Hadoop源码分析14: IPC流程(9) SelectionKey
1.SelectionKey.OP_ACCEPT
publicclassServerListenerextendsThread{
publicServerListener(Serverserver) throwsIOException{
this.server=server;
address=newInetSocketAddress(server.bindAddress,server.port);
// Create anew server socket and set to non blocking mode
acceptChannel= ServerSocketChannel.open();
acceptChannel.configureBlocking(false);
// Bind theserver socket to the local host and port
Server.bind(acceptChannel.socket(),address, backlogLength);
server.port=acceptChannel.socket().getLocalPort();
// create aselector;
selector =Selector.open();
readers=newServerListenerReader[server.readThreads];
readPool=Executors.newFixedThreadPool(server.readThreads);
for(inti = 0;i ＜server.readThreads;i++) {
Selector readSelector = Selector.open();
ServerListenerReader reader = newServerListenerReader(
readSelector, this);
readers[i]= reader;
readPool.execute(reader);
}
acceptChannel.register(selector,SelectionKey.OP_ACCEPT);
this.setName("IPCServer listener on " +server.port);
this.setDaemon(true);
}
}
2. SelectionKey.OP_READ
public classServerListenerextends Thread{
voiddoAccept(SelectionKeykey) throwsIOException,OutOfMemoryError {
ServerConnection c = null;
ServerSocketChannel serverSocketChannel=(ServerSocketChannel)key.channel();
SocketChannel channel;
while((channel=serverSocketChannel.accept())!= null){
channel.configureBlocking(false);
channel.socket().setTcpNoDelay(this.server.tcpNoDelay);
ServerListenerReader reader = readers[(currentReader+ 1) %readers.length];
try{
reader.startAdd();
SelectionKey readKey = channel.register(reader.readSelector,SelectionKey.OP_READ);
c = newServerConnection(readKey,channel,
System.currentTimeMillis(), this.server);
readKey.attach(c);
synchronized(this.server.connectionList){
this.server.connectionList.add(this.server.numConnections,
c);
this.server.numConnections++;
}
} finally{
reader.finishAdd();
}
}
}
}
3. SelectionKey.OP_WRITE
publicclassServerResponderextendsThread{
privatebooleanprocessResponse(LinkedList＜Call＞responseQueue,
booleaninHandler)throwsIOException{
booleanerror= true;
booleandone =false;
intnumElements =0;
Call call = null;
try{
synchronized(responseQueue){
numElements = responseQueue.size();
if(numElements== 0) {
error = false;
returntrue; // no moredata for this channel.
}
call = responseQueue.removeFirst();
SocketChannelchannel = call.connection.channel;
intnumBytes =channelWrite(channel, call.response);
if(numBytes＜0){
returntrue;
}
if(!call.response.hasRemaining()){
call.connection.decRpcCount();
if(numElements== 1){ // last callfully processes.
done = true; // no moredata for this channel.
} else{
done = false; // morecalls pending to be sent.
}
} else{
call.connection.responseQueue.addFirst(call);
if(inHandler){
// set theserve time when the response has to be sent later
call.timestamp=System.currentTimeMillis();
incPending();
try{
writeSelector.wakeup();
channel.register(writeSelector, SelectionKey.OP_WRITE,call);
} catch(ClosedChannelExceptione) {
//Its ok.channel might be closed else where.
done = true;
} finally{
decPending();
}
}
}
error = false; //everything went off well
}
} finally{
if(error&& call != null){
done = true; // error. nomore data for this channel.
closeConnection(call.connection);
}
}
returndone;
}
}
