前言
无论是事件和消息驱动，都是解耦的有力手段之一。ZStack作为一个大型软件项目，也使用了这些方案对整个架构进行了解耦。
EventFacade
EventFacade是一个很有意思的组件，因为它几乎是自举的。这就意味着有兴趣的朋友可以copy and paste，然后稍作修改就可以在自己的项目里工作起来了。
如何使用它
在ZStack的repo中，同样提供了相应的case：
代码语言：javascript复制package org.zstack.test.core.cloudbus;
/**
* Created with IntelliJ IDEA.
* User: frank
* Time: 12:38 AM
* To change this template use File | Settings | File Templates.
*/
public class TestCanonicalEvent {
CLogger logger = Utils.getLogger(TestCanonicalEvent.class);
ComponentLoader loader;
EventFacade evtf;
boolean success;
@Before
public void setUp() throws Exception {
BeanConstructor con = new BeanConstructor();
loader = con.build();
evtf = loader.getComponent(EventFacade.class);
((EventFacadeImpl) evtf).start();
}
@Test
public void test() throws InterruptedException {
String path = "/test/event";
evtf.on(path, new EventRunnable() {
@Override
public void run() {
success = true;
}
});
evtf.fire(path, null);
TimeUnit.SECONDS.sleep(1);
Assert.assertTrue(success);
}
}使用方法非常简单，先注册一个路径用于接收事件，然后沿着该路径发送一个事件，该事件注册的函数则会被调用。
接口定义
代码语言：javascript复制package org.zstack.core.cloudbus;
import java.util.Map;
/**
* Created with IntelliJ IDEA.
* User: frank
* Time: 11:29 PM
* To change this template use File | Settings | File Templates.
*/
public interface EventFacade {
void on(String path, AutoOffEventCallback cb);
void on(String path, EventCallback cb);
void on(String path, EventRunnable runnable);
void off(AbstractEventFacadeCallback cb);
void onLocal(String path, AutoOffEventCallback cb);
void onLocal(String path, EventCallback cb);
void onLocal(String path, EventRunnable runnable);
void fire(String path, Object data);
boolean isFromThisManagementNode(Map tokens);
String META_DATA_MANAGEMENT_NODE_ID = "metadata::managementNodeId";
String META_DATA_PATH = "metadata::path";
String WEBHOOK_TYPE = "CanonicalEvent";
}源码解读
on
代码语言：javascript复制 @Override
public void on(String path, AutoOffEventCallback cb) {
global.put(cb.uniqueIdentity, new CallbackWrapper(path, cb));
}
@Override
public void on(String path, final EventCallback cb) {
global.put(cb.uniqueIdentity, new CallbackWrapper(path, cb));
}
@Override
public void on(String path, EventRunnable cb) {
global.put(cb.uniqueIdentity, new CallbackWrapper(path, cb));
}on方法仅仅是将一个属于EventRunnable 的uuid作为key，并将Callback作为value放入global这个map中。**为什么要这么做呢？**因为在Map的key是不可重复的，存path肯定是不妥的。
EventFacadeImpl的方法签名以及成员变量：
代码语言：javascript复制public class EventFacadeImpl implements EventFacade, CloudBusEventListener, Component, GlobalApiMessageInterceptor {
@Autowired
private CloudBus bus;
private final Map<String, CallbackWrapper> global = Collections.synchronizedMap(new HashMap<>());
private final Map<String, CallbackWrapper> local = new ConcurrentHashMap<>();
private EventSubscriberReceipt unsubscriber;fire
相对的fire方法：
@Override
public void fire(String path, Object data) {
assert path != null;
CanonicalEvent evt = new CanonicalEvent();
evt.setPath(path);
evt.setManagementNodeId(Platform.getManagementServerId());
if (data != null) {
/*
if (!TypeUtils.isPrimitiveOrWrapper(data.getClass()) && !data.getClass().isAnnotationPresent(NeedJsonSchema.class)) {
throw new CloudRuntimeException(String.format("data[%s] passed to canonical event is not annotated by @NeedJsonSchema", data.getClass().getName()));
}
*/
evt.setContent(data);
}
//从local这个map中找到对应的event并调用
fireLocal(evt);
//将事件发送给对应的webhook
callWebhooks(evt);
//通过cloudBus发送事件，关于cloudBus的源码之后会讲到
bus.publish(evt);
}onLocal和on的区别
在上面的分析中并没有看到global的event是如何被触发的，如果想完全了解其中的过程，还得从CloudBus说起，我们稍后就会提到它。但是已经可以猜到为何要区分on和onLocal了。一个是通过消息总线触发，一个是在当前JVM进程内触发——这意味着一个支持ManagerNode集群事件，一个只支持单个MN事件。这也是来自于ZStack的业务场景——有些事情需要MN一起做，有些事情一个MN做了其他MN就不用做了。介于篇幅，有兴趣的读者可以自行翻看代码，这里不再详举。
WebHook
WebHook是ZStack向前端主动通信的手段之一。在注册了相应EventPath后，该path被调用后则会向相应的URL发送content。从case——CanonicalEventWebhookCase和WebhookCase可以看到它的正确使用姿势。
CanonicalEventWebhookCase
代码语言：javascript复制class CanonicalEventWebhookCase extends SubCase {
EnvSpec envSpec
@Override
void clean() {
envSpec.delete()
}
@Override
void setup() {
INCLUDE_CORE_SERVICES = false
spring {
include("webhook.xml")
}
}
String WEBHOOK_PATH = "/canonical-event-webhook"
void testErrorToCreateWebhookifOpaqueFieldMissing() {
expect(AssertionError.class) {
createWebhook {
name = "webhook1"
url = "http://127.0.0.1:8989$WEBHOOK_PATH"
type = EventFacade.WEBHOOK_TYPE
}
}
}
void testCanonicalEventWithVariableInPath() {
String path = "/test/{uuid}/event"
int count = 0
WebhookInventory hook1 = createWebhook {
name = "webhook1"
url = "http://127.0.0.1:8989$WEBHOOK_PATH"
type = EventFacade.WEBHOOK_TYPE
opaque = path
}
// this webhook will not be called because path unmatching
WebhookInventory hook2 = createWebhook {
name = "webhook1"
url = "http://127.0.0.1:8989$WEBHOOK_PATH"
type = EventFacade.WEBHOOK_TYPE
opaque = "/this-path-does-not-match"
}
CanonicalEvent evt
envSpec.simulator(WEBHOOK_PATH) { HttpEntity<String> e ->
evt = json(e.getBody(), CanonicalEvent.class)
count
return [:]
}
String content = "hello world"
String eventPath = "/test/${Platform.uuid}/event"
bean(EventFacade.class).fire(eventPath, content)
retryInSecs {
assert count == 1
assert evt != null
assert evt.path == eventPath
assert evt.content == content
assert evt.managementNodeId == Platform.getManagementServerId()
}
}
void testCanonicalEventUseWebhook() {
String path = "/test/event"
WebhookInventory hook1 = createWebhook {
name = "webhook1"
url = "http://127.0.0.1:8989$WEBHOOK_PATH"
type = EventFacade.WEBHOOK_TYPE
opaque = path
}
WebhookInventory hook2 = createWebhook {
