Feat/data storage layer

[akintewe]

feat(aggregator): implement Redis-backed Data Storage Layer

Summary

• Implements a StorageService backed by Redis (ioredis) to persist aggregated prices with configurable TTL
• Maintains per-symbol price history as a time-series using Redis Sorted Sets
• Exposes batch read/write operations for the API service to query efficiently
• Degrades gracefully to no-op mode when REDIS_URL is not configured — the service starts cleanly and aggregation is never interrupted
• Adds 3 new Prometheus metrics for cache hits, misses, and operation duration
• 52 unit tests with mocked ioredis achieving >95% line coverage on StorageService
• Adds docker-compose.yml at the project root with a Redis 7.2-alpine service
• Also fixes a pre-existing build error in the ingestor service (missing SchedulerService import)

Redis Key Schema

Key Pattern	Type	TTL	Purpose
price:latest:{SYMBOL}	STRING (JSON)	REDIS_PRICE_TTL_SECONDS (default 300 s)	Latest aggregated price per symbol
price:history:{SYMBOL}	SORTED SET (score = computedAt ms)	None (bounded by trim)	Time-series history per symbol
price:symbols	SET	None	Index of all tracked symbols

New Environment Variables

Variable	Default	Description
REDIS_URL	(unset)	Redis connection URL. When absent, service runs in no-op mode.
REDIS_PRICE_TTL_SECONDS	300	TTL for latest price key in seconds (5 min default)
REDIS_HISTORY_MAX_ENTRIES	100	Max history entries kept per symbol
REDIS_KEY_PREFIX	price	Key namespace prefix (useful for shared Redis instances)

Files Changed

New Files

• apps/aggregator/src/services/storage.service.ts — Core Redis service with 9 public methods
• apps/aggregator/src/services/storage.service.spec.ts — 52 unit tests (>95% line coverage)
• apps/aggregator/src/modules/storage.module.ts — NestJS feature module
• apps/aggregator/src/interfaces/storage-options.interface.ts — Typed options interfaces
• apps/aggregator/src/config/redis.config.ts — ConfigFactory for Redis env vars
• docker-compose.yml — Redis 7.2-alpine with health check and LRU eviction policy

Modified Files

• apps/aggregator/src/services/aggregation.service.ts — Injects StorageService @Optional(), calls storePrice fire-and-forget after each aggregation
• apps/aggregator/src/metrics/metrics.service.ts — Adds storageCacheHits, storageCacheMisses, storageOperationDuration Prometheus instruments
• apps/aggregator/src/app.module.ts — Registers StorageModule; also fixes pre-existing bugs (missing HttpModule/EventEmitterModule imports, duplicate ConfigModule.forRoot)
• apps/aggregator/package.json — Removes duplicate axios entry
• apps/aggregator/.env.example — Documents all 4 REDIS_* environment variables
• apps/aggregator/README.md — Adds Redis Storage section with schema, env vars, metrics, and graceful degradation docs
• apps/ingestor/src/modules/prices.module.ts — Fixes missing SchedulerService import (pre-existing build error)

How to Test

# Start Redis
docker compose up -d redis

# Configure
echo "REDIS_URL=redis://localhost:6379" >> apps/aggregator/.env

# Run the service
cd apps/aggregator && npm run start:dev

# Health check (Redis should show "up")
curl http://localhost:3001/health

# Storage metrics visible at
curl http://localhost:3001/metrics | grep aggregator_storage

# Run unit tests
cd apps/aggregator && npm test -- --coverage

Closes #20