public boolean isCancelled() {
    assert op != null : "No operation";
    return op.isCancelled();
  }
Whether or not the Operation associated with this OperationFuture has been
canceled.

One scenario in which this can occur is if the connection is lost and the
Operation has been sent over the network.  In this case, the operation may
or may not have reached the server before the connection was dropped.

@return true if the Operation has been canceled
src/main/java/net/spy/memcached/internal/OperationFuture.java