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This KIP proposes to allow Kafka producer and consumer clients to repeat the bootstrap process when fetching updating metadata if none of the known nodes are available. The A node is unavailable when the client doesn't have an established connection with it and cannot establish a connection (e.g. due to the reconnect backoff).

During the rebootstrap process, the client forgets the nodes it knows about and falls back on the bootstrap nodes (i.e. provided by bootstrap.servers which was originally provided via by the client configuration is used for this) as if it had just been initialized.

The client will check the cluster ID returned by the broker during the rebootstrap process. If no cluster ID was known to the client (i.e. it was originally bootstrapped with an old broker version that doesn't support cluster IDs), any returned value will be considered valid. Otherwise, the client will fail if the returned cluster ID doesn't match the previously known one.

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