From 491b92aa19e894b93bc2aa8d596809b5bfa2ae0a Mon Sep 17 00:00:00 2001
From: Greg Schrock <gschrock@juniper.net>
Date: Thu, 11 Sep 2025 12:18:46 -0400
Subject: [PATCH] t128_tank: stream from the beginning if parsing the index
 fails

I95-62311 #time 4h
---
 plugins/inputs/t128_tank/reader.go         |  4 +---
 plugins/inputs/t128_tank/t128_tank_test.go | 28 +++++++++++++++++++---
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/plugins/inputs/t128_tank/reader.go b/plugins/inputs/t128_tank/reader.go
index 7cf65090fe4ba..98b8f706a7c30 100644
--- a/plugins/inputs/t128_tank/reader.go
+++ b/plugins/inputs/t128_tank/reader.go
@@ -128,9 +128,7 @@ func (r *Reader) Run(mainCtx context.Context) {
 	var observedValue uint64
 	lastIndex, err := r.getIndex(r.indexPath, r.defaultIndex)
 	if err != nil {
-		r.log.Errorf("Error in get index %v", err)
-		readCtxCancel()
-		return
+		r.log.Infof("Failed to get index %v", err)
 	}
 	nextSaveCheck := time.NewTicker(2 * time.Second)
 	defer func() {
diff --git a/plugins/inputs/t128_tank/t128_tank_test.go b/plugins/inputs/t128_tank/t128_tank_test.go
index 061d72a604675..96b57a02b9caf 100644
--- a/plugins/inputs/t128_tank/t128_tank_test.go
+++ b/plugins/inputs/t128_tank/t128_tank_test.go
@@ -30,6 +30,7 @@ func TestT128TankReader(t *testing.T) {
 		Name                   string
 		IndexFile              string
 		IndexFileContent       string
+		IndexFileEmpty         bool
 		Topic                  string
 		PortNumber             int
 		ServerAddress          string
@@ -38,7 +39,7 @@ func TestT128TankReader(t *testing.T) {
 		ExpectedMetrics        []IndexedMessage
 	}{
 		{
-			Name:          "index file with no value",
+			Name:          "index file does not exist",
 			Topic:         "events",
 			PortNumber:    11011,
 			ServerAddress: "127.0.0.2",
@@ -54,6 +55,24 @@ func TestT128TankReader(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name:           "index file empty",
+			Topic:          "events",
+			IndexFileEmpty: true,
+			PortNumber:     11011,
+			ServerAddress:  "127.0.0.2",
+			DefaultIndex:   StartIndex,
+			TankReadCommandContext: func(ctx context.Context, name string, arg ...string) *exec.Cmd {
+				cmd := exec.CommandContext(ctx, "echo", "seq=1:measurement,core=2,node=test-1,port=corp-dmz-p value=0i 1586886775")
+				return cmd
+			},
+			ExpectedMetrics: []IndexedMessage{
+				{
+					Message: []byte("measurement,core=2,node=test-1,port=corp-dmz-p value=0i 1586886775"),
+					Index:   index{value: 1},
+				},
+			},
+		},
 		{
 			Name:             "index file with value",
 			IndexFileContent: "150",
@@ -87,7 +106,7 @@ func TestT128TankReader(t *testing.T) {
 			var wg sync.WaitGroup
 			indexFileName := strings.ReplaceAll(testcase.Name, " ", "_")
 			plugin.IndexFile = path.Join(t.TempDir(), fmt.Sprintf("%s.index", indexFileName))
-			if testcase.IndexFileContent != "" {
+			if testcase.IndexFileContent != "" || testcase.IndexFileEmpty {
 				err := os.WriteFile(plugin.IndexFile, []byte(testcase.IndexFileContent), 0755)
 				assert.NoError(t, err)
 			}
@@ -116,9 +135,12 @@ func TestT128TankReader(t *testing.T) {
 
 			cancel()
 
+			if len(testcase.ExpectedMetrics) > 0 {
+				assert.NotNil(t, receivedMessages)
+			}
+
 			if len(testcase.ExpectedMetrics) > 0 && receivedMessages != nil {
 				assert.Equal(t, testcase.ExpectedMetrics, receivedMessages)
-
 			}
 		})
 	}