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Public Interfaces

We should add two new metrics :identifying how many consumer groups are in each state.

• NumGroupsRebalancing: the number of consumer groups which are currently in the PreparingRebalance state.
  
• NumGroupsAwaitingSync: the number of consumer groups which are currently in the AwaitingSync state.
• NumGroupsStable: the number of groups which are currently in the Stable state.
• NumGroupsDead: the number of groups which are currently in the Dead state.
• NumGroupsEmpty: the number of groups which are currently in the Empty state.

In combination with the existing NumGroups metric, this will show what percentage of groups are rebalancing or preparing to finish a rebalance at any in a particular state at a given time.

Compatibility, Deprecation, and Migration Plan

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