Ignite

Your users click. Your function is already awake.

Firebase Cloud Functions cold start in 800ms–2s. Ignite eliminates that by detecting hover intent 150ms before a click and firing a non-blocking warm-up signal through a Rust edge proxy — so by the time the user's finger lifts, the container is hot.

How it works

1. User hovers over a button for >150ms — intent detected (onFocus for keyboard, onTouchStart for mobile)
2. sendBeacon fires a POST to the Rust proxy — non-blocking, zero impact on the user
3. Proxy authenticates, checks the allowlist, triggers warm-up via ctx.wait_until — returns 200 OK instantly
4. Firebase function receives __ignite: true, verifies the secret, exits early — container is now warm
5. User clicks — real request hits a warm container, cold start eliminated

Packages

Setup

Prerequisites

• Cloudflare account + Wrangler CLI for the proxy
• Firebase project with Cloud Functions v2

1. Deploy the Proxy

The proxy is a Rust/Wasm Cloudflare Worker that sits between your frontend and Firebase.

# Install Rust + wrangler if you haven't
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
npm install -g wrangler && wrangler login

cd packages/proxy
wrangler secret put IGNITE_SECRET       # shared auth key — keep this private
wrangler secret put FIREBASE_BASE_URL   # e.g. https://us-central1-your-project.cloudfunctions.net
wrangler secret put ALLOWED_FUNCTIONS   # comma-separated: createProject,processPayment,loginUser
wrangler deploy

The allowlist uses exact-match validation — createProject will never match createProjectAdmin.

2. Wrap your Firebase Function

import { igniteWrapper, igniteMiddleware } from '@farhanmansuri/ignite-firebase';

// onCall
export const createProject = igniteWrapper(async (req) => {
  // your logic here — never reached on warm signals
}, process.env.IGNITE_SECRET);

// onRequest
export const processPayment = igniteMiddleware(async (req, res) => {
  // your logic here
}, process.env.IGNITE_SECRET);

3. Add to your frontend

React

import { useIgnite } from '@farhanmansuri/ignite-react';

const ignite = useIgnite('createProject', {
  proxyUrl: 'https://your-proxy.workers.dev',
  onWarm: (fn, ms) => console.log(`${fn} warmed in ${ms}ms`),
  onError: (err) => console.error(err),
});

<button {...ignite} onClick={handleSubmit}>
  Create Project
</button>

Vue 3

<template>
  <button
    @mouseenter="onMouseEnter"
    @mouseleave="onMouseLeave"
    @click="handleSubmit"
  >
    Create Project
  </button>
</template>

<script setup lang="ts">
import { useIgnite } from '@farhanmansuri/ignite-vue';

const { onMouseEnter, onMouseLeave } = useIgnite('createProject', {
  proxyUrl: 'https://your-proxy.workers.dev',
});
</script>

Svelte

<script>
  import { ignite } from '@farhanmansuri/ignite-svelte';
</script>

<button
  use:ignite={{ functionName: 'createProject', proxyUrl: 'https://your-proxy.workers.dev' }}
  on:click={handleSubmit}
>
  Create Project
</button>

Security

• Shared secret — X-Ignite-Key header verified on the proxy and re-verified on the Firebase function. Never exposed to the browser.
• Exact-match allowlist — ALLOWED_FUNCTIONS env var on the proxy. split(',').any(|s| s.trim() == name) — no substring bypass possible.
• Early exit — the Firebase function returns { status: "ignited" } before touching any business logic or incurring billing for real work.

Architecture

Browser
  │  mouseenter (150ms)
  ▼
ignite-react / vue / svelte
  │  sendBeacon (non-blocking)
  ▼
ignite-proxy  (Rust · Cloudflare Worker)
  │  auth + allowlist + ctx.wait_until
  ▼
Firebase Function  →  __ignite: true  →  early exit, container warm

Troubleshooting

Warm signals are firing but cold starts still happen

Most likely cause: The Firebase function container spun down between the warm signal and the click.

• Check that your hoverTimeout (default 150ms) is appropriate — increase it if users tend to click slowly after hovering
• Confirm the warm signal is reaching Firebase: add onWarm: (fn, ms) => console.log(...) and check the browser console
• Firebase containers can spin down in as little as a few minutes of inactivity — Ignite only prevents cold starts when the user hovers shortly before clicking

The proxy returns 401 Unauthorized

The X-Ignite-Key header doesn't match IGNITE_SECRET on the proxy.

1. Verify the secret is set on the proxy: wrangler secret list
2. Verify the secret matches what you pass as apiKey in the frontend options
3. If you recently rotated the secret, redeploy the proxy: wrangler deploy

The proxy returns 403 Forbidden

The function name is not in ALLOWED_FUNCTIONS.

1. Check the exact value: wrangler secret list (won't show the value, but confirms it exists)
2. The allowlist is exact-match and case-sensitive — CreateProject ≠ createProject
3. Update the allowlist: wrangler secret put ALLOWED_FUNCTIONS then redeploy

The proxy returns 429 Too Many Requests

Rate limit hit — 30 warm signals per IP per 60 seconds.

• This is normal if you're testing rapidly from the same machine
• In production this should never trigger for real users — each user hovers once before clicking
• If you need a higher limit, change RATE_LIMIT_MAX in packages/proxy/src/lib.rs and redeploy

sendBeacon fires but nothing reaches Firebase

The proxy deployed successfully but the background ctx.wait_until call to Firebase is failing silently.

1. Check FIREBASE_BASE_URL is set and correct: wrangler secret list
2. The URL should be the base path — no trailing slash, e.g. https://us-central1-myapp.cloudfunctions.net
3. Confirm the function name matches exactly: createProject not createProject-v2
4. Check Firebase Function logs in the Google Cloud console for errors

Firebase function is being called but onWarm is never triggered

sendBeacon doesn't return a response body — onWarm latency is measured from queue time, not execution. This is expected.

If using the fetch fallback (sendBeacon unavailable), onWarm fires after the fetch resolves.

onError fires with AbortError

The fetch fallback timed out (default 5 seconds). The proxy may be slow or unreachable.

1. Check your Cloudflare Worker is deployed and healthy in the Cloudflare dashboard
2. Try increasing the timeout by modifying FETCH_TIMEOUT_MS in packages/core/src/index.ts if your proxy is in a distant region

Warm signals work in dev but not in production

CORS: Make sure the proxy wrangler.toml is deployed — the Access-Control-Allow-Origin: * header is set by the Worker, not by Firebase.

CSP: If your app uses a Content-Security-Policy, add your proxy URL to connect-src:

Content-Security-Policy: connect-src 'self' https://your-proxy.workers.dev;

How to rotate IGNITE_SECRET

1. Generate a new secret: openssl rand -hex 32
2. Update the proxy: wrangler secret put IGNITE_SECRET → enter new value → wrangler deploy
3. Update Firebase env: re-deploy your Firebase functions with the new secret value
4. Update your frontend apiKey option and redeploy your app
5. The old secret stops working immediately after step 2

Debugging locally

# Run the proxy locally (requires wrangler + Rust toolchain)
cd packages/proxy
wrangler dev

# Test it directly
curl -X POST "http://localhost:8787/warm?fn=createProject" \
  -H "X-Ignite-Key: your-secret" \
  -H "Content-Type: application/json" \
  -d '{"__ignite": true}'
# Expected: "Ignited"

Development

pnpm install
pnpm build        # builds all JS packages
pnpm test         # runs all test suites (46 tests)

# Proxy tests (requires Rust)
cd packages/proxy && cargo test