A control module is introduced to communicate with an application workload scheduler of a distributed computing application, such as a Job Tracker node of a Hadoop cluster, and with the virtualized computing environment underlying the application. The control module periodically queries for resource consumption data, such as CPU utilization, and uses the data to calculate how MapReduce task slots should be allocated on each task node of the Hadoop cluster. The control module passes the task slot allocation to the application workload scheduler, which honors the allocation by adjusting task assignments to task nodes accordingly. The task nodes may also activate and deactivate task slots according to the changed slot allocation. As a result, the distributed computing application is able to scale up and down when other workloads sharing the virtualized computing environment change.