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1. Reads all child nodes in /brokers/ids/ to get current brokers with broker generation
2. Detect new brokers, dead brokers and bounced brokers:
   • new brokers:  brokers exist in current brokers list and do not exist in controller context
   • dead brokers: brokers exist in controller context but do not exist in current brokers list
   • bounce brokers: brokers exist in both current brokers list and controller context but have higher generation than the cached value in controller context
3. Update the broker info (broker id + broker generation) live broker ids in controller context
4. Handle broker state change:
   • new brokers: update broker generation in controller context for new brokers, then invoke onBrokerStartUp(...new brokers)
   • dead brokers: invoke onBrokerFailure(...dead brokers)
   • bounced brokers: invoke onBrokerFailure(...bounced brokers) first, then update broker generation in controller context for bounced brokers, finally invoke onBrokerStartUp(...bounced brokers)

Compatibility, Deprecation, and Migration Plan

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