1. An information processing system comprising: a job management unit configured to manage a job consisting of multiple tasks that is generated in accordance with a user request; and multiple back-end units configured to acquire tasks from the job management unit if a processing standby status exists, and carry out specific task processing, wherein the back-end units periodically notify the job management unit that task processing is in progress, and wherein the job management unit issues a command to suspend task processing to the back-end unit that has not completed the task processing within a prescribed time, and issues a command for alternative execution of task processing to a back-end unit capable of task processing that is identical to the task processing.