WASI: WebAssembly di Luar Browser

WASI (WebAssembly System Interface) memungkinkan Wasm berjalan di server, CLI, dan embedded systems — bukan hanya browser. WASI menyediakan interface standar ke filesystem, network, clock, dan resource sistem lainnya.

Kenapa WASI?

• Universal binary — Compile sekali, jalan di mana saja (Linux, macOS, Windows, Edge)
• Sandboxed by default — Tidak bisa akses file/network tanpa izin eksplisit
• Near-native speed — Lebih cepat dari container Docker untuk cold start
• Tiny footprint — Wasm module biasanya beberapa MB vs ratusan MB Docker image

Runtime: Wasmtime

# Install wasmtime
curl https://wasmtime.dev/install.sh -sSf | bash

# Rust → WASI
rustup target add wasm32-wasip1

# Compile
cargo build --target wasm32-wasip1 --release

# Jalankan
wasmtime target/wasm32-wasip1/release/myapp.wasm

# Dengan akses filesystem (sandboxed)
wasmtime --dir=./data target/wasm32-wasip1/release/myapp.wasm

Contoh: CLI Tool

// src/main.rs (target: wasm32-wasip1)
use std::env;
use std::fs;
use std::io::{self, BufRead};

fn main() {
    let args: Vec<String> = env::args().collect();

    if args.len() < 2 {
        eprintln!("Usage: wordcount <file>");
        std::process::exit(1);
    }

    let content = fs::read_to_string(&args[1])
        .expect("Cannot read file");

    let lines = content.lines().count();
    let words = content.split_whitespace().count();
    let chars = content.chars().count();

    println!("{} lines, {} words, {} chars", lines, words, chars);
}

WASI Preview

• Preview 1 — Stabil. File I/O, args, env vars, clock, random
• Preview 2 — Networking (HTTP), streams, component model integration

WASI vs Docker

• Startup time — WASI: ~1ms, Docker: ~500ms-2s
• Image size — WASI: 1-5MB, Docker: 50-500MB
• Security — WASI: capability-based (deny by default), Docker: namespace isolation
• Portability — WASI: true cross-platform binary, Docker: Linux-only (VM di macOS/Windows)

Use Cases Server-Side

• Serverless functions — Cold start super cepat (Fermyon Spin, Wasmtime)
• Plugin system — Jalankan kode user dalam sandbox aman
• Edge computing — Deploy binary kecil ke CDN edge nodes
• Embedded — IoT devices dengan resource terbatas