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:
receiving a request to update a stack of resources as specified in a template that indicates a desired end state for the stack of resources; determining one or more modifications that should be made to at least one resource in the stack and an order in which said one or more modifications should be performed in order to bring the stack to the end state indicated in the template; performing the one or more modifications to the at least one resource in the stack; determining whether the one or more modifications were successful such that the stack reached the end state indicated in the template; if the one or more modifications were unsuccessful, rolling back the one or more modifications that have been made to the at least one resource in the stack; determining a set of dependencies associated with the resource; determining whether the set of dependencies require any cascading changes to one or more other resources in order to update the resource; and if any cascading changes are required, resolving the set of dependencies by performing the cascading changes to the one or more other resources.