Merge pull request #8 from illinois-cs-coursework/aryan

V1 GOSSIP DONE

MP2/.gitignore

@@ -0,0 +1 @@
+scripts

MP2/peer.py

@@ -8,61 +8,92 @@ import json
 def utc_time():
     return datetime.now(timezone.utc).timestamp()
 
-INTRODUCER_IP = "172.22.156.3"
+INTRODUCER_IP = "172.22.156.3" #hardcoded ip
-IP = socket.gethostbyname(socket.gethostname())
+IP = socket.gethostbyname(socket.gethostname()) #the vm IP address
-SERVER_PORT = 6767
+SERVER_PORT = 8989
 INTRODUCER_FLAG = (INTRODUCER_IP == IP)
-HEART_BEAT_INTERVAL = 5
+HEART_BEAT_INTERVAL = 0.25
-GOSSIP_INTERVAL = 10.0
+GOSSIP_INTERVAL = 0.25
-FAILURE_TIMEOUT = 3.0
+FAILURE_TIMEOUT = 2.5
+FAILURE_T_CLEANUP = 10.0
+RETRY_INTERVAL = 5.0
+FANOUT = 1
+
+#message json example:
+# {
+#     type: "GOSSIP", or "JOIN", ...
+#     sender_id: (ip, port, timestamp),
+#     members: [
+#         {
+#             ip: "
+#             port: 8989,
+#             timestamp: 1234567890.123456,
+#             heart_beat: 1,
+#             state: "alive"
+#         },
+#         ...
 
 members_list = {}
+dead_members = set() #[BASICALLY VERSION TRACKING]this tracks members that have been marked as failed and removed from the membership list.
 members_list_lock = threading.Lock()
 
+#adding its self to the membership list
 SELF_ID = (IP, SERVER_PORT, utc_time())
 members_list[SELF_ID] = {
     "heart_beat": 1,
-    "last_seen": utc_time()
+    "local_last_seen": utc_time(),
+    "state": "alive",
+    "local_failed_since" : None,
+    "local_suspected_since" : None
 }
-print(f"Starting peer: IP={IP}, port={SERVER_PORT}, introducer={INTRODUCER_FLAG}, self_id={SELF_ID}")
 
-stop_event = threading.Event()
+stop_event = threading.Event() #trigger to stop all threads when the program is exiting
 
+#one socket for all threads to use
 server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
 server_socket.bind((IP, SERVER_PORT))
 server_socket.settimeout(1.0)
 
+#responsible for handling incoming gossip messages, join requests on the introducer, and updating the membership list based on the received messages
 def worker_1():
-    if not INTRODUCER_FLAG:
+    has_joined = INTRODUCER_FLAG #if this is the introducer, it has already joined
-        join_payload = {
+    last_join_time = 0 #flag to track the last time a join request was sent to retry
-            "type": "JOIN",
-            "sender_id": SELF_ID
-        }
-        server_socket.sendto(json.dumps(join_payload).encode('utf-8'), (INTRODUCER_IP, SERVER_PORT))
     
     while not stop_event.is_set():
+        # If the node has not joined and enough time has passed since the last join attempt, send a JOIN request to the introducer
+        if not has_joined and (utc_time() - last_join_time > RETRY_INTERVAL):
+            join_payload = {
+                "type": "JOIN",
+                "sender_id": SELF_ID
+            }
+            server_socket.sendto(json.dumps(join_payload).encode('utf-8'), (INTRODUCER_IP, SERVER_PORT))
+            last_join_time = utc_time()
+
         try:
             data, addr = server_socket.recvfrom(65535) 
             
-            try:
+            msg = json.loads(data.decode('utf-8'))
-                msg = json.loads(data.decode('utf-8'))
-            except json.JSONDecodeError:
-                continue
                 
             msg_type = msg.get("type")
-            print(f"Processing message type={msg_type} from {addr}")
             
