用于 Rust 应用程序的小而快的 Docker 映像

以下步骤将使用 Rocket “hello world” 应用程序作为演示。

Dockerfile 正常来说基本配置将是：

# Dockerfile.plain

ARG BASE_IMAGE=rust:1.52.1-slim-buster

FROM $BASE_IMAGE
WORKDIR app
COPY . .
RUN cargo build --release
CMD ["./target/release/hello"]

然后构建镜像

time docker build -f Dockerfile.plain -t hello:0.1.0 .

我们可以看到生成1.38GB 的​​镜像，构建时间为12 分钟。

# build
real    12m13.412s
user    0m0.135s
sys     0m0.095s

REPOSITORY    TAG                  IMAGE ID       CREATED          SIZE
hello         0.1.0                ac4e1a72ba05   2 minutes ago    1.38GB
rust          1.52.1-slim-buster   61cb3c65a6ba   3 weeks ago      621MB

接下来使用多阶段构建和 cargo-chef 来使镜像尺寸更小

# Dockerfile.chef

ARG BASE_IMAGE=rust:1.52.1-slim-buster

FROM $BASE_IMAGE as planner
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY . .
RUN cargo chef prepare  --recipe-path recipe.json

FROM $BASE_IMAGE as cacher
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --recipe-path recipe.json

FROM $BASE_IMAGE as builder
WORKDIR app
COPY . .
# Copy over the cached dependencies
COPY --from=cacher /app/target target
COPY --from=cacher $CARGO_HOME $CARGO_HOME
RUN  cargo build --release

FROM $BASE_IMAGE
COPY --from=builder /app/target/release/hello /
CMD ["./hello"]

它会生成628MB的图像大小，最后一次由于缓存的原因构建只需要1 分钟左右。

# first test omitted
# second test
real    19m32.836s
user    0m0.188s
sys     0m0.088s

# third test
real    1m52.982s
user    0m0.060s
sys     0m0.088s

REPOSITORY   TAG    IMAGE ID       CREATED              SIZE
hello        0.1.0  ca1a9e1e5948   About a minute ago   628MB

更可以通过 distroless 或者 scratch 镜像来再加速构建，但是这里如果是 scratch 必须将工具链目标更改为 musl。

scratch:

# Dockerfile.musl

ARG BASE_IMAGE=rust:1.52.1-slim-buster

FROM $BASE_IMAGE as planner
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY . .
RUN cargo chef prepare  --recipe-path recipe.json

FROM $BASE_IMAGE as cacher
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --recipe-path recipe.json

FROM $BASE_IMAGE as builder
WORKDIR app
COPY . .
# Copy over the cached dependencies
COPY --from=cacher /app/target target
COPY --from=cacher $CARGO_HOME $CARGO_HOME
# We need static linking for musl
RUN rustup target add x86_64-unknown-linux-musl
# `cargo build` doesn't work in static linking, need `cargo install`
RUN cargo install --target x86_64-unknown-linux-musl --path .

FROM scratch
COPY --from=builder /usr/local/cargo/bin/hello .
CMD ["./hello"]

结果：

# first test ommitted
# second test
real    9m22.049s
user    0m0.113s
sys     0m0.103s

# third test
real    9m46.035s
user    0m0.120s
sys     0m0.085s

REPOSITORY   TAG    IMAGE ID       CREATED          SIZE
hello        0.1.0  332ce3b4f717   30 seconds ago   8.38MB

distroless:

# Dockerfile.distroless

ARG BASE_IMAGE=rust:1.52.1-slim-buster

FROM $BASE_IMAGE as planner
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY . .
RUN cargo chef prepare  --recipe-path recipe.json

FROM $BASE_IMAGE as cacher
WORKDIR app
RUN cargo install cargo-chef --version 0.1.20
COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --recipe-path recipe.json

FROM $BASE_IMAGE as builder
WORKDIR app
COPY . .
# Copy over the cached dependencies
COPY --from=cacher /app/target target
COPY --from=cacher $CARGO_HOME $CARGO_HOME
RUN cargo build --release

FROM gcr.io/distroless/cc-debian10
COPY --from=builder /app/target/release/hello /
CMD ["./hello"]

结果：

# first test ommitted
# second test
real    1m57.033s
user    0m0.045s
sys     0m0.038s

# third test
real    2m12.585s
user    0m0.093s
sys     0m0.096s

REPOSITORY   TAG    IMAGE ID       CREATED          SIZE
hello        0.1.0  118da37bdfe7   25 seconds ago   29MB

以上结果还是非常可观的。

结论 第一次尝试生成 1.38GB 的​​映像大小，构建时间为 12m。现在我们可以生成一个非常小的图像，并且构建速度非常快。选择权在你手中。如果您对 musl 目标没问题，请使用 scratch 镜像。否则，选择 distroless 。

• https://azzamsa.com/n/rust-docker/

什么时候不使用 Rust？

Rust 在软件可靠性和性能方面向前迈出了一大步，这直接转化为节省的金钱和时间。Rust 解决了我作为开发人员每天面临的许多问题，例如不变性和良好的抽象。但与所有技术一样，Rust 也有一些缺点并使之不会成为您项目的最佳选择。今天 Sylvain Kerkour 想探讨一下他认为 Rust 的不好用例。

• https://kerkour.com/why-not-rust

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