From a666eae508f0b260024de74215c5012c388a14c2 Mon Sep 17 00:00:00 2001
From: Aryan Singh <asing271@illinois.edu>
Date: Sun, 25 Oct 2026 01:07:52 -0500
Subject: [PATCH] REDESIGNED MP2 FOR MP3

---
 MP3/membership.go | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/MP3/membership.go b/MP3/membership.go
index 3b7408a..ff217a5 100644
--- a/MP3/membership.go
+++ b/MP3/membership.go
@@ -245,7 +245,33 @@ func (m *MembershipService) handle_failure_detection(ctx context.Context, socket
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			// TODO: Implement failure detection logic
+			m.mutex.Lock()
+			now := time.Now()
+
+			for id, info := range m.members_list {
+				// Don't check ourselves or already failed nodes
+				if id == m.self_id || info.State == "down" {
+					continue
+				}
+
+				if info.LocalLastSeen == nil {
+					info.LocalLastSeen = &now
+					m.members_list[id] = info
+					continue
+				}
+
+				// No heartbeat advancement for 2.5 seconds
+				if now.Sub(*info.LocalLastSeen) > 2500*time.Millisecond {
+					info.State = "down"
+					info.LocalFailedSince = &now
+
+					m.members_list[id] = info
+
+					logger.Warn("Member marked DOWN", "member", id)
+				}
+			}
+
+			m.mutex.Unlock()
 		}
 	}
 }