WIP Draft - Example that deploys a golang backend, postgres db and a react frontend where they all talk with each other

go-postgres-react/README.md

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+# go-postgres-react
+
+This is for creating a Contacts application with the following components:
+
+- [x] a Golang backend
+- [x] a Postgresql database for saving data
+      -- the corresponding Volume for persistent storage
+- [] a react frontend app for serving the UI
+
+## Create a volume and deploy postgresql
+
+```console
+$ cd github.com/kraftcloud/examples/postgres
+
+github.com/kraftcloud/examples/postgres$ kraft cloud volume create --name postgres --size 200
+
+github.com/kraftcloud/examples/postgres$ kraft cloud deploy --metro fra0 -M 1024 -e POSTGRES_PASSWORD=unikraft -e PGDATA=/volume/postgres -v postgres:/volume -p 5432:5432/tls .
+(Search for `service group` in the output)
+
+# Port-forward postgresql to localhost
+github.com/kraftcloud/examples/postgres$ kraft cloud tunnel <SERVICE_GROUP_FROM_ABOVE> 5432:5432
+
+
+$ psql -U postgres -h localhost
+Password for user postgres: unikraft
+psql (16.2)
+Type "help" for help.
+
+postgres=# CREATE TABLE contacts (id SERIAL PRIMARY KEY, name TEXT, email TEXT);
+CREATE TABLE
+postgres=#
+
+
+```
+
+## Deploy the backend:
+
+```console
+github.com/kraftcloud/examples/go-postgres-react/go$ kraft cloud deploy --metro fra0 -p 443:8080 .
+(Search for `domain` in the output)
+
+# Ensure that the backend API works fine by talking to the db
+
+# Empty response first
+$ curl -vv https://DOMAIN_FROM_ABOVE.fra0.kraft.host/contacts
+null
+
+# Create contact next
+$ curl -v https://DOMAIN_FROM_ABOVE.fra0.kraft.host/contacts -d '{ "name": "example1", "email": "one@example.com" }'
+
+# Ensure the new contact is saved and retrieved from db via the backend
+$ curl https://DOMAIN_FROM_ABOVE.fra0.kraft.host/contacts
+[{"name":"example1","email":"one@example.com"}]
+
+# Above backend API confirms data is saved, but let us check in DB also
+$ psql -U postgres -h localhost
+Password for user postgres: unikraft
+psql (16.2)
+Type "help" for help.
+
+postgres=# select * from contacts;
+ id |   name   |      email
+----+----------+-----------------
+  1 | example1 | one@example.com
+(1 row)
+
+postgres=#
+
+```

go-postgres-react/go/Dockerfile

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+FROM --platform=linux/x86_64 golang:1.22.3-bookworm AS build
+
+WORKDIR /src
+
+COPY . /src/
+
+RUN set -xe; \
+  go build \
+  -buildmode=pie \
+  -ldflags "-linkmode external -extldflags -static-pie" \
+  -tags netgo \
+  -o /server server.go \
+  ;
+
+FROM scratch
+
+COPY --from=build /server /server
+COPY --from=build /lib/x86_64-linux-gnu/libc.so.6 /lib/x86_64-linux-gnu/
+COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/

go-postgres-react/go/Kraftfile

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+spec: v0.6
+
+runtime: base:latest
+
+rootfs: ./Dockerfile
+
+cmd: ["/server"]

go-postgres-react/go/README.md

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+# Simple Go 1.21 HTTP Server
+
+This is a simple HTTP server written in the [Go](https://go.dev/) programming language.
+
+To run this example on KraftCloud, first [install the `kraft` CLI tool](https://unikraft.org/docs/cli).
+Then clone this examples repository and `cd` into this directory, and invoke:
+
+```console
+kraft cloud deploy --metro fra0 -p 443:8080 .
+```
+
+The command will build and deploy the `server.go` source code file.
+
+After deploying, you can query the service using the provided URL.
+
+## Learn more
+
+- [Go's Documentation](https://go.dev/doc/)
+- [KraftCloud's Documentation](https://docs.kraft.cloud)
+- [Building `Dockerfile` Images with `Buildkit`](https://unikraft.org/guides/building-dockerfile-images-with-buildkit)

go-postgres-react/go/go.mod

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+module github.com/kraftcloud/examples/go-postgres-react/go
+
+go 1.22.3
+
+require github.com/lib/pq v1.10.9

go-postgres-react/go/go.sum

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+github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
+github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=

go-postgres-react/go/server.go

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+package main
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	_ "github.com/lib/pq"
+)
+
+type Contact struct {
+	Name  string `json:"name"`
+	Email string `json:"email"`
+}
+
+var db *sql.DB
+
+func main() {
+	var err error
+	db, err = sql.Open(
+		"postgres",
+		"user=postgres dbname=postgres password=unikraft host=postgres-wahr0.internal sslmode=disable",
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	http.HandleFunc("/contacts", contactsHandler)
+
+	fmt.Println("Listening on :8080...")
+	http.ListenAndServe(":8080", nil)
+}
+
+func contactsHandler(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case http.MethodGet:
+		rows, err := db.Query("SELECT name, email FROM contacts")
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		defer rows.Close()
+
+		var contacts []Contact
+		for rows.Next() {
+			var c Contact
+			if err := rows.Scan(&c.Name, &c.Email); err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			contacts = append(contacts, c)
+		}
+
+		json.NewEncoder(w).Encode(contacts)
+	case http.MethodPost:
+		var c Contact
+		json.NewDecoder(r.Body).Decode(&c)
+
+		_, err := db.Exec(
+			"INSERT INTO contacts(name, email) VALUES($1, $2)",
+			c.Name,
+			c.Email,
+		)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		json.NewEncoder(w).Encode(c)
+	default:
+		http.Error(w, "Invalid request method", http.StatusMethodNotAllowed)
+	}
+}