update docker sample by caching dependencies

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

docker_sample/Dockerfile

@@ -1,15 +1,24 @@
-FROM rust:1 as builder
+FROM rust:1-slim-buster AS base
 
-COPY . .
+ENV USER=root
 
-RUN cargo build --release
+WORKDIR /code
+RUN cargo init
+COPY Cargo.toml /code/Cargo.toml
+RUN cargo fetch
 
-FROM rust:1-slim-stretch
+COPY src /code/src
 
-COPY --from=builder /target/release/docker_sample .
+CMD [ "cargo", "test", "--offline" ]
 
-RUN ls -la /docker_sample
+FROM base AS builder
+
+RUN cargo build --release --offline
+
+FROM rust:1-slim-buster
+
+COPY --from=builder /code/target/release/docker_sample /usr/bin/docker_sample
 
 EXPOSE 5000
 
-ENTRYPOINT ["/docker_sample"]
+ENTRYPOINT [ "/usr/bin/docker_sample" ]

docker_sample/README.MD

@@ -1,23 +1,22 @@
+# Docker sample
 
-Build image:
+## Build image
 
 ```shell
-  docker build -t docker_sample --force-rm --no-cache -f  Dockerfile .
+docker build -t docker_sample .
 ```
 
-Run image:
+## Run built image
 
 ```shell
-  
-  echo "== start sample_docker"
-  docker run -d -p 5000:5000 docker_sample &
-  docker ps
+docker run -d -p 5000:5000 docker_sample
+# and the server should start instantly
+curl http://localhost:5000
+```
 
-  echo "== wait 3s for startup"
-  sleep 3s
+## Running unit tests
 
-  echo "== curl both routes"
-  curl http://localhost:5000
-  curl http://localhost:5000/again 
-
-```
+```shell
+docker build -t docker_sample:test --target base .
+docker run --rm docker_sample:test
+```

docker_sample/src/main.rs

@@ -24,3 +24,11 @@ async fn main() -> std::io::Result<()> {
         .run()
         .await
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn sample_test() {
+        assert!(true);
+    }
+}