开篇
这篇博文的主要目的是为了理清楚Tomcat监听的初始化流程，所谓的监听初始化流程是指Tomcat启动后直至Accept过程就绪能够监听连接到来为止。
只有理清楚监听的初始化后流程后才能更好的理解Tomcat处理请求的过程，所以也算是基础的一部分吧。
整篇博文的思路脉络是先讲解初始化过程中各个组件的关联（架构图+源码），然后讲解清楚初始化的过程（时序图+源码），我想应该是可以讲明白的。
文末惯例有招聘信息彩蛋。
组件关联说明
说明：
-
- Service组件（StandardService）包含Connector组件。
-
- Connector组件包含ProtocolHandler组件。
-
- ProtocolHandler组件包含AbstractEndpoint组件。
-
- Connector包含CoyoteAdapter对象，CoyoteAdapter保存至ProtocolHandler对象。
StandardService
public class StandardService extends LifecycleMBeanBase implements Service {
protected Connector connectors[] = new Connector[0];
}说明：
-
- StandardService包含Connector对象。
- StandardService包含Connector对象。
Connector
public class Connector extends LifecycleMBeanBase {
protected Service service = null;
protected int port = -1;
// 默认的protocolHandler的实现类
protected String protocolHandlerClassName =
"org.apache.coyote.http11.Http11NioProtocol";
// protocolHandler对象
protected final ProtocolHandler protocolHandler;
// CoyoteAdapter对象
protected Adapter adapter = null;说明：
- Connector对象包含ProtocolHandler对象。
ProtocolHandler
说明：
- ProtocolHandler具体实现包括ajp和http两类。
public abstract class AbstractProtocol<S> implements ProtocolHandler,
MBeanRegistration {
private final AbstractEndpoint<S> endpoint;
private Handler<S> handler;
}说明：
- ProtocolHandler的抽象实现类AbstractProtocol包含EndPoint对象。
public class Http11NioProtocol extends AbstractHttp11JsseProtocol<NioChannel> {
public Http11NioProtocol() {
super(new NioEndpoint());
}
}说明：
- Http11NioProtocol作为ProtocolHandler的实现类之一，注意EndPoint的对象的创建。
Endpoint
说明：
-
- AbstractEndpoint的实现类包括NioEndpoint、Nio2Endpoint、AprEndpoint。
public abstract class AbstractEndpoint<S> {
protected Acceptor[] acceptors;
private int port;
private InetAddress address;
}说明：
-
- AbstractEndpoint包含 Acceptor[] acceptors。
-
- AbstractEndpoint包含监听port和address。
监听初始化流程
说明：
-
- 监听的初始化过程包括三个阶段，体现在Connector创建&初始化&启动。
-
- Connector创建包括创建Connector、protocolHandler、Endpoint核心对象。
-
- Connector的初始化包括初始化Connector、protocolHandler、Endpoint核心对象。
-
- Connector的启动包括启动Connector、protocolHandler、Endpoint核心对象。
-
- TCP当中经典server端启动过程在Endpoint对象中实现，负责处理连接请求。
Connector
public class Connector extends LifecycleMBeanBase {
public Connector(String protocol) {
setProtocol(protocol);
ProtocolHandler p = null;
try {
Class<?> clazz = Class.forName(protocolHandlerClassName);
p = (ProtocolHandler) clazz.getConstructor().newInstance();
} catch (Exception e) {
} finally {
this.protocolHandler = p;
}
}
protected void initInternal() throws LifecycleException {
super.initInternal();
adapter = new CoyoteAdapter(this);
protocolHandler.setAdapter(adapter);
try {
protocolHandler.init();
} catch (Exception e) {
}
}
protected void startInternal() throws LifecycleException {
setState(LifecycleState.STARTING);
try {
protocolHandler.start();
} catch (Exception e) {
}
}
}说明：
-
- Connector包含创建、初始化、启动三个阶段。
-
- Connector的三个阶段对应protocolHnalder的创建、初始化、启动三个阶段。
protocolHandler
public abstract class AbstractProtocol<S> implements ProtocolHandler,
MBeanRegistration {
private final AbstractEndpoint<S> endpoint;
private Handler<S> handler;
public AbstractProtocol(AbstractEndpoint<S> endpoint) {
this.endpoint = endpoint;
setSoLinger(Constants.DEFAULT_CONNECTION_LINGER);
setTcpNoDelay(Constants.DEFAULT_TCP_NO_DELAY);
}
public void init() throws Exception {
if (getLog().isInfoEnabled()) {
getLog().info(sm.getString("abstractProtocolHandler.init", getName()));
}
if (oname == null) {
// Component not pre-registered so register it
oname = createObjectName();
if (oname != null) {
Registry.getRegistry(null, null).registerComponent(this, oname, null);
}
}
if (this.domain != null) {
rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName());
Registry.getRegistry(null, null).registerComponent(
getHandler().getGlobal(), rgOname, null);
}
String endpointName = getName();
endpoint.setName(endpointName.substring(1, endpointName.length()-1));
endpoint.setDomain(domain);
endpoint.init();
}
public void start() throws Exception {
endpoint.start();
asyncTimeout = new AsyncTimeout();
Thread timeoutThread = new Thread(asyncTimeout, getNameInternal() + "-AsyncTimeout");
int priority = endpoint.getThreadPriority();
if (priority < Thread.MIN_PRIORITY || priority > Thread.MAX_PRIORITY) {
priority = Thread.NORM_PRIORITY;
}
timeoutThread.setPriority(priority);
timeoutThread.setDaemon(true);
timeoutThread.start();
}
}
public class Http11NioProtocol extends AbstractHttp11JsseProtocol<NioChannel> {
public Http11NioProtocol() {
super(new NioEndpoint());
}
}说明：
