mqtt-kafka feature (enhanced)

[jfallows]

MQTT v5 specification
MQTT v3.1.1 specification

Enhanced

• binding-kafka
  • Connection pool for kafka binding heartbeat requests #462
• binding-mqtt handles network protocol, abstracting differences between v5 and v3.1.1
  • Support mqtt protocol v3.1.1 #541
  • Support mqtt topics scoped by trusted identity #421
  • Handle data fragmentation for MQTT binding #282
  • security guard integration via AUTH packet, expiration and challenge-response via $SYS/auth/challenge
  • support quic transport
• binding-mqtt-kafka handles the mapping
  • Distribute MQTT topic space across different Kafka topics #426
  • Shard MQTT topic space for client-id specific subset #427
  • MQTT subscribe QoS 1 as stateful Kafka fetch with consumerId for message delivery retry #602
  • MQTT subscribe QoS 2 as stateful Kafka fetch with consumerId for message delivery retry #603
  • MQTT publish QoS 1 as Kafka produce with acks in_sync_replicas #604
  • Support idempotent mqtt qos 2 publish to kafka #677
  • Support MQTT message expiry in mqtt-kafka mapping #631
  • shared subscriptions use tiered consumer group members
    • system consumer group member reads messages from topic partition
    • system consumer group members redistributed across zilla instances
    • virtual consumer group members read messages with same key to support consistent ordering per key
    • virtual consumer group members redistributed within same zilla instance
    • detach system consumer group member instance when no remaining virtual members to avoid delivery starvation