From 1a035ee1fd9477c8bbeaec6363c0ae436dd8531c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C4=90=E1=BB=97=20Tr=E1=BB=8Dng=20H=E1=BA=A3i?=
 <41283691+hainenber@users.noreply.github.com>
Date: Thu, 8 Feb 2024 10:29:47 +0700
Subject: [PATCH] fix(comp): prevent divide-by-zero error when calculating
 array size for sharded targets (#6326)

---
 CHANGELOG.md                                |  2 ++
 component/discovery/discovery.go            | 10 ++++++++--
 component/loki/source/podlogs/reconciler.go | 10 ++++++++--
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1805a76bca0a..78b628221fb7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -73,6 +73,8 @@ Main (unreleased)
 - Fix an issue with static integrations-next marshaling where non singletons
   would cause `/-/config` to fail to marshal. (@erikbaranowski)
 
+- Fix divide-by-zero issue when sharding targets. (@hainenber) 
+
 ### Other changes
 
 - Removed support for Windows 2012 in line with Microsoft end of life. (@mattdurham)
diff --git a/component/discovery/discovery.go b/component/discovery/discovery.go
index cacd9559070d..ebeca72ecd5a 100644
--- a/component/discovery/discovery.go
+++ b/component/discovery/discovery.go
@@ -43,7 +43,13 @@ func (t *DistributedTargets) Get() []Target {
 		return t.targets
 	}
 
-	res := make([]Target, 0, (len(t.targets)+1)/len(t.cluster.Peers()))
+	peerCount := len(t.cluster.Peers())
+	resCap := (len(t.targets) + 1)
+	if peerCount != 0 {
+		resCap = (len(t.targets) + 1) / peerCount
+	}
+
+	res := make([]Target, 0, resCap)
 
 	for _, tgt := range t.targets {
 		peers, err := t.cluster.Lookup(shard.StringKey(tgt.NonMetaLabels().String()), 1, shard.OpReadWrite)
@@ -53,7 +59,7 @@ func (t *DistributedTargets) Get() []Target {
 			// back to owning the target ourselves.
 			res = append(res, tgt)
 		}
-		if peers[0].Self {
+		if len(peers) == 0 || peers[0].Self {
 			res = append(res, tgt)
 		}
 	}
diff --git a/component/loki/source/podlogs/reconciler.go b/component/loki/source/podlogs/reconciler.go
index 4d2ec87495f2..66baba5e86f7 100644
--- a/component/loki/source/podlogs/reconciler.go
+++ b/component/loki/source/podlogs/reconciler.go
@@ -131,7 +131,13 @@ func distributeTargets(c cluster.Cluster, targets []*kubetail.Target) []*kubetai
 		return targets
 	}
 
-	res := make([]*kubetail.Target, 0, (len(targets)+1)/len(c.Peers()))
+	peerCount := len(c.Peers())
+	resCap := len(targets) + 1
+	if peerCount != 0 {
+		resCap = (len(targets) + 1) / peerCount
+	}
+
+	res := make([]*kubetail.Target, 0, resCap)
 
 	for _, target := range targets {
 		peers, err := c.Lookup(shard.StringKey(target.Labels().String()), 1, shard.OpReadWrite)
@@ -141,7 +147,7 @@ func distributeTargets(c cluster.Cluster, targets []*kubetail.Target) []*kubetai
 			// back to owning the target ourselves.
 			res = append(res, target)
 		}
-		if peers[0].Self {
+		if len(peers) == 0 || peers[0].Self {
 			res = append(res, target)
 		}
 	}