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dockerrustdockerfilerust-cargo

how I can use --config command in docker for rust

I run development using --config file on my Rust API, it is something like this cargo run --config dev-config.toml where the dev-config.toml is like my Environments like this

[env]
APP_ENV = "development"
APP_PORT = "8181"
APP_TIMEOUT = "3" # in seconds
APP_MAX_ATTEMPTS = "50" # in attempts ( 50 request in 60 seconds )
MONGO_URI="balblaaa"
...

I can build image in my docker like this to copy the file

# Use the official Rust image as the base image
FROM rust:latest as builder

# Set the current working directory inside the Docker image
WORKDIR /usr/src

# Copy the Cargo.toml file and your source code into the Docker image
COPY Cargo.toml .
COPY src ./src
COPY secrets ./secrets
# Copy the dev-config.toml file
COPY dev-config.toml .

# Build the application in release mode
RUN cargo build --release --config dev-config.toml

# Start a new build stage
FROM rust:latest

# Copy the binary from the builder stage to the current stage
COPY --from=builder /usr/src/target/release/my-api /usr/local/bin

# Set the command to run your application
CMD ["my-api"]

when I run docker run -p 8080:8080 my-api I got error the env was empty and not set

[INFO] - "Trying to Connect MongoDB..."
thread 'main' panicked at src/db.rs:43:75:
MONGO_URI must be set.: NotPresent
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

is that something I miss here and other way to use --config ? instead set manual env

I have been read cases on internet, but there is none of my topic out there because rust is new,

Solution

  • The [env] from using a cargo --config file only affects cargo invocations with it (i.e. cargo build, cargo run, etc.). So you could make this work as-is by using:

    CMD = ["cargo", "run", "--release", "--config", "dev-config.toml"]

    Though I don't actually recommend that even if cargo build was ran beforehand.

    Instead, I would suggest reading How do I pass environment variables to Docker containers? Options there like using a --env-file or launching with a docker-compose configuration would likely be more palatable. If you go with a .env file, you could change your Rust code to load from it using the dotenvy crate instead of provided by cargo's config.