public List<Event> call() throws Exception {
List<Event> events = ugi.doAs(new PrivilegedExceptionAction<List<Event>>() {
@Override
public List<Event> run() throws Exception {
TezRootInputInitializer initializer = createInitializer();
TezRootInputInitializerContext context = new TezRootInputInitializerContextImpl(vertexID,
dagName, vertexName, input.getEntityName(), input.getDescriptor(),
numTasks, numClusterNodes, vertexTaskResource, totalResource,
dagAttemptNumber);
return initializer.initialize(context);
}