream(in);
// clean up all calls
if (closeException == null) {
if (!calls.isEmpty()) {
LOG.warn(
"A connection is closed for no cause and calls are not empty");
// clean up calls anyway
closeException = new IOException("Unexpected closed connection");
cleanupCalls();
}
} else {
// log the info
if (LOG.isDebugEnabled()) {
LOG.debug("closing ipc connection to " + server + ": " +
closeException.getMessage(),closeException);
}
// cleanup calls
cleanupCalls();
}
if (LOG.isDebugEnabled())
LOG.debug(getName() + ": closed");
}
/* Cleanup all calls and mark them as done */
private void cleanupCalls() {
Iterator<Entry<Integer, Call>> itor = calls.entrySet().iterator() ;
while (itor.hasNext()) {
Call c = itor.next().getValue();
c.setException(closeException); // local exception
itor.remove();
}
}
}
/** Call implementation used for parallel calls. */
private class ParallelCall extends Call {
private ParallelResults results;
private int index;
public ParallelCall(Writable param, ParallelResults results, int index) {
super(param);
this.results = results;
this.index = index;
}
/** Deliver result to result collector. */
protected void callComplete() {
results.callComplete(this);
}
}
/** Result collector for parallel calls. */
private static class ParallelResults {
private Writable[] values;
private int size;
private int count;
public ParallelResults(int size) {
this.values = new Writable[size];
this.size = size;
}
/** Collect a result. */
public synchronized void callComplete(ParallelCall call) {
values[call.index] = call.value; // store the value
count++; // count it
if (count == size) // if all values are in
notify(); // then notify waiting caller
}
}
/** Construct an IPC client whose values are of the given {@link Writable}
* class. */
public Client(Class<? extends Writable> valueClass, Configuration conf,
SocketFactory factory) {
this.valueClass = valueClass;
this.maxIdleTime =
conf.getInt("ipc.client.connection.maxidletime", 10000); //10s
this.maxRetries = conf.getInt("ipc.client.connect.max.retries", 10);
this.tcpNoDelay = conf.getBoolean("ipc.client.tcpnodelay", false);
this.pingInterval = getPingInterval(conf);
if (LOG.isDebugEnabled()) {
LOG.debug("The ping interval is" + this.pingInterval + "ms.");
}
this.conf = conf;
this.socketFactory = factory;
}
/**
* Construct an IPC client with the default SocketFactory
* @param valueClass
* @param conf
*/
public Client(Class<? extends Writable> valueClass, Configuration conf) {
this(valueClass, conf, NetUtils.getDefaultSocketFactory(conf));
}
/** Return the socket factory of this client
*
* @return this client's socket factory
*/
SocketFactory getSocketFactory() {
return socketFactory;
}
/** 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 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) {
}
}
}
/** Make a call, passing <code>param</code>, to the IPC server running at
* <code>address</code>, returning the value. Throws exceptions if there are
* network problems or if the remote code threw an exception.
* @deprecated Use {@link #call(Writable, InetSocketAddress, Class, UserGroupInformation)} instead
*/
@Deprecated
public Writable call(Writable param, InetSocketAddress address)
throws InterruptedException, IOException {
return call(param, address, null);
}
/** Make a call, passing <code>param</code>, to the IPC server running at
* <code>address</code> with the <code>ticket</code> credentials, returning
* the value.
* Throws exceptions if there are network problems or if the remote code
* threw an exception.
