3、若干个Reader线程，读取连接请求的数据，整个运行过程中加锁，锁为Reader.this
public void run() {
synchronized(this) {
while(running){
readSelector.select();
while(adding){
this.wait(1000);
}
Iterator＜SelectionKey＞iter = readSelector.selectedKeys().iterator();
while(iter.hasNext()){
SelectionKey key = iter.next();
iter.remove();
if(key.isValid() && key.isReadable()) {
doRead(key);
}
}
}
}
}
在readSelector被唤醒后，若adding为true，即Listener线程正在正在注册READ事件，则先wait()一会，adding为false后，被Listener线程notify()，获得锁Reader.this，得以继续往下运行。
void doRead(SelectionKey key) {
Connection c =(Connection)key.attachment();
count = c.readAndProcess();
}
public int readAndProcess(){
while(true){
int count =channelRead(channel,data);
processOneRpc(data.array());
}
}
private void processOneRpc(byte[] buf) {
if(headerRead){
processData(buf);
}
}
private void processData(byte[] buf) {
DataInputStream dis =
new DataInputStream(new ByteArrayInputStream(buf));
intid =dis.readInt();
Writable param =ReflectionUtils.newInstance(paramClass,conf);
param.readFields(dis);
Call call =new Call(id, param,this);
callQueue.put(call); //queue the call; maybe blocked here
incRpcCount(); // Increment therpc count
}
Reader线程读取完连接的数据之后，将其封装成一个Call对象，放入容器callQueue(一个阻塞队列LinkedBlockingQueue)。
4、若干个Handler线程，处理连接Call，在处理结果时候加锁， 锁为responseQueue (一个普通LinkedList)
public void run() {
while(running){
final Call call =callQueue.take();
Writable value =call(call.connection.protocol,call.param,
call.timestamp);
synchronized(call.connection.responseQueue){
setupResponse(buf, call,
(error==null)? Status.SUCCESS:Status.ERROR,
value, errorClass, error);
responder.doRespond(call);
}
}
}
void doRespond(Call call) {
synchronized(call.connection.responseQueue){
call.connection.responseQueue.addLast(call);
if(call.connection.responseQueue.size()== 1) {
processResponse(call.connection.responseQueue,true);
}
}
}
private boolean processResponse(LinkedList＜Call＞ responseQueue,
boolean inHandler) {
synchronized(responseQueue) {
Call call = responseQueue.removeFirst();
SocketChannel channel = call.connection.channel;
channelWrite(channel, call.response);
if(call.response.hasRemaining()){
call.connection.responseQueue.addFirst(call);
if(inHandler) {
incPending();
writeSelector.wakeup();
channel.register(writeSelector,SelectionKey.OP_WRITE,call);
decPending();
}
}
}
}
}
private synchronized void incPending(){ // call waitingto be enqueued.
pending++;
}
private synchronized void decPending() { // call doneenqueueing.
pending--;
notify();
}
当responseQueue只有一个元素时，Handler线程自己处理结果，若大于1，则让唤醒Response线程的writeSelector，为writeSelector注册OP_WRITE事件。
5、1个Responder线程，处理结果responseQueue，并且清理超时的Response.锁为responseQueue(一个普通LinkedList)
public void run() {
while(running){
waitPending(); // Ifa channel is being registered, wait.
writeSelector.select(PURGE_INTERVAL);
Iterator＜SelectionKey＞iter = writeSelector.selectedKeys().iterator();
while(iter.hasNext()){
SelectionKey key = iter.next();
iter.remove();
if(key.isValid() &&key.isWritable()) {
doAsyncWrite(key);
}
}
......................
long now =System.currentTimeMillis();
if(now＜lastPurgeTime +PURGE_INTERVAL){
continue;
}
lastPurgeTime = now;
ArrayList＜Call＞calls;
//get the list of channels from list of keys.
