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import time
import socket
import struct
import random
from django.conf import settings
from graphite.render.hashing import ConsistentHashRing
from graphite.logger import log
from graphite.util import load_module, unpickle, parseHosts
from graphite.singleton import ThreadSafeSingleton
try:
import six.moves.cPickle as pickle
except ImportError:
import pickle
def load_keyfunc():
if settings.CARBONLINK_HASHING_KEYFUNC:
module_path, func_name = settings.CARBONLINK_HASHING_KEYFUNC.rsplit(':', 1)
log.cache("Using keyfunc %s found in %s" % (str(func_name), str(module_path)))
return load_module(module_path, member=func_name)
else:
return lambda x: x
class CarbonLinkRequestError(Exception):
pass
class CarbonLinkPool(object):
def __init__(self, hosts, timeout):
self.hosts = [ (server, instance) for (server, port, instance) in hosts ]
self.ports = { (server, instance): port for (server, port, instance) in hosts }
self.timeout = float(timeout)
servers = set([server for (server, port, instance) in hosts])
if len(servers) < settings.REPLICATION_FACTOR:
raise Exception("REPLICATION_FACTOR=%d cannot exceed servers=%d" % (
settings.REPLICATION_FACTOR, len(servers)))
self.hash_ring = ConsistentHashRing(
self.hosts, hash_type=settings.CARBONLINK_HASHING_TYPE)
self.keyfunc = load_keyfunc()
self.connections = {}
self.last_failure = {}
# Create a connection pool for each host
for host in self.hosts:
self.connections[host] = set()
def select_host(self, metric):
"Returns the carbon host that has data for the given metric"
key = self.keyfunc(metric)
nodes = []
servers = set()
for node in self.hash_ring.get_nodes(key):
(server, instance) = node
if server in servers:
continue
servers.add(server)
nodes.append(node)
if len(servers) >= settings.REPLICATION_FACTOR:
break
available = [ n for n in nodes if self.is_available(n) ]
return random.choice(available or nodes)
def is_available(self, host):
now = time.time()
last_fail = self.last_failure.get(host, 0)
return (now - last_fail) < settings.CARBONLINK_RETRY_DELAY
def get_connection(self, host):
# First try to take one out of the pool for this host
(server, instance) = host
port = self.ports[host]
connectionPool = self.connections[host]
try:
return connectionPool.pop()
except KeyError:
pass #nothing left in the pool, gotta make a new connection
log.cache("CarbonLink creating a new socket for %s" % str(host))
try:
connection = socket.create_connection((server, port), self.timeout)
except socket.error:
self.last_failure[host] = time.time()
raise
else:
connection.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
return connection
def query(self, metric):
request = dict(type='cache-query', metric=metric)
results = self.send_request(request)
log.cache("CarbonLink cache-query request for %s returned %d datapoints" % (
metric, len(results['datapoints'])))
return results['datapoints']
def get_metadata(self, metric, key):
request = dict(type='get-metadata', metric=metric, key=key)
results = self.send_request(request)
log.cache("CarbonLink get-metadata request received for %s:%s" % (metric, key))
return results['value']
def set_metadata(self, metric, key, value):
request = dict(type='set-metadata', metric=metric, key=key, value=value)
results = self.send_request(request)
log.cache("CarbonLink set-metadata request received for %s:%s" % (metric, key))
return results
def send_request(self, request):
metric = request['metric']
serialized_request = pickle.dumps(request, protocol=settings.CARBONLINK_PICKLE_PROTOCOL)
len_prefix = struct.pack("!L", len(serialized_request))
request_packet = len_prefix + serialized_request
result = {}
result.setdefault('datapoints', [])
if metric.startswith(settings.CARBON_METRIC_PREFIX):
return self.send_request_to_all(request)
if not self.hosts:
log.cache("CarbonLink is not connected to any host. Returning empty nodes list")
return result
host = self.select_host(metric)
conn = self.get_connection(host)
log.cache("CarbonLink sending request for %s to %s" % (metric, str(host)))
try:
conn.sendall(request_packet)
result = self.recv_response(conn)
except Exception as e:
self.last_failure[host] = time.time()
log.cache("Exception getting data from cache %s: %s" % (str(host), e))
else:
self.connections[host].add(conn)
if 'error' in result:
log.cache("Error getting data from cache: %s" % result['error'])
raise CarbonLinkRequestError(result['error'])
log.cache("CarbonLink finished receiving %s from %s" % (str(metric), str(host)))
return result
def send_request_to_all(self, request):
metric = request['metric']
serialized_request = pickle.dumps(request, protocol=settings.CARBONLINK_PICKLE_PROTOCOL)
len_prefix = struct.pack("!L", len(serialized_request))
request_packet = len_prefix + serialized_request
results = {}
results.setdefault('datapoints', {})
for host in self.hosts:
conn = self.get_connection(host)
log.cache("CarbonLink sending request for %s to %s" % (metric, str(host)))
try:
conn.sendall(request_packet)
result = self.recv_response(conn)
except Exception as e:
self.last_failure[host] = time.time()
log.cache("Exception getting data from cache %s: %s" % (str(host), e))
else:
self.connections[host].add(conn)
if 'error' in result:
log.cache("Error getting data from cache %s: %s" % (str(host), result['error']))
else:
if len(result['datapoints']) > 1:
results['datapoints'].update(result['datapoints'])
log.cache("CarbonLink finished receiving %s from %s" % (str(metric), str(host)))
return results
def recv_response(self, conn):
len_prefix = self.recv_exactly(conn, 4)
body_size = struct.unpack("!L", len_prefix)[0]
body = self.recv_exactly(conn, body_size)
return unpickle.loads(body)
@staticmethod
def recv_exactly(conn, num_bytes):
buf = b''
while len(buf) < num_bytes:
data = conn.recv(num_bytes - len(buf))
if not data:
raise Exception("Connection lost")
buf += data
return buf
@ThreadSafeSingleton
class GlobalCarbonLinkPool(CarbonLinkPool):
def __init__(self):
hosts = parseHosts(settings.CARBONLINK_HOSTS)
timeout = settings.CARBONLINK_TIMEOUT
CarbonLinkPool.__init__(self, hosts, timeout)
def CarbonLink():
"""Handy accessor for the global singleton."""
return GlobalCarbonLinkPool.instance()
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