implementation-plan.md

Implementation Notes (Phase 1)

Phase 1 scope: single-node log engine + broker + server/RPC. See PROGRESS.md for phase plan.

Build Order (dependency graph)

Message (core)
  -> Segment (stores messages)
    -> Index (offset lookup)
    -> TimeIndex (time lookup)
      -> Partition (collection of segments)
        -> Topic (collection of partitions)
          -> Broker (manages topics)
            -> Producer (writes to broker)
            -> Consumer (reads from broker)
              -> Consumer Group (coordinates consumers)

Phase	What	Depends on	Testable independently
1	Message format	Nothing	Yes
2	Segment (append, read, rotate)	Message	Yes
3	Index + TimeIndex	Segment	Yes
4	Partition + Topic	Segment, Index	Yes
5	Broker (single node)	Topic	Yes
6	Producer/Consumer RPC	Broker	Yes
7	Consumer Group	Consumer, Broker	Yes

Each phase builds on the previous. Message is the core entity all others depend on.

Design References

• pkg/log/DESIGN.md — segment storage design
• docs/shared/kafka-paper-study.md — Kafka paper study notes
• docs/shared/kafka-paper-section5.md — experimental results
• docs/phase2/exactly-once-penalty.md — 2PC performance analysis