Module recorder 

Downstream consumer that records completed fills into the competition tables.

This is the ingestion side of competitions, decoupled from the websocket broadcast path. The recorder consumes a stream of [EngineMessage] and, for each OrderFilled, persists a competition fill.

Source-agnostic by design

run takes a plain mpsc::UnboundedReceiver<EngineMessage>, so it does not care where the fill stream comes from. Today the runtime feeds it from the in-process engine EventBus (TOPIC_FILLS subscription). When the engine runs out-of-process (see the transport-evolution roadmap), the same recorder is fed by a NATS JetStream consumer instead, with no change here. Other downstream services (analytics, auditors) subscribe to the same stream the same way.

Failure handling

A competition write failure is logged and metered but does NOT crash the engine node. The previous implementation recorded fills inline in the websocket forwarder and triggered a full process shutdown on failure, so a transient leaderboard DB error could take down trading. Fill recording is idempotent (record_competition_fill is ON CONFLICT (trade_id, wallet) DO NOTHING), so a dropped fill is safely re-recordable.

Durability caveat (not yet a durable follower)

This consumes an in-memory event stream. Fills already written to competition_fill_events survive restart, but a fill emitted but not yet recorded when the node dies is NOT recovered: engine replay rebuilds engine state without re-emitting fills to the event bus. Closing that crash window requires making competition a durable external-follower projection that replays the fill stream from the journal/NATS at a recorded offset (tracked separately).

Structs

CompetitionFillRecorder

Consumes the engine fill stream and records competition fills.

Traits

CompetitionFillSink

Minimal sink the recorder depends on: persist one competition fill.