Comment 6 for bug 1362744

And even better approach is to have such deployment scripts (shell etc.) that are idempotent e.g. can be run several times without causing errors. Typical script will check the state of the system and apply only the minimal needed actions to bring the system to desired state. Thus application redeployment will be very fix as there will be no changes in Heat stack resources and all scripts executed on VMs will actually do nothing and exit quickly. But if something was accidentally removed from VM or got broken script will repair it back ensuring that the application is in predictable state after deployment even if no properties were changed