name = "webhook2"
url = "http://127.0.0.1:8989$WEBHOOK_PATH"
type = EventFacade.WEBHOOK_TYPE
opaque = path
}
def testFireTwoEvents = {
List<CanonicalEvent> evts = []
envSpec.simulator(WEBHOOK_PATH) { HttpEntity<String> e ->
CanonicalEvent evt = json(e.getBody(), CanonicalEvent.class)
evts.add(evt)
return [:]
}
String content = "hello world"
bean(EventFacade.class).fire(path, content)
retryInSecs {
assert evts.size() == 2
CanonicalEvent evt1 = evts[0]
CanonicalEvent evt2 = evts[1]
assert evt1.path == path
assert evt1.content == content
assert evt1.managementNodeId == Platform.getManagementServerId()
assert evt2.path == path
assert evt2.content == content
assert evt2.managementNodeId == Platform.getManagementServerId()
}
}
def testOneEventsGetAfterDeleteOneHook = {
deleteWebhook { uuid = hook1.uuid }
List<CanonicalEvent> evts = []
envSpec.simulator(WEBHOOK_PATH) { HttpEntity<String> e ->
CanonicalEvent evt = json(e.getBody(), CanonicalEvent.class)
evts.add(evt)
return [:]
}
String content = "hello world"
bean(EventFacade.class).fire(path, content)
retryInSecs {
assert evts.size() == 1
}
}
def testNoEventGetAfterDeleteAllHooks = {
deleteWebhook { uuid = hook2.uuid }
List<CanonicalEvent> evts = []
envSpec.simulator(WEBHOOK_PATH) { HttpEntity<String> e ->
CanonicalEvent evt = json(e.getBody(), CanonicalEvent.class)
evts.add(evt)
return [:]
}
String content = "hello world"
bean(EventFacade.class).fire(path, content)
retryInSecs {
assert evts.size() == 0
}
}
testFireTwoEvents()
testOneEventsGetAfterDeleteOneHook()
testNoEventGetAfterDeleteAllHooks()
}
@Override
void environment() {
envSpec = env {
// nothing
}
}
@Override
void test() {
envSpec.create {
testCanonicalEventUseWebhook()
testCanonicalEventWithVariableInPath()
testErrorToCreateWebhookifOpaqueFieldMissing()
}
}
}WebhookCase
代码语言：javascript复制class WebhookCase extends SubCase {
EnvSpec envSpec
@Override
void clean() {
envSpec.delete()
}
@Override
void setup() {
INCLUDE_CORE_SERVICES = false
spring {
include("webhook.xml")
}
}
@Override
void environment() {
envSpec = env {
// nothing
}
}
void testWebhooksCRUD() {
WebhookInventory hook = null
def testCreateWebhook = {
def params = null
hook = createWebhook {
name = "webhook"
type = "custom-type"
url = "http://127.0.0.1:8080/webhook"
description = "desc"
opaque = "test data"
params = delegate
}
assert dbIsExists(hook.uuid, WebhookVO.class)
assert hook.name == params.name
assert hook.type == params.type
assert hook.url == params.url
assert hook.description == params.description
assert hook.opaque == params.opaque
}
def testQueryWebhook = {
List<WebhookInventory> invs = queryWebhook {
conditions = ["name=${hook.name}"]
}
assert invs.size() == 1
assert invs[0].uuid == hook.uuid
}
def testDeleteWebhook = {
deleteWebhook {
uuid = hook.uuid
}
assert !dbIsExists(hook.uuid, WebhookVO.class)
}
testCreateWebhook()
testQueryWebhook()
testDeleteWebhook()
}
void testInvalidUrl() {
expect(AssertionError.class) {
createWebhook {
name = "webhook"
type = "custom-type"
url = "this is not a url"
description = "desc"
opaque = "test data"
}
}
}
@Override
void test() {
envSpec.create {
testWebhooksCRUD()
testInvalidUrl()
}
}
}CloudBus
CloudBus可以说是ZStack中最重要的组件了，ZStack各个模块的通信全部是由Message来完成的，而CloudBus就是它们的通信媒介，接下来我们来看它的源码。
本节适合对AMQP有一定了解同学，如果不了解可以先看我的博客MQ学习小记
如何使用它
先看一个相关的Case：
代码语言：javascript复制package org.zstack.test.core.cloudbus;
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
import org.zstack.core.cloudbus.CloudBusIN;
import org.zstack.core.componentloader.ComponentLoader;
import org.zstack.header.AbstractService;
import org.zstack.header.Service;
import org.zstack.header.message.Message;
import org.zstack.header.message.MessageReply;
import org.zstack.header.message.NeedReplyMessage;
import org.zstack.test.BeanConstructor;
import org.zstack.utils.Utils;
import org.zstack.utils.logging.CLogger;
import java.util.concurrent.TimeUnit;
public class TestCloudBusCall {
CLogger logger = Utils.getLogger(TestCloudBusCall.class);
ComponentLoader loader;
CloudBusIN bus;
Service serv;
public static class HelloWorldMsg extends NeedReplyMessage {
private String greet;
public String getGreet() {
return greet;
}
public void setGreet(String greet) {
this.greet = greet;
}
}
public static class HelloWorldReply extends MessageReply {
private String greet;
public String getGreet() {
return greet;
}
public void setGreet(String greet) {
this.greet = greet;
}
}
class FakeService extends AbstractService {
@Override
public boolean start() {
bus.registerService(this);
bus.activeService(this);
return true;
}
@Override
public boolean stop() {
bus.deActiveService(this);
bus.unregisterService(this);
return true;
}
@Override
public void handleMessage(Message msg) {
if (msg.getClass() == HelloWorldMsg.class) {
HelloWorldMsg hmsg = (HelloWorldMsg) msg;
HelloWorldReply r = new HelloWorldReply();
r.setGreet(hmsg.getGreet());
bus.reply(msg, r);
}
}
@Override
public String getId() {
return this.getClass().getCanonicalName();
}
}
@Before
public void setUp() throws Exception {
BeanConstructor con = new BeanConstructor();
loader = con.build();
bus = loader.getComponent(CloudBusIN.class);
serv = new FakeService();
serv.start();
}
@Test
public void test() throws InterruptedException, ClassNotFoundException {
HelloWorldMsg msg = new HelloWorldMsg();
msg.setGreet("Hello");
msg.setServiceId(FakeService.class.getCanonicalName());
msg.setTimeout(TimeUnit.SECONDS.toMillis(10));
HelloWorldReply r = (HelloWorldReply) bus.call(msg);
