AMBARI-19435, HOU now uses the role command ordering to determine how to start components on a host. This is because some components (such as NodeManager and DataNode) require their masters to be online first in order to register correctly. When co-located on the same host, masters and slaves must be started in the correct order.
However, some ordering defined on the stack will not work for HOU. For example, the stack doesn't enforce that NameNode start before DataNode. This is because in a normal start command, the DataNode can wait for up to 30 minutes for the NameNode to come online. During an upgrade, the upgrade logic waits to ensure that the DataNode is online and registered before moving on. Since the role ordering allows DataNode to start first, this start always fails during an upgrade.
There are several ways of implementing this: