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proxy.py
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proxy.py
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from argparse import ArgumentParser
from datetime import datetime
from collections import OrderedDict
import select
import socket
MAX_LISTENS = 5
class LastUpdatedDict(OrderedDict):
"""Dict that keeps track of the order in which items were added/updated"""
def __setitem__(self, key, value):
if key in self:
del self[key]
OrderedDict.__setitem__(self, key, value)
class LRUCache(object):
"""Least Recently Used Cache supporting eviction based on capacity & TTL"""
def __init__(self, capacity=None, ttl=None):
if not capacity:
raise TypeError("Capacity cannot be None for LRUCache")
if not ttl:
raise TypeError("TTL cannot be None for LRUCache")
self.capacity = capacity
self.ttl = ttl
self.cache = LastUpdatedDict()
def get(self, key):
"""Checks if key is in cache
:param key (str)
:returns: val (str) if exists or None
"""
if self.cache.get(key) is not None:
val, time_added = self.cache.pop(key)
if (datetime.now() - time_added).total_seconds() >= self.ttl:
return None
self.cache[key] = (val, datetime.now())
return val
else:
return None
def set(self, key, val):
"""Sets key-val pair in self.cache
:param key (str):
:param val (str):
"""
if len(self.cache) >= self.capacity:
self.cache.popitem(last=False)
self.cache[key] = (val, datetime.now())
class RedisProxy(object):
"""Lightweight Read Cache for Redis GET commands"""
def __init__(self,
host_addr=None,
port=6379,
capacity=100,
ttl=7200,
timeout=30,
):
"""Settings are configurable for Redis Proxy:
:param host_addr (str): IP address of backing Redis instance
:param port (int): Port for Redis socket
:param capacity (int): number of keys to hold in cache
:param ttl (int): # of seconds that a key can live in cache
:param timeout (int), seconds after which to timeout network request
"""
self.cache = LRUCache(capacity, ttl)
self.socket_list = []
self.max_listens = MAX_LISTENS
if not host_addr:
host_addr = ''
# Open Redis connection
self.redis_socket = self._open_redis_connection(host_addr, port, timeout)
self.socket_list.append(self.redis_socket)
# Open Client socket
self.client_socket = self._open_client_connection(host='', port=5555)
self.socket_list.append(self.client_socket)
print "Running RedisProxy. Use CTRL-C to stop."
def _open_redis_connection(self, host_addr, port, timeout):
redis_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
redis_socket.settimeout(timeout)
redis_socket.connect((host_addr, port))
print "Connected to Redis on %s:%s" % (host_addr, port)
return redis_socket
def run(self):
running = True
while running:
# Listen for input sources (Redis & any client)
try:
in_ready, out_ready, err_ready = select.select(
self.socket_list,
[],
[],
0,
)
for src in in_ready:
# New client connection, creates new client socket
if src == self.client_socket:
new_sock, addr = self.client_socket.accept()
new_sock.sendall(
"Connected to RedisProxy\nYou can send GET {key} commands to the proxy\nUse QUIT to end connection\n",
)
self.socket_list.append(new_sock)
# Input from a client connection that we've already seen
else:
data = src.recv(4096).strip()
if data != "QUIT":
data = data.split()
if len(data) != 2 or data[0] != "GET":
src.sendall("Please use Redis 'GET key' command format\n\r")
continue
ret_val = self.get(data[1])
if ret_val is None:
src.sendall("Nothing exists for key %s in Redis\n\r" % (data[1]))
continue
ret_val = ret_val + "\n\r"
src.sendall(ret_val)
else:
if src in self.socket_list:
src.sendall("Bye-bye!\n")
self.socket_list.remove(src)
src.close()
print "Client connection closed"
except KeyboardInterrupt:
print "Shutting down RedisProxy"
running = False
self.redis_socket.close()
self.client_socket.close()
print "Done"
def get(self, key):
"""Takes in a key, checks cache then backing Redis for value.
Stores unstored keys in cache.
:param key (str):
:returns: value stored in Redis, if not already in cache
"""
# First, check the cache
cached_val = self.cache.get(key)
if cached_val:
return cached_val
get_str = "*2\r\n$3\r\nGET\r\n$%s\r\n%s\r\n" % (len(key), key)
self.redis_socket.sendall(get_str)
resp = self.redis_socket.recv(4096)
# If Redis responds w/ a nil bulk string, return None to client
if resp == "$-1\r\n":
return None
msg_type, body = resp[0], resp[1:].split("\r\n")
length = body[0]
redis_val = body[1]
# Save it in the cache, if it's not already there
self.cache.set(key, redis_val)
return redis_val
def _open_client_connection(self, host=None, port=None, timeout=30):
if not host:
host = 'localhost'
if not port:
raise TypeError("No port for listening socket passed in")
try:
my_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
my_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
my_socket.settimeout(timeout)
my_socket.bind((host, port))
my_socket.listen(MAX_LISTENS)
print "Listening on %s:%s" % (host, port)
except socket.error, (value, msg):
if my_socket:
my_socket.close()
print "Could not open socket: ", msg
return my_socket
if __name__ == "__main__":
parser = ArgumentParser()
parser.add_argument(
'--addr',
type=str,
dest='addr',
default='',
action='store',
required=False,
help='Enter addr of backing Redis (Defaults to '')',
)
parser.add_argument(
'--ttl',
type=int,
dest='ttl',
default=7200,
action='store',
required=False,
help='Enter TTL (in sec. for keys in cache)',
)
parser.add_argument(
'--capacity',
type=int,
dest='capacity',
default=1000,
action='store',
required=False,
help='Enter max. # of cache keys before LRU eviction',
)
args = parser.parse_args()
RedisProxy(host_addr=args.addr, ttl=args.ttl, capacity=args.capacity).run()