refactor: optimize Docker build with caching + fix build issues

Dockerfile

@@ -1,40 +1,68 @@
-ARG BUILDER_DIR=/srv/lnp
+# This image uses cargo-chef to build the application in order to compile
+# the dependencies apart from the main application. This allows the compiled
+# dependencies to be cached in the Docker layer and greatly reduce the
+# build time when there isn't any dependency changes.
+#
+# https://github.com/LukeMathWalker/cargo-chef
 
+ARG SRC_DIR=/usr/local/src/lnp
+ARG BUILDER_DIR=/srv/lnp
 
-FROM rust:1.59.0-slim-buster as builder
+# Base image
+FROM rust:1.59.0-slim-bullseye as chef
 
-ARG SRC_DIR=/usr/local/src/lnp
+ARG SRC_DIR
 ARG BUILDER_DIR
 
-WORKDIR "$SRC_DIR"
+RUN apt-get update && apt-get install -y build-essential
+
+RUN rustup default stable
+RUN rustup update
+RUN cargo install cargo-chef --locked
 
-COPY doc ${SRC_DIR}/doc
-COPY shell ${SRC_DIR}/shell
-COPY src ${SRC_DIR}/src
-COPY build.rs Cargo.lock Cargo.toml codecov.yml config_spec.toml \
-     LICENSE license_header README.md ${SRC_DIR}/
+WORKDIR $SRC_DIR
 
-WORKDIR ${SRC_DIR}
+# Cargo chef step that analyzes the project to determine the minimum subset of
+# files (Cargo.lock and Cargo.toml manifests) required to build it and cache
+# dependencies
+FROM chef AS planner
 
-RUN mkdir "${BUILDER_DIR}"
+COPY . .
+RUN cargo chef prepare --recipe-path recipe.json
 
-RUN cargo install --path . --root "${BUILDER_DIR}" --bins --all-features
+FROM chef AS builder
 
+ARG SRC_DIR
+ARG BUILDER_DIR
 
-FROM debian:buster-slim
+COPY --from=planner "${SRC_DIR}/recipe.json" recipe.json
+
+# Build dependencies - this is the caching Docker layer
+RUN cargo chef cook --release --recipe-path recipe.json --target-dir "${BUILDER_DIR}"
+
+# Copy all files and build application
+COPY . .
+RUN cargo build --release --target-dir "${BUILDER_DIR}" --bins --all-features
+
+# Final image with binaries
+FROM debian:bullseye-slim as final
 
 ARG BUILDER_DIR
 ARG BIN_DIR=/usr/local/bin
-ARG DATA_DIR=/var/lib/lnp
-ARG USER=lnpd
+ARG DATA_DIR=/var/lib/lnpd
+ARG USER=lnp
 
 RUN adduser --home "${DATA_DIR}" --shell /bin/bash --disabled-login \
         --gecos "${USER} user" ${USER}
 
 COPY --from=builder --chown=${USER}:${USER} \
-     "${BUILDER_DIR}/bin/" "${BIN_DIR}"
+     "${BUILDER_DIR}/release" "${BIN_DIR}"
 
 WORKDIR "${BIN_DIR}"
+
+# Remove build artifacts in order to keep only the binaries
+RUN rm -rf */ *.d .[^.] .??*
+
 USER ${USER}
 
 VOLUME "$DATA_DIR"
@@ -44,4 +72,4 @@ EXPOSE 62962
 
 ENTRYPOINT ["lnpd"]
 
-CMD ["-vvv", "--data-dir", "/var/lib/lnp"]
+CMD ["-vvv", "--data-dir", "/var/lib/lnpd"]