I spend a day on getting a smooth process for building small docker images with my rust app. I had some native c things in my dependencies (such as rdkafka). I found the process a little bit cumbersome but finally I found a well working solution that I hope can help someone else!
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Awesome thank you!
I like your docker ideas on building dependencies only when the cargo file changes.
Thank You! Actually I have learned that trick from other clever developers while I optimized some java and nodejs deploy pipelines, it is a very useful.
However, I miss a cargo command that just download and build dependencies. At least, I have not found one.
isn't it doing the other way around? i think docker is caching everything unless there is a change? so without adding the cargo.toml & .lock files it wouldn't update anything?
I think the little problem with docker and cargo is that in order to run cargo build I have to add src. When things change in src it invalidates the cached build. I would personally prefer a command in cargo that allow me to do something like this
COPY Cargo.lock .
COPY Cargo.toml .
cargo some-kind-of-download-and-build-dependencies-command
COPY src ./src
cargo build --target x86_64-unknown-linux-musl --release
Then docker will cache the dependencies until the Cargo.toml and Cargo.lock is modified. This is essentially what the work around with dummy main do.
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Ahh, ok, so you're adding a docker-layer only for the dependencies by building a dummy.
For node a simple RUN npm install would be enough to do that.
Exactly 
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