refactor GRPC connection management

src/lib/kernel/grpc.go

@@ -1,36 +1,48 @@
 package kernel
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net"
+	"time"
 
 	"google.golang.org/grpc"
 )
 
-type ServerBuilder func(grpc.ServiceRegistrar)
+type ServerBuilder func(grpc.ServiceRegistrar, string)
 
 var (
 	grpcServerInstance *grpc.Server
 	listener           net.Listener
 )
 
-func StartGRPCServer(port int, sb ServerBuilder, opts ...grpc.ServerOption) (err error) {
+func StartGRPCServer(ctx context.Context, port int, sb ServerBuilder, opts ...grpc.ServerOption) (endpoint string, err error) {
 	if grpcServerInstance != nil {
-		return errors.New("There can only be one GRPC server running at a time")
+		err = errors.New("There can only be one GRPC server running at a time")
+		return
 	}
 
-	listener, err = net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", port))
+	endpoint = fmt.Sprintf("0.0.0.0:%d", port)
+	listener, err = net.Listen("tcp", endpoint)
 	if err != nil {
-		return fmt.Errorf("could not start tcp listener: %w", err)
+		endpoint = ""
+		err = fmt.Errorf("could not start tcp listener: %w", err)
+		return
 	}
 
 	grpcServerInstance = grpc.NewServer(opts...)
 
-	sb(grpcServerInstance)
+	sb(grpcServerInstance, endpoint)
 
-	InfoLog.Printf("Listening on 0.0.0.0:%d", port)
-	return grpcServerInstance.Serve(listener)
+	if err = grpcServerInstance.Serve(listener); err != nil {
+		endpoint = ""
+		err = fmt.Errorf("could not serve GRPC server over listener: %w", err)
+		return
+	}
+
+	InfoLog.Printf("Listening for GRPC requests on %s", endpoint)
+	return
 }
 
 func StopGRPCServer() error {

src/runner/internal/handler.go

@@ -10,8 +10,8 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-func NewRunnerServer(d *runner.Domain) func(grpcServer grpc.ServiceRegistrar) {
-	return func(grpcServer grpc.ServiceRegistrar) {
+func NewRunnerServer(d *runner.Domain) func(grpcServer grpc.ServiceRegistrar, endpoint string) {
+	return func(grpcServer grpc.ServiceRegistrar, endpoint string) {
 		api.RegisterRunnerServer(grpcServer, &runnerHandler{domain: d})
 	}
 }

src/runner/main.go

@@ -81,7 +81,13 @@ func (app *RunnerApp) Start(ctx context.Context) error {
 	})
 
 	return ioc.Invoke(func(d *runner.Domain) error {
-		return kernel.StartGRPCServer(app.Port, internal.NewRunnerServer(d))
+		runnerService := internal.NewRunnerServer(d)
+
+		if _, err := kernel.StartGRPCServer(ctx, app.Port, runnerService); err != nil {
+			return err
+		}
+
+		return nil
 	})
 }