Initial version of the Orchard orchestration system (#3)

* Initial version of the Orchard orchestration system

* Update README.md

Co-authored-by: Fedor Korotkov <fedor.korotkov@gmail.com>

Co-authored-by: Fedor Korotkov <fedor.korotkov@gmail.com>

internal/controller/controller.go

@@ -0,0 +1,96 @@
+package controller
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	storepkg "github.com/cirruslabs/orchard/internal/controller/store"
+	"go.uber.org/zap"
+	"net"
+	"net/http"
+)
+
+type Controller struct {
+	dataDir    string
+	listenAddr string
+	tlsConfig  *tls.Config
+	listener   net.Listener
+	httpServer *http.Server
+	store      *storepkg.Store
+	logger     *zap.SugaredLogger
+}
+
+func New(opts ...Option) (*Controller, error) {
+	controller := &Controller{}
+
+	// Apply options
+	for _, opt := range opts {
+		opt(controller)
+	}
+
+	// Apply defaults
+	if controller.dataDir == "" {
+		return nil, fmt.Errorf("%w: please specify the data directory path with WithDataDir()")
+	}
+	if controller.listenAddr == "" {
+		controller.listenAddr = ":6120"
+	}
+	if controller.logger == nil {
+		controller.logger = zap.NewNop().Sugar()
+	}
+
+	// Instantiate controller
+	store, err := storepkg.New(controller.dbPath())
+	if err != nil {
+		return nil, err
+	}
+	controller.store = store
+
+	listener, err := net.Listen("tcp", controller.listenAddr)
+	if err != nil {
+		return nil, err
+	}
+	if controller.tlsConfig != nil {
+		controller.listener = tls.NewListener(listener, controller.tlsConfig)
+	} else {
+		controller.listener = listener
+	}
+
+	controller.httpServer = &http.Server{
+		Handler: controller.initAPI(),
+	}
+
+	return controller, nil
+}
+
+func (controller *Controller) Run(ctx context.Context) error {
+	// Run the scheduler so that each VM will eventually
+	// be assigned to a specific Worker
+	go func() {
+		err := runScheduler(controller.store)
+		if err != nil {
+			panic(err)
+		}
+	}()
+
+	// Run the janitor so that inactive workers
+	// will eventually be removed from the DB
+	go func() {
+		err := controller.runJanitor(controller.store)
+		if err != nil {
+			panic(err)
+		}
+	}()
+
+	// A helper function to shut down the HTTP server on context cancellation
+	go func() {
+		<-ctx.Done()
+		controller.httpServer.Shutdown(ctx)
+	}()
+
+	if err := controller.httpServer.Serve(controller.listener); err != nil {
+		return err
+	}
+
+	return nil
+}