Nextjs Cache Handler MCP Server

@leejpsd/nextjs-cache-handler

v0.3.0 — install with npm install @leejpsd/nextjs-cache-handler. Production-validated against AWS ECS Fargate with multi-instance Redis (v0.1: 24h live-traffic soak; v0.3: fresh multi-instance verification incl. a live Redis-reboot drill with zero 5xx — see docs/staging-verification-2026-08-01.md).

v0.3 adds: Next.js 15 support (ISR handler), reconnect with exponential backoff (no more permanent memory-only latch), request-scoped GET deduplication, transparent gzip/brotli compression, Redis Sentinel support, a built-in OpenTelemetry emitter at /otel, and an LRU-bounded memory fallback.

🤖 For AI agents

Working with Claude Code / Codex / Cursor? Give your agent this URL and it will install and wire everything (version detection, wrapper files, next.config patch, verification):

https://raw.githubusercontent.com/leejpsd/nextjs-cache-handler/main/setup-instructions/setup.md

An agent skill with decision tables, invalidation semantics, and a troubleshooting playbook ships in the package (AGENTS.md, skills/nextjs-redis-cache/SKILL.md) and via npx skills add leejpsd/nextjs-cache-handler.

For cache operations from your agent (health, tag state, safe invalidation), the companion MCP server is on the official registry as io.github.leejpsd/nextjs-cache-handler-mcp — or one command: npx nextjs-cache-handler init --yes wires handlers, rules, and .mcp.json together.

---

The Redis cache handler for Next.js 15/16 that ships both cacheHandler (ISR / Pages Router) and cacheHandlers ('use cache' directive, cacheComponents: true) — the area where @fortedigital/nextjs-cache-handler currently lists "Help needed".

// next.config.ts
const nextConfig = {
  cacheComponents: true,
  cacheHandler: require.resolve("./cache-incremental.cjs"),
  cacheHandlers: { default: require.resolve("./cache-components.cjs") },
};

// cache-components.cjs
const { createCacheComponentsHandler } = require("@leejpsd/nextjs-cache-handler/cache-components");
module.exports = createCacheComponentsHandler({
  client: { type: "redis", url: process.env.REDIS_URL },
  buildNamespace: process.env.DEPLOYMENT_VERSION, // auto-isolates deploys
});

That's it. 'use cache', revalidateTag, updateTag, cacheLife all work.

---

Why this exists

Next.js 16 split caching into two handler interfaces:

As of 2026-05, the leading OSS Redis handler @fortedigital/nextjs-cache-handler@3.2.0 declares peerDependencies.next: ">=16.1.5" but the README marks the new plural interface as ❌ "Not yet supported - Help needed":

📅 Compatibility matrix re-verified 2026-07-31 (from each project's published README/registry metadata). The OSS Next.js cache handler ecosystem moves quickly — please verify @fortedigital and nextjs-turbo-redis-cache directly before relying on this comparison.

PR #207 on @fortedigital (their cacheHandlers attempt) was held up in review over PHASE_PRODUCTION_BUILD handling — which this package has from the start.

---

Quick start

Install

npm install @leejpsd/nextjs-cache-handler redis
# or
npm install @leejpsd/nextjs-cache-handler ioredis

redis and ioredis are optional peer dependencies — install whichever client you use. Both can be present.

Wire up

Two CommonJS wrapper files in your project root (Next.js's require.resolve pattern doesn't accept ESM directly):

// cache-components.cjs
const { createCacheComponentsHandler } = require("@leejpsd/nextjs-cache-handler/cache-components");
module.exports = createCacheComponentsHandler({
  client: { type: "redis", url: process.env.REDIS_URL },
  buildNamespace: process.env.DEPLOYMENT_VERSION,
  abortTimeoutMs: 1500,
});

// cache-incremental.cjs
const { createIncrementalCacheHandler } = require("@leejpsd/nextjs-cache-handler/incremental");
module.exports = createIncrementalCacheHandler({
  client: { type: "redis", url: process.env.REDIS_URL },
  buildNamespace: process.env.DEPLOYMENT_VERSION,
  abortTimeoutMs: 1500,
});

// next.config.ts
import path from "path";
import type { NextConfig } from "next";

const enabled = !!process.env.REDIS_URL && process.env.DISABLE_REDIS_CACHE_HANDLER !== "true";

const nextConfig: NextConfig = {
  output: "standalone",
  outputFileTracingRoot: path.join(__dirname),
  cacheComponents: true,
  deploymentId: process.env.DEPLOYMENT_VERSION,
  generateBuildId: async () => process.env.DEPLOYMENT_VERSION ?? "dev-build",
  cacheMaxMemorySize: 0, // delegate everything to the Redis handler
  cacheHandler: enabled ? require.resolve("./cache-incremental.cjs") : undefined,
  cacheHandlers: enabled ? { default: require.resolve("./cache-components.cjs") } : {},
};
export default nextConfig;

