Module 34: Docker

Practice Tasks

Complete these tasks to reinforce what you learned in this module.

Task 1: Write a minimal Dockerfile

Write a Dockerfile that (1) uses FROM rust:1-bookworm AS builder, sets WORKDIR /app, copies Cargo.toml and src/, and runs cargo build --release. (2) Uses FROM debian:bookworm-slim, copies the binary from the builder stage to /usr/local/bin/, and sets CMD to run it. Use the binary name for this crate (e.g. the package name or the default binary name). No need to run Docker in the task; just produce the Dockerfile.

Expected Output:

A Dockerfile that builds and runs the course_34_docker binary (or the name you chose). Building with `docker build -t course34 .` and running with `docker run course34` should work from the crate directory.

Hint: Use two stages: a build stage with a Rust image (copy manifest and source, run cargo build --release) and a run stage with a slim image. Copy only the binary from the builder; set CMD to run it. The theory shows the structure.

Starter Code:

task.rs

// Task 1: Write minimal Dockerfile. See tasks/TASKS.md.
// Produce the Dockerfile in this crate directory (e.g. 34_docker/Dockerfile.task1).

fn main() {
    println!("See tasks/TASKS.md: write a minimal Dockerfile");
}

Task 2: Add dependency caching

Extend the Dockerfile so that the build stage first copies only Cargo.toml and Cargo.lock (create a minimal Cargo.lock if needed), then copies a dummy src/main.rs (e.g. fn main() {}), runs cargo build --release, then copies the real src/ and runs cargo build --release again. The goal is to cache the dependency compilation layer. Document in a comment why the dummy copy is used.

Expected Output:

Second and later builds are faster when only application code changes, because the dependency layer is cached.

Hint: To cache dependency compilation, copy only the manifest (and optionally a dummy source file) and run a first build; then copy the real source and build again. The second build recompiles only your code when deps are unchanged.

Starter Code:

task.rs

// Task 2: Add dependency caching to Dockerfile. See tasks/TASKS.md.

fn main() {
    println!("See tasks/TASKS.md: extend Dockerfile with dependency caching");
}

// Task 1: Write minimal Dockerfile. See tasks/TASKS.md. // Produce the Dockerfile in this crate directory (e.g. 34_docker/Dockerfile.task1). fn main() { println!("See tasks/TASKS.md: write a minimal Dockerfile"); }