USING A TEMPLATE TO UPDATE A STACK OF RESOURCES

摘要

Techniques are described that enable a user to upgrade a stack of resources by providing a template that reflects the desired end state of the stack. Upon receiving a new template, the system automatically detects changes that should be performed and determines the order in which the changes should be performed. The system can also detect if the desired changes to the stack are a result of direct modifications; because parameters to the resources have changed; or the changes are indirectly caused by other dependency/attribute changing. Additionally, the system determines whether the changes require creating new resources or if the changes can be made to the resources live. In case of replacement of resources, the system will first create the new resource, move that new resource into the stack and remove the old resource(s). In case of failures, the system ensures that the stack rolls back to the initial state.

主权项

1. A computer implemented method for updating resources in a network-accessible service environment, said method comprising:
instantiating a stack of resources that operate together to provide at least one network-accessible service, the stack of resources being associated with a first template; receiving a request to update the stack of resources, the request including a second template that specifies at least a desired end state for the stack of resources; computing a difference that is introduced to at least one resource in the stack between the first template and the second template and determining a set of changes that should be made to the resources of the stack; determining whether the changes can be implemented as a running update or require a destructive update; if the changes can be implemented as a running update, modifying the resource while the resource is running, otherwise if the changes require a destructive update, creating at least one new resource, adding the new resource into the stack and removing a previous version of said resource from the stack; and if the request to update the stack is unsuccessful, rolling back any changes that have been made to the resources of the stack in order to return the stack to a state specified in the first template.