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server.py
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server.py
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import os
import socket
import sys
import _thread
import threading
import time
import re
import json
import pickle
from config import *
from block import Block, Operation
from blockchain import Blockchain
from hashlib import sha256
from random import randint
from ast import literal_eval as make_tuple
mutex = threading.Lock()
monitor = threading.Condition()
seq_num = 0
server_sockets = {}
# stores all operations not added to blockchain yet
queue = []
# stores key values
kv_store = {}
# blockchain contains dicts with operation, nonce, hash
blockchain = Blockchain()
# simulates failed link between src (current process) and process in set
failed_links = set()
# leader
leader = None
ballot_num = list()
accept_num = [-1, -1, -1]
accept_val = Block()
majority_accept = threading.Event()
DELAY = 2
def writeToFile(pid):
with open("blockchain_{}.json".format(pid), "w") as f:
arr = []
for block in blockchain.chain:
print(block.operation)
arr.append(block.to_dict())
json.dump(arr, f, indent=4)
def readFromFile(pid):
with open("blockchain_{}.json".format(pid), "r") as f:
blocklist = json.load(f)
for block in blocklist:
operation = Operation(block["operation"]["op"],block["operation"]["key"],block["operation"]["value"])
blockchain.append(Block(operation, block["nonce"], block["hash"]))
if(block["operation"]["op"] == "put"):
kv_store[block["operation"]["key"]] = dict(block["operation"]["value"])
def get_hash(prev_block):
"""get hash pointer based on contents of previous block"""
if not prev_block:
return None
hash = sha256((str(prev_block.operation) + str(prev_block.nonce) + str(prev_block.hash)).encode())
return hash.hexdigest()
def get_nonce(operation):
"""find nonce where last character in sha256 concatenated string is between 0 and 2"""
nonce = ""
result = "-1"
while True:
nonce = randint(0, 1000)
result = sha256((str(operation) + str(nonce)).encode()).hexdigest()
if result[-1] in ["0", "1", "2"]:
return nonce
def close_connections():
for processID in server_sockets:
server_sockets[processID].close()
# connection[0].close()
os._exit(0)
def open_connections():
for i in range(5):
if i != pid:
conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
conn.connect((IP, pid_ports[i]))
server_sockets[i] = conn
#server_sockets.append((conn, i))
def handle_input():
while True:
user_input = input()
if user_input == "c":
open_connections()
elif user_input == "exit":
close_connections()
# failLink
elif user_input.split(' ')[0] == "faill":
print("Failing link to " + user_input.split(' ')[1])
failed_links.add(int(user_input.split(' ')[1]))
# fixLink
elif user_input.split(' ')[0] == "fixl":
print("Fixing link to " + user_input.split(' ')[1])
if int(user_input.split(' ')[1]) in failed_links:
failed_links.remove(int(user_input.split(' ')[1]))
# failProcess
elif user_input == "fp":
writeToFile(pid)
close_connections()
# printBlockchain
elif user_input == "pb":
print(blockchain)
# printKVStore
elif user_input == "pkv":
print(kv_store)
# printQueue
elif user_input == "pq":
print(queue)
else:
# TODO
# print("Sending message: ", user_input)
# for processID in server_sockets:
# server_sockets[processID].sendall(user_input.encode())
pass
def process_queue():
while True:
# wait for non-empty queue
with monitor:
monitor.wait_for(lambda: queue)
operation = queue[0]
nonce = get_nonce(queue[0])
hash = get_hash(blockchain.last())
new_block = Block(operation, nonce, hash)
# max_ballot = promises[0][2]
# max_val = promises[0][3]
# all_vals_null = True
# for promise in promises:
# if tuple(promise[2]) > tuple(max_ballot):
# max_ballot = promise[2]
# max_val = promise[3]
# if not promise[3].is_empty():
# all_vals_null = False
# my_val = new_block if all_vals_null else max_val
msg = ["accept",ballot_num,new_block]
accepts = []
time.sleep(DELAY)
for processID in server_sockets:
if processID not in failed_links:
try:
server_sockets[processID].sendall(pickle.dumps(msg))
except:
