The disclosure relates to a method of switching data sources during a rolling upgrade of a leader-based distributed service. In at least one implementation, the method includes establishing, at a computing device in a cluster of devices in a network, a watch for notification of completion of a rolling upgrade on all devices in the cluster; restarting the computing device on completion of the rolling upgrade; switching, at the computing device, from a first data source to a second data source once the rolling upgrade is complete on all devices in the cluster; if the computing device is a leader device in the cluster, migrating tasks from the first data source to the second data source after completion of the rolling upgrade; and if the computing device is a non-leader device in the cluster, determining if task migration to the second data source is done and, when done, sending a store object to the second data source.