Kafka metadata describes topics, active brokers, partition assignments, and partition leaders. The controller manages partition and replica state; when a broker fails, it can reassign partitions and select new leaders. section 4.3.1
Clients need metadata to find which broker leads each topic partition. Brokers cache this information, and clients request it from a broker when connecting. A bootstrap server can be any broker, but specifying several brokers—or using load balancing through a load balancer or DNS—avoids relying on one broker to start. section 7.4
Figure 4.11 Kafka uses either a KRaft-based or a ZooKeeper-based coordination cluster. Both should consist of an odd number of nodes (usually three or five) and use a protocol to find a consensus.
The diagram contrasts ZooKeeper-based and KRaft-based coordination clusters and notes their consensus setup. section 4.3.1
$ kafka-topics.sh \
--list \
--bootstrap-server \
localhost:9092,localhost:9093,localhost:9094
This topic-listing command shows how to provide multiple bootstrap brokers instead of depending on a single broker. section 7.4