+            #handle join type
             if msg_type == "JOIN":
                 join_ip, join_port, join_timestamp = msg["sender_id"]
                 join_id = (join_ip, join_port, join_timestamp)
                 
                 with members_list_lock:
+                    #if in dead members, ignore the join request
+                    if join_id in dead_members:
+                        continue
+
                     if join_id not in members_list:
                         members_list[join_id] = {
                             "heart_beat": 1,
-                            "last_seen": utc_time()
+                            "local_last_seen": utc_time(),
+                            "state": "alive",
+                            "local_failed_since" : None,
+                            "local_suspected_since" : None
                         }
-                        print(f"Added member: {join_id}")
                     
                     members_payload = []
                     for m_id, m_data in members_list.items():
@@ -70,56 +101,80 @@ def worker_1():
                             "ip": m_id[0],
                             "port": m_id[1],
                             "timestamp": m_id[2],
-                            "heart_beat": m_data["heart_beat"]
+                            "heart_beat": m_data["heart_beat"],
+                            "state": m_data["state"]
                         })
-                        
-                print(f"New member joined: {join_id}")
                 
-                # Send the initial state directly to the joining node
+                #send the current membership list to the joining node
                 reply_payload = {
                     "type": "GOSSIP",
                     "sender_id": SELF_ID,
                     "members": members_payload
                 }
                 server_socket.sendto(json.dumps(reply_payload).encode('utf-8'), (join_ip, join_port))
-                print(f"Sent initial membership state to {(join_ip, join_port)}: {reply_payload}")
 
+            #handle gossip type
             elif msg_type == "GOSSIP":
+                #first time receiving a gossip message, mark the node as joined
+                if not has_joined:
+                    has_joined = True
+
                 members_json = msg.get('members', [])
 
                 with members_list_lock:
                     for member in members_json:
                         member_id = (member['ip'], member['port'], member['timestamp'])
-                        member_hb = member['heart_beat']
+                        
-
+                        if member_id == SELF_ID or member_id in dead_members:
-                        if member_id == SELF_ID:
                             continue
 
-                        if member_id not in members_list:
+                        incoming_state = member['state']
-                            members_list[member_id] = {
+                        incoming_hb = member['heart_beat']
-                                "heart_beat": member_hb,
+                            
-                                "last_seen": utc_time()
+                        local_member = members_list.get(member_id)
-                            }
+
-                            print(f"Added gossip member: {member_id}, heartbeat={member_hb}")
+                        if local_member is None:
-                        elif member_hb > members_list[member_id]["heart_beat"]:
+                            if incoming_state == "failed":
-                            members_list[member_id]["heart_beat"] = member_hb
+                                dead_members.add(member_id)
-                            members_list[member_id]["last_seen"] = utc_time()
+                                continue
-                            print(f"Updated member: {member_id}, heartbeat={member_hb}")
+                            else:
+                                members_list[member_id] = {
+                                    "heart_beat": incoming_hb,
+                                    "local_last_seen": utc_time(),
+                                    "state": incoming_state,
+                                    "local_failed_since" : None,
+                                    "local_suspected_since" : None
+                                }
+                            continue
+
+                        if local_member["state"] == "failed":
+                            continue
+
+                        if incoming_state == "failed":
+                            local_member["state"] = "failed"
+                            local_member["local_failed_since"] = utc_time()
+                            print(f"Member {member_id} marked as failed due to gossip.")
+                        elif incoming_hb > local_member["heart_beat"]:
+                            local_member["heart_beat"] = incoming_hb
+                            local_member["local_last_seen"] = utc_time()
                 
         except socket.timeout:
             continue
 
+#handles incrementing the local node's heartbeat counter at regular intervals
 def worker_2():
     while not stop_event.is_set():
         with members_list_lock:
             members_list[SELF_ID]["heart_beat"] += 1
-            print(f"Updated my heartbeat: {members_list[SELF_ID]['heart_beat']}")
         time.sleep(HEART_BEAT_INTERVAL)
 