-
- ProtocolHandler包含创建、初始化、启动三个阶段。
-
- ProtocolHandler的三个阶段对应Endpoint的创建、初始化、启动三个阶段。
Endpoint
public abstract class AbstractEndpoint<S> {
public void init() throws Exception {
if (bindOnInit) {
bind();
bindState = BindState.BOUND_ON_INIT;
}
if (this.domain != null) {
// Register endpoint (as ThreadPool - historical name)
oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\"");
Registry.getRegistry(null, null).registerComponent(this, oname, null);
for (SSLHostConfig sslHostConfig : findSslHostConfigs()) {
registerJmx(sslHostConfig);
}
}
}
public final void start() throws Exception {
if (bindState == BindState.UNBOUND) {
bind();
bindState = BindState.BOUND_ON_START;
}
startInternal();
}
public abstract void startInternal() throws Exception;
public abstract void bind() throws Exception;
}说明：
-
- Endpoint包含创建、初始化、启动三个阶段。
-
- AbstractEndpoint类板设计模式提供init&start方法。
-
- AbstractEndpoint类init方法实现bind操作，start方法负责启动监听。
public class NioEndpoint extends AbstractJsseEndpoint<NioChannel> {
public void bind() throws Exception {
if (!getUseInheritedChannel()) {
serverSock = ServerSocketChannel.open();
socketProperties.setProperties(serverSock.socket());
InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
serverSock.socket().bind(addr,getAcceptCount());
} else {
// Retrieve the channel provided by the OS
Channel ic = System.inheritedChannel();
if (ic instanceof ServerSocketChannel) {
serverSock = (ServerSocketChannel) ic;
}
if (serverSock == null) {
throw new IllegalArgumentException(sm.getString("endpoint.init.bind.inherited"));
}
}
serverSock.configureBlocking(true); //mimic APR behavior
// Initialize thread count defaults for acceptor, poller
if (acceptorThreadCount == 0) {
// FIXME: Doesn't seem to work that well with multiple accept threads
acceptorThreadCount = 1;
}
if (pollerThreadCount <= 0) {
//minimum one poller thread
pollerThreadCount = 1;
}
setStopLatch(new CountDownLatch(pollerThreadCount));
// Initialize SSL if needed
initialiseSsl();
selectorPool.open();
}
public void startInternal() throws Exception {
if (!running) {
running = true;
paused = false;
processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getProcessorCache());
eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getEventCache());
nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getBufferPool());
// Create worker collection
if ( getExecutor() == null ) {
createExecutor();
}
initializeConnectionLatch();
// Start poller threads
pollers = new Poller[getPollerThreadCount()];
for (int i=0; i<pollers.length; i++) {
pollers[i] = new Poller();
Thread pollerThread = new Thread(pollers[i], getName() + "-ClientPoller-"+i);
pollerThread.setPriority(threadPriority);
pollerThread.setDaemon(true);
pollerThread.start();
}
startAcceptorThreads();
}
}
protected class Acceptor extends AbstractEndpoint.Acceptor {
public void run() {
int errorDelay = 0;
while (running) {
while (paused && running) {
state = AcceptorState.PAUSED;
try {
Thread.sleep(50);
} catch (InterruptedException e) {
// Ignore
}
}
if (!running) {
break;
}
state = AcceptorState.RUNNING;
try {
countUpOrAwaitConnection();
SocketChannel socket = null;
try {
socket = serverSock.accept();
} catch (IOException ioe) {
}
errorDelay = 0;
if (running && !paused) {
if (!setSocketOptions(socket)) {
closeSocket(socket);
}
} else {
closeSocket(socket);
}
} catch (Throwable t) {
}
}
state = AcceptorState.ENDED;
}
}
protected boolean setSocketOptions(SocketChannel socket) {
try {
socket.configureBlocking(false);
Socket sock = socket.socket();
socketProperties.setProperties(sock);
NioChannel channel = nioChannels.pop();
if (channel == null) {
SocketBufferHandler bufhandler = new SocketBufferHandler(
socketProperties.getAppReadBufSize(),
socketProperties.getAppWriteBufSize(),
socketProperties.getDirectBuffer());
if (isSSLEnabled()) {
channel = new SecureNioChannel(socket, bufhandler, selectorPool, this);
} else {
channel = new NioChannel(socket, bufhandler);
}
} else {
channel.setIOChannel(socket);
channel.reset();
}
getPoller0().register(channel);
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
try {
log.error("",t);
} catch (Throwable tt) {
ExceptionUtils.handleThrowable(tt);
}
// Tell to close the socket
return false;
}
return true;
}
}说明：
-
- NioEndpoint是AbstractEndpoint的具体实现类之一。
-
- NioEndpoint实现具体的bind和start方法。
-
- NioEndpoint的Acceptor作为具体的实现负责监听连接。
-
- setSocketOptions负责处理新连接并通过getPoller0().register(channel)注册。
参考文章
谈谈 Tomcat 请求处理流程
Tomcat 请求处理流程详解