serv.stop();
Assert.assertEquals("Hello", r.getGreet());
}
}
我们注册了一个Service，并覆写HandleMessage方法，在Case中，我们成功收到了消息并通过了断言。
再看一个：
~~~java
package org.zstack.test.core.cloudbus;
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
import org.zstack.core.cloudbus.CloudBusCallBack;
import org.zstack.core.cloudbus.CloudBusIN;
import org.zstack.core.componentloader.ComponentLoader;
import org.zstack.header.AbstractService;
import org.zstack.header.Service;
import org.zstack.header.message.Message;
import org.zstack.header.message.MessageReply;
import org.zstack.header.message.NeedReplyMessage;
import org.zstack.test.BeanConstructor;
import org.zstack.utils.Utils;
import org.zstack.utils.logging.CLogger;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
public class TestCloudBusSendCallback {
CLogger logger = Utils.getLogger(TestCloudBusSendCallback.class);
ComponentLoader loader;
CloudBusIN bus;
CountDownLatch latch = new CountDownLatch(1);
boolean isSuccess = false;
Service serv;
public static class HelloWorldMsg extends NeedReplyMessage {
private String greet;
public String getGreet() {
return greet;
}
public void setGreet(String greet) {
this.greet = greet;
}
}
public static class HelloWorldReply extends MessageReply {
private String greet;
public String getGreet() {
return greet;
}
public void setGreet(String greet) {
this.greet = greet;
}
}
class FakeService extends AbstractService {
@Override
public boolean start() {
bus.registerService(this);
bus.activeService(this);
return true;
}
@Override
public boolean stop() {
bus.deActiveService(this);
bus.unregisterService(this);
return true;
}
@Override
public void handleMessage(Message msg) {
if (msg.getClass() == HelloWorldMsg.class) {
HelloWorldMsg hmsg = (HelloWorldMsg) msg;
HelloWorldReply r = new HelloWorldReply();
r.setGreet(hmsg.getGreet());
bus.reply(msg, r);
}
}
@Override
public String getId() {
return this.getClass().getCanonicalName();
}
}
@Before
public void setUp() throws Exception {
BeanConstructor con = new BeanConstructor();
loader = con.build();
bus = loader.getComponent(CloudBusIN.class);
serv = new FakeService();
serv.start();
}
@Test
public void test() throws InterruptedException, ClassNotFoundException {
HelloWorldMsg msg = new HelloWorldMsg();
msg.setGreet("Hello");
msg.setServiceId(FakeService.class.getCanonicalName());
msg.setTimeout(TimeUnit.SECONDS.toMillis(10));
bus.send(msg, new CloudBusCallBack(null) {
@Override
public void run(MessageReply reply) {
if (reply instanceof HelloWorldReply) {
HelloWorldReply hr = (HelloWorldReply) reply;
if ("Hello".equals(hr.getGreet())) {
isSuccess = true;
}
}
latch.countDown();
}
});
latch.await(15, TimeUnit.SECONDS);
serv.stop();
Assert.assertEquals(true, isSuccess);
}
}同样也是注册了一个Service，然后使用了CallBack，如果运行一下发现断言是可以通过的——意味着CallBack有被调用。
综上，使用CloudBus很简单——只需要注册你的Service，使用CloudBus指定Service发送，Service就能收到，如果你需要注册你的CallBack，也能很简单完成。
代码语言：javascript复制## 接口定义
这么好用的东西，内部实现恐怕不会太简单。我们先从[接口](https://github.com/zstackio/zstack/blob/d6f511e6c15a2fab3e57a93637ada63cc4b3ee6c/core/src/main/java/org/zstack/core/cloudbus/CloudBus.java)开始看：
~~~java
package org.zstack.core.cloudbus;
import org.zstack.header.Component;
import org.zstack.header.Service;
import org.zstack.header.errorcode.ErrorCode;
import org.zstack.header.exception.CloudConfigureFailException;
import org.zstack.header.message.*;
import java.util.List;
public interface CloudBus extends Component {
void send(Message msg);
<T extends Message> void send(List<T> msgs);
void send(NeedReplyMessage msg, CloudBusCallBack callback);
@Deprecated
void send(List<? extends NeedReplyMessage> msgs, CloudBusListCallBack callBack);
@Deprecated
void send(List<? extends NeedReplyMessage> msgs, int parallelLevel, CloudBusListCallBack callBack);
@Deprecated
void send(List<? extends NeedReplyMessage> msgs, int parallelLevel, CloudBusSteppingCallback callback);
void route(List<Message> msgs);
void route(Message msg);
void reply(Message request, MessageReply reply);
void publish(List<Event> events);
void publish(Event event);
MessageReply call(NeedReplyMessage msg);
<T extends NeedReplyMessage> List<MessageReply> call(List<T> msg);
void registerService(Service serv) throws CloudConfigureFailException;
void unregisterService(Service serv);
EventSubscriberReceipt subscribeEvent(CloudBusEventListener listener, Event...events);
void dealWithUnknownMessage(Message msg);
void replyErrorByMessageType(Message msg, Exception e);
void replyErrorByMessageType(Message msg, String err);
void replyErrorByMessageType(Message msg, ErrorCode err);
void logExceptionWithMessageDump(Message msg, Throwable e);
String makeLocalServiceId(String serviceId);
void makeLocalServiceId(Message msg, String serviceId);
String makeServiceIdByManagementNodeId(String serviceId, String managementNodeId);
void makeServiceIdByManagementNodeId(Message msg, String serviceId, String managementNodeId);
String makeTargetServiceIdByResourceUuid(String serviceId, String resourceUuid);
void makeTargetServiceIdByResourceUuid(Message msg, String serviceId, String resourceUuid);
void installBeforeDeliveryMessageInterceptor(BeforeDeliveryMessageInterceptor interceptor, Class<? extends Message>...classes);
void installBeforeSendMessageInterceptor(BeforeSendMessageInterceptor interceptor, Class<? extends Message>...classes);
void installBeforePublishEventInterceptor(BeforePublishEventInterceptor interceptor, Class<? extends Event>...classes);
}接口的命名语义较为清晰，在这里不多做解释。开始我们的源码阅读之旅。
源码解读
CloudBus在ZStack Starting的时候做了什么？
