KIP-214 — Add zookeeper.max.in.flight.requests config to the broker

Accepted Kafka 1.1 Broker

Adds a broker-side zookeeper.max.in.flight.requests config to cap the number of concurrent outstanding ZooKeeper requests sent by the pipelined ZooKeeperClient wrapper. The scatter-gather ZooKeeperClient introduced in KAFKA-5501 could overwhelm ZooKeeper by issuing unbounded parallel requests, and ZooKeeper's own zookeeper.globalOutstandingLimit provided only cluster-wide, cross-connection throttling insufficient to protect against a single misbehaving broker.

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