feat(nb): Scaffolding of backend(/workspaces/backend)

Signed-off-by: Eder Ignatowicz <ignatowicz@gmail.com>

workspaces/backend/.gitignore

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+# 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
+*.swp
+*.swo
+*~

workspaces/backend/.golangci.yml

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+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

workspaces/backend/Dockerfile

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+# Use the golang image to build the application
+FROM golang:1.22.2 AS builder
+ARG TARGETOS
+ARG TARGETARCH
+
+WORKDIR /workspace
+
+# Copy the Go Modules manifests
+COPY go.mod go.sum ./
+
+# Download dependencies
+RUN go mod download
+
+# Copy the go source files
+COPY cmd/ cmd/
+COPY api/ api/
+COPY config/ config/
+COPY data/ data/
+COPY integrations/ integrations/
+
+# Build the Go application
+RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o backend ./cmd/main.go
+
+# Use distroless as minimal base image to package the application binary
+FROM gcr.io/distroless/static:nonroot
+WORKDIR /
+COPY --from=builder /workspace/backend ./
+USER 65532:65532
+
+# Expose port 4000
+EXPOSE 4000
+
+# Define environment variables
+ENV PORT 4001
+ENV ENV development
+
+ENTRYPOINT ["/backend"]

workspaces/backend/Makefile

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+CONTAINER_TOOL ?= docker
+IMG ?= nbv2-backend:latest
+
+.PHONY: all
+all: build
+
+.PHONY: help
+help: ## Display this help.
+	@awk 'BEGIN {FS = ":.*##"; printf "\nUsage:\n  make \033[36m<target>\033[0m\n"} /^[a-zA-Z_0-9-]+:.*?##/ { printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2 } /^##@/ { printf "\n\033[1m%s\033[0m\n", substr($$0, 5) } ' $(MAKEFILE_LIST)
+
+.PHONY: fmt
+fmt:
+	go fmt ./...
+
+.PHONY: vet
+vet:  .
+	go vet ./...
+
+.PHONY: build
+build: fmt vet
+	go build -o bin/backend cmd/main.go
+
+.PHONY: run
+run: fmt vet
+	PORT=4000 ENV=development go run ./cmd/main.go
+
+.PHONY: docker-build
+docker-build:
+	$(CONTAINER_TOOL) build -t ${IMG} .

workspaces/backend/README.md

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+# Workspaces backend
+This component serves as a BFF layer for Workspaces Frontend.
+
+# Building and Deploying
+TBD
+
+# Development
+## Getting started
+
+### Endpoints
+
+| URL Pattern         | Handler            | Action                        |
+|---------------------|--------------------|-------------------------------|
+| GET /v1/healthcheck | HealthcheckHandler | Show application information. |
+
+
+### Sample local calls
+```
+# GET /v1/healthcheck
+curl -i localhost:4000/api/v1/healthcheck/
+```

workspaces/backend/api/app.go

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+/*
+Copyright 2024.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package api
+
+import (
+	"github.com/kubeflow/notebooks/workspaces/backend/config"
+	"github.com/kubeflow/notebooks/workspaces/backend/data"
+	"log/slog"
+	"net/http"
+
+	"github.com/julienschmidt/httprouter"
+)
+
+const (
+	Version         = "1.0.0"
+	HealthCheckPath = "/api/v1/healthcheck/"
+)
+
+type App struct {
+	config config.EnvConfig
+	logger *slog.Logger
+	models data.Models
+}
+
+func NewApp(cfg config.EnvConfig, logger *slog.Logger) *App {
+	app := &App{
+		config: cfg,
+		logger: logger,
+	}
+	return app
+}
+
+func (app *App) Routes() http.Handler {
+	router := httprouter.New()
+
+	router.NotFound = http.HandlerFunc(app.notFoundResponse)
+	router.MethodNotAllowed = http.HandlerFunc(app.methodNotAllowedResponse)
+
+	router.GET(HealthCheckPath, app.AttachKubernetesClient(app.HealthcheckHandler))
+
+	return app.RecoverPanic(app.enableCORS(router))
+}

