由上一篇博客我們知道,消費者端調用服務,實際上是調用代理的invoke方法,內部是調用傳入的handler的invoke()方法。
這裏是調用了InvokerInvocationHandler的invoke()方法,我們來看下具體邏輯。
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String methodName = method.getName();
Class<?>[] parameterTypes = method.getParameterTypes();
if (method.getDeclaringClass() == Object.class) {
return method.invoke(invoker, args);
}
if ("toString".equals(methodName) && parameterTypes.length == 0) {
return invoker.toString();
}
if ("hashCode".equals(methodName) && parameterTypes.length == 0) {
return invoker.hashCode();
}
if ("equals".equals(methodName) && parameterTypes.length == 1) {
return invoker.equals(args[0]);
}
return invoker.invoke(new RpcInvocation(method, args)).recreate();
}
這裏invoker攔截了一些Object的方法,toString,hashCode,equals等方法,其他服務的方法調用invoker.invoke,傳入的參數是根據參數跟方法構造的RpcInvocation。
這裏,默認調用的是FailoverClusterInvoker的父類AbstractClusterInvoker的invoke方法
public Result invoke(final Invocation invocation) throws RpcException {
checkWhetherDestroyed();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
先通過list()方法,根據傳入的invocation(僅僅封裝了服務名稱,參數等數據)根據調用的服務信息找到相應的具體的服務調用地址集合invokers。
protected List<Invoker<T>> list(Invocation invocation) throws RpcException {
List<Invoker<T>> invokers = directory.list(invocation);
return invokers;
}
我們看list具體邏輯,在AbstractDirectory中
public List<Invoker<T>> list(Invocation invocation) throws RpcException {
if (destroyed){
throw new RpcException("Directory already destroyed .url: "+ getUrl());
}
List<Invoker<T>> invokers = doList(invocation);
List<Router> localRouters = this.routers; // local reference
if (localRouters != null && localRouters.size() > 0) {
for (Router router: localRouters){
try {
if (router.getUrl() == null || router.getUrl().getParameter(Constants.RUNTIME_KEY, true)) {
invokers = router.route(invokers, getConsumerUrl(), invocation);
}
} catch (Throwable t) {
logger.error("Failed to execute router: " + getUrl() + ", cause: " + t.getMessage(), t);
}
}
}
return invokers;
}
這裏無非從子類的doList返回的invokers跟本地的localRouters中找到符合路由的invokers,具體看下RegisterDirectory的doList() public List<Invoker<T>> doList(Invocation invocation) {
if (forbidden) {
throw new RpcException(RpcException.FORBIDDEN_EXCEPTION, "Forbid consumer " + NetUtils.getLocalHost()
+ " access service " + getInterface().getName() + " from registry " + getUrl().getAddress()
+ " use dubbo version " + Version.getVersion() + ", Please check registry access list (whitelist/blacklist).");
}
List<Invoker<T>> invokers = null;
Map<String, List<Invoker<T>>> localMethodInvokerMap = this.methodInvokerMap; // local reference
if (localMethodInvokerMap != null && localMethodInvokerMap.size() > 0) {
String methodName = RpcUtils.getMethodName(invocation);
Object[] args = RpcUtils.getArguments(invocation);
if(args != null && args.length > 0 && args[0] != null
&& (args[0] instanceof String || args[0].getClass().isEnum())) {
invokers = localMethodInvokerMap.get(methodName + "." + args[0]); // 可根據第一個參數枚舉路由
}
if(invokers == null) {
invokers = localMethodInvokerMap.get(methodName);
}
if(invokers == null) {
invokers = localMethodInvokerMap.get(Constants.ANY_VALUE);
}
if(invokers == null) {
Iterator<List<Invoker<T>>> iterator = localMethodInvokerMap.values().iterator();
if (iterator.hasNext()) {
invokers = iterator.next();
}
}
}
return invokers == null ? new ArrayList<Invoker<T>>(0) : invokers;
}
從localMethodInvokerMap中尋找相應的服務,如果localMethodInvokerMap爲空,則返回空list。
在註冊目錄RegisterDirectory中,找到相應的服務地址invokers之後,使用loadBalance來選擇負載均衡策略(默認實現是RandomLoadBalance,即隨機負載均衡)。
回到AbstractClusterInvoker的invoke方法,在得到invkoers跟loadBalance之後,調用抽象方法doInvoke,默認實現在子類FailoverClusterInvoker中。
public Result doInvoke(Invocation invocation, final List<Invoker<T>> invokers, LoadBalance loadbalance)
throws RpcException {
List<Invoker<T>> copyinvokers = invokers;
checkInvokers(copyinvokers, invocation);
int len = getUrl().getMethodParameter(invocation.getMethodName(), Constants.RETRIES_KEY, Constants.DEFAULT_RETRIES)
+ 1;
if (len <= 0) {
len = 1;
}
// retry loop.