init
init是在bean处于加载器，Spring提供的一个钩子。在xml中我们可以看到声明：
代码语言：javascript复制<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:zstack="http://zstack.org/schema/zstack"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://zstack.org/schema/zstack
http://zstack.org/schema/zstack/plugin.xsd"
default-init-method="init" default-destroy-method="destroy">
<bean id="TimeoutManager" class="org.zstack.core.timeout.ApiTimeoutManagerImpl" />
<bean id="CloudBus" class = "org.zstack.core.cloudbus.CloudBusImpl2" depends-on="ThreadFacade,ThreadAspectj">
<zstack:plugin>
<zstack:extension interface="org.zstack.header.managementnode.ManagementNodeChangeListener" order="9999"/>
</zstack:plugin>
</bean>
<bean id="EventFacade" class = "org.zstack.core.cloudbus.EventFacadeImpl">
<zstack:plugin>
<zstack:extension interface="org.zstack.header.Component" />
<zstack:extension interface="org.zstack.header.apimediator.GlobalApiMessageInterceptor" />
</zstack:plugin>
</bean>
<bean id="ResourceDestinationMaker" class="org.zstack.core.cloudbus.ResourceDestinationMakerImpl" />
<bean id="MessageIntegrityChecker" class="org.zstack.core.cloudbus.MessageIntegrityChecker">
<zstack:plugin>
<zstack:extension interface="org.zstack.header.Component" />
</zstack:plugin>
</bean>
</beans>init方法：
代码语言：javascript复制 void init() {
trackerClose = CloudBusGlobalProperty.CLOSE_TRACKER;
serverIps = CloudBusGlobalProperty.SERVER_IPS;
tracker = new MessageTracker();
ConnectionFactory connFactory = new ConnectionFactory();
List<Address> addresses = CollectionUtils.transformToList(serverIps, new Function<Address, String>() {
@Override
public Address call(String arg) {
return Address.parseAddress(arg);
}
});
connFactory.setAutomaticRecoveryEnabled(true);
connFactory.setRequestedHeartbeat(CloudBusGlobalProperty.RABBITMQ_HEART_BEAT_TIMEOUT);
connFactory.setNetworkRecoveryInterval((int) TimeUnit.SECONDS.toMillis(CloudBusGlobalProperty.RABBITMQ_NETWORK_RECOVER_INTERVAL));
connFactory.setConnectionTimeout((int) TimeUnit.SECONDS.toMillis(CloudBusGlobalProperty.RABBITMQ_CONNECTION_TIMEOUT));
logger.info(String.format("use RabbitMQ server IPs: %s", serverIps));
try {
if (CloudBusGlobalProperty.RABBITMQ_USERNAME != null) {
connFactory.setUsername(CloudBusGlobalProperty.RABBITMQ_USERNAME);
logger.info(String.format("use RabbitMQ username: %s", CloudBusGlobalProperty.RABBITMQ_USERNAME));
}
if (CloudBusGlobalProperty.RABBITMQ_PASSWORD != null) {
connFactory.setPassword(CloudBusGlobalProperty.RABBITMQ_PASSWORD);
logger.info("use RabbitMQ password: ******");
}
if (CloudBusGlobalProperty.RABBITMQ_VIRTUAL_HOST != null) {
connFactory.setVirtualHost(CloudBusGlobalProperty.RABBITMQ_VIRTUAL_HOST);
logger.info(String.format("use RabbitMQ virtual host: %s", CloudBusGlobalProperty.RABBITMQ_VIRTUAL_HOST));
}
conn = connFactory.newConnection(addresses.toArray(new Address[]{}));
logger.debug(String.format("rabbitmq connection is established on %s", conn.getAddress()));
((Recoverable)conn).addRecoveryListener(new RecoveryListener() {
@Override
public void handleRecovery(Recoverable recoverable) {
logger.info(String.format("rabbitmq connection is recovering on %s", conn.getAddress().toString()));
}
});
channelPool = new ChannelPool(CloudBusGlobalProperty.CHANNEL_POOL_SIZE, conn);
createExchanges();
outboundQueue = new BusQueue(makeMessageQueueName(SERVICE_ID), BusExchange.P2P);
Channel chan = channelPool.acquire();
chan.queueDeclare(outboundQueue.getName(), false, false, true, queueArguments());
chan.basicConsume(outboundQueue.getName(), true, consumer);
chan.queueBind(outboundQueue.getName(), outboundQueue.getBusExchange().toString(), outboundQueue.getBindingKey());
channelPool.returnChannel(chan);
maid.construct();
noRouteEndPoint.construct();
tracker.construct();
tracker.trackService(SERVICE_ID);
} catch (Exception e) {
throw new CloudRuntimeException(e);
}
}简单来说，该函数尝试获取配置文件中与RabbitMQ中相关的配置，并初始化Connection，并以此为基础创建了channel poll。然后将一个channel和一个messageQueue绑定在了一起。同时构造了EventMaid和noRouteEndPoint和tracker，后二者都是Message的消费者，看名字就可以看出来，一个用于订阅/发布模型（绑定此交换器的队列都会收到消息），一个用于track。
start
start则是ZStack定义的一个钩子，当ManagerNode起来的时候，start会被调用到。
代码语言：javascript复制 @Override
public boolean start() {
populateExtension();
prepareStatistics();
for (Service serv : services) {
assert serv.getId() != null : String.format("service id can not be null[%s]", serv.getClass().getName());
registerService(serv);
}
jmxf.registerBean("CloudBus", this);
return true;
}一个个看：
代码语言：javascript复制 private void populateExtension() {
services = pluginRgty.getExtensionList(Service.class);
for (ReplyMessagePreSendingExtensionPoint extp : pluginRgty.getExtensionList(ReplyMessagePreSendingExtensionPoint.class)) {
List<Class> clazzs = extp.getReplyMessageClassForPreSendingExtensionPoint();
if (clazzs == null || clazzs.isEmpty()) {
continue;
}
for (Class clz : clazzs) {
if (!(APIEvent.class.isAssignableFrom(clz)) && !(MessageReply.class.isAssignableFrom(clz))) {
throw new CloudRuntimeException(String.format("ReplyMessagePreSendingExtensionPoint can only marshal APIEvent or MessageReply. %s claimed by %s is neither APIEvent nor MessageReply",
clz.getName(), extp.getClass().getName()));
}
List<ReplyMessagePreSendingExtensionPoint> exts = replyMessageMarshaller.get(clz);
if (exts == null) {
exts = new ArrayList<ReplyMessagePreSendingExtensionPoint>();
replyMessageMarshaller.put(clz, exts);
}
exts.add(extp);
}
}
}首先收集了所有继承于Service的类，然后加载会改变msg reply的extensionPoint。
代码语言：javascript复制 private void prepareStatistics() {
