From 281142567c7b02b6c0467a5da312ca50ba11f348 Mon Sep 17 00:00:00 2001
From: Samuel Berthe <dev@samuel-berthe.fr>
Date: Mon, 16 Mar 2026 03:25:27 +0100
Subject: [PATCH] fix: use proper zero-traffic guard in Envoy ratio alerts
 (#511) (#513)

Replace `+ 1` denominator hack with `and ... > 0` filter in upstream
timeout rate and upstream 5xx error rate queries for mathematical
correctness and repo consistency.
---
 _data/rules.yml | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/_data/rules.yml b/_data/rules.yml
index 0e78127..4e989f7 100644
--- a/_data/rules.yml
+++ b/_data/rules.yml
@@ -2363,18 +2363,14 @@ groups:
                 for: 5m
               - name: Envoy high cluster upstream request timeout rate
                 description: "More than 5% of upstream requests are timing out in cluster {{ $labels.envoy_cluster_name }} on {{ $labels.instance }}"
-                query: "increase(envoy_cluster_upstream_rq_timeout[5m]) / (increase(envoy_cluster_upstream_rq_completed[5m]) + 1) * 100 > 5"
+                query: "increase(envoy_cluster_upstream_rq_timeout[5m]) / increase(envoy_cluster_upstream_rq_completed[5m]) * 100 > 5 and increase(envoy_cluster_upstream_rq_completed[5m]) > 0"
                 severity: warning
                 for: 5m
-                comments: |
-                  The +1 in the denominator guards against division by zero.
               - name: Envoy high cluster upstream 5xx error rate
                 description: "More than 5% of upstream requests return 5xx in cluster {{ $labels.envoy_cluster_name }} on {{ $labels.instance }}"
-                query: 'increase(envoy_cluster_upstream_rq_xx{envoy_response_code_class="5"}[5m]) / (increase(envoy_cluster_upstream_rq_completed[5m]) + 1) * 100 > 5'
+                query: 'increase(envoy_cluster_upstream_rq_xx{envoy_response_code_class="5"}[5m]) / increase(envoy_cluster_upstream_rq_completed[5m]) * 100 > 5 and increase(envoy_cluster_upstream_rq_completed[5m]) > 0'
                 severity: critical
                 for: 1m
-                comments: |
-                  The +1 in the denominator guards against division by zero.
               - name: Envoy cluster health check failures
                 description: "Health checks are consistently failing in cluster {{ $labels.envoy_cluster_name }} on {{ $labels.instance }}"
                 query: "increase(envoy_cluster_health_check_failure[5m]) > 5"