synchronized(writeSelector.keys()){
calls =new ArrayList＜Call＞(writeSelector.keys().size());
iter =writeSelector.keys().iterator();
while(iter.hasNext()){
SelectionKey key = iter.next();
Call call = (Call)key.attachment();
if(call !=null && key.channel() ==call.connection.channel){
calls.add(call);
}
}
}
for(Call call : calls) {
doPurge(call, now);
}
}
}
private synchronized void waitPending(){
while(pending＞0){
wait();
}
}
private void doAsyncWrite(SelectionKeykey) throws IOException{
Call call = (Call)key.attachment();
synchronized(call.connection.responseQueue){
if(processResponse(call.connection.responseQueue,false)){
key.interestOps(0);
}
}
}
private boolean processResponse(LinkedList＜Call＞responseQueue,
boolean inHandler) {
synchronized(responseQueue) {
Call call = responseQueue.removeFirst();
SocketChannel channel = call.connection.channel;
channelWrite(channel, call.response);
if(call.response.hasRemaining()){
call.connection.responseQueue.addFirst(call);
if(inHandler) {
incPending();
writeSelector.wakeup();
channel.register(writeSelector, SelectionKey.OP_WRITE, call);
decPending();
}
}
}
}
}
private void doPurge(Call call, long now) {
LinkedList＜Call＞responseQueue = call.connection.responseQueue;
synchronized(responseQueue){
Iterator＜Call＞iter =responseQueue.listIterator(0);
while(iter.hasNext()){
call = iter.next();
if(now＞call.timestamp+PURGE_INTERVAL){
closeConnection(call.connection);
break;
}
}
}
}
总结：Listener 通过 ReadSelector注册OP_READ 唤醒Reader， Reader 通过将Call加入阻塞队列callQueue 唤醒Handler， Handler检查responseQueue通过WriterSelector注册OP_WRITE唤醒Responser
二、客户端线程
1、主线程main，锁为请求的封装对象call
public Writable call(Writable param, ConnectionId remoteId) {
Call call =new Call(param);
Connection connection =getConnection(remoteId,call);
connection.sendParam(call); //send the parameter
boolean interrupted = false;
synchronized(call){
while(!call.done){
call.wait(); //wait for the result
}
return call.value;
}
}
private Connection getConnection(ConnectionIdremoteId,
Call call) {
Connection connection;
do{
synchronized(connections){
connection =connections.get(remoteId);
if(connection ==null){
connection =new Connection(remoteId);
connections.put(remoteId,connection);
}
}
} while(!connection.addCall(call));
connection.setupIOstreams();
return connection;
}
以下方法的锁为Connection.this，notify()唤醒一个线程来获取释放的锁Connection.this
private synchronized boolean addCall(Call call) {
if(shouldCloseConnection.get())
return false;
calls.put(call.id,call);
notify();
return true;
}
2.Connection线程，锁为Connection.this
public void run(){
while(waitForWork()) {
receiveResponse();
}
close();
}
private synchronized boolean waitForWork() {
if(calls.isEmpty()&& !shouldCloseConnection.get()&&running.get()) {
long timeout =maxIdleTime-
(System.currentTimeMillis()-lastActivity.get());
if(timeout＞0) {
wait(timeout);
}
}
if(!calls.isEmpty()&& !shouldCloseConnection.get()&&running.get()){
return true;
}else if(shouldCloseConnection.get()){
return false;
}else if(calls.isEmpty()){// idleconnection closed or stopped
markClosed(null);
return false;
}else{// get stoppedbut there are still pending requests
markClosed((IOException)new IOException().initCause(
new InterruptedException()));
return false;
}
}
可见calls不为空，则不再继续wait()。
private void receiveResponse(){
if(shouldCloseConnection.get()){
return;
}
touch();
int id =in.readInt();
Call call =calls.get(id);
int state =in.readInt();
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){
}else if(state ==Status.FATAL.state){
}
}
readInt() 最后会调用 PingInputStream.read()，这是一个阻塞方法，当输入流读不到数据时，会一直阻塞直到超时。
public int read(byte[] buf, int off, int len) {
do{
try{
return super.read(buf, off, len);
}catch(SocketTimeoutException e) {
handleTimeout(e);
}
}while(true);
}
}
以下两个方法的锁为Call.this
public synchronized void setValue(Writable value) {
this.value= value;
callComplete();
}
protected synchronized void callComplete(){
this.done=true;
notify(); //notify caller
}
可见Connection线程在调用方法call.setValue时，会将call.done设置为true，并唤醒主线程在获得锁Call.this，从而使得主线程可以进一步运行下去。
总结：Main通过将Call加入calls，唤醒Connection，Connection通过读取Call的结果，再唤醒Main
