@nextlegacy/sveltekit-adapter-deno NPM

SvelteKit Adapter for Deno 🦕

Adapter for SvelteKit apps that generates a standalone Deno server. 🦕

This adapter aims to be a drop-in replacement for @sveltejs/adapter-node, utilizing Deno's built-in Deno.serve for handling HTTP requests and serving static files, removing the need for Node.js ecosystem dependencies like Polka or Sirv. ✨

For more information on SvelteKit adapters in general, see the official documentation.

Key Features 🔥

🦕 Deno Runtime: Uses Deno's built-in features for handling HTTP requests and serving static files.
📦 Basically no runtime Dependencies: Finished build only uses Deno's standard library and Node.js compatible imports.
🔄 Drop-in Replacement: Designed to work seamlessly as a replacement for adapter-node in most configurations.

Installation 🛠️

Install the adapter as a development dependency in your SvelteKit project:

# Using deno
deno install npm:@nextlegacy/sveltekit-adapter-deno

# Using npm
npm install -D @nextlegacy/sveltekit-adapter-deno

# Using yarn
yarn add -D @nextlegacy/sveltekit-adapter-deno

# Using pnpm
pnpm add -D @nextlegacy/sveltekit-adapter-deno

Usage 🚀

Configure svelte.config.js: Update your configuration to use the adapter:

import adapter from "@nextlegacy/sveltekit-adapter-deno";

/** @type {import("@sveltejs/kit").Config} */
const config = {
  kit: {
    adapter: adapter({
      // Optional: specify adapter options here (see Configuration below)
    }),

    // other kit options...
  }
};

export default config;

Build your application: Use the Deno task defined in your deno.json (or the corresponding npm script):

# Using Deno tasks (recommended)
deno task build

# Or using npm scripts (if configured)
# npm run build

Run the Deno server: Execute the generated entry point build/index.ts with Deno, granting necessary permissions:
```
deno run --allow-net --allow-read --allow-env build/index.ts
```

Example Project 🌟

For a complete example setup, check out my template repository: NextLegacy/SvelteKit-Deno-Tempalte

Configuration ⚙️

This adapter accepts the same options object as the official @sveltejs/adapter-node:

Option	Type	Default	Description
`out`	`string`	`'build'`	The directory to write the server files to.
`precompress`	`boolean`	`true`	If `true`, precompresses static assets using gzip and brotli.
`envPrefix`	`string`	`''`	Specifies a prefix for environment variables passed to the server. See SvelteKit docs.

Refer to the adapter-node documentation for details on all available options.

Environment Variables 📑

This adapter recognizes a subset of the environment variables used by @sveltejs/adapter-node to control the built server's behavior.

Note: Variables related to client address headers (ADDRESS_HEADER, XFF_DEPTH), origin determination (ORIGIN, PROTOCOL_HEADER, HOST_HEADER, PORT_HEADER), and systemd socket activation (LISTEN_PID, LISTEN_FDS) are not currently implemented in this adapter.

The following variables are supported:

Variable	Default	Description
`HOST`	`'0.0.0.0'`	The IP address to bind to.
`PORT`	`3000` (if `SOCKET_PATH` unset)	The port to listen on.
`SOCKET_PATH`	`false`	Unix socket path to listen on (overrides `HOST`/`PORT`).
`BODY_SIZE_LIMIT`	`512K`	Maximum request body size (e.g., `512K`, `1M`, `Infinity`).
`SHUTDOWN_TIMEOUT`	`30`	Seconds to wait for graceful shutdown.
`IDLE_TIMEOUT`	`0`	Seconds of inactivity before server exits (useful for socket activation).

For a detailed explanation of each variable and its usage, please refer to the @sveltejs/adapter-node Environment Variables Documentation.

Benchmarks 📊

I plan to add better real-world benchmarks soon. For now, here's a simple proof of concept benchmark using autocannon and a relatively simple SvelteKit project that I had lying around:

(Note: Benchmarks run using autocannon -c 100 -d 5 -p 10. Your results may vary based on hardware and application complexity.) (run locally w/ Deno 2.3.1)

@nextlegacy/adapter-deno:

┌─────────┬────────┬────────┬────────┬────────┬───────────┬──────────┬────────┐
│ Stat    │ 2.5%   │ 50%    │ 97.5%  │ 99%    │ Avg       │ Stdev    │ Max    │
├─────────┼────────┼────────┼────────┼────────┼───────────┼──────────┼────────┤
│ Latency │ 147 ms │ 222 ms │ 239 ms │ 240 ms │ 219.4 ms  │ 23.84 ms │ 250 ms │
└─────────┴────────┴────────┴────────┴────────┴───────────┴──────────┴────────┘
┌───────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┐
│ Stat      │ 1%      │ 2.5%    │ 50%     │ 97.5%   │ Avg     │ Stdev   │ Min     │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Req/Sec   │ 4,203   │ 4,203   │ 4,523   │ 4,535   │ 4,453.2 │ 126.89  │ 4,201   │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Bytes/Sec │ 70.8 MB │ 70.8 MB │ 76.2 MB │ 76.4 MB │ 75 MB   │ 2.15 MB │ 70.8 MB │
└───────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

@sveltejs/adapter-node:

┌─────────┬────────┬────────┬────────┬────────┬───────────┬─────────┬────────┐
│ Stat    │ 2.5%   │ 50%    │ 97.5%  │ 99%    │ Avg       │ Stdev   │ Max    │
├─────────┼────────┼────────┼────────┼────────┼───────────┼─────────┼────────┤
│ Latency │ 250 ms │ 336 ms │ 448 ms │ 481 ms │ 345.96 ms │ 48.07 ms│ 535 ms │
└─────────┴────────┴────────┴────────┴────────┴───────────┴─────────┴────────┘
┌───────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┬─────────┐
│ Stat      │ 1%      │ 2.5%    │ 50%     │ 97.5%   │ Avg     │ Stdev   │ Min     │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Req/Sec   │ 2,197   │ 2,197   │ 2,967   │ 3,131   │ 2,807   │ 336.18  │ 2,197   │
├───────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ Bytes/Sec │ 37 MB   │ 37 MB   │ 50 MB   │ 52.8 MB │ 47.3 MB │ 5.66 MB │ 37 MB   │
└───────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

Production Readiness ✅

I am slowly starting to use this adapter in production environments as a drop-in replacement for adapter-node without issues so far.

However, as a community project leveraging newer Deno APIs, I recommend performing thorough testing for your specific use case before deploying to critical production systems. 🧪 While it aims for stability and follows @sveltejs/adapter-node's behavior closely, 100% production readiness compared to the more battle-tested @sveltejs/adapter-node cannot be guaranteed at this stage.