YARN-2022 adds a flag in RMContainer to indicate whether the container is an AM or not to skip pre-emption of AM containers. This JIRA proposes propagating this information to NMs as it's required by the AMRMProxy ( YARN-2884/ YARN-3666) to identify if the container is an AM for:
1) Security - for authorizing only AMs to communicate with RMs. For e.g.: this is useful to prevent DDos attacks by all containers of a malicious app.
2) Federation - to allow for transparently spanning an app across multiple sub-clusters