RpcException le = null; // last exception.
List<Invoker<T>> invoked = new ArrayList<Invoker<T>>(copyinvokers.size()); // invoked invokers.
Set<String> providers = new HashSet<String>(len);
for (int i = 0; i < len; i++) {
//重試時,進行重新選擇,避免重試時invoker列表已發生變化.
//注意:如果列表發生了變化,那麼invoked判斷會失效,因爲invoker示例已經改變
if (i > 0) {
checkWhetherDestroyed();
copyinvokers = list(invocation);
//重新檢查一下
checkInvokers(copyinvokers, invocation);
}
Invoker<T> invoker = select(loadbalance, invocation, copyinvokers, invoked);
invoked.add(invoker);
RpcContext.getContext().setInvokers((List)invoked);
try {
Result result = invoker.invoke(invocation);
if (le != null && logger.isWarnEnabled()) {
logger.warn("Although retry the method " + invocation.getMethodName()
+ " in the service " + getInterface().getName()
+ " was successful by the provider " + invoker.getUrl().getAddress()
+ ", but there have been failed providers " + providers
+ " (" + providers.size() + "/" + copyinvokers.size()
+ ") from the registry " + directory.getUrl().getAddress()
+ " on the consumer " + NetUtils.getLocalHost()
+ " using the dubbo version " + Version.getVersion() + ". Last error is: "
+ le.getMessage(), le);
}
return result;
} catch (RpcException e) {
if (e.isBiz()) { // biz exception.
throw e;
}
le = e;
} catch (Throwable e) {
le = new RpcException(e.getMessage(), e);
} finally {
providers.add(invoker.getUrl().getAddress());
}
}
throw new RpcException(le != null ? le.getCode() : 0, "Failed to invoke the method "
+ invocation.getMethodName() + " in the service " + getInterface().getName()
+ ". Tried " + len + " times of the providers " + providers
+ " (" + providers.size() + "/" + copyinvokers.size()
+ ") from the registry " + directory.getUrl().getAddress()
+ " on the consumer " + NetUtils.getLocalHost() + " using the dubbo version "
+ Version.getVersion() + ". Last error is: "
+ (le != null ? le.getMessage() : ""), le != null && le.getCause() != null ? le.getCause() : le);
}
FailoverClusterInvoker類給出的註釋:失敗轉移,當出現失敗,重試其它服務器,通常用於讀操作,但重試會帶來更長延遲。從上文邏輯中我們可以清楚看到,先得到配置的嘗試次數len,每次調用一旦異常會繼續多次嘗試直到達到最大次數。每一次調用先通過loadBalance的負載均衡select得到一個新的invoker,再調用invoker.invoke();嘗試調用遠程服務。
這裏invoker.invoke的邏輯在AbstractInvoker中
public Result invoke(Invocation inv) throws RpcException {
if(destroyed) {
throw new RpcException("Rpc invoker for service " + this + " on consumer " + NetUtils.getLocalHost()
+ " use dubbo version " + Version.getVersion()
+ " is DESTROYED, can not be invoked any more!");
}
RpcInvocation invocation = (RpcInvocation) inv;
invocation.setInvoker(this);
if (attachment != null && attachment.size() > 0) {
invocation.addAttachmentsIfAbsent(attachment);
}
Map<String, String> context = RpcContext.getContext().getAttachments();
if (context != null) {
invocation.addAttachmentsIfAbsent(context);
}
if (getUrl().getMethodParameter(invocation.getMethodName(), Constants.ASYNC_KEY, false)){
invocation.setAttachment(Constants.ASYNC_KEY, Boolean.TRUE.toString());
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
try {
return doInvoke(invocation);
} catch (InvocationTargetException e) { // biz exception
Throwable te = e.getTargetException();
if (te == null) {
return new RpcResult(e);
} else {
if (te instanceof RpcException) {
((RpcException) te).setCode(RpcException.BIZ_EXCEPTION);
}
return new RpcResult(te);
}
} catch (RpcException e) {
if (e.isBiz()) {
return new RpcResult(e);
} else {
throw e;
}
