From 92bd50c0e232d43fd9821c681c793be89a50e50f Mon Sep 17 00:00:00 2001
From: Chris Eager <chris@signal.org>
Date: Wed, 29 Apr 2026 15:55:54 -0500
Subject: [PATCH] Add metrics to SetAuditorHead and Distinguished updates

---
 cmd/kt-server/distinguished.go    | 6 ++++++
 tree/transparency/transparency.go | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/cmd/kt-server/distinguished.go b/cmd/kt-server/distinguished.go
index e5f37ad..a55d041 100644
--- a/cmd/kt-server/distinguished.go
+++ b/cmd/kt-server/distinguished.go
@@ -67,6 +67,12 @@ func distinguishedUpdate(updateHandler *KtUpdateHandler) {
 		}, 5*time.Second)
 		metrics.IncrCounterWithLabels([]string{"distinguished_update"}, 1, []metrics.Label{successLabel(err)})
 		if err == nil {
+			treeHead, _, err := updateHandler.tx.GetHead()
+			if err != nil {
+				util.Log().Warnf("failed to fetch head: %v", err)
+				return
+			}
+			metrics.SetGauge([]string{"distinguished.tree_size"}, float32(treeHead.TreeSize))
 			return
 		}
 		util.Log().Warnf("Failed to update distinguished key: %v", err)
diff --git a/tree/transparency/transparency.go b/tree/transparency/transparency.go
index d912153..433f734 100644
--- a/tree/transparency/transparency.go
+++ b/tree/transparency/transparency.go
@@ -1043,6 +1043,10 @@ func (t *Tree) SetAuditorHead(head *pb.AuditorTreeHead, auditorName string) erro
 		return err
 	}
 
+	labels := []metrics.Label{{"auditor", auditorName}}
+	metrics.SetGaugeWithLabels([]string{"set_auditor_head.signature_latency_seconds"}, float32(time.Duration(now-then)/time.Second), labels)
+	metrics.SetGaugeWithLabels([]string{"set_auditor_head.tree_size"}, float32(head.TreeSize), labels)
+
 	return nil
 }