Docker + WebAssembly - A New Era for Containers

Docker + WebAssembly Overview

Docker has started native support for WebAssembly (Wasm) workloads. You can manage traditional containers and Wasm containers with the same toolchain, enabling lighter and faster execution environments.

Why Wasm

Comparing Containers and Wasm

Creating Wasm Containers

Example in Rust

// main.rs
fn main() {
    println!("Hello from WebAssembly!");
}

# Build for Wasm target
rustup target add wasm32-wasip1
cargo build --target wasm32-wasip1 --release

Creating Dockerfile

# syntax=docker/dockerfile:1
FROM scratch
COPY ./target/wasm32-wasip1/release/hello.wasm /hello.wasm
ENTRYPOINT ["/hello.wasm"]

Build and Run

# Build Wasm image
docker buildx build --platform wasi/wasm -t hello-wasm .

# Run
docker run --runtime=io.containerd.wasmedge.v1 hello-wasm

WASIp2 (WASI Preview 2)

The new WASI specification enables more features.

// Filesystem access
use std::fs;

fn main() {
    let content = fs::read_to_string("/data/config.txt").unwrap();
    println!("Config: {}", content);
}

# Mount host directory
docker run --runtime=io.containerd.wasmedge.v1 \
  -v ./data:/data \
  hello-wasm

Docker Compose Integration

# docker-compose.yml
services:
  api:
    image: my-wasm-api
    platform: wasi/wasm
    runtime: io.containerd.wasmedge.v1
    ports:
      - "8080:8080"

  web:
    image: nginx
    depends_on:
      - api

Use Cases

Edge Computing

flowchart TB
    Cloud["Cloud<br/>(Full features)"]
    Edge["Edge<br/>(Resource limited)<br/>← Run lightweight with Wasm"]
    Device["Device"]

    Cloud --> Edge --> Device

Serverless Functions

• Fast cold start
• Good memory efficiency
• Safe in multi-tenant environments

Plugin Systems

• Sandboxed plugin execution
• Language-agnostic plugins

Supported Runtimes

# Check runtime
docker info | grep -i wasm

Limitations

Current limitations:
- Network functionality is limited
- Some system calls are not supported
- GPU/hardware access is restricted
- Existing Linux binaries cannot be directly executed

Summary

Docker + WebAssembly provides a new option in container technology. It’s expected to be utilized in workloads that require lightweight and fast startup, especially in edge and serverless environments. As WASI matures, it will support more use cases.