cmd/osbuild-worker-executor: import verbatim from mvo5/oaas

This commit imports the repository https://github.com/mvo5/oaas
without keeping the history. The history is largely unimportant
and can be looked up in https://github.com/mvo5/oaas/commits/main
if needed.

cmd/osbuild-worker-executor/main.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"sync"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// based on the excellent post
+// https://grafana.com/blog/2024/02/09/how-i-write-http-services-in-go-after-13-years/
+
+var logrusNew = logrus.New
+
+func newServer(logger *logrus.Logger, config *Config) http.Handler {
+	mux := http.NewServeMux()
+	addRoutes(mux, logger, config)
+	var handler http.Handler = mux
+	// todo: consider centralize logginer here?
+	//handler = loggingMiddleware(handler)
+	return handler
+}
+
+func run(ctx context.Context, args []string, getenv func(string) string) error {
+	ctx, cancel := signal.NotifyContext(ctx, os.Interrupt)
+	defer cancel()
+
+	logger := logrusNew()
+	config, err := newConfigFromCmdline(args)
+	if err != nil {
+		return err
+	}
+
+	srv := newServer(logger, config)
+	httpServer := &http.Server{
+		Addr:    net.JoinHostPort(config.Host, config.Port),
+		Handler: srv,
+	}
+	go func() {
+		logger.Printf("listening on %s\n", httpServer.Addr)
+		if err := httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			fmt.Fprintf(os.Stderr, "error listening and serving: %s\n", err)
+		}
+	}()
+
+	// todo: this seems kinda complicated, why a waitgroup and not
+	// do it flat?
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		<-ctx.Done()
+		shutdownCtx := context.Background()
+		shutdownCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
+		defer cancel()
+		if err := httpServer.Shutdown(shutdownCtx); err != nil {
+			fmt.Fprintf(os.Stderr, "error shutting down http server: %s\n", err)
+		}
+	}()
+	wg.Wait()
+
+	// cleanup
+	if err := os.RemoveAll(config.BuildDirBase); err != nil {
+		logger.Errorf("cannot cleanup: %v", err)
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	ctx := context.Background()
+	if err := run(ctx, os.Args, os.Getenv); err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		os.Exit(1)
+	}
+}