1. A computer-implemented method for controlling message flow in a parallel computing system having a plurality of compute nodes, the method comprising: assigning a first set of compute nodes to a first node pool, wherein a first message flow control policy is assigned to each compute node of the first node pool, and wherein the message flow control policy specifies at least one of logging and/or tracing activity to be performed by an instance of an application running on at least a first compute node assigned to the first node pool; initiating execution of the application on each of the compute nodes in the first node pool; and while executing the application on at least the first compute node, generating one or more logging or tracing messages according to the first message flow control policy.