} catch (Throwable e) {
return new RpcResult(e);
}
}
無非是一些配置的處理,核心是調用抽象方法doInvoke,實現在子類DubboInvoker中。 @Override
protected Result doInvoke(final Invocation invocation) throws Throwable {
RpcInvocation inv = (RpcInvocation) invocation;
final String methodName = RpcUtils.getMethodName(invocation);
inv.setAttachment(Constants.PATH_KEY, getUrl().getPath());
inv.setAttachment(Constants.VERSION_KEY, version);
ExchangeClient currentClient;
if (clients.length == 1) {
currentClient = clients[0];
} else {
currentClient = clients[index.getAndIncrement() % clients.length];
}
try {
boolean isAsync = RpcUtils.isAsync(getUrl(), invocation);
boolean isOneway = RpcUtils.isOneway(getUrl(), invocation);
int timeout = getUrl().getMethodParameter(methodName, Constants.TIMEOUT_KEY,Constants.DEFAULT_TIMEOUT);
if (isOneway) {
boolean isSent = getUrl().getMethodParameter(methodName, Constants.SENT_KEY, false);
currentClient.send(inv, isSent);
RpcContext.getContext().setFuture(null);
return new RpcResult();
} else if (isAsync) {
ResponseFuture future = currentClient.request(inv, timeout) ;
RpcContext.getContext().setFuture(new FutureAdapter<Object>(future));
return new RpcResult();
} else {
RpcContext.getContext().setFuture(null);
return (Result) currentClient.request(inv, timeout).get();
}
} catch (TimeoutException e) {
throw new RpcException(RpcException.TIMEOUT_EXCEPTION, "Invoke remote method timeout. method: "
+ invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
} catch (RemotingException e) {
throw new RpcException(RpcException.NETWORK_EXCEPTION, "Failed to invoke remote method: "
+ invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
}
}
先得到下一個相應的exchangeClient來準備發送消息,然後根據同步異步oneway來選擇接下來的操作:
如果是同步調用,則直接通過exchangeClient的request()發送消息,並返回一個future,調用future的get()方法阻塞直到數據返回或者超時。
如果是異步調用,則直接通過exchangeClient的request()發送消息,並將返回的future設置到context,以備數據返回後通知,實現異步調用。
如果是oneway,則發送消息後,直接返回。
最後可以來看下DefaultFuture的get邏輯
public Object get(int timeout) throws RemotingException {
if (timeout <= 0) {
timeout = Constants.DEFAULT_TIMEOUT;
}
if (! isDone()) {
long start = System.currentTimeMillis();
lock.lock();
try {
while (! isDone()) {
done.await(timeout, TimeUnit.MILLISECONDS);
if (isDone() || System.currentTimeMillis() - start > timeout) {
break;
}
}
} catch (InterruptedException e) {
throw new RuntimeException(e);
} finally {
lock.unlock();
}
if (! isDone()) {
throw new TimeoutException(sent > 0, channel, getTimeoutMessage(false));
}
}
return returnFromResponse();
}
private Object returnFromResponse() throws RemotingException {
Response res = response;
if (res == null) {
throw new IllegalStateException("response cannot be null");
}
if (res.getStatus() == Response.OK) {
return res.getResult();
}
if (res.getStatus() == Response.CLIENT_TIMEOUT || res.getStatus() == Response.SERVER_TIMEOUT) {
throw new TimeoutException(res.getStatus() == Response.SERVER_TIMEOUT, channel, res.getErrorMessage());
}
throw new RemotingException(channel, res.getErrorMessage());
}
無非阻塞timeout的時間,或者等待數據到來阻塞的喚醒,最後狀態ok時返回response.getResult();
回到InvokerInvocationHandler的invoke中,得到Result後,調用其recreate()方法。以下是註釋給的代碼。
* if (hasException()) {
* throw getException();
* } else {
* return getValue();
* }
分析到此,代理調用算是結束了。
小結
消費者端調用所需的服務,實際上是調用了消費者代理的invoke()方法,內部調用了invokerhandler的invoke()方法,通過傳入的invocation在註冊目錄下找到相應的服務地址集合,通過負載均衡,調用其中一個服務地址,通過exchangeClient發送消息,進行遠程調用,並得到response的服務調用結果。
大致思路如此,具體細節在文中也都有體現。