pass
for processID in server_sockets:
if processID not in failed_links:
data = b""
while True:
try:
packet = server_sockets[processID].recv(4096)
data += packet
if len(packet) < 4096:
break
except:
pass
if not data:
continue
data = pickle.loads(data)
print(data)
accepts.append(data)
if (len(accepts) > 1):
blockchain.append(new_block)
majority_accept.set()
queue.pop(0)
msg = ["decide",ballot_num,new_block]
time.sleep(DELAY)
for processID in server_sockets:
if processID not in failed_links:
try:
server_sockets[processID].sendall(pickle.dumps(msg))
except:
pass
else:
queue.pop(0)
def elect_leader():
print("elect leader")
with mutex:
ballot_num[1] += 1
ballot_num[2] = pid
promises = []
time.sleep(DELAY)
for processID in server_sockets:
if processID not in failed_links:
msg = ["prepare", ballot_num]
try:
server_sockets[processID].sendall(pickle.dumps(msg))
except:
pass
for processID in server_sockets:
if processID not in failed_links:
data = b""
while True:
try:
packet = server_sockets[processID].recv(4096)
data += packet
if len(packet) < 4096:
break
except:
pass
if not data:
continue
data = pickle.loads(data)
print(data)
promises.append(data)
# check majority vote
if (len(promises) < 2):
return False
threading.Thread(target = process_queue).start()
return True
def handle_conn(conn):
global leader
while True:
data = b""
while True:
try:
packet = conn.recv(4096)
data += packet
if len(packet) < 4096:
break
except:
pass
if not data:
break
encoded = data
data = pickle.loads(data)
print("received msg: " + str(data))
print("leader is " + str(leader))
if data == "Leader":
leader = pid
# execute leader election
if elect_leader():
time.sleep(DELAY)
conn.sendall("ack".encode())
# Operation
elif isinstance(data, str) and data.split(' ')[0] == "Operation":
if leader != pid:
time.sleep(DELAY)
print("sending to leader")
try:
server_sockets[leader].sendall(encoded)
except:
continue
res = server_sockets[leader].recv(1024)
time.sleep(DELAY)
conn.sendall(res)
return
op = data.split(' ')[1]
netid = data.split(' ')[2]
try:
phone = {"phone":data.split(' ')[3]}
except:
phone = None
if op == "get":
with mutex:
queue.append(Operation(op, netid, phone))
with monitor:
monitor.notify_all()
majority_accept_set = majority_accept.wait()
if majority_accept_set:
time.sleep(DELAY)
if netid in kv_store:
conn.sendall(str(kv_store[netid]).encode())
else:
conn.sendall("NO_KEY".encode())
majority_accept.clear()
elif op == "put":
with mutex:
queue.append(Operation(op, netid, phone))
with monitor:
monitor.notify_all()
majority_accept_set = majority_accept.wait()
if majority_accept_set:
kv_store[netid] = phone
time.sleep(DELAY)
conn.sendall("ack".encode())
majority_accept.clear()
else:
global ballot_num, accept_num, accept_val
if data[0] == "prepare":
print("Received prepare message")
recv_ball_num = tuple(data[1])
if recv_ball_num >= tuple(ballot_num):
ballot_num = data[1]
# global leader
leader = ballot_num[2]
msg = ["promise", ballot_num, accept_num, accept_val]
time.sleep(DELAY)
conn.sendall(pickle.dumps(msg))
elif data[0] == "accept":
recv_ball_num = tuple(data[1])
if recv_ball_num >= tuple(ballot_num):
accept_num = data[1]
accept_val = data[2]
msg = ["accepted", data[1], data[2]]
time.sleep(DELAY)
conn.sendall(pickle.dumps(msg))
elif data[0] == "decide":
blockchain.append(data[2])
if data[2].operation.op == "put":
kv_store[data[2].operation.key] = data[2].operation.value
if __name__ == "__main__":
if len(sys.argv) != 2:
print(f"Usage: python {sys.argv[0]} <processID>")
sys.exit()
IP = socket.gethostname()
pid = int(sys.argv[1])
PORT = pid_ports[pid]
print("Listening on " + str(IP) + ":" + str(PORT))
server_socket = socket.socket()
server_socket.bind((IP, PORT))
server_socket.listen()
input_thread = threading.Thread(target=handle_input)
input_thread.start()
try:
readFromFile(pid)
except Exception as e:
print(e)
# print(str(blockchain))
print(kv_store)
# ballot num
ballot_num = [len(blockchain.chain), 0, pid]
# elect_leader()
while True:
conn, addr = server_socket.accept()
print(addr)
threading.Thread(target=handle_conn, args=(conn,)).start()