Fenix implements rolling infrastructure maintenance and upgrade in interaction with application on top of it. In Telco world we talk about VNFM, but one can implement own simple manager for any application.

Infrastructure admin can call Fenix API to start a maintenance workflow session. This session will make needed maintenance and upgrade operations to infrastructure in interaction with application manager to guarantee zero down time for its service. Interaction gives ability for application manager to know about new capabilities coming over maintenance to make his own upgrade. Application can have a time window to finish what he is doing, make own action to re-instantiate his instance or have Fenix to make migration. Also scaling application or retirement will be possible.

As Fenix will have project specific messaging with instances affected towards application manager, it will also have admin level messaging, so infrastructure components will know certain host is under maintenance. This could also support adding or removing host.