ADR 0006: Shared local infrastructure from local-infra

• Status: accepted, superseded in part by ADR 0023 (Elysion has its own Valkey and does not need local-infra; the key prefix and the RustFS ports below stay)
• Date: 2026-10-04
• Issues: #149, #157, #158, #159, #160
• Pull requests: #153, #161

Context

The developer machine already runs a shared stack in ../local-infra: Valkey on 6379, RabbitMQ on 5672/15672 and Portainer on 9000, all bound to 127.0.0.1. Its README makes the rule explicit: these run once per machine and are shared by all local projects instead of each bringing its own copy. Elysion's compose file still defined its own redis, which collided on port 6379, and its RustFS object store asked for port 9000, which Portainer owns.

Decision

1. Elysion's compose file does not define Valkey, RabbitMQ or Portainer. It defines only what is Elysion's own: Traefik, Postgres, RustFS. Apps on the host use localhost:6379 (REDIS_URL overrides it); apps running as containers join the external local-infra network and use valkey:6379.
2. Everything Elysion stores in Valkey is namespaced with elysion:, following local-infra's multi-tenancy rule (one key prefix per project). Realtime's channels are elysion:presence:<boardId> and its state hashes elysion:presence:state:<boardId>.
3. RustFS' host ports are 9100 (S3) and 9101 (console), overridable through infra/docker/.env.
4. The full-stack launch checks local-infra first. A VS Code task fails with a hint when the Valkey container is not running, before infra: up starts Elysion's own services.

Consequences

• Elysion needs local-infra running; a fresh clone alone does not give a working backend. The README and AGENTS.md say so.
• Other projects use the same Valkey. Pub/sub channels are not isolated by database number, so the prefix is the only protection; new code must prefix every key and channel.
• The realtime end-to-end tests write into the shared instance. They use prefixed, per-run keys; presence hashes expire a day after their last write, so the tests leave nothing behind for long.
• Valkey is Redis-protocol compatible, not identical to Redis 7. ioredis works against it; features Elysion adds later should be checked against Valkey, not assumed.
• RabbitMQ is available if Elysion needs messaging, with a vhost of its own as local-infra prescribes.