Use in your code

// app/blog/page.tsx
import { cacheLife, cacheTag, revalidateTag } from "next/cache";

async function getPosts() {
  "use cache";
  cacheLife("hours");
  cacheTag("posts");
  return await db.post.findMany();
}

// Server Action — invalidate
async function publishPost(formData: FormData) {
  "use server";
  await db.post.create({ data: Object.fromEntries(formData) });
  revalidateTag("posts", "max");
}

export default async function Page() {
  const posts = await getPosts();
  return <ul>{posts.map((p) => <li key={p.id}>{p.title}</li>)}</ul>;
}

---

Configuration reference

interface CacheHandlerOptions {
  client: RedisClientFactory | RedisClientConfig;
  keyPrefix?: string;             // default: "next-cache:" / "next-incremental:"
  buildNamespace?: string | (() => string);  // default: env DEPLOYMENT_VERSION || GIT_HASH || "unversioned"
  abortTimeoutMs?: number;        // default: 1500
  fallback?: "auto" | "always" | "never";    // default: "auto"
  staleWhileRevalidate?: boolean; // default: true (cache-components only)
  singleFlight?: boolean;         // default: false — see "Single-flight refresh lock" below
  singleFlightLockTtlSec?: number; // default: 10
  isBuildPhase?: () => boolean;   // override PHASE_PRODUCTION_BUILD detection
  hashTag?: boolean;              // default: false (set true on Redis Cluster)
  memoryMaxEntries?: number;      // default: 1000 — LRU cap for the in-memory fallback
  compression?: "gzip" | "brotli"; // default: off — transparent value compression (node:zlib)
  onMetric?: (event: MetricEvent) => void;
  logger?: Logger;
}

type RedisClientConfig =
  | { type: "redis";    url: string; password?: string; tls?: boolean; connectTimeout?: number }
  | { type: "ioredis";  url: string; password?: string; tls?: boolean; connectTimeout?: number }
  | { type: "cluster";  nodes: { host: string; port: number }[]; password?: string; tls?: boolean }
  | { type: "sentinel"; sentinels: { host: string; port: number }[]; name: string;
      password?: string; sentinelPassword?: string; tls?: boolean; connectTimeout?: number };

Full reference: docs/api.md.

---

Production checklist

• DEPLOYMENT_VERSION env injected at runtime — every entry key is prefixed with this so old prerender HTML can't bleed across deploys. For Docker, set ENV DEPLOYMENT_VERSION=... in your runner stage, not just the builder. (See docs/build-phase.md.)
• cacheMaxMemorySize: 0 — turn off Next's local LRU so multi-instance reads always hit Redis (or the explicit memory fallback).
• outputFileTracingRoot pinned — required for output: "standalone" to avoid static-chunk-404 issues during a deploy.
• abortTimeoutMs: 1500 (default) — protects against a stuck Redis connection from hanging the request thread.
• Redis Cluster: set hashTag: true — multi-key Lua scripts (set-with-tags.lua, revalidate-hard.lua) require all KEYS to land on the same hash slot. Without hashTag, cluster deployments will hit CROSSSLOT Keys in request don't hash to the same slot. The flag wraps the namespace in {} so every key for a given deploy hashes together. Cluster support is validated by a dedicated e2e suite against a real 3-master cluster (npm run test:cluster, also in CI) — covering the multi-key Lua scripts, per-master SCAN propagation, and both handlers. Not yet load-tested at production scale.
• Redis maxmemory-policy: allkeys-lru or noeviction — if you need bounded memory, choose allkeys-lru. Otherwise noeviction keeps tag indices intact.
• TLS — use rediss:// URLs (e.g. ElastiCache in-transit encryption). The library auto-detects from the URL scheme.
• Health check — call your own /api/health that pings Redis (separate from the handler) so a Redis outage surfaces in your monitoring without inducing 5xx in user requests.