List<Class> needReplyMsgs = BeanUtils.scanClassByType("org.zstack", NeedReplyMessage.class);
needReplyMsgs = CollectionUtils.transformToList(needReplyMsgs, new Function<Class, Class>() {
@Override
public Class call(Class arg) {
return !APIMessage.class.isAssignableFrom(arg) || APISyncCallMessage.class.isAssignableFrom(arg) ? arg : null;
}
});
for (Class clz : needReplyMsgs) {
MessageStatistic stat = new MessageStatistic();
stat.setMessageClassName(clz.getName());
statistics.put(stat.getMessageClassName(), stat);
}
}为需要回复的msg设置统计信息。
之后就是把所有的Service收集起来，方便Msg的分发。
常用方法
CloudBus.makeLocalServiceId
代码语言：javascript复制 @Override
public String makeLocalServiceId(String serviceId) {
return serviceId "." Platform.getManagementServerId();
}
@Override
public void makeLocalServiceId(Message msg, String serviceId) {
msg.setServiceId(makeLocalServiceId(serviceId));
}如ZStack的伸缩性秘密武器：无状态服务中所说一般，每个管理节点都会注册一堆服务队列。因此我们要按照其格式组装，这样消息才能被服务所接收。
CloudBus.makeTargetServiceIdByResourceUuid
代码语言：javascript复制 @Override
public String makeTargetServiceIdByResourceUuid(String serviceId, String resourceUuid) {
DebugUtils.Assert(serviceId!=null, "serviceId cannot be null");
DebugUtils.Assert(resourceUuid!=null, "resourceUuid cannot be null");
//得到资源所在的MN UUID
String mgmtUuid = destMaker.makeDestination(resourceUuid);
return serviceId "." mgmtUuid;
}
@Override
public void makeTargetServiceIdByResourceUuid(Message msg, String serviceId, String resourceUuid) {
String targetService = makeTargetServiceIdByResourceUuid(serviceId, resourceUuid);
msg.setServiceId(targetService);
}在ZStack中，ManagerNode很有可能是集群部署的，每个MN管控不同的资源。那么就需要一致性哈希环来确定资源所在哪个MN。
CloudBus.send
代码语言：javascript复制 @Override
public void send(final NeedReplyMessage msg, final CloudBusCallBack callback) {
//给msg一个超时时间
evaluateMessageTimeout(msg);
//new继承于Envelope的匿名内部类
Envelope e = new Envelope() {
//用来判断这个msg是否已经发出去了
AtomicBoolean called = new AtomicBoolean(false);
final Envelope self = this;
//计算超时，往线程池提交一个任务
TimeoutTaskReceipt timeoutTaskReceipt = thdf.submitTimeoutTask(new Runnable() {
@Override
public void run() {
self.timeout();
}
}, TimeUnit.MILLISECONDS, msg.getTimeout());
@Override
//msg 发送成功时候调用这个方法
public void ack(MessageReply reply) {
//计算该msg耗时
count(msg);
//根据msg的唯一UUID移除在这个map中的记录
envelopes.remove(msg.getId());
//如果更新失败，说明这个消息已经被发送过了。返回
if (!called.compareAndSet(false, true)) {
return;
}
//取消一个计算超时的任务
timeoutTaskReceipt.cancel();
//调用注册的callback
callback.run(reply);
}
//消息超时时调用的逻辑
@Override
public void timeout() {
// 根据msg的唯一UUID移除在这个map中的记录
envelopes.remove(msg.getId());
// 如何已经被调用过则返回
if (!called.compareAndSet(false, true)) {
return;
}
//内部构造一个超时reply返回给callback
callback.run(createTimeoutReply(msg));
}
//用于getWaitingReplyMessageStatistic
@Override
List<Message> getRequests() {
List<Message> requests = new ArrayList<Message>();
requests.add(msg);
return requests;
}
};
//往envelopes这个map里放入msg的唯一UUID和刚刚构造的envelope
envelopes.put(msg.getId(), e);
//发送消息
send(msg, false);
}私有方法：send
代码语言：javascript复制 private void send(Message msg, Boolean noNeedReply) {
//msg的serviceID不允许为空，不然不能
if (msg.getServiceId() == null) {
throw new IllegalArgumentException(String.format("service id cannot be null: %s", msg.getClass().getName()));
}
//为msg构建基本属性
basicProperty(msg);
//设置msg header属性
msg.putHeaderEntry(CORRELATION_ID, msg.getId());
//消息的回复队列设置
msg.putHeaderEntry(REPLY_TO, outboundQueue.getBindingKey());
if (msg instanceof APIMessage) {
// API always need reply
msg.putHeaderEntry(NO_NEED_REPLY_MSG, Boolean.FALSE.toString());
} else if (msg instanceof NeedReplyMessage) {
// for NeedReplyMessage sent without requiring receiver to reply,
// mark it, then it will not be tracked and replied
msg.putHeaderEntry(NO_NEED_REPLY_MSG, noNeedReply.toString());
}
buildRequestMessageMetaData(msg);
wire.send(msg);
}该函数是一段公用逻辑。所有的消息都是从这里进去然后由rabbitMQ发出去的。所以在这里需要多说几句。
代码语言：javascript复制 protected void basicProperty(Message msg) {
AMQP.BasicProperties.Builder builder = new AMQP.BasicProperties.Builder();
msg.setAMQPProperties(builder.deliveryMode(1).expiration(String.valueOf(TimeUnit.SECONDS.toMillis(CloudBusGlobalProperty.MESSAGE_TTL))).build());
}这个函数设置了msg基础属性——持久化策略（否）和超时。
那么再看buildRequestMessageMetaData方法
private void buildRequestMessageMetaData(Message msg) {
if (msg instanceof APIMessage || (msg instanceof NeedReplyMessage && !Boolean.valueOf((String)msg.getHeaderEntry(NO_NEED_REPLY_MSG)))) {
RequestMessageMetaData metaData;
if (msg instanceof LockResourceMessage) {
LockResourceMessage lmsg = (LockResourceMessage) msg;
LockMessageMetaData lmetaData = new LockMessageMetaData();
lmetaData.unlockKey = lmsg.getUnlockKey();
lmetaData.reason = lmsg.getReason();
lmetaData.senderManagementUuid = Platform.getManagementServerId();
metaData = lmetaData;
} else {
metaData = new RequestMessageMetaData();
}
metaData.needApiEvent = msg instanceof APIMessage && !(msg instanceof APISyncCallMessage);
metaData.msgId = msg.getId();
metaData.replyTo = msg.getHeaderEntry(REPLY_TO);
metaData.timeout = msg instanceof NeedReplyMessage ? ((NeedReplyMessage) msg).getTimeout() : null;
metaData.serviceId = msg.getServiceId();
metaData.messageName = msg.getClass().getName();
metaData.className = metaData.getClass().getName();
msg.getAMQPHeaders().put(MESSAGE_META_DATA, JSONObjectUtil.toJsonString(metaData));
}
}方法buildRequestMessageMetaData将消息所需的metaData从msg里取了出来并放入了msg的真正Header中。
然后是wire.send:
代码语言：javascript复制 public void send(Message msg) {
// for unit test finding invocation chain
MessageCommandRecorder.record(msg.getClass());
