batchAggregator.initialize(runtimeContext); if (isMapPhase) { return getTrackedEmitKeyStep(new MapperAggregatorTransformation(batchAggregator, mapOutputKeyClassName, mapOutputValClassName), stageMetrics, taskContext.getDataTracer(stageName), collector); batchJoiner.initialize(runtimeContext); if (isMapPhase) { return getTrackedEmitKeyStep( new MapperJoinerTransformation(batchJoiner, mapOutputKeyClassName, mapOutputValClassName), stageMetrics, taskContext.getDataTracer(stageName), collector);