Lab 2, bonus task

Author: kolayne

app_go/.dockerignore

@@ -0,0 +1 @@
+.gitignore

app_go/DOCKER.md

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+# Dockerfile for `app_go`
+
+## Best practices employed
+
+-   Explicit base image tag version.
+
+-   An alpine base image is used, so as to reduce the resulting image
+    size.
+
+-   .dockerignore is used and is symlinked to .gitignore. What's not to
+    appear in the repo is also not to be included in the image.
+
+-   Run instructions in the dockerfile are in the exec form, not shell
+    form.
+
+-   A multi-stage build is used. The final stage consists of just two
+    layers and takes up about 8MB.
+
+-   Root owns the executable file, which is not to be modified.
+
+-   A non-root user executes the app.
+
+-   The port to be exposed is explicitly mentioned in the Dockerfile.
+
+Not sure what else to say, but just look at it: it's almost perfect!
+
+The only thing one can argue about is the use of a hardcoded UID in the
+Dockerfile. But, firstly, there is no native way to add a user in a bare
+image, secondly, there is nothing to exchange with between host and container,
+so there's no reason to.

app_go/Dockerfile

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+FROM golang:1.22.0-alpine3.19 as builder
+
+WORKDIR /usr/src/app/
+
+COPY go.mod *.go /usr/src/app/
+# No dependencies yet
+#RUN go mod download && go mod verify
+
+RUN ["env", "CGO_ENABLED=0", "go", "build", "-o", "catfact_webapp", "."]
+
+
+# Like `FROM scratch` but with SSL
+FROM damdo/sscratch
+
+EXPOSE 5000
+
+COPY --from=builder /usr/src/app/catfact_webapp /
+USER 2004:2004
+ENTRYPOINT ["/catfact_webapp"]

app_go/README.md

@@ -14,3 +14,35 @@ variable).
 
 In the project directory run `go build .`. This will create an executable file
 `catfact_webapp`. Run it to start the web app.
+
+## Docker
+
+To build, in the project directory do:
+
+```bash
+docker build . -t IMAGE_TAG_NAME
+```
+
+where `IMAGE_TAG_NAME` is the tag you want for the image.
+
+### Pull
+
+You can also run a pre-built version of the image. To pull it:
+
+```bash
+docker pull kolay0ne/app_go
+```
+
+Use `kolay0ne/app_go` as the image name for future docker operations.
+
+### Run
+
+Run a container based on the image, select options depending on your needs. For
+instance, to run it in the background, exposing the port `5000` to a randomly
+selected port on the host machine and automatically remove the container ones
+it's stopped, do: 
+```bash
+docker run --rm -d -p 5000 kolay0ne/app_go
+```
+
+Replace `kolay0ne/app_go` with your image/tag name if you built it manually.