From 070627d11e48421d798f7340ac8de9928d8472d6 Mon Sep 17 00:00:00 2001
From: Owen Diehl <ow.diehl@gmail.com>
Date: Mon, 3 May 2021 11:57:24 -0400
Subject: [PATCH] better handle metrics for state transitions (#33648)

---
 pkg/services/ngalert/state/cache.go | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/pkg/services/ngalert/state/cache.go b/pkg/services/ngalert/state/cache.go
index fa481ffc4f5..427090c070c 100644
--- a/pkg/services/ngalert/state/cache.go
+++ b/pkg/services/ngalert/state/cache.go
@@ -123,7 +123,15 @@ func (c *cache) trim() {
 	c.mtxStates.Lock()
 	defer c.mtxStates.Unlock()
 
-	ct := make(map[eval.State]int)
+	// Set default values to zero such that gauges are reset
+	// after all values from a single state disappear.
+	ct := map[eval.State]int{
+		eval.Normal:   0,
+		eval.Alerting: 0,
+		eval.Pending:  0,
+		eval.NoData:   0,
+		eval.Error:    0,
+	}
 
 	for _, v := range c.states {
 		if len(v.Results) > 100 {