From 7698b28e16cd2e6548bbddd658c3fafc6d9b44d0 Mon Sep 17 00:00:00 2001
From: Gary Yu <gairy.yu@gmail.com>
Date: Sat, 12 Jan 2019 07:38:27 +0800
Subject: [PATCH] fix: wait_for_min_peers shouldn't wait forever when all peers
 are in same work (#2340)

---
 p2p/src/peers.rs                | 16 ++++++++++++++++
 servers/src/grin/sync/syncer.rs | 10 +++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/p2p/src/peers.rs b/p2p/src/peers.rs
index 1dcd0d90b..a67e8ffd6 100644
--- a/p2p/src/peers.rs
+++ b/p2p/src/peers.rs
@@ -199,6 +199,22 @@ impl Peers {
 		max_peers
 	}
 
+	// Return number of connected peers that currently advertise more/same work
+	// (total_difficulty) than/as we do.
+	pub fn more_or_same_work_peers(&self) -> usize {
+		let peers = self.connected_peers();
+		if peers.len() == 0 {
+			return 0;
+		}
+
+		let total_difficulty = self.total_difficulty();
+
+		peers
+			.iter()
+			.filter(|x| x.info.total_difficulty() >= total_difficulty)
+			.count()
+	}
+
 	/// Returns single random peer with more work than us.
 	pub fn more_work_peer(&self) -> Option<Arc<Peer>> {
 		self.more_work_peers().pop()
diff --git a/servers/src/grin/sync/syncer.rs b/servers/src/grin/sync/syncer.rs
index 3599da380..f66856c28 100644
--- a/servers/src/grin/sync/syncer.rs
+++ b/servers/src/grin/sync/syncer.rs
@@ -77,18 +77,18 @@ impl SyncRunner {
 		let mut n = 0;
 		const MIN_PEERS: usize = 3;
 		loop {
-			let wp = self.peers.more_work_peers();
+			let wp = self.peers.more_or_same_work_peers();
 			// exit loop when:
-			// * we have more than MIN_PEERS more_work peers
+			// * we have more than MIN_PEERS more_or_same_work peers
 			// * we are synced already, e.g. grin was quickly restarted
 			// * timeout
-			if wp.len() > MIN_PEERS
-				|| (wp.len() == 0
+			if wp > MIN_PEERS
+				|| (wp == 0
 					&& self.peers.enough_peers()
 					&& head.total_difficulty > Difficulty::zero())
 				|| n > wait_secs
 			{
-				if wp.len() > 0 || !global::is_production_mode() {
+				if wp > 0 || !global::is_production_mode() {
 					break;
 				}
 			}