微服务框架ServiceComb源码解析之一Edge边缘服务

Edge

顾名思义，边缘，是外部流量的入口，因此在edge可以做一些通用流量治理和统一鉴权的事情。

ServiceComb自带的3个Edge Dispatcher，可以满足大部分需求，当然开发者也可以自定义Dispatcher,自带的Dispatcher如下：
org.apache.servicecomb.edge.core.DefaultEdgeDispatcher
org.apache.servicecomb.edge.core.URLMappedEdgeDispatcher
org.apache.servicecomb.edge.core.CommonHttpEdgeDispatcher

如何配置可以参考项目demo中的demo-edge

1.重要类的继承关系

2.consumer、producer、edge调用链，来自InvocationStageTrace类注释

以demo-edge为例
edge调用链：
EncryptEdgeDispatcher->edgeInvocation.edgeInvoke()->创建Invocation (InvocationFactory.forConsumer)->Hanlder列表:

AuthHandler
LoadbalanceHandler
TransportClientHandler

consumer调用链:
CseClientHttpRequest -> 创建Invocation (InvocationFactory.forConsumer)->Hanlder列表:
LoadbalanceHandler
TransportClientHandler

Producer调用链:
VertxRestDispatcher->VertxRestInvocation->创建Invocation (InvocationFactory.forProvider)->Handler链：
ProducerOperationHandler

运行态线程分析

edge处理过程，都是在eventloop线程进行，那么是如何实现的呢

1.以demo-edge为例，首先我们看到，有新的请求过来，进入EncryptEdgeDispatcher，此时是执行是在eventloop中

2.接着进入EncryptEdgeInvocation 的edgeInvoke方法，最终到operationMeta.getExecutor().execute()中执行，debug一看，还是在eventloop线程执行。那么operationMeta的Executor是如何设置为eventloop线程的呢？

如下是跟踪OperationMeta创建过程，

得知，OperationMeta的Executor来自:
this.executor = schemaMeta.getMicroserviceMeta().getScbEngine().getExecutorManager().findExecutor(this);

ExecutorManager找excutor，最终找到是ReactiveExecutor，这个Excutor是在eventloop线程就地执行。

// ExecutorManager找excutor
  public Executor findExecutor(OperationMeta operationMeta, Executor defaultOperationExecutor) {
...
    // 寻找config-key指定的default
    executor = findByKey(KEY_EXECUTORS_DEFAULT);
    if (executor != null) {
      return executor;
    }
...
}

// EdgeBootListener的KEY_EXECUTORS_DEFAULT配置
  public void onBootEvent(BootEvent event) {
...
configuration.setProperty(ExecutorManager.KEY_EXECUTORS_DEFAULT, ExecutorManager.EXECUTOR_REACTIVE);
}

// ExecutorManager 的EXECUTOR_REACTIVE设置，是ReactiveExecutor
  public ExecutorManager() {
    registerExecutor(EXECUTOR_REACTIVE, new ReactiveExecutor());
  }

// ExecutorManager从executors获取EXECUTOR_REACTIVE
  public Executor findExecutorById(String id) {
    Executor executor = executors.get(id);
}

Edge调用超时设置

由于edge都是在eventloop进行，不能耗时过长，因此设置了超时时间。isInQueueTimeout，默认30s

// AbstractRestInvocation

    try {
      operationMeta.getExecutor().execute(() -> {
        synchronized (this.requestEx) {
          try {
            if (isInQueueTimeout()) {
              throw new InvocationException(Status.INTERNAL_SERVER_ERROR, "Timeout when processing the request.");
            }

// 超时配置nanoRestRequestWaitInPoolTimeout，在OperationConfig的setMsRestRequestWaitInPoolTimeout

  public void setMsRestRequestWaitInPoolTimeout(long msRestRequestWaitInPoolTimeout) {
    this.msRestRequestWaitInPoolTimeout = msRestRequestWaitInPoolTimeout;
    this.nanoRestRequestWaitInPoolTimeout = TimeUnit.MILLISECONDS.toNanos(msRestRequestWaitInPoolTimeout);
    registerRequestWaitInPoolTimeout(Const.RESTFUL, msRestRequestWaitInPoolTimeout);
  }

// setMsRestRequestWaitInPoolTimeout的调用，经过InjectProperty注入，默认值是30000毫秒，30秒
  @InjectProperty(keys = {
      "Provider.requestWaitInPoolTimeout${op-priority}",
      "rest.server.requestWaitInPoolTimeout"}, defaultValue = "30000")
  private long msRestRequestWaitInPoolTimeout;