FuturesTest.java

package water;


import org.junit.Assert;
import org.junit.BeforeClass;
import org.junit.Test;

import java.util.concurrent.*;

/**
 * Created by tomas on 8/16/16.
 */
public class FuturesTest extends TestUtil {

  @BeforeClass
  public static void setup() { stall_till_cloudsize(1); }

  public static class TstFuture implements Future {
    private boolean _isDone;
    private boolean _isCancelled;
    public ExecutionException _exex;
    public RuntimeException _rex;

    @Override
    public synchronized boolean cancel(boolean mayInterruptIfRunning) {
      _isCancelled = true;
      notifyAll();
      return true;
    }

    public synchronized void complete(){
      _isDone = true;
      notifyAll();
    }

    public synchronized void complete(Throwable t){
      if(t instanceof ExecutionException)
        _exex = (ExecutionException) t;
      else if(t instanceof RuntimeException)
        _rex = (RuntimeException) t;
      else throw new IllegalArgumentException();
      _isDone = true;
      notifyAll();
    }


    @Override
    public boolean isCancelled() {return _isCancelled;}

    @Override
    public boolean isDone() {return _isDone || _isCancelled;}

    @Override
    public Object get() throws InterruptedException, ExecutionException {
      while(!isDone()){
        synchronized(this){
          wait();
        }
      }
      if(_isCancelled) throw new CancellationException();
      if(_exex != null) throw _exex;
      if(_rex != null) throw _rex;
      return this;
    }

    @Override
    public Object get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
      return null;
    }
  }
  private static class TstException extends RuntimeException {
    public TstException(String msg){super(msg);}
  }

  @Test
  // Test exceptions are correctly rethrown even if the future is eagerly removed
  public void testExceptions(){
    // 0 test exception from pending task is thrown
    Futures fs = new Futures();
    TstFuture cf = new TstFuture();
    fs.add(cf);
    Assert.assertEquals(1,fs._pending_cnt); // task is already completed
    cf.complete(new ExecutionException(new TstException("a")));
    try{
      fs.blockForPending();
      Assert.assertTrue("should've thrown",false);
    } catch(RuntimeException t) {
      Assert.assertTrue(t.getCause() instanceof TstException);
    }
    // 1 test exception from already completed task is rethrown in blockForPending
    fs = new Futures();
    cf = new TstFuture();
    cf.complete(new ExecutionException(new TstException("a")));
    fs.add(cf);
    Assert.assertEquals(0,fs._pending_cnt); // task is already completed
    try{
      fs.blockForPending();
      Assert.assertTrue("should've thrown",false);
    } catch(RuntimeException t) {
      Assert.assertTrue(t.getCause() instanceof TstException);
    }
    // 2 test exception is recorded and re-thrown if task is eagerly cleaned
    fs = new Futures();
    cf = new TstFuture();
    fs.add(cf);
    Assert.assertEquals(1,fs._pending_cnt);
    cf.complete(new TstException("eager cleanup"));
    for(int i =0; i < 3; ++i) {
      fs.add(cf = new TstFuture());
      Assert.assertEquals(1, fs._pending_cnt);
      cf.complete();
    }
    try{
      fs.blockForPending();
      Assert.assertTrue("should've thrown",false);
    } catch(RuntimeException t) {
      Assert.assertTrue(t.getCause() instanceof TstException);
      Assert.assertEquals("eager cleanup",t.getCause().getMessage());
    }
    // 3 test cancellation exceptions are ignored
    fs = new Futures();
    cf = new TstFuture();
    cf.cancel(true);
    fs.add(cf);
    fs.blockForPending();

  }
}