From 23b70dd0b234011d3ab9ef4e07445e4409192b5a Mon Sep 17 00:00:00 2001
From: Bora Tanrikulu <me@bora.sh>
Date: Sun, 25 Jan 2026 17:46:08 +0300
Subject: [PATCH] [SC-23705] fix(sematext): deduplicate corrupted measurement
 name prefixes
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Fix Apache metrics corruption where field names contained 64+ repeated
"apache." prefixes (e.g., "apache.apache.apache...bytespersec").

The root cause: when originalName arrives corrupted, the lookup key
becomes "apache.apache.apache.BusyWorkers" which doesn't match
fieldReplaces["apache.BusyWorkers"], falling back to ChangeNames()
which preserves the corruption.

The fix adds deduplicatePrefix() to normalize measurement names before
building lookup keys (e.g., "apache.apache.apache" → "apache").
---
 plugins/outputs/sematext/processors/rename.go | 28 ++++++++++++
 .../sematext/processors/rename_test.go        | 43 +++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/plugins/outputs/sematext/processors/rename.go b/plugins/outputs/sematext/processors/rename.go
index aa7dbbdcbd272..9334a756499ec 100644
--- a/plugins/outputs/sematext/processors/rename.go
+++ b/plugins/outputs/sematext/processors/rename.go
@@ -210,6 +210,10 @@ func NewRename() BatchProcessor { return &Rename{} }
 func (r *Rename) Process(points []telegraf.Metric) []telegraf.Metric {
 	for _, point := range points {
 		originalName := point.Name()
+
+		// Fix corrupted measurement names (e.g., "apache.apache.apache" → "apache")
+		originalName = deduplicatePrefix(originalName)
+
 		replace, ok := measurementReplaces[originalName]
 		if !ok {
 			replace = ChangeNames(originalName)
@@ -275,3 +279,27 @@ func ChangeNames(name string) string {
 }
 
 func (Rename) Close() {}
+
+// deduplicatePrefix fixes recursive prefix corruption.
+// Example: "apache.apache.apache" → "apache"
+func deduplicatePrefix(name string) string {
+	parts := strings.Split(name, ".")
+	if len(parts) < 2 {
+		return name
+	}
+
+	prefix := parts[0]
+	count := 0
+	for count < len(parts) && parts[count] == prefix {
+		count++
+	}
+
+	if count > 1 {
+		remaining := parts[count:]
+		if len(remaining) > 0 {
+			return prefix + "." + strings.Join(remaining, ".")
+		}
+		return prefix
+	}
+	return name
+}
diff --git a/plugins/outputs/sematext/processors/rename_test.go b/plugins/outputs/sematext/processors/rename_test.go
index 8f8e335f5ca10..bd044f59cb68a 100644
--- a/plugins/outputs/sematext/processors/rename_test.go
+++ b/plugins/outputs/sematext/processors/rename_test.go
@@ -34,6 +34,49 @@ func TestRename(t *testing.T) {
 	assert.Equal(t, "mongodb_shard_stats.in_use", results[8].FieldList()[0].Key)
 }
 
+func TestDeduplicatePrefix(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"apache", "apache"},
+		{"apache.apache", "apache"},
+		{"apache.apache.apache", "apache"},
+		{"apache.apache.apache.apache", "apache"},
+		{"nginx", "nginx"},
+		{"nginx.nginx", "nginx"},
+		{"nginx.nginx.nginx", "nginx"},
+		{"mongodb", "mongodb"},
+		{"mongodb.mongodb.mongodb", "mongodb"},
+		// Edge cases
+		{"", ""},
+		{"a", "a"},
+		{"a.b", "a.b"},
+		{"a.a.b", "a.b"},
+		{"foo.foo.bar.baz", "foo.bar.baz"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			result := deduplicatePrefix(tt.input)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestRenameWithCorruptedMeasurementName(t *testing.T) {
+	r := Rename{}
+
+	// Simulate corrupted measurement name with 64+ repeated prefixes
+	corruptedName := "apache.apache.apache.apache.apache"
+	m := newMetric(corruptedName, nil, map[string]interface{}{"BusyWorkers": 10})
+
+	results := r.Process([]telegraf.Metric{m})
+
+	assert.Equal(t, "apache", results[0].Name())
+	assert.Equal(t, "workers.busy", results[0].FieldList()[0].Key)
+}
+
 func newMetric(name string, tags map[string]string, fields map[string]interface{}) telegraf.Metric {
 	if tags == nil {
 		tags = map[string]string{}