From a87e9c870d5a881eb7bedb0b1fb7a08a70683155 Mon Sep 17 00:00:00 2001
From: arkpar <arkady.paronyan@gmail.com>
Date: Mon, 11 Jul 2022 21:48:42 +0200
Subject: [PATCH 1/3] Fixed sync target detection

---
 client/network/sync/src/lib.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/client/network/sync/src/lib.rs b/client/network/sync/src/lib.rs
index 5b5216c745c98..763efbc0ed6fe 100644
--- a/client/network/sync/src/lib.rs
+++ b/client/network/sync/src/lib.rs
@@ -578,7 +578,17 @@ where
 
 	/// Returns the best seen block.
 	fn best_seen(&self) -> Option<NumberFor<B>> {
-		let mut best_seens = self.peers.values().map(|p| p.best_number).collect::<Vec<_>>();
+		let mut best_seens = self
+			.peers
+			.values()
+			.filter_map(|p| {
+				if p.best_number > self.best_queued_number {
+					Some(p.best_number)
+				} else {
+					None
+				}
+			})
+			.collect::<Vec<_>>();
 
 		if best_seens.is_empty() {
 			None

From f104f67ab53b4f8adce706de90eadcf595fe163a Mon Sep 17 00:00:00 2001
From: arkpar <arkady.paronyan@gmail.com>
Date: Tue, 12 Jul 2022 20:47:24 +0200
Subject: [PATCH 2/3] Always report sync_target metric

---
 client/service/src/metrics.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/client/service/src/metrics.rs b/client/service/src/metrics.rs
index 555023f894488..56b145ccdf7f7 100644
--- a/client/service/src/metrics.rs
+++ b/client/service/src/metrics.rs
@@ -298,9 +298,10 @@ impl MetricsService {
 						UniqueSaturatedInto::<u64>::unique_saturated_into(num)
 					});
 
-				if let Some(best_seen_block) = best_seen_block {
-					metrics.block_height.with_label_values(&["sync_target"]).set(best_seen_block);
-				}
+				metrics
+					.block_height
+					.with_label_values(&["sync_target"])
+					.set(best_seen_block.unwrap_or(best_number));
 			}
 		}
 	}

From 53f182508bc7de9cb362a6697261785e0b5c497e Mon Sep 17 00:00:00 2001
From: arkpar <arkady.paronyan@gmail.com>
Date: Fri, 15 Jul 2022 11:13:32 +0200
Subject: [PATCH 3/3] Clamp median across all peers

---
 client/network/sync/src/lib.rs | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/client/network/sync/src/lib.rs b/client/network/sync/src/lib.rs
index 236b828f78b71..2f837cd6c4f51 100644
--- a/client/network/sync/src/lib.rs
+++ b/client/network/sync/src/lib.rs
@@ -1719,19 +1719,9 @@ where
 		Ok(sync)
 	}
 
-	/// Returns the best seen block.
+	/// Returns the best seen block number if we don't have that block yet, `None` otherwise.
 	fn best_seen(&self) -> Option<NumberFor<B>> {
-		let mut best_seens = self
-			.peers
-			.values()
-			.filter_map(|p| {
-				if p.best_number > self.best_queued_number {
-					Some(p.best_number)
-				} else {
-					None
-				}
-			})
-			.collect::<Vec<_>>();
+		let mut best_seens = self.peers.values().map(|p| p.best_number).collect::<Vec<_>>();
 
 		if best_seens.is_empty() {
 			None
@@ -1739,7 +1729,12 @@ where
 			let middle = best_seens.len() / 2;
 
 			// Not the "perfect median" when we have an even number of peers.
-			Some(*best_seens.select_nth_unstable(middle).1)
+			let median = *best_seens.select_nth_unstable(middle).1;
+			if median > self.best_queued_number {
+				Some(median)
+			} else {
+				None
+			}
 		}
 	}