List<BeforeSendMessageInterceptor> interceptors = beforeSendMessageInterceptors.get(msg.getClass());
if (interceptors != null) {
for (BeforeSendMessageInterceptor interceptor : interceptors) {
interceptor.intercept(msg);
/*
if (logger.isTraceEnabled()) {
logger.trace(String.format("called %s for message[%s]", interceptor.getClass(), msg.getClass()));
}
*/
}
}
for (BeforeSendMessageInterceptor interceptor : beforeSendMessageInterceptorsForAll) {
interceptor.intercept(msg);
/*
if (logger.isTraceEnabled()) {
logger.trace(String.format("called %s for message[%s]", interceptor.getClass(), msg.getClass()));
}
*/
}
send(msg, true);
}逻辑一目了然：
- 记录它的调用链
- 调用它专属的发送前拦截器进行拦截
- 调用所有msg的发送前拦截器进行拦截
send(msg, true);:
public void send(final Message msg, boolean makeQueueName) {
/*
StopWatch watch = new StopWatch();
watch.start();
*/
String serviceId = msg.getServiceId();
if (makeQueueName) {
//获取真正的队列名
serviceId = makeMessageQueueName(serviceId);
}
// build json schema
buildSchema(msg);
//当前的thread Context中获取必要信息。每个api调用所携带的uuid就是这样传递下去的
evalThreadContextToMessage(msg);
if (logger.isTraceEnabled() && logMessage(msg)) {
logger.trace(String.format("[msg send]: %s", wire.dumpMessage(msg)));
}
//从channel poll 中取出一个channel
Channel chan = channelPool.acquire();
try {
//接下来单独解释
new RecoverableSend(chan, msg, serviceId, outboundQueue.getBusExchange()).send();
/*
watch.stop();
logger.debug(String.mediaType("sending %s cost %sms", msg.getClass().getName(), watch.getTime()));
*/
} catch (IOException e) {
throw new CloudRuntimeException(e);
} finally {
//返回给channel poll
channelPool.returnChannel(chan);
}
}单独分析 new RecoverableSend(chan, msg, serviceId, outboundQueue.getBusExchange()).send();：
private class RecoverableSend {
Channel chan;
byte[] data;
String serviceId;
Message msg;
BusExchange exchange;
RecoverableSend(Channel chan, Message msg, String serviceId, BusExchange exchange) throws IOException {
data = compressMessageIfNeeded(msg);
this.chan = chan;
this.serviceId = serviceId;
this.msg = msg;
this.exchange = exchange;
}
void send() throws IOException {
try {
chan.basicPublish(exchange.toString(), serviceId,
true, msg.getAMQPProperties(), data);
} catch (ShutdownSignalException e) {
if (!(conn instanceof AutorecoveringConnection) || serverIps.size() <= 1 || !Platform.IS_RUNNING) {
// the connection is not recoverable
throw e;
}
logger.warn(String.format("failed to send a message because %s; as the connection is recoverable,"
"we are doing recoverable send right now", e.getMessage()));
if (!recoverSend()) {
throw e;
}
}
}
private byte[] compressMessageIfNeeded(Message msg) throws IOException {
if (!CloudBusGlobalProperty.COMPRESS_NON_API_MESSAGE || msg instanceof APIEvent || msg instanceof APIMessage) {
return gson.toJson(msg, Message.class).getBytes();
}
msg.getAMQPHeaders().put(AMQP_PROPERTY_HEADER__COMPRESSED, "true");
return Compresser.deflate(gson.toJson(msg, Message.class).getBytes());
}
private boolean recoverSend() throws IOException {
int interval = conn.getHeartbeat() / 2;
interval = interval > 0 ? interval : 1;
int count = 0;
// as the connection is lost, there is no need to wait heart beat missing 8 times
// so we use reflection to fast the process
RecoveryAwareAMQConnection delegate = FieldUtils.getFieldValue("delegate", conn);
DebugUtils.Assert(delegate != null, "cannot get RecoveryAwareAMQConnection");
Field _missedHeartbeats = FieldUtils.getField("_missedHeartbeats", RecoveryAwareAMQConnection.class);
DebugUtils.Assert(_missedHeartbeats!=null, "cannot find _missedHeartbeats");
_missedHeartbeats.setAccessible(true);
try {
_missedHeartbeats.set(delegate, 100);
} catch (IllegalAccessException e) {
throw new CloudRuntimeException(e);
}
while (count < CloudBusGlobalProperty.RABBITMQ_RECOVERABLE_SEND_TIMES) {
try {
TimeUnit.SECONDS.sleep(interval);
} catch (InterruptedException e1) {
logger.warn(e1.getMessage());
}
try {
chan.basicPublish(exchange.toString(), serviceId,
true, msg.getAMQPProperties(), data);
return true;
} catch (ShutdownSignalException e) {
logger.warn(String.format("recoverable send fails %s times, will continue to retry %s times; %s",
count, CloudBusGlobalProperty.RABBITMQ_RECOVERABLE_SEND_TIMES-count, e.getMessage()));
count ;
}
}
return false;
}
}最核心的代码即是：
代码语言：javascript复制 chan.basicPublish(exchange.toString(), serviceId,
true, msg.getAMQPProperties(), data);根据交换器、绑定器的key和msg的基本属性还有已经序列化的msg在RabbitMQ中发送消息。
我们可以看一下该方法签名：
代码语言：javascript复制 /**
* Publish a message
* @see com.rabbitmq.client.AMQP.Basic.Publish
* @param exchange the exchange to publish the message to
* @param routingKey the routing key
* @param mandatory true if the 'mandatory' flag is to be set
* @param props other properties for the message - routing headers etc
* @param body the message body
* @throws java.io.IOException if an error is encountered
*/
void basicPublish(String exchange, String routingKey, boolean mandatory, BasicProperties props, byte[] body)
throws IOException;当mandatory标志位设置为true时，如果exchange根据自身类型和消息routeKey无法找到一个符合条件的queue，那么会调用basic.return方法将消息返还给生产者；当mandatory设为false时，出现上述情形broker会直接将消息扔掉。
还有一个附有immediate的方法：
代码语言：javascript复制 /**
* Publish a message
* @see com.rabbitmq.client.AMQP.Basic.Publish
* @param exchange the exchange to publish the message to
* @param routingKey the routing key
* @param mandatory true if the 'mandatory' flag is to be set
* @param immediate true if the 'immediate' flag is to be
* set. Note that the RabbitMQ server does not support this flag.
