From 24be9d9ab3402795be715f3f7897ed3e70ac8a76 Mon Sep 17 00:00:00 2001
From: frh-td <73470898+frh-td@users.noreply.github.com>
Date: Thu, 25 Sep 2025 12:37:15 +0200
Subject: [PATCH] Fix when multiple label names normalize to the same string

Signed-off-by: frh-td <73470898+frh-td@users.noreply.github.com>
---
 .../io/prometheus/cloudwatch/CloudWatchCollector.java     | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/main/java/io/prometheus/cloudwatch/CloudWatchCollector.java b/src/main/java/io/prometheus/cloudwatch/CloudWatchCollector.java
index 71ff755c..f5ea9a79 100644
--- a/src/main/java/io/prometheus/cloudwatch/CloudWatchCollector.java
+++ b/src/main/java/io/prometheus/cloudwatch/CloudWatchCollector.java
@@ -639,8 +639,12 @@ private void scrape(List<MetricFamilySamples> mfs) {
             // "tag_" prefix
             // The AWS tags are case sensitive, so to avoid loosing information and label
             // collisions, tag keys are not snaked cased
-            labelNames.add("tag_" + safeLabelName(tag.key()));
-            labelValues.add(tag.value());
+            String labelName = "tag_" + safeLabelName(tag.key());
+            // If multiple labels end up with the same safe label name, use only the first
+            if (!labelNames.contains(labelName)) {
+              labelNames.add(labelName);
+              labelValues.add(tag.value());
+            }
           }
 
           infoSamples.add(