NOISSUE - V-Sock reconnect for agent (#215)

* vsock reconnect

Signed-off-by: Sammy Oina <sammyoina@gmail.com>

* use backoff

Signed-off-by: Sammy Oina <sammyoina@gmail.com>

---------

Signed-off-by: Sammy Oina <sammyoina@gmail.com>

cmd/agent/main.go

@@ -9,8 +9,10 @@ import (
 	"io"
 	"log"
 	"log/slog"
+	"time"
 
 	"github.com/absmach/magistrala/pkg/prometheus"
+	"github.com/cenkalti/backoff/v4"
 	"github.com/google/go-sev-guest/client"
 	"github.com/mdlayher/vsock"
 	"github.com/ultravioletrs/cocos/agent"
@@ -32,6 +34,7 @@ import (
 const (
 	svcName        = "agent"
 	defSvcGRPCPort = "7002"
+	retryInterval  = 5 * time.Second
 )
 
 func main() {
@@ -43,7 +46,7 @@ func main() {
 		log.Fatalf("failed to read agent configuration from vsock %s", err.Error())
 	}
 
-	conn, err := vsock.Dial(vsock.Host, manager.ManagerVsockPort, nil)
+	conn, err := dialVsock()
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -95,6 +98,22 @@ func main() {
 
 	gs := grpcserver.New(ctx, cancel, svcName, grpcServerConfig, registerAgentServiceServer, logger, qp, authSvc)
 
+	g.Go(func() error {
+		for {
+			if _, err := io.Copy(io.Discard, conn); err != nil {
+				log.Printf("vsock connection lost: %v, reconnecting...", err)
+				conn.Close()
+				conn, err = dialVsock()
+				if err != nil {
+					log.Fatal("failed to reconnect: ", err)
+				}
+				handler = agentlogger.NewProtoHandler(conn, &slog.HandlerOptions{Level: level})
+				logger = slog.New(handler)
+			}
+			time.Sleep(retryInterval)
+		}
+	})
+
 	g.Go(func() error {
 		return gs.Start()
 	})
@@ -158,3 +177,23 @@ func readConfig() (agent.Computation, error) {
 	}
 	return ac, nil
 }
+
+func dialVsock() (*vsock.Conn, error) {
+	var conn *vsock.Conn
+	var err error
+
+	err = backoff.Retry(func() error {
+		conn, err = vsock.Dial(vsock.Host, manager.ManagerVsockPort, nil)
+		if err == nil {
+			log.Println("vsock connection established")
+			return nil
+		}
+		log.Printf("vsock connection failed, retrying in %s... Error: %v", retryInterval, err)
+		return err
+	}, backoff.NewExponentialBackOff())
+	if err != nil {
+		return nil, err
+	}
+
+	return conn, nil
+}