forked from mariolpantunes/load-balancer
-
Notifications
You must be signed in to change notification settings - Fork 0
/
load_balancer.py
178 lines (133 loc) · 4.43 KB
/
load_balancer.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
# coding: utf-8
import socket
import selectors
import signal
import logging
import argparse
# configure logger output format
logging.basicConfig(level=logging.DEBUG,format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',datefmt='%m-%d %H:%M:%S')
logger = logging.getLogger('Load Balancer')
# used to stop the infinity loop
done = False
sel = selectors.DefaultSelector()
policy = None
mapper = None
# implements a graceful shutdown
def graceful_shutdown(signalNumber, frame):
logger.debug('Graceful Shutdown...')
global done
done = True
# n to 1 policy
class N2One:
def __init__(self, servers):
self.servers = servers
def select_server(self):
return self.servers[0]
def update(self, *arg):
pass
# round robin policy
class RoundRobin:
def __init__(self, servers):
self.servers = servers
def select_server(self):
pass
def update(self, *arg):
pass
# least connections policy
class LeastConnections:
def __init__(self, servers):
self.servers = servers
def select_server(self):
pass
def update(self, *arg):
pass
# least response time
class LeastResponseTime:
def __init__(self, servers):
self.servers = servers
def select_server(self):
pass
def update(self, *arg):
pass
POLICIES = {
"N2One": N2One,
"RoundRobin": RoundRobin,
"LeastConnections": LeastConnections,
"LeastResponseTime": LeastResponseTime
}
class SocketMapper:
def __init__(self, policy):
self.policy = policy
self.map = {}
def add(self, client_sock, upstream_server):
client_sock.setblocking(False)
sel.register(client_sock, selectors.EVENT_READ, read)
upstream_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
upstream_sock.connect(upstream_server)
upstream_sock.setblocking(False)
sel.register(upstream_sock, selectors.EVENT_READ, read)
logger.debug("Proxying to %s %s", *upstream_server)
self.map[client_sock] = upstream_sock
def delete(self, sock):
paired_sock = self.get_sock(sock)
sel.unregister(sock)
sock.close()
sel.unregister(paired_sock)
paired_sock.close()
if sock in self.map:
self.map.pop(sock)
else:
self.map.pop(paired_sock)
def get_sock(self, sock):
for client, upstream in self.map.items():
if upstream == sock:
return client
if client == sock:
return upstream
return None
def get_upstream_sock(self, sock):
return self.map.get(sock)
def get_all_socks(self):
""" Flatten all sockets into a list"""
return list(sum(self.map.items(), ()))
def accept(sock, mask):
client, addr = sock.accept()
logger.debug("Accepted connection %s %s", *addr)
mapper.add(client, policy.select_server())
def read(conn,mask):
data = conn.recv(4096)
if len(data) == 0: # No messages in socket, we can close down the socket
mapper.delete(conn)
else:
mapper.get_sock(conn).send(data)
def main(addr, servers, policy_class):
global policy
global mapper
# register handler for interruption
# it stops the infinite loop gracefully
signal.signal(signal.SIGINT, graceful_shutdown)
policy = policy_class(servers)
mapper = SocketMapper(policy)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(addr)
sock.listen()
sock.setblocking(False)
sel.register(sock, selectors.EVENT_READ, accept)
try:
logger.debug("Listening on %s %s", *addr)
while not done:
events = sel.select(timeout=1)
for key, mask in events:
if(key.fileobj.fileno()>0):
callback = key.data
callback(key.fileobj, mask)
except Exception as err:
logger.error(err)
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Pi HTTP server')
parser.add_argument('-a', dest='policy', choices=POLICIES)
parser.add_argument('-p', dest='port', type=int, help='load balancer port', default=8080)
parser.add_argument('-s', dest='servers', nargs='+', type=int, help='list of servers ports')
args = parser.parse_args()
servers = [('localhost', p) for p in args.servers]
main(('127.0.0.1', args.port), servers, POLICIES[args.policy])