Google patents method to schedule virtual machine moves to cut downtime

1. A system comprising: one or more processors configured to, during one or more migration cycles of a migration of multiple virtual machines from one or more source computing environments to one or more target computing environments: identify, from a plurality of interdependent virtual machines, a first plurality of virtual machines from a source computing environment of the one or more source computing environments, wherein the plurality of interdependent virtual machines collectively execute a service, and wherein at least one virtual machine of the plurality of interdependent virtual machines is configured to execute operations that receive, as input, data generated by another virtual machine of the plurality of interdependent virtual machines; generate a schedule for performing the migration of the multiple virtual machines, the schedule including cut-over operations for completing the migration of each of the first plurality of virtual machines, wherein the cut-over operations are temporally ordered such that a cut-over operation of each of the first plurality of virtual machines is scheduled to occur within a predetermined threshold of time relative to the cut-over operations of other virtual machines of the first plurality virtual machines based on interdependencies among the first plurality of virtual machines and to reduce a downtime of the service incurred by performing the cut-over operations; perform the migration of the first plurality of virtual machines in accordance with the generated schedule; query constraint data from the source computing environment, while performing the migration of the first plurality of virtual machines, to determine a maximum number of a second plurality of virtual machines from the plurality of interdependent virtual machines, which can be migrated in parallel at any given point in time; update the generated schedule based on the determined maximum number of the second plurality of virtual machines; and perform migration of the second plurality of virtual machines based on the updated schedule, wherein the updated schedule specifies performing operations related to migration for the first plurality of virtual machines and the second plurality of virtual machines, at least partially in parallel.