25WinterCamp-lab2 report

A - 快速入门与教育 2025寒期训练营
4

补充（解决源码修改后，重新构建镜像时间开销大）：

问题所在：

不修改源码的run build again不会导致时间开销增大很多，因为docker has cached all intermediate build artifacts,但是修改源码发生在RUN cargo build --release之前，所以需要重新执行build，重新下载和安装所有包，时间开销增大。
参考文章：https://depot.dev/blog/rust-dockerfile-best-practices

基本思想：

将整个任务拆分隔离，避免对于编译完成的并且不需要修改的dependencies进行rebuilt，即add more FROM satements to create a mutile-stage build

修改教程的Dockerfile:

(注: 这里直接使用了教程的optimization3)
详情请看代码注释：

# Image pre-built from the official Rust image
# base on the Debian Bullseye slim image
FROM rust:1.83.0-slim-bullseye AS base
RUN apt-get update && apt-get install -y pkg-config libssl-dev
# sccache will cache individual compilation artifacts so that they can be reused.
# This allows you to recompile individual dependencies only when needed.
RUN cargo install sccache 
# # cargo-chef will analyse the dependencise of the project and create a recipe(配方)
# # which will cache the dependencies and the build artifacts that are not changed.
# # so that,only the changed dependencies will be recompiled.
RUN cargo install cargo-chef
# # Set the environment variables for sccache
# # this means that when running cargo build, the sccache will run as a wrapper for rustc
# # and the cache will be stored in the /sccache directory
ENV RUSTC_WRAPPER=sccache SCCACHE_DIR=/sccachge


FROM base AS planner
WORKDIR /app
COPY . .
# cache cargo registry and sccache directory
RUN --mount=type=cache,target=/usr/local/cargo/registry \
    --mount=type=cache,target=$SCCACHE_DIR,sharing=locked \
    cargo chef prepare --recipe-path recipe.json


FROM base AS builder
WORKDIR /app
COPY --from=planner /app/recipe.json recipe.json
RUN --mount=type=cache,target=/usr/local/cargo/registry \
    --mount=type=cache,target=$SCCACHE_DIR,sharing=locked \
    cargo chef cook --release --recipe-path recipe.json
COPY . .
RUN --mount=type=cache,target=/usr/local/cargo/registry \
    --mount=type=cache,target=$SCCACHE_DIR,sharing=locked \
    cargo build  --release



# # Image to run the final binary
FROM debian:bullseye-slim

# # It's usual to set the working directory to /app
WORKDIR /app

# # Only copy the final binary from the build stage
# # The binary is located at /app/target/release/example-actix-helloworld, 
# #   since we are using the release profile.
COPY --from=builder /app/target/release/hello-world /app/hello-world

# Finally, we run the binary
CMD ["./hello-world"]

实验结果：

image
(注：没有验证时间具体快多少，因为肉眼可见的快OVO)

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