Today, ClusterRole is defined by a bit mask that contains different combinations of its enumeration. This enum is composed of None, ShardServer, RouterServer and ConfigServer. But not all combinations for the clusterRole of a node are possible. After a lot of changes by the config shard and shards can act as routers, the values of the bit mask of each ClusterRole instance can be:

{ None } => Standalone / RS
{ ShardServer, RouterServer } => Shard
{ ShardServer, ConfigServer, RouterServer } => Config / Config-Shard
{ RouterServer } => MongoS

Goal

We need to remove the bit mask of the cluster role in order to move to a more restrictive API that only let the user check which is the role of the process in a simple manner. I propose to have different getters to know the specific role of the process (isShard, isConfig, isRouterOnly, ...).

References

 - ClusterRole enum

Estimation

 - User impact: Improvement.
 - Raw Estimation (man-day): 5