ServCache

ServCache is the distributed, high-performance caching service for the Servverse ecosystem. It exposes a low-latency REST API backed by pluggable engines (in-memory or Redis) with native support for OpenTelemetry context propagation, read-through/write-behind database synchronisation, key pattern invalidation, and multi-region replication.

Features

• Pluggable Engines: Swap transparently between thread-safe local in-memory storage and high-throughput Redis/Valkey clusters.
• TTL Eviction: Automatic, background time-based pruning of expired cache keys.
• Key Pattern Invalidation: Delete matching keys dynamically via wildcards and prefix matching.
• Read-Through Cache: Cache misses automatically load data from a backend database (SERV_CACHE_BACKEND_DB) and populate the cache.
• Write-Behind Cache: Writes asynchronously update the backend database in the background to ensure eventually consistent writes without blocking clients.
• Multi-Region Replication: Forward mutations asynchronously to peer cache nodes (SERV_CACHE_PEERS) to maintain global cache consistency.
• OTel Instrumentation: Standardized hit/miss/latency metrics automatically exported via OTel tracing context.

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API Endpoints

1. Health Checks

• GET /health - Health probe showing cache readiness and connection status.

2. Cache Operations

Set Cache Entry

• Path: POST /api/cache
• Headers: Content-Type: application/json
• Body:

  {
    "key": "user:101",
    "value": { "name": "Alice", "role": "admin" },
    "ttl": "5m"
  }

  (TTL uses standard Go duration strings like 10s, 5m, 1h)

Get Cache Entry

• Path: GET /api/cache/{key}
• Response (200 OK):

  {
    "key": "user:101",
    "value": { "name": "Alice", "role": "admin" }
  }

• Response (404 Not Found): If key doesn't exist (and no database read-through is configured/succeeds).

Delete Cache Entry

• Path: DELETE /api/cache/{key}

Clear Cache / Invalidate Pattern

• Path: DELETE /api/cache
• Query Parameters:
  • pattern (Optional) - Wildcard pattern matching keys to delete (e.g. user:*). If omitted, fully clears the cache.
  • replicated (Internal) - Used by peer nodes to denote replication loops.

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Configuration (Environment Variables)

Configure ServCache dynamically by setting these parameters at startup:

Variable	Description	Default
PORT	HTTP Server port	8088
REDIS_URL	Redis cluster URL (e.g. redis://localhost:6379). Uses in-memory engine if unset.	(In-Memory)
SERV_CACHE_BACKEND_DB	Endpoint URL of the backend database for read-through & write-behind sync.	(Disabled)
SERV_CACHE_PEERS	Comma-separated URLs of peer ServCache nodes to replicate mutations (e.g. http://peer1:8088,http://peer2:8088).	(Disabled)

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Running Locally

1. In-Memory Mode

go run main.go --addr :8088

2. Redis Mode

go run main.go --addr :8088 --redis-url redis://localhost:6379

3. Verification Suite

Run integration and unit tests:

go test -v ./...