1. A computer-implemented method comprising: receiving, by one or more configured computing systems of a program execution service, configuration information that indicates a program to be executed in a distributed manner; selecting, by the one or more configured computing systems, multiple computing nodes provided by the program execution service to use as a cluster for executing the indicated program; initiating, by the one or more configured computing systems, the executing of the indicated program in a distributed manner on the selected multiple computing nodes of the cluster such that one or more jobs of the indicated program are attempted to be executed on each of the selected multiple computing nodes; determining, by the one or more configured computing systems and while at least one of the selected multiple computing nodes is still executing at least one of the jobs of the indicated program, that an actual amount of computing resources being used by the multiple computing nodes to execute the indicated program differs from an expected amount of computing resources; and initiating, based at least in part on the determining, a change in a quantity of the multiple computing nodes of the cluster for use in continuing executing the indicated program.