Build Docker Containers from a Monorepo

Written 2024-02-29 — Updated 2024-03-02

A .dockerignore file is very important here to reduce the amount of context that needs to be sent to the builder process. Note that the .dockerfile file requires prepending **/ to any match that you want to apply outside of the root directory.
- ```
**/node_modules
**/*.js
**/*.ts
**/apps
**/target
!apps/my-app
apps/my-app/target
```

Then you will want to build with the context directory being the root of the monorepo

#!/bin/bash
docker build \
  -t $NAME \
  -f Dockerfile \
  --ignorefile .dockerignore \
  ../../ # The monorepo root

Building for Rust
If your application is built in Rust, then you can use cargo-chef to help speed up the builds, but the default recipe needs a few directory tweaks if your application has dependencies elsewhere in the monorepo.
Something like this works well:

# This Dockerfile works with cargo chef, which prebuilds dependencies in a
# separate Docker image to speed up builds.

FROM lukemathwalker/cargo-chef:latest-rust-1 AS chef
RUN apt-get update && apt-get install -y pkg-config libssl-dev
WORKDIR /app/apps/my-app

FROM chef as planner
COPY ./libs/some-lib /app/libs/some-lib
COPY ./apps/my-app /app/apps/my-app
RUN cargo chef prepare --recipe-path recipe.json

FROM chef as builder
COPY --from=planner /app/apps/my-app/recipe.json recipe.json
# Build dependencies - this is the caching Docker layer!
COPY ./libs/some-lib /app/libs/some-lib
RUN cargo chef cook --release --recipe-path recipe.json
# Build application
COPY ./apps/my-app /app/apps/my-app
RUN cargo build --release --bin my-app

FROM debian:bookworm-slim as runtime
RUN apt-get update && apt-get install -y pkg-config libssl-dev ca-certificates
RUN update-ca-certificates
COPY --from=builder /app/apps/my-app/target/release/my-app /usr/local/bin
ENTRYPOINT ["/usr/local/bin/my-app"]

If building from Mac or Windows, you may also see benefits from increasing the amount of RAM available to the Docker VM. For example, the default VM from Podman uses only 2GB and while the Rust compiler can run within those boundaries, it's very slow. Using a 16 or 32GB VM can speed up the compilation by an order of magnitude.

Build Docker Containers from a Monorepo

Building for Rust