Merge pull request #4577 from LiskHQ/4351-adding_condition_to_select_…

…peers_for_connection

Add P2P condition to select peers for connection - Closed #4351

elements/lisk-p2p/src/utils/select.ts

@@ -127,9 +127,12 @@ export const selectPeersForConnection = (
 	}
 
 	// LIP004 https://github.com/LiskHQ/lips/blob/master/proposals/lip-0004.md#peer-discovery-and-selection
-	const x =
-		input.triedPeers.length / (input.triedPeers.length + input.newPeers.length);
 	const minimumProbability = 0.5;
+	const x =
+		input.triedPeers.length < 100
+			? minimumProbability
+			: input.triedPeers.length /
+			  (input.triedPeers.length + input.newPeers.length);
 	const r = Math.max(x, minimumProbability);
 
 	const shuffledTriedPeers = shuffle(input.triedPeers);

elements/lisk-p2p/test/unit/utils/select.ts

@@ -351,6 +351,35 @@ describe('peer selector', () => {
 			});
 		});
 
+		describe('when there are less than 100 peers', () => {
+			it('should return peers uniformly from both lists', () => {
+				const triedPeers = initPeerInfoListWithSuffix('111.112.113', 25);
+				const newPeers = initPeerInfoListWithSuffix('111.112.114', 75);
+
+				const selectedPeers = selectPeersForConnection({
+					triedPeers,
+					newPeers,
+					peerLimit: 50,
+				});
+				expect(selectedPeers)
+					.to.be.an('array')
+					.of.length(50);
+
+				expect([...triedPeers, ...newPeers]).to.include.members(selectedPeers);
+
+				let triedCount = 0;
+				let newCount = 0;
+				for (const peer of selectedPeers) {
+					if (triedPeers.find(triedPeer => peer.peerId === triedPeer.peerId)) {
+						triedCount++;
+					}
+					newCount++;
+				}
+				expect(triedCount).to.gte(23);
+				expect(newCount).to.gte(23);
+			});
+		});
+
 		describe('when there are multiple peer from same IP with different height', () => {
 			it('should return only unique IPs', () => {
 				let uniqIpAddresses: Array<string> = [];