fix(inputs.gnmi): Register connection statistics before creating client (#16171)

plugins/inputs/gnmi/gnmi.go

@@ -7,6 +7,7 @@ import (
 	_ "embed"
 	"errors"
 	"fmt"
+	"net"
 	"strings"
 	"sync"
 	"time"
@@ -272,8 +273,14 @@ func (c *GNMI) Start(acc telegraf.Accumulator) error {
 		go func(addr string) {
 			defer c.wg.Done()
 
+			host, port, err := net.SplitHostPort(addr)
+			if err != nil {
+				acc.AddError(fmt.Errorf("unable to parse address %s: %w", addr, err))
+				return
+			}
 			h := handler{
-				address:             addr,
+				host:                host,
+				port:                port,
 				aliases:             c.internalAliases,
 				tagsubs:             c.TagSubscriptions,
 				maxMsgSize:          int(c.MaxMsgSize),

plugins/inputs/gnmi/handler.go

@@ -33,7 +33,8 @@ import (
 const eidJuniperTelemetryHeader = 1
 
 type handler struct {
-	address             string
+	host                string
+	port                string
 	aliases             map[*pathInfo]string
 	tagsubs             []tagSubscription
 	maxMsgSize          int
@@ -72,7 +73,14 @@ func (h *handler) subscribeGNMI(ctx context.Context, acc telegraf.Accumulator, t
 		opts = append(opts, grpc.WithKeepaliveParams(h.ClientParameters))
 	}
 
-	client, err := grpc.NewClient(h.address, opts...)
+	// Used to report the status of the TCP connection to the device. If the
+	// GNMI connection goes down, but TCP is still up this will still report
+	// connected until the TCP connection times out.
+	connectStat := selfstat.Register("gnmi", "grpc_connection_status", map[string]string{"source": h.host})
+	defer connectStat.Set(0)
+
+	address := net.JoinHostPort(h.host, h.port)
+	client, err := grpc.NewClient(address, opts...)
 	if err != nil {
 		return fmt.Errorf("failed to dial: %w", err)
 	}
@@ -88,21 +96,14 @@ func (h *handler) subscribeGNMI(ctx context.Context, acc telegraf.Accumulator, t
 	if err := subscribeClient.Send(request); err != nil && !errors.Is(err, io.EOF) {
 		return fmt.Errorf("failed to send subscription request: %w", err)
 	}
-
-	h.log.Debugf("Connection to gNMI device %s established", h.address)
-
-	// Used to report the status of the TCP connection to the device. If the
-	// GNMI connection goes down, but TCP is still up this will still report
-	// connected until the TCP connection times out.
-	connectStat := selfstat.Register("gnmi", "grpc_connection_status", map[string]string{"source": h.address})
 	connectStat.Set(1)
+	h.log.Debugf("Connection to gNMI device %s established", address)
 
-	defer h.log.Debugf("Connection to gNMI device %s closed", h.address)
+	defer h.log.Debugf("Connection to gNMI device %s closed", address)
 	for ctx.Err() == nil {
 		var reply *gnmi.SubscribeResponse
 		if reply, err = subscribeClient.Recv(); err != nil {
 			if !errors.Is(err, io.EOF) && ctx.Err() == nil {
-				connectStat.Set(0)
 				return fmt.Errorf("aborted gNMI subscription: %w", err)
 			}
 			break
@@ -121,8 +122,6 @@ func (h *handler) subscribeGNMI(ctx context.Context, acc telegraf.Accumulator, t
 			h.handleSubscribeResponseUpdate(acc, response, reply.GetExtension())
 		}
 	}
-
-	connectStat.Set(0)
 	return nil
 }
 
@@ -164,11 +163,7 @@ func (h *handler) handleSubscribeResponseUpdate(acc telegraf.Accumulator, respon
 	prefix := newInfoFromPath(response.Update.Prefix)
 
 	// Add info to the tags
-	var err error
-	headerTags["source"], _, err = net.SplitHostPort(h.address)
-	if err != nil {
-		h.log.Errorf("unable to parse address %s: %v", h.address, err)
-	}
+	headerTags["source"] = h.host
 	if !prefix.empty() {
 		headerTags["path"] = prefix.fullPath()
 	}