Rolling updates

A Service Fabric application is a collection of services. Every service, the ones which are part of the Service Fabric framework or the ones which are hosted on it, will require an upgrade at some point in time. To achieve high availability and low downtime of services during upgrades, Service Fabric supports rolling updates. This means that the upgrade is performed in stages. The concept of update domains is used to divide the nodes in a cluster into logical groups which are updated one at a time.

First, the application manifests of the new and existing deployments are compared to identify services which need an upgrade and only the ones requiring an update is refreshed. During the process of an upgrade, the cluster may contain a version of new and old services running in parallel. This forces the upgrades to be backward-compatible. A multi-phased upgrade can be used as a solution to achieve upgrade of non-compatible versions of services. In a multi-phased upgrade, the service is first upgraded to an intermediate version which is compatible with the old version of the service. Once this is successful, the intermediate version is upgraded to the final version of the service.

Service Fabric also supports non-rolling updates of services deployed in a cluster, a process also known as unmonitored upgrade.