example and doc update

Makefile

@@ -11,4 +11,10 @@ dependencies_up: dependencies_down
 .PHONY: tests
 ## tests: runs tests against a locally running mongo container
 tests:
-	go test -v ./...
+	go test -v ./...
+
+.PHONY: example
+## example: runs an http-server locally
+example:
+	go build -o bin/server streamingconfig/example/server
+	./bin/server

README.md

@@ -25,7 +25,7 @@ fields.
 
 ## Usage
 
-checkout the [example](./example/main.go).
+checkout the [example](./example/server/main.go).
 
 1. Define a configuration with `json` field tags (and optionally with `default` field tags):
 2. Make sure that your configuration type implements the `streamingconfig.Config` interface:
@@ -36,4 +36,35 @@ checkout the [example](./example/main.go).
 ```shell
 make dependencies_up
 make tests
-```
+```
+
+### Run example server
+
+```shell
+make dependencies_up
+make example
+```
+
+Optionally, you can also start a second server to check that the changes happening in one server will be reflected in the other:
+
+```shell
+HTTP_PORT=8081 make example
+```
+
+#### Getting latest configuration request
+```shell
+curl -X GET --location "http://localhost:8080/configs/latest"
+```
+#### Changing latest configuration request
+```shell
+curl -X PUT --location "http://localhost:8080/configs/latest" \
+    -H "user-id: mark" \
+    -d '{
+  "name": "betty",
+  "age": 35
+}'
+```
+#### Listing multiple versions
+```shell
+curl -X GET --location "http://localhost:8080/configs?fromVersion=0&toVersion=21"
+```

example/server/configs.http

@@ -0,0 +1,15 @@
+### GET latest config
+GET http://localhost:8080/configs/latest
+
+
+### Modify latest config
+PUT http://localhost:8080/configs/latest
+user-id: mark
+
+{
+  "name": "stark",
+  "age": 35
+}
+
+### List config versions
+GET http://localhost:8080/configs?fromVersion=0&toVersion=21

example/server/main.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	config "streamingconfig"
+
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+type conf struct {
+	Name string `json:"name" default:"john"`
+	Age  int    `json:"age"`
+}
+
+func (c *conf) Update(new config.Config) error {
+	newCfg, ok := new.(*conf)
+	if !ok {
+		return errors.New("wrong configuration")
+	}
+	c.Name = newCfg.Name
+	c.Age = newCfg.Age
+	return nil
+}
+
+func main() {
+	port := os.Getenv("HTTP_PORT")
+	if port == "" {
+		port = "8080"
+	}
+	runnableCtx, cancelRunnables := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer cancelRunnables()
+	repo, done := initRepo(runnableCtx)
+	s := &server{repo: repo, lgr: slog.Default()}
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /configs/latest", s.latestConfigHandler)
+	mux.HandleFunc("PUT /configs/latest", s.putConfigHandler)
+	mux.HandleFunc("GET /configs", s.listConfigsHandler)
+	// Create a new server
+	srv := &http.Server{
+		Addr:    fmt.Sprintf(":%s", port),
+		Handler: mux,
+	}
+	// Start the server in a goroutine
+	go func() {
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			log.Fatal(err)
+		}
+	}()
+	fmt.Printf("Server listening on port %s\n", port)
+	// until shutdown signal is sent
+	<-runnableCtx.Done()
+	// Graceful shutdown
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer func() {
+		cancel()
+	}()
+
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Println("Error during shutdown:", err)
+	}
+	log.Println("Server stopped")
+	<-done
+}
+
+func initRepo(ctx context.Context) (*config.WatchedRepo[*conf], <-chan struct{}) {
+	lgr := slog.Default()
+	db := getDb()
+	repo, err := config.NewWatchedRepo[*conf](
+		config.Args{
+			Logger: lgr,
+			DB:     db,
+		})
+	if err != nil {
+		log.Fatal(err)
+	}
+	done, err := repo.Start(ctx)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return repo, done
+}
+
+func getDb() *mongo.Database {
+	ctx, cnl := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cnl()
+	// use test name as db name to parallel tests.
+	opts := options.Client()
+	opts.ApplyURI("mongodb://localhost:27017/?connect=direct")
+	client, err := mongo.Connect(ctx, opts)
+	if err != nil {
+		panic(fmt.Errorf("run `make dependencies_up` before, error: %w", err))
+	}
+	err = client.Ping(ctx, nil)
+	if err != nil {
+		panic(fmt.Errorf("error %v\nrun `make dependencies_up` before running main\n", err))
+	}
+	return client.Database("test")
+}