1. A computing system for visualizing a dataflow of a distributed application in a locally simulated execution environment, the computing system comprising: one or more processors; and one or more storage media having stored computer-executable instructions which, when executed by the one or more processors, cause the computing system to perform a method for visualizing a dataflow of a distributed application in a locally simulated execution environment, wherein the method includes: an act of receiving a subscription to receive dataflow process data from a dataflow visualizer, the dataflow visualizer being configured to display various aspects of a simulated distributed application execution; an act of monitoring the dataflow process data during execution of the distributed application, wherein the distributed application comprises a plurality of computational vertices that correspond to a job graph of the distributed application to at least determine one or more of the plurality of computation vertices as ready for execution in the locally simulated execution environment based at least in part on the currently available processing resources of the locally simulated execution environment; and an act of sending the monitored dataflow process data to the dataflow visualizer for display, wherein the dataflow process data is displayed as the application is being executed, the dataflow visualizer including: a stage visualizer that displays the job graph as initially received at the stage visualizer; and a graph visualizer that is configured to display: the job graph at different stages; computational vertices that have been executed; computational vertices that are ready to run; and computational vertices that are not ready to run.