* @deprecated Use {@link #call(Writable, InetSocketAddress, Class, UserGroupInformation)} instead
*/
@Deprecated
public Writable call(Writable param, InetSocketAddress addr,
UserGroupInformation ticket)
throws InterruptedException, IOException {
return call(param, addr, null, ticket);
}
/** 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. */
public Writable call(Writable param, InetSocketAddress addr,
Class<?> protocol, UserGroupInformation ticket)
throws InterruptedException, IOException {
Call call = new Call(param);
Connection connection = getConnection(addr, protocol, ticket, call);
connection.sendParam(call); // send the parameter
boolean interrupted = false;
synchronized (call) {
while (!call.done) {
try {
call.wait(); // wait for the result
} catch (InterruptedException ie) {
// save the fact that we were interrupted
interrupted = true;
}
}
if (interrupted) {
// set the interrupt flag now that we are done waiting
Thread.currentThread().interrupt();
}
if (call.error != null) {
if (call.error instanceof RemoteException) {
call.error.fillInStackTrace();
throw call.error;
} else { // local exception
throw wrapException(addr, call.error);
}
} else {
return call.value;
}
}
}
/**
* 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
*/
private 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 on socket timeout exception: "
+ exception).initCause(exception);
} else {
return (IOException)new IOException(
"Call to " + addr + " failed on local exception: " + exception)
.initCause(exception);
}
}
/**
* Makes a set of calls in parallel. Each parameter is sent to the
* corresponding address. When all values are available, or have timed out
* or errored, the collected results are returned in an array. The array
* contains nulls for calls that timed out or errored.
* @deprecated Use {@link #call(Writable[], InetSocketAddress[], Class, UserGroupInformation)} instead
*/
@Deprecated
public Writable[] call(Writable[] params, InetSocketAddress[] addresses)
throws IOException {
return call(params, addresses, null, null);
}
/** Makes a set of calls in parallel. Each parameter is sent to the
* corresponding address. When all values are available, or have timed out
* or errored, the collected results are returned in an array. The array
* contains nulls for calls that timed out or errored. */
public Writable[] call(Writable[] params, InetSocketAddress[] addresses,
Class<?> protocol, UserGroupInformation ticket)
throws IOException {
if (addresses.length == 0) return new Writable[0];
ParallelResults results = new ParallelResults(params.length);
synchronized (results) {
for (int i = 0; i < params.length; i++) {
ParallelCall call = new ParallelCall(params[i], results, i);
try {
Connection connection =
getConnection(addresses[i], protocol, ticket, call);
connection.sendParam(call); // send each parameter
} catch (IOException e) {
// log errors
LOG.info("Calling "+addresses[i]+" caught: " +
e.getMessage(),e);
results.size--; // wait for one fewer result
}
}
while (results.count != results.size) {
try {
results.wait(); // wait for all results
} catch (InterruptedException e) {}
}
return results.values;
}
}
/** 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. */
private Connection getConnection(InetSocketAddress addr,
Class<?> protocol,
UserGroupInformation ticket,
Call call)
throws IOException {
if (!running.get()) {
// the client is stopped
throw new IOException("The client is stopped");
}
Connection connection;
/* we could avoid this allocation for each RPC by having a
* connectionsId object and with set() method. We need to manage the
* refs for keys in HashMap properly. For now its ok.
*/
ConnectionId remoteId = new ConnectionId(addr, protocol, ticket);
do {
synchronized (connections) {
connection = connections.get(remoteId);
if (connection == null) {
connection = new Connection(remoteId);
connections.put(remoteId, connection);
}
}
} while (!connection.addCall(call));
//we don't invoke the method below inside "synchronized (connections)"
//block above. The reason for that is if the server happens to be slow,
//it will take longer to establish a connection and that will slow the
//entire system down.
connection.setupIOstreams();
return connection;
}
/**
* This class holds the address and the user ticket. The client connections
* to servers are uniquely identified by <remoteAddress, protocol, ticket>
*/
private static class ConnectionId {
InetSocketAddress address;
UserGroupInformation ticket;
Class<?> protocol;
private static final int PRIME = 16777619;
ConnectionId(InetSocketAddress address, Class<?> protocol,
UserGroupInformation ticket) {
this.protocol = protocol;
this.address = address;
this.ticket = ticket;
}
InetSocketAddress getAddress() {
return address;
}
Class<?> getProtocol() {
return protocol;
}
UserGroupInformation getTicket() {
return ticket;
}
@Override
public boolean equals(Object obj) {
if (obj instanceof ConnectionId) {
ConnectionId id = (ConnectionId) obj;
return address.equals(id.address) && protocol == id.protocol &&
ticket == id.ticket;
//Note : ticket is a ref comparision.
}
return false;
}
@Override
public int hashCode() {
return (address.hashCode() + PRIME * System.identityHashCode(protocol)) ^
System.identityHashCode(ticket);
}
}
}