Add Prometheus metrics endpoint for operational visibility

[prodbycorne]

Overview

There is currently no way to observe the service's health in production beyond logs. A /metrics endpoint in Prometheus format enables dashboards, alerting, and SLA tracking.

Metrics to Expose

Price Oracle

Metric	Type	Description
smartdrop_price_fetch_total	Counter	Price fetches by source and status (success/error)
smartdrop_price_cache_hit_total	Counter	Redis cache hits
smartdrop_price_cache_miss_total	Counter	Redis cache misses
smartdrop_price_anomaly_total	Counter	Price anomalies detected by asset
smartdrop_price_usd	Gauge	Current price per asset

HTTP

Metric	Type	Description
http_request_duration_seconds	Histogram	Request latency by route and status
http_requests_total	Counter	Total requests by method, route, status

System

Metric	Type	Description
redis_connected	Gauge	1 if Redis is reachable, 0 otherwise
process_uptime_seconds	Gauge	Service uptime

Implementation

npm install prom-client

• Create src/metrics.js with all metric definitions and a getRegistry() export
• Add HTTP middleware to record latency and status per route
• Expose GET /metrics (plain text, no auth — restrict at infra level)
• Instrument priceOracle.js at each source call and cache operation

Acceptance Criteria

• prom-client installed and default metrics enabled
• GET /metrics returns valid Prometheus text format
• All metrics above implemented
• Middleware automatically instruments all routes
• /metrics excluded from rate limiting
• Integration test asserts metric names appear in response

[abioye-emma]

Hi there, I carefully reviewed the issue details and I’m confident I can deliver a clean and efficient solution.

[abioye-emma]

Hi there, I carefully reviewed the issue details and I’m confident I can deliver a clean and efficient solution.

[grantfox-oss]

🦊 GrantFox — @abioye-emma has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #18)
2. Your PR will be reviewed by the SmartDropLabs maintainers

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