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Redis

Status: Implemented · Tier: 1 · Instances: Single

AS-IS: In-memory data store serving as the real-time status bus for the Silvasonic ecosystem. Provides two mechanisms: key-value snapshots with TTL (current state) and Pub/Sub channels (live updates, nudge signals, log streaming).

1. The Problem / The Gap

  • No Real-Time Status: Without Redis, the Web-Interface has no way to display live service health — it would need to poll each service individually.
  • No Immediate Control: The State Reconciliation Pattern requires a wake-up signal (nudge) so the Controller acts immediately instead of waiting for its reconciliation timer.

2. User Benefit

  • Live Dashboard: The Web-Interface shows real-time health and activity of all services via the Read+Subscribe Pattern.
  • Instant Response: When a user toggles a service in the Web-Interface, the Controller receives the nudge within milliseconds.

3. Core Responsibilities

Inputs

  • Heartbeat payloads from all services via SET silvasonic:status:<id> <json> EX <TTL> (see heartbeat.py for TTL value).
  • Nudge signal from Web-Interface via PUBLISH silvasonic:nudge "reconcile".

Processing

  • Key expiry (TTL) — keys auto-expire after the configured TTL if a service stops publishing.
  • Pub/Sub message relay — zero processing, pure message passthrough.

Outputs

  • Status snapshots readable via KEYS silvasonic:status:* + GET.
  • Live status update stream subscribable via SUBSCRIBE silvasonic:status.
  • Live log stream subscribable via SUBSCRIBE silvasonic:logs.
  • State reconciliation trigger via PUBLISH silvasonic:nudge.

4. Operational Constraints & Rules

Aspect Value / Rule
Immutable No (managed by Compose/Quadlet, standard Redis config)
DB Access No — Redis is independent of PostgreSQL
Concurrency Single-threaded event loop (Redis default)
State Ephemeral — all data is volatile, no persistence required
Privileges Rootless (ADR-0007)
Resources Low — minimal memory footprint (< 10 MB)
QoS Priority oom_score_adj=0 (default) — Tier 1 infrastructure

[!IMPORTANT] Redis is best-effort infrastructure. If Redis goes down, the critical path (recording, ingestion, analysis) continues uninterrupted via filesystem/DB polling. Only the Web-Interface loses real-time status updates. See Messaging Patterns §1.1.

5. Configuration & Environment

Variable / Mount Description Default / Example
SILVASONIC_REDIS_PORT Host-exposed port 6379
Named Volume Redis data (ephemeral) silvasonic-redis

6. Technology Stack

  • Image: redis:7-alpine (official, minimal)
  • Persistence: None (--save "" or default, data is volatile)

7. Open Questions & Future Ideas

  • Redis Sentinel or replication: Not needed for single-device deployment.
  • Persistence: Currently disabled. Could enable AOF if nudge reliability becomes critical.

8. Out of Scope

  • Does NOT store persistent state (Database's job).
  • Does NOT queue work for workers (Workers use DB polling — ADR-0018).
  • Does NOT use Redis Streams or Consumer Groups — only SET/GET + Pub/Sub.

9. References