Compatibility with Redis-protocol services

---

Single-flight refresh lock (v0.2)

The cacheHandlers (plural) interface returns stale entries inside the SWR window so users get an instant response while the background refresh completes. With many instances, the moment an entry crosses the revalidate boundary, every instance independently triggers its own refresh — N parallel re-renders for the same key, each hitting your origin once.

singleFlight: true adds an opt-in Redis lock (refresh-tag-lock.lua, default TTL 10s) at the SWR boundary. The first instance to acquire it becomes the leader and runs the refresh; the rest become followers, keep serving the same stale entry, and wait for the leader's write to land. The lock is observability-only at the handler layer — Next.js still drives the actual refresh; we just suppress the stampede.

createCacheComponentsHandler({
  client: { type: "redis", url: process.env.REDIS_URL },
  singleFlight: true,         // default false
  singleFlightLockTtlSec: 10, // default 10
});

Two new MetricEvent types appear on onMetric:

If lock acquisition fails (Redis hiccup, TTL race), the handler defaults to the follower path — the stale entry is always served, never dropped. This is intentional: the lock is an optimization, not a correctness-critical primitive.

When not to enable single-flight: small fleets (1–2 instances) where Next's per-process serialization already covers the stampede risk. Adding a Redis round-trip per stale read isn't free.

See docs/architecture.md for the full state machine and a reference to the Lua script body.

---

OpenTelemetry instrumentation (v0.2)

The handler doesn't bundle @opentelemetry/api (zero runtime dependencies stays a goal). Instead, the onMetric(event) hook gives strictly-typed events you can pipe into whatever observability stack you already run.

examples/opentelemetry/ is a copy-paste reference wrapper that:

• exposes a nextjs_cache.events_total counter dimensioned on type / freshness / backend / reason / op
• exposes a nextjs_cache.op_latency_ms histogram for events that carry an ms field
• keeps cardinality bounded — cache keys and tag names are never emitted as attributes

See examples/opentelemetry/README.md for setup and three suggested dashboards (hit rate, single-flight leadership distribution, op latency tails).

---

How it differs from @fortedigital/nextjs-cache-handler

Three deliberate departures, all rooted in lessons from production incidents (see docs/):

1. Build-phase skip is the default, not an opt-in. Every Redis call goes through a shouldUseRedis() gate that short-circuits when process.env.NEXT_PHASE === "phase-production-build". PR #207 on @fortedigital was rejected for missing exactly this.
2. Deployment isolation is automatic. Every entry key includes BUILD_NAMESPACE (=process.env.DEPLOYMENT_VERSION) by default. New deploys can never read entries written by old ones — fixes the "static chunk 404 after deploy" failure mode without manual cache flushes.
3. Lua-atomic tag updates. set writes the entry and updates tag indices in a single Lua transaction. updateTags(..., {expire: 0}) removes matching entries with one EVALSHA. No window for half-applied sets to leak dangling tag members.

When @fortedigital ships its cacheHandlers support (PR #207 / feature branch feature/cache-components), this package will continue to differ on (2) and (3). For (1), we consider it table-stakes; the upstream's eventual implementation should converge on the same behavior.

---

Compatibility

• Next.js: >=15.0.0 <17
  • cacheHandler (singular, ISR): Next 15 and 16 — the handler accepts both ctx shapes (Next 15's ctx.revalidate / kindHint, Next 16's ctx.cacheControl / kind)
  • cacheHandlers (plural, 'use cache'): Next >=16.1.5 only — the interface does not exist before 16
• Node.js: >=20
• redis: >=5.0.0 (peer, optional)
• ioredis: >=5.0.0 (peer, optional) — also powers type: "cluster" and type: "sentinel" (Sentinel master discovery with automatic failover)

ESM and CJS dual-published, full TypeScript types, validated via arethetypeswrong and publint.

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Roadmap

• v0.1.0 (2026-05) — Both handlers, SWR, Lua atomicity, build-phase skip, redis@5 + ioredis adapters, AbortSignal, in-memory fallback with TTL, soft-tag freshness check ✅
• v0.2.0 (2026-05) — Single-flight refresh lock with leader/follower metrics, OpenTelemetry reference adapter, integration tests against real Redis 7 (21 scenarios over redis@5 + ioredis), GitHub Actions OIDC publish path with provenance attestation ✅
• v0.3.0 (2026-08) — Next.js 15 ISR support, reconnect backoff (no permanent connect-failure latch), request-scoped GET deduplication, gzip/brotli compression, Redis Sentinel, built-in OpenTelemetry emitter (/otel), LRU-bounded memory fallback, ESM peer-loading fixes ✅
• v0.4.0 — Build-phase cache seeding (prepopulate prebuilt pages), pub/sub-based tag propagation, Redis Cluster e2e validation, Vercel KV / Upstash adapter, 'use cache: remote' multi-tier setup

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License

MIT © 2026 Eddy Lee