Rebulding in Go with the Operator SDK (#21)

After seeing that the Python `kopf` operator framework is considered not ready
for production use, I decided to go with the more stable and widely used
[Operator SDK](https://sdk.operatorframework.io/) for Go.  This is a reboot and
re-scaffolding the project with the SDK's tools.

.dockerignore

@@ -1,13 +1,3 @@
-.bookkeeping
-.coverage
-.envrc*
-.github
-.mypy_cache
-.pre-commit-config.yaml
-.pytest_cache
-.python-version
-.vscode
-Dockerfile
-Makefile
-tests
-**/*.pyc
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore build and test binaries.
+bin/

.gitignore

@@ -1,9 +1,27 @@
-.bookkeeping
-.coverage
-*.egg-info
-.mypy_cache
-__pycache__
-.pytest_cache
-.python-version
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+bin/*
+Dockerfile.cross
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Go workspace file
+go.work
+
+# Kubernetes Generated files - skip generated files, except for vendored files
+!vendor/**/zz_generated.*
+
+# editor and IDE paraphernalia
+.idea
 .vscode
-.ruff_cache
+*.swp
+*.swo
+*~

.golangci.yml

@@ -0,0 +1,40 @@
+run:
+  timeout: 5m
+  allow-parallel-runners: true
+
+issues:
+  # don't skip warning about doc comments
+  # don't exclude the default set of lint
+  exclude-use-default: false
+  # restore some of the defaults
+  # (fill in the rest as needed)
+  exclude-rules:
+    - path: "api/*"
+      linters:
+        - lll
+    - path: "internal/*"
+      linters:
+        - dupl
+        - lll
+linters:
+  disable-all: true
+  enable:
+    - dupl
+    - errcheck
+    - exportloopref
+    - goconst
+    - gocyclo
+    - gofmt
+    - goimports
+    - gosimple
+    - govet
+    - ineffassign
+    - lll
+    - misspell
+    - nakedret
+    - prealloc
+    - staticcheck
+    - typecheck
+    - unconvert
+    - unparam
+    - unused

Dockerfile

@@ -1,20 +1,33 @@
-FROM python:3.12.4-slim-bookworm
-
-RUN apt-get update && apt-get install -y git && apt-get clean
-
-WORKDIR /app
-ENTRYPOINT [ "prefect-operator" ]
-CMD [ "run" ]
-
-RUN pip install -U pip uv
-
-COPY requirements.txt .
-
-RUN uv pip install --system -r requirements.txt
-
-COPY pyproject.toml .
-COPY src src
-
-RUN --mount=source=.git,target=.git,type=bind pip install --no-cache-dir -e .
-
-RUN prefect-operator --version
+# Build the manager binary
+FROM golang:1.21 AS builder
+ARG TARGETOS
+ARG TARGETARCH
+
+WORKDIR /workspace
+# Copy the Go Modules manifests
+COPY go.mod go.mod
+COPY go.sum go.sum
+# cache deps before building and copying source so that we don't need to re-download as much
+# and so that source changes don't invalidate our downloaded layer
+RUN go mod download
+
+# Copy the go source
+COPY cmd/main.go cmd/main.go
+COPY api/ api/
+COPY internal/controller/ internal/controller/
+
+# Build
+# the GOARCH has not a default value to allow the binary be built according to the host where the command
+# was called. For example, if we call make docker-build in a local env which has the Apple Silicon M1 SO
+# the docker BUILDPLATFORM arg will be linux/arm64 when for Apple x86 it will be linux/amd64. Therefore,
+# by leaving it empty we can ensure that the container and binary shipped on it will have the same platform.
+RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o manager cmd/main.go
+
+# Use distroless as minimal base image to package the manager binary
+# Refer to https://github.com/GoogleContainerTools/distroless for more details
+FROM gcr.io/distroless/static:nonroot
+WORKDIR /
+COPY --from=builder /workspace/manager .
+USER 65532:65532
+
+ENTRYPOINT ["/manager"]