+#handles sending gossip messages to a subset of alive peers at regular intervals
 def worker_3():
+    peer_queue = []
+    
     while not stop_event.is_set():
         with members_list_lock:
-            peers = list(members_list.keys())
+            current_peers = [member_id for member_id in members_list.keys() if member_id != SELF_ID and members_list[member_id]["state"] == "alive"]
             
             members_payload = []
             for m_id, m_data in members_list.items():
@@ -127,36 +182,93 @@ def worker_3():
                     "ip": m_id[0],
                     "port": m_id[1],
                     "timestamp": m_id[2],
-                    "heart_beat": m_data["heart_beat"]
+                    "heart_beat": m_data["heart_beat"],
+                    "state": m_data["state"]
                 })
+        
+        if current_peers:
+            #remove any peers from the queue that are no longer alive 
+            peer_queue = [p for p in peer_queue if p in current_peers]
             
-        if SELF_ID in peers:
+            selected_peers = []
-            peers.remove(SELF_ID)
+            num_to_select = min(FANOUT, len(current_peers))
             
-        if peers:
+            for _ in range(num_to_select):
-            random_peer = random.choice(peers)
+                if not peer_queue:
-            peer_ip, peer_port, _ = random_peer
+                    peer_queue = list(current_peers)
+                    random.shuffle(peer_queue)
+                
+                if peer_queue:
+                    selected_peers.append(peer_queue.pop(0))
             
-            payload = {
+            for peer in selected_peers:
-                "type": "GOSSIP",
+                peer_ip, peer_port, _ = peer
-                "sender_id": SELF_ID,
+                
-                "members": members_payload
+                payload = {
-            }
+                    "type": "GOSSIP",
-            
+                    "sender_id": SELF_ID,
-            json_string = json.dumps(payload)
+                    "members": members_payload
-            print(f"Sending GOSSIP to {(peer_ip, peer_port)}: {payload}")
+                }
-            server_socket.sendto(json_string.encode('utf-8'), (peer_ip, peer_port))
+                
+                json_string = json.dumps(payload)
+                server_socket.sendto(json_string.encode('utf-8'), (peer_ip, peer_port))
             
         time.sleep(GOSSIP_INTERVAL)
 
+# handle failure detection and cleanup of failed members from the membership list
+def worker_4():
+    while not stop_event.is_set():
+        current_time = utc_time()
+        to_remove = []
+        
+        with members_list_lock:
+            for member_id, member_data in members_list.items():
+                if member_id == SELF_ID:
+                    continue
+                
+                if member_data["state"] == "alive":
+                    last_seen = member_data["local_last_seen"]
+                    time_since_last_seen = current_time - last_seen
+                    
+                    if time_since_last_seen > FAILURE_TIMEOUT:
+                        member_data["state"] = "failed"
+                        member_data["local_failed_since"] = current_time
+                
+                last_failed_since = member_data.get("local_failed_since")
+                if last_failed_since is not None and (current_time - last_failed_since) > FAILURE_T_CLEANUP:
+                    to_remove.append(member_id)
+            
+            for member_id in to_remove:
+                dead_members.add(member_id)
+                del members_list[member_id]
+                
+        time.sleep(0.5)
+
+#for monitoring purposes
+def worker_monitoring():
+    while not stop_event.is_set():
+        with members_list_lock:
+            local_ml = {
+                member_id: member_data.copy()
+                for member_id, member_data in members_list.items()
+            }
+        
+        with open("membership_list.txt", "w") as f:
+            for member_id, member_data in local_ml.items():
+                f.write(f"{member_id}: {member_data}\n")
+        time.sleep(0.5)
 
 t1 = threading.Thread(target=worker_1)
 t2 = threading.Thread(target=worker_2)
 t3 = threading.Thread(target=worker_3)
+t4 = threading.Thread(target=worker_4)
+t5 = threading.Thread(target=worker_monitoring)
 
 t1.start()
 t2.start()
 t3.start()
+t4.start()
+t5.start()
 
 try:
     while not stop_event.is_set():
@@ -168,4 +280,6 @@ except KeyboardInterrupt:
 t1.join()
 t2.join()
 t3.join()
+t4.join()
+t5.join()
 server_socket.close()