mqtt-kafka feature (baseline)

[jfallows]

MQTT v5 specification
MQTT v3.1.1 specification

Baseline

• binding-mqtt handles network protocol
  • encoding and decoding mqtt protocol frames (v5)
  • lifecycle of publish and subscribe application level streams
  • flow control of multiple subscriber application streams on the same network stream
  • security guard integration via CONNECT packet, password field, e.g. jwt access token
  • support load balancer bypass via server redirection
• binding-mqtt-kafka handles the mapping
  • publish qos 0 as produce, acks none
  • subscribe qos 0 as fetch
  • subscribe retained as fetch log compacted
  • session stealing, group-wide not just same instance, requires async coordination across instances
  • last will messages delivered after will delay
    • will message delivery canceled if client reconnects
  • session state storage abstraction
    • log-compacted kafka topic, queryable by clientId message key, configurable name
    • subscription state as log-compacted topic, queryable by clientId message key, configurable name
      • support out-of-band subscribe or unsubscribe for client
  • session expiry via consumer group offset on sessions kafka topic
  • request-response over mqtt maps response topic to zilla:reply-to topic
  • support load balancer bypass via server redirection