workspaces/backend/api/errors.go

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+/*
+Copyright 2024.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package api
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+)
+
+type HTTPError struct {
+	StatusCode int `json:"-"`
+	ErrorResponse
+}
+
+type ErrorResponse struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+func (app *App) LogError(r *http.Request, err error) {
+	var (
+		method = r.Method
+		uri    = r.URL.RequestURI()
+	)
+
+	app.logger.Error(err.Error(), "method", method, "uri", uri)
+}
+
+func (app *App) badRequestResponse(w http.ResponseWriter, r *http.Request, err error) {
+	httpError := &HTTPError{
+		StatusCode: http.StatusBadRequest,
+		ErrorResponse: ErrorResponse{
+			Code:    strconv.Itoa(http.StatusBadRequest),
+			Message: err.Error(),
+		},
+	}
+	app.errorResponse(w, r, httpError)
+}
+
+func (app *App) errorResponse(w http.ResponseWriter, r *http.Request, error *HTTPError) {
+
+	env := Envelope{"error": error}
+
+	err := app.WriteJSON(w, error.StatusCode, env, nil)
+
+	if err != nil {
+		app.LogError(r, err)
+		w.WriteHeader(error.StatusCode)
+	}
+}
+
+func (app *App) serverErrorResponse(w http.ResponseWriter, r *http.Request, err error) {
+	app.LogError(r, err)
+
+	httpError := &HTTPError{
+		StatusCode: http.StatusInternalServerError,
+		ErrorResponse: ErrorResponse{
+			Code:    strconv.Itoa(http.StatusInternalServerError),
+			Message: "the server encountered a problem and could not process your request",
+		},
+	}
+	app.errorResponse(w, r, httpError)
+}
+
+func (app *App) notFoundResponse(w http.ResponseWriter, r *http.Request) {
+
+	httpError := &HTTPError{
+		StatusCode: http.StatusNotFound,
+		ErrorResponse: ErrorResponse{
+			Code:    strconv.Itoa(http.StatusNotFound),
+			Message: "the requested resource could not be found",
+		},
+	}
+	app.errorResponse(w, r, httpError)
+}
+
+func (app *App) methodNotAllowedResponse(w http.ResponseWriter, r *http.Request) {
+
+	httpError := &HTTPError{
+		StatusCode: http.StatusMethodNotAllowed,
+		ErrorResponse: ErrorResponse{
+			Code:    strconv.Itoa(http.StatusMethodNotAllowed),
+			Message: fmt.Sprintf("the %s method is not supported for this resource", r.Method),
+		},
+	}
+	app.errorResponse(w, r, httpError)
+}
+
+func (app *App) failedValidationResponse(w http.ResponseWriter, r *http.Request, errors map[string]string) {
+
+	message, err := json.Marshal(errors)
+	if err != nil {
+		message = []byte("{}")
+	}
+	httpError := &HTTPError{
+		StatusCode: http.StatusUnprocessableEntity,
+		ErrorResponse: ErrorResponse{
+			Code:    strconv.Itoa(http.StatusUnprocessableEntity),
+			Message: string(message),
+		},
+	}
+	app.errorResponse(w, r, httpError)
+}

workspaces/backend/api/healthcheck_handler.go

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+/*
+Copyright 2024.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package api
+
+import (
+	"github.com/julienschmidt/httprouter"
+	"github.com/kubeflow/notebooks/workspaces/backend/data"
+	"github.com/kubeflow/notebooks/workspaces/backend/integrations"
+	"net/http"
+)
+
+func (app *App) HealthcheckHandler(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
+
+	client, ok := r.Context().Value(k8sClientKey).(*integrations.KubernetesClient)
+	if !ok {
+		healthCheck := data.HealthCheckModel{
+			Status: "unavailable",
+			SystemInfo: data.SystemInfo{
+				Environment: app.config.Env.String(),
+				Version:     Version,
+			},
+			Dependencies: data.Dependencies{
+				Kubernetes: "unavailable",
+			},
+		}
+		app.WriteJSON(w, http.StatusServiceUnavailable, healthCheck, nil)
+		return
+	}
+
+	healthCheck, err := app.models.HealthCheck.HealthCheck(client, app.config.Env, Version)
+	if err != nil {
+		app.serverErrorResponse(w, r, err)
+		return
+	}
+
+	err = app.WriteJSON(w, http.StatusOK, healthCheck, nil)
+
+	if err != nil {
+		app.serverErrorResponse(w, r, err)
+	}
+
+}