DaprHttpBuilder

private DaprHttp buildDaprHttp() {
    // 双重检查锁
    if (OK_HTTP_CLIENT == null) {
      synchronized (LOCK) {
        if (OK_HTTP_CLIENT == null) {
          OkHttpClient.Builder builder = new OkHttpClient.Builder();
          Duration readTimeout = Duration.ofSeconds(Properties.HTTP_CLIENT_READ_TIMEOUT_SECONDS.get());
          builder.readTimeout(readTimeout);

          Dispatcher dispatcher = new Dispatcher();
          dispatcher.setMaxRequests(Properties.HTTP_CLIENT_MAX_REQUESTS.get());
          //这里有一个超级大坑！
          // The maximum number of requests for each host to execute concurrently.
          // Default value is 5 in okhttp which is totally UNACCEPTABLE!
          // For sidecar case, set it the same as maxRequests.
          dispatcher.setMaxRequestsPerHost(Properties.HTTP_CLIENT_MAX_REQUESTS.get());
          builder.dispatcher(dispatcher);

          ConnectionPool pool = new ConnectionPool(Properties.HTTP_CLIENT_MAX_IDLE_CONNECTIONS.get(),
                  KEEP_ALIVE_DURATION, TimeUnit.SECONDS);
          builder.connectionPool(pool);

          OK_HTTP_CLIENT = builder.build();
        }
      }
    }

    return new DaprHttp(Properties.SIDECAR_IP.get(), Properties.HTTP_PORT.get(), OK_HTTP_CLIENT);
  }
}