Advanced Cache (advCache)

High‑performance in‑memory HTTP cache & reverse proxy for latency‑sensitive workloads. Built in Go on top of fasthttp, with sharded storage, TinyLFU admission, background refresh, upstream controls, and minimal‑overhead observability (Prometheus + OpenTelemetry).

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Why advCache?

• Throughput: 160–170k RPS locally; ~250k RPS sustained on 24‑core bare‑metal with a 50GB cache.
• Memory safety: 1.5–3GB overhead at 50GB (no traces); ~7GB at 100% OTEL sampling.
• Hot path discipline: zero allocations, sharded counters, per‑shard LRU, TinyLFU admission.
• Control plane: runtime API for toggles (admission, eviction, refresh, compression, observability).
• Observability: Prometheus/VictoriaMetrics metrics + OpenTelemetry tracing.
• Kubernetes‑friendly: health probes, config via ConfigMap, Docker image.

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Quick start (production‑capable starter config)

Edit the CHANGEME fields and run. This is a complete config based on advcache.cfg.yaml, trimmed for a fast start but fully runnable.

cache:
  env: prod
  enabled: true
  logs:
    level: debug
  runtime:
    gomaxprocs: 0
  api:
    name: advCache.local
    port: '8020             # <-- CHANGEME: API port to listen on'
  upstream:
    backend:
      id: example-ams-web
      enabled: true
      policy: deny
      host: service-example:8080
      scheme: http
      rate: 15000
      concurrency: 4096
      timeout: 10s
      max_timeout: 1m
      use_max_timeout_header: ''
      healthcheck: /healthcheck
      addr: http://127.0.0.1:8081  # <-- CHANGEME: your upstream origin URL
      health_path: /health
  compression:
    enabled: true
    level: 1
  data:
    dump:
      enabled: true
      dump_dir: public/dump
      dump_name: cache.dump
      crc32_control_sum: true
      max_versions: 3
      gzip: false
    mock:
      enabled: false
      length: 1000000
  storage:
    mode: listing
    size: 53687091200
  admission:
    enabled: true
    capacity: 2000000
    sample_multiplier: 4
    shards: 256
    min_table_len_per_shard: 65536
    door_bits_per_counter: 12
  eviction:
    enabled: true
    replicas: 32
    soft_limit: 0.8
    hard_limit: 0.99
    check_interval: 100ms
  lifetime:
    enabled: true
    ttl: 2h
    on_ttl: refresh
    beta: 0.35
    rate: 1000
    replicas: 32
    coefficient: 0.25
  observability:
    enabled: true
    service_name: advCache.local
    service_version: dev
    service_tenant: star
    exporter: http
    endpoint: 127.0.0.1:4318     # <-- CHANGEME: your OTEL Collector (http/4318 or grpc/4317)
    insecure: true
    sampling_mode: ratio
    sampling_rate: 0.1
    export_batch_size: 512
    export_batch_timeout: 3s
    export_max_queue: 1024
  forceGC:
    enabled: true
    interval: 6m
  metrics:
    enabled: true
  k8s:
    probe:
      timeout: 5s
  rules:
    /api/v2/pagedata:
      cache_key:
        query:
          - project
          - language
          - timezone
        headers:
          - Accept-Encoding
      cache_value:
        headers:
          - Vary
          - Server
          - Content-Type
          - Content-Length
          - Content-Encoding
          - Cache-Control

What to change first:

• cache.api.port — the port advCache listens on.
• cache.upstream.backend.addr — point to your origin.
• cache.compression.enabled — enable if latency budget allows (runtime‑toggle also available).
• cache.observability.* — set enabled: true and endpoint of your OTEL Collector; adjust sampling.
• cache.admission.enabled — true to protect hot set; details of TinyLFU/Doorkeeper in the main config comments.
• cache.upstream.policy — both deny and await are production‑ready; choose behavior:
  • deny → fail‑fast under pressure (good for synthetic load / when back‑pressure is handled elsewhere).
  • await → apply back‑pressure (preferred default in many prod setups).

Full field descriptions and advanced knobs are documented inline in the canonical advcache.cfg.yaml.

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Endpoints (runtime control plane)

• Main: GET /{any:*}
• Health: GET /k8s/probe
• Metrics: GET /metrics (Prometheus/VictoriaMetrics)
• Bypass: /cache/bypass, /on, /off
• Compression: /cache/http/compression, /on, /off
• Config dump: /cache/config
• Entry by key: /cache/entry?key=<uint64>
• Clear (two‑step): /cache/clear → then /cache/clear?token=<...>
• Invalidate: /cache/invalidate (supports X-Entries-Remove for remove entries and _path + any queries)
• Upstream policy: /cache/upstream/policy, /await, /deny
• Evictor: /cache/eviction, /on, /off, /scale?to=<n>
• Lifetime manager: /cache/lifetime-manager, /on, /off, /rate?to=<n>, /scale?to=<n>, /policy, /policy/remove, /policy/refresh
• Force GC: /cache/force-gc, /on, /off, /call
• Admission: /cache/admission, /on, /off
• Tracing: /cache/observability, /on, /off

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Observability: traces with minimal overhead

• Spans: ingress (server), upstream (client on miss/proxy), refresh (background).
• When disabled: fast no‑op provider (atomic toggle only).
• When enabled: stdout exporter → sync; OTLP (grpc/http) → batch exporter.

Enable quickly: set in YAML and/or toggle at runtime:

GET /cache/observability/on    # enable tracing now
GET /cache/observability/off   # disable tracing

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Build & Run

go build -o advCache ./cmd/main.go
./advCache -cfg ./advcache.starter.yaml
# Docker
docker build -t advcache .
docker run --rm -p 8020:8020 -v "$PWD/public/dump:/app/public/dump" advcache -cfg /app/advcache.starter.yaml

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Notes on performance

Remember that this depends largely on the specifics of your load.

• Local (4–6 CPU, 1–16KB docs, 20–25GB store): 160–170k RPS steady.
• Bare‑metal (24 CPU, 50GB store, prod traffic): ~250k RPS sustained.
• Memory overhead at 50GB: 1.5–3GB (no traces) • ~7GB (100% sampling).

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Testing

go test ./...

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Benching

go test -bench . -benchmem ./...

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License & Maintainer

Apache‑2.0 — see LICENSE.
Maintainer: Borislav Glazunov — [email protected] · Telegram @gl_c137