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 dataflow 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; and an act of sending the monitored dataflow data to the dataflow visualizer for display, wherein the dataflow data is displayed as the application is being executed.