/*
* 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.thrift.server;
import org.apache.thrift.transport.TNonblockingServerTransport;
import org.apache.thrift.transport.TNonblockingTransport;
import org.apache.thrift.transport.TTransportException;
import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.util.Iterator;
/**
* A nonblocking TServer implementation. This allows for fairness amongst all
* connected clients in terms of invocations.
*
* This server is inherently single-threaded. If you want a limited thread pool
* coupled with invocation-fairness, see THsHaServer.
*
* To use this server, you MUST use a TFramedTransport at the outermost
* transport, otherwise this server will be unable to determine when a whole
* method call has been read off the wire. Clients must also use TFramedTransport.
*/
public class TNonblockingServer extends AbstractNonblockingServer {
public static class Args extends AbstractNonblockingServerArgs<Args> {
public Args(TNonblockingServerTransport transport) {
super(transport);
}
}
// Flag for stopping the server
private volatile boolean stopped_ = true;
private SelectAcceptThread selectAcceptThread_;
public TNonblockingServer(AbstractNonblockingServerArgs args) {
super(args);
}
/**
* Start the selector thread to deal with accepts and client messages.
*
* @return true if everything went ok, false if we couldn't start for some
* reason.
*/
@Override
protected boolean startThreads() {
// start the selector
try {
selectAcceptThread_ = new SelectAcceptThread((TNonblockingServerTransport)serverTransport_);
stopped_ = false;
selectAcceptThread_.start();
return true;
} catch (IOException e) {
LOGGER.error("Failed to start selector thread!", e);
return false;
}
}
@Override
protected void waitForShutdown() {
joinSelector();
}
/**
* Block until the selector thread exits.
*/
protected void joinSelector() {
// wait until the selector thread exits
try {
selectAcceptThread_.join();
} catch (InterruptedException e) {
// for now, just silently ignore. technically this means we'll have less of
// a graceful shutdown as a result.
}
}
/**
* Stop serving and shut everything down.
*/
@Override
public void stop() {
stopped_ = true;
if (selectAcceptThread_ != null) {
selectAcceptThread_.wakeupSelector();
}
}
/**
* Perform an invocation. This method could behave several different ways
* - invoke immediately inline, queue for separate execution, etc.
*/
@Override
protected boolean requestInvoke(FrameBuffer frameBuffer) {
frameBuffer.invoke();
return true;
}
public boolean isStopped() {
return selectAcceptThread_.isStopped();
}
/**
* The thread that will be doing all the selecting, managing new connections
* and those that still need to be read.
*/
protected class SelectAcceptThread extends AbstractSelectThread {
// The server transport on which new client transports will be accepted
private final TNonblockingServerTransport serverTransport;
/**
* Set up the thread that will handle the non-blocking accepts, reads, and
* writes.
*/
public SelectAcceptThread(final TNonblockingServerTransport serverTransport)
throws IOException {
this.serverTransport = serverTransport;
serverTransport.registerSelector(selector);
}
public boolean isStopped() {
return stopped_;
}
/**
* The work loop. Handles both selecting (all IO operations) and managing
* the selection preferences of all existing connections.
*/
public void run() {
try {
while (!stopped_) {
select();
processInterestChanges();
}
for (SelectionKey selectionKey : selector.keys()) {
cleanupSelectionKey(selectionKey);
}
} catch (Throwable t) {
LOGGER.error("run() exiting due to uncaught error", t);
} finally {
stopped_ = true;
}
}
/**
* Select and process IO events appropriately:
* If there are connections to be accepted, accept them.
* If there are existing connections with data waiting to be read, read it,
* buffering until a whole frame has been read.
* If there are any pending responses, buffer them until their target client
* is available, and then send the data.
*/
private void select() {
try {
// wait for io events.
selector.select();
// process the io events we received
Iterator<SelectionKey> selectedKeys = selector.selectedKeys().iterator();
while (!stopped_ && selectedKeys.hasNext()) {
SelectionKey key = selectedKeys.next();
selectedKeys.remove();
// skip if not valid
if (!key.isValid()) {
cleanupSelectionKey(key);
continue;
}
// if the key is marked Accept, then it has to be the server
// transport.
if (key.isAcceptable()) {
handleAccept();
} else if (key.isReadable()) {
// deal with reads
handleRead(key);
} else if (key.isWritable()) {
// deal with writes
handleWrite(key);
} else {
LOGGER.warn("Unexpected state in select! " + key.interestOps());
}
}
} catch (IOException e) {
LOGGER.warn("Got an IOException while selecting!", e);
}
}
/**
* Accept a new connection.
*/
private void handleAccept() throws IOException {
SelectionKey clientKey = null;
TNonblockingTransport client = null;
try {
// accept the connection
client = (TNonblockingTransport)serverTransport.accept();
clientKey = client.registerSelector(selector, SelectionKey.OP_READ);
// add this key to the map
FrameBuffer frameBuffer = new FrameBuffer(client, clientKey,
SelectAcceptThread.this);
clientKey.attach(frameBuffer);
} catch (TTransportException tte) {
// something went wrong accepting.
LOGGER.warn("Exception trying to accept!", tte);
tte.printStackTrace();
if (clientKey != null) cleanupSelectionKey(clientKey);
if (client != null) client.close();
}
}
} // SelectAcceptThread
}