* @param props other properties for the message - routing headers etc
* @param body the message body
* @throws java.io.IOException if an error is encountered
*/
void basicPublish(String exchange, String routingKey, boolean mandatory, boolean immediate, BasicProperties props, byte[] body)
throws IOException;当immediate标志位设置为true时，如果exchange在将消息route到queue(s)时发现对应的queue上没有消费者，那么这条消息不会放入队列中。当与消息routeKey关联的所有queue(一个或多个)都没有消费者时，该消息会通过basic.return方法返还给生产者。
CloudBus.reply
代码语言：javascript复制 @Override
public void reply(Message request, MessageReply reply) {
if (Boolean.valueOf((String) request.getHeaderEntry(NO_NEED_REPLY_MSG))) {
if (logger.isTraceEnabled()) {
logger.trace(String.format("%s in message%s is set, drop reply%s", NO_NEED_REPLY_MSG,
wire.dumpMessage(request), wire.dumpMessage(reply)));
}
return;
}
AMQP.BasicProperties.Builder builder = new AMQP.BasicProperties.Builder();
reply.setAMQPProperties(builder.deliveryMode(1).build());
reply.getHeaders().put(IS_MESSAGE_REPLY, Boolean.TRUE.toString());
reply.putHeaderEntry(CORRELATION_ID, request.getId());
reply.setServiceId((String) request.getHeaderEntry(REPLY_TO));
buildResponseMessageMetaData(reply);
if (request instanceof NeedReplyMessage) {
callReplyPreSendingExtensions(reply, (NeedReplyMessage) request);
}
wire.send(reply, false);
}其他属性之前都有提到。 reply.setServiceId((String) request.getHeaderEntry(REPLY_TO));则是将reply统一经过outboundQueue这个队列，同时根据correlationId返回给原发送者。
callReplyPreSendingExtensions则会根据需求改变reply结果。之后就是wire.send，之前已经分析过了。
CloudBus.publish
代码语言：javascript复制 @Override
public void publish(Event event) {
if (event instanceof APIEvent) {
APIEvent aevt = (APIEvent) event;
DebugUtils.Assert(aevt.getApiId() != null, String.format("apiId of %s cannot be null", aevt.getClass().getName()));
}
//和前面的msgProperty一样
eventProperty(event);
//构建metaData
buildResponseMessageMetaData(event);
//前面分析过了
callReplyPreSendingExtensions(event, null);
//调用beforeEventPublishInterceptors。为了抛出异常的时候方便track，声明了这样的一个变量。
BeforePublishEventInterceptor c = null;
try {
List<BeforePublishEventInterceptor> is = beforeEventPublishInterceptors.get(event.getClass());
if (is != null) {
for (BeforePublishEventInterceptor i : is) {
c = i;
i.beforePublishEvent(event);
}
}
for (BeforePublishEventInterceptor i : beforeEventPublishInterceptorsForAll) {
c = i;
i.beforePublishEvent(event);
}
} catch (StopRoutingException e) {
if (logger.isTraceEnabled()) {
logger.trace(String.format("BeforePublishEventInterceptor[%s] stop publishing event: %s",
c == null ? "null" : c.getClass().getName(), JSONObjectUtil.toJsonString(event)));
}
return;
}
wire.publish(event);
}接下来看wire.publish方法
代码语言：javascript复制 public void publish(Event evt) {
/*
StopWatch watch = new StopWatch();
watch.start();
*/
buildSchema(evt);
evalThreadContextToMessage(evt);
if (logger.isTraceEnabled() && logMessage(evt)) {
logger.trace(String.format("[event publish]: %s", wire.dumpMessage(evt)));
}
Channel chan = channelPool.acquire();
try {
new RecoverableSend(chan, evt, evt.getType().toString(), BusExchange.BROADCAST).send();
/*
watch.stop();
logger.debug(String.mediaType("sending %s cost %sms", evt.getClass().getName(), watch.getTime()));
*/
} catch (IOException e) {
throw new CloudRuntimeException(e);
} finally {
channelPool.returnChannel(chan);
}
}大部分方法和send无异。但是在Event的类中定义了两种Type：
package org.zstack.header.message;
import org.zstack.header.rest.APINoSee;
public abstract class Event extends Message {
/**
* @ignore
*/
@APINoSee
private String avoidKey;
public String getAvoidKey() {
return avoidKey;
}
public void setAvoidKey(String avoidKey) {
this.avoidKey = avoidKey;
}
public abstract Type getType();
public abstract String getSubCategory();
public static final String BINDING_KEY_PERFIX = "key.event.";
public static enum Category {
LOCAL,
API,
}
public static class Type {
private final String _name;
public Type(Category ctg, String subCtg) {
_name = BINDING_KEY_PERFIX ctg.toString() "." subCtg;
}
@Override
public String toString() {
return _name;
}
@Override
public int hashCode() {
return _name.hashCode();
}
@Override
public boolean equals(Object t) {
if (!(t instanceof Type)) {
return false;
}
Type type = (Type) t;
return _name.equals(type.toString());
}
}
}即Local和API。从名字上很好看出来，一个用来回复APIMsg的，一个用来发布本地消息。不过要了解这里面的细节，就得看EventMaid了。
EventMaid
代码语言：javascript复制 private class EventMaid extends AbstractConsumer {
Map<String, List<EventListenerWrapper>> listeners = new ConcurrentHashMap<String, List<EventListenerWrapper>>();
Channel eventChan;
String queueName = makeEventQueueName(String.format("eventMaid.%s", Platform.getUuid()));
public void construct() {
try {
eventChan = conn.createChannel();
eventChan.queueDeclare(queueName, false, false, true, queueArguments());
eventChan.basicConsume(queueName, true, this);
} catch (IOException e) {
throw new CloudRuntimeException(e);
}
}
public void destruct() {
try {
eventChan.close();
} catch (IOException e) {
throw new CloudRuntimeException(e);
}
}
public void listen(Event evt, EventListenerWrapper l) {
String type = evt.getType().toString();
try {
synchronized (listeners) {
List<EventListenerWrapper> lst = listeners.get(type);
if (lst == null) {
lst = new CopyOnWriteArrayList<EventListenerWrapper>();
listeners.put(type, lst);
eventChan.queueBind(queueName, BusExchange.BROADCAST.toString(), type);
logger.debug(String.format("[listening event]: %s", type));
}
