imap.setAsync throws an erroneous java.lang.ClassCastException inside the returned iCompletableFuture

[vmarquez]

We are using Hazeclast version 3.7.4.
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)

We use Hazelcast with Scala, but I don't believe the issue has anything to do with that. Here is a simple bit of code to replicate the problem.

import com.hazelcast.core.Hazelcast
import com.hazelcast.core.HazelcastInstance
import com.hazelcast.config._
import com.hazelcast.core._

object HazelcastTest {
  
  val hz = Hazelcast.newHazelcastInstance()
  val hazelcastMap: com.hazelcast.core.IMap[String, Int] = hz.getMap("mymap")
  val f: ICompletableFuture[Void] = hazelcastMap.setAsync("a", 5)
   //throws an Exception
  f.andThen(new ExecutionCallback[Void]() { override def onResponse(a: Void): Unit = println("HELLO WORLD"); 
  override def onFailure(t: Throwable): Unit = println("failure = " + t);
  }) 

  val fp: ICompletableFuture[Int] = hazelcastMap.putAsync("a", 5)
  //works as expected
  fp.andThen(new ExecutionCallback[Int]() { override def onResponse(a: Int): Unit = println("HELLO WORLD i =" + a); 
  override def onFailure(t: Throwable): Unit = println("failure = " + t);
  })
}

setAsync's onResponse is called but before the callback can be run the following Exception is thrown:

java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.Void                                                                                                                                                                                                              
at $sess.cmd9$$anon$1.onResponse(cmd9.sc:1)                                                                                                                                                                                                                                           
at com.hazelcast.util.executor.DelegatingFuture$DelegatingExecutionCallback.onResponse(DelegatingFuture.java:172)                                                                                                                                                                     
at com.hazelcast.spi.impl.AbstractInvocationFuture$1.run(AbstractInvocationFuture.java:251)                                                                                                                                                                                           
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)                                                                                                                                                                                                    
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)                                                                                                                                                                                                    at java.lang.Thread.run(Thread.java:745)                                                                                                                                                                                                                                              
at com.hazelcast.util.executor.HazelcastManagedThread.executeRun(HazelcastManagedThread.java:76)                                                                                                                                                                                      
at com.hazelcast.util.executor.HazelcastManagedThread.run(HazelcastManagedThread.java:92)         

However, the set did succeed and I can see my values inside the map.

[pveentjer]

I checked the code and I do see that the SetOperation returns a boolean.

public class SetOperation extends BasePutOperation {

    private boolean newRecord;

    @Override
    public void run() {
        newRecord = recordStore.set(dataKey, dataValue, ttl);
    }

    @Override
    public Object getResponse() {<------
        return newRecord;
    }
}

So it explains you running into the ClassCastException.

Here is a java reproducer:

public class Main {

    public static void main(String[] args){
        HazelcastInstance hz = Hazelcast.newHazelcastInstance();
        IMap map = hz.getMap("map");
        ICompletableFuture a = map.setAsync("1", "a");

        a.andThen(new ExecutionCallback() {
            @Override
            public void onResponse(Object response) {
                System.out.println("response.class = "+response.getClass().getName());
            }

            @Override
            public void onFailure(Throwable t) {

            }
        });
    }
}

My big question is why the Set Operation is returning a response. I guess it is related to updating internal on completion like statistics.

[pveentjer]

For the time being, can you run with an untyped future? If the future is returning void; then you are not interested in a result value anyway.

[vmarquez]

@pveentjer There isn't really a way to do that as the return type of setAsync is the parameterized over Void. I can use putAsync for now. Thanks for your quick response and identifying the offending code!

[pveentjer]

the putAsync will be a bit more expensive than the set because the put will return the old value. So there is more network traffic + deserialization involved.

I'm going to close this ticket since the fix will be in the latest maintenance release which should be released one of these days.