Set timeout on thread execution and save return value

Question

Hello,

I have a web service, with backend in java 7. At some point, the backend makes a broadcast RPC call to N servers that are listening. Except that there is no predefined timeout in the call, I have no way to control the response time of N servers. I do not have access to the source code of N servers.

result = RPC.call(params, liveAddresses, conf);

The proposed solution was to convert the code to multi-threading, creating N threads. Each one is responsible for calling 1 address (server). If you follow the previous strategy:

It is possible in java to launch multiple threads with a maximum wait time each one ends. Getting the main thread the results of all threads ?

I accept ideas for other strategies to follow.

Thank you.

Answer 1

An alternative would be the use of Executorservice

Basic Example:

Rpcresult.class:

public class RpcResult {

  private int clientId;
  private String response;

  // getters and setters...
}

Rpcexecutor.class:

public class RpcExecutor implements Callable<RpcResult>{

  private int clientId;

  public RpcExecutor(int clientId) {
    this.clientId = clientId;
  }

  public RpcResult call() throws Exception {    
    RpcResult result = new RpcResult();
    result.setClientId(clientId);
    result.setResponse("Resposta do cliente: " + clientId);

    return result;
  }

}

Execution:

ExecutorService executor = Executors.newFixedThreadPool(3);             
List<Callable<RpcResult>> list = new ArrayList<Callable<RpcResult>>();

for (int i = 1; i <= 3; i++) {
  list.add(new RpcExecutor(i));        
}

// 3 segundos de timeout
List<Future<RpcResult>> future = executor.invokeAll(list, 3L, TimeUnit.SECONDS);

for(Future<RpcResult> f : future) {           
  try {
    if (!f.isCancelled()) {
      RpcResult result = f.get();
      System.out.println(result.getClientId());
      System.out.println(result.getResponse());
    }
  } catch (InterruptedException e) {
    e.printStackTrace();
  } catch (ExecutionException e) {
    e.printStackTrace();
  }      
};

executor.shutdown();

To simulate the timeout of a client just add a Thread.Sleep() in the call() method of the Rpcexecutor class:

public RpcResult call() throws Exception {
    if (clientId == 2)
        Thread.sleep(15000);

    RpcResult result = new RpcResult();
    result.setClientId(clientId);
    result.setResponse("Resposta do cliente: " + clientId);

    return result;
}

EDIT

---

According to the new information related to the current project structure, this solution would not have scalability.

If you keep in mind that your application will never have many users, ok, go for the simplest solution. Now, if your application needs to scale, this could be one of the alternatives(simplified model):