Introduce ORCHARD_LICENSE_TIER environment variable (#111)

* Introduce ORCHARD_LICENSE_TIER environment variable

* Only parse ORCHARD_LICENSE_TIER if it was provided

internal/controller/controller.go

@@ -20,6 +20,7 @@ import (
 	"google.golang.org/grpc/keepalive"
 	"net"
 	"net/http"
+	"os"
 	"strings"
 	"time"
 )
@@ -29,6 +30,12 @@ var (
 	ErrAdminTaskFailed = errors.New("controller administrative task failed")
 )
 
+const (
+	maxWorkersPerDefaultLicense  = 4
+	maxWorkersPerGoldLicense     = 20
+	maxWorkersPerPlatinumLicense = 200
+)
+
 type Controller struct {
 	dataDir              *DataDir
 	listenAddr           string
@@ -44,6 +51,7 @@ type Controller struct {
 	proxy                *proxy.Proxy
 	enableSwaggerDocs    bool
 	workerOfflineTimeout time.Duration
+	maxWorkersPerLicense uint
 
 	rpc.UnimplementedControllerServer
 }
@@ -53,6 +61,7 @@ func New(opts ...Option) (*Controller, error) {
 		workerNotifier:       notifier.NewNotifier(),
 		proxy:                proxy.NewProxy(),
 		workerOfflineTimeout: 3 * time.Minute,
+		maxWorkersPerLicense: maxWorkersPerDefaultLicense,
 	}
 
 	// Apply options
@@ -60,6 +69,20 @@ func New(opts ...Option) (*Controller, error) {
 		opt(controller)
 	}
 
+	// Apply environment variables
+	orchardLicenseTier, ok := os.LookupEnv("ORCHARD_LICENSE_TIER")
+	if ok {
+		switch orchardLicenseTier {
+		case "gold":
+			controller.maxWorkersPerLicense = maxWorkersPerGoldLicense
+		case "platinum":
+			controller.maxWorkersPerLicense = maxWorkersPerPlatinumLicense
+		default:
+			return nil, fmt.Errorf("%w: invalid ORCHARD_LICENSE_TIER value: %q",
+				ErrInitFailed, orchardLicenseTier)
+		}
+	}
+
 	// Apply defaults
 	if controller.dataDir == nil {
 		return nil, fmt.Errorf("%w: please specify the data directory path with WithDataDir()",