private static JobTaskVertex createReducer( JobGraph jobGraph, int numSubTasks, TypeSerializerFactory<?> inputSerializer, TypeComparatorFactory<?> inputComparator, TypeSerializerFactory<?> outputSerializer) { // ---------------- the tail (co group) -------------------- JobTaskVertex tail = JobGraphUtils.createTask( IterationTailPactTask.class, "Reduce / Iteration Tail", jobGraph, numSubTasks, numSubTasks); TaskConfig tailConfig = new TaskConfig(tail.getConfiguration()); tailConfig.setIterationId(ITERATION_ID); tailConfig.setIsWorksetUpdate(); // inputs and driver tailConfig.setDriver(ReduceDriver.class); tailConfig.setDriverStrategy(DriverStrategy.SORTED_GROUP); tailConfig.addInputToGroup(0); tailConfig.setInputSerializer(inputSerializer, 0); tailConfig.setDriverComparator(inputComparator, 0); tailConfig.setInputLocalStrategy(0, LocalStrategy.SORT); tailConfig.setInputComparator(inputComparator, 0); tailConfig.setMemoryInput(0, MEMORY_PER_CONSUMER * JobGraphUtils.MEGABYTE); tailConfig.setFilehandlesInput(0, 128); tailConfig.setSpillingThresholdInput(0, 0.9f); // output tailConfig.addOutputShipStrategy(ShipStrategyType.FORWARD); tailConfig.setOutputSerializer(outputSerializer); // the udf tailConfig.setStubWrapper( new UserCodeObjectWrapper<RecomputeClusterCenter>(new RecomputeClusterCenter())); return tail; }