if (!lst.contains(l)) {
lst.add(l);
}
}
} catch (IOException e) {
throw new CloudRuntimeException(e);
}
}
public void unlisten(Event evt, EventListenerWrapper l) {
String type = evt.getType().toString();
try {
synchronized (listeners) {
List<EventListenerWrapper> lst = listeners.get(type);
if (lst == null) {
return;
}
lst.remove(l);
if (lst.isEmpty()) {
listeners.remove(type);
eventChan.queueUnbind(queueName, BusExchange.BROADCAST.toString(), type);
logger.debug(String.format("[unlistening event]: %s", type));
}
}
} catch (IOException e) {
throw new CloudRuntimeException(e);
}
}
@SyncThread(level = 10)
@MessageSafe
private void dispatch(Event evt, EventListenerWrapper l) {
setThreadLoggingContext(evt);
l.callEventListener(evt);
}
private void handle(Event evt) {
String type = evt.getType().toString();
List<EventListenerWrapper> lst = listeners.get(type);
if (lst == null) {
return;
}
if (logger.isTraceEnabled()) {
logger.trace(String.format("[event received]: %s", wire.dumpMessage(evt)));
}
for (EventListenerWrapper l : lst) {
dispatch(evt, l);
}
}
@Override
public void handleDelivery(String s, com.rabbitmq.client.Envelope envelope, AMQP.BasicProperties basicProperties, byte[] bytes) throws IOException {
Event evt = null;
try {
evt = (Event) wire.toMessage(bytes, basicProperties);
handle(evt);
} catch (final Throwable t) {
final Event fevt = evt;
throwableSafe(new Runnable() {
@Override
public void run() {
if (fevt != null) {
logger.warn(String.format("unhandled throwable when handling event[%s], dump: %s", fevt.getClass().getName(), wire.dumpMessage(fevt)), t);
} else {
logger.warn(String.format("unhandled throwable"), t);
}
}
});
}
}
}这段代码得先从handleDelivery开始看：
@Override
public void handleDelivery(String s, com.rabbitmq.client.Envelope envelope, AMQP.BasicProperties basicProperties, byte[] bytes) throws IOException {
Event evt = null;
try {
evt = (Event) wire.toMessage(bytes, basicProperties);
handle(evt);
} catch (final Throwable t) {
final Event fevt = evt;
throwableSafe(new Runnable() {
@Override
public void run() {
if (fevt != null) {
logger.warn(String.format("unhandled throwable when handling event[%s], dump: %s", fevt.getClass().getName(), wire.dumpMessage(fevt)), t);
} else {
logger.warn(String.format("unhandled throwable"), t);
}
}
});
}
}可以看到，这里是重载了Consumer接口的handleDelivery，我们看一下它的方法注释：
/**
* Called when a <code><b>basic.deliver</b></code> is received for this consumer.
* @param consumerTag the <i>consumer tag</i> associated with the consumer
* @param envelope packaging data for the message
* @param properties content header data for the message
* @param body the message body (opaque, client-specific byte array)
* @throws IOException if the consumer encounters an I/O error while processing the message
* @see Envelope
*/
void handleDelivery(String consumerTag,
Envelope envelope,
AMQP.BasicProperties properties,
byte[] body)
throws IOException;这样保证EventMaid的对象能够接收到Msg。在try代码块中，从byte转换出了Event，然后走向了handle逻辑。
代码语言：javascript复制 private void handle(Event evt) {
//前面提过，有两种Type，API和Local
String type = evt.getType().toString();
//所以只会取出两种List
List<EventListenerWrapper> lst = listeners.get(type);
if (lst == null) {
return;
}
if (logger.isTraceEnabled()) {
logger.trace(String.format("[event received]: %s", wire.dumpMessage(evt)));
}
for (EventListenerWrapper l : lst) {
//跳到下一个逻辑
dispatch(evt, l);
}
} @SyncThread(level = 10)
@MessageSafe
private void dispatch(Event evt, EventListenerWrapper l) {
setThreadLoggingContext(evt);
//跳至下一段逻辑
l.callEventListener(evt);
} @Override
public EventSubscriberReceipt subscribeEvent(final CloudBusEventListener listener, final Event... events) {
final EventListenerWrapper wrapper = new EventListenerWrapper() {
@Override
public void callEventListener(Event e) {
//走到各自的handle逻辑，如果返回true则unlisten
if (listener.handleEvent(e)) {
maid.unlisten(e, this);
}
}
};
// 一个event对应一个ListenWrapper
for (Event e : events) {
maid.listen(e, wrapper);
}
return new EventSubscriberReceipt() {
@Override
public void unsubscribe(Event e) {
maid.unlisten(e, wrapper);
}
@Override
public void unsubscribeAll() {
for (Event e : events) {
maid.unlisten(e, wrapper);
}
}
};
}再看listen:
代码语言：javascript复制 public void listen(Event evt, EventListenerWrapper l) {
String type = evt.getType().toString();
try {
synchronized (listeners) {
List<EventListenerWrapper> lst = listeners.get(type);
if (lst == null) {
lst = new CopyOnWriteArrayList<EventListenerWrapper>();
listeners.put(type, lst);
eventChan.queueBind(queueName, BusExchange.BROADCAST.toString(), type);
logger.debug(String.format("[listening event]: %s", type));
}
if (!lst.contains(l)) {
lst.add(l);
}
}
} catch (IOException e) {
throw new CloudRuntimeException(e);
}
}首先加锁了listeners这个put，并根据type取出相应的list。同时将这个list转换为CopyOnWriteArrayList，这样这个list的引用就不会泄露出去了。然后绑定一个channel作为通道。另外，如果EventListenerWrapper List中不存在提交的EventListenerWrapper，则添加进去。
相信讲了这么多，有一部分读者可能已经绕晕了。这边写一个关于EventMaid的逻辑调用小结：
- 在ZStack的每个Component启动时，会向CloudBus订阅event。
- 当CloudBus收到需要publish的event，会向所有实现
CloudBusEventListener接口的对象发送事件，由他们自己选择是否处理这些事件。
CloudBus和EventFascade就是这样协同工作的。
小结
在本文，我们一起浏览的ZStack中提供消息驱动特性组件的源码——显然，这两个组件的API非常好用，简洁明了。但在具体逻辑中有几个可以改进的点：
- handleEvent返回boolean的判断为ture则取消listen，语义上不是很好理解
- listen方法中的listeners可以用并发容器——ConcurrentHashMap代替，以增加吞吐量。
- listeners的v完全可以用Set来代替。CopyOnWriteArrayList也可以用CopyOnWriteArraySet来代替。我们在listen方法中可以看到，如果lst不包含l，则add。这说明lst是不应该重复的。
