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network: introduce NUM_STICKY_SERVERS

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SomberNight
2020-04-14 19:58:22 +02:00
parent 34e3e48ba5
commit ac749f3a19
1 changed files with 18 additions and 10 deletions
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28
electrum/network.py
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@@ -72,6 +72,7 @@ _logger = get_logger(__name__)
NUM_TARGET_CONNECTED_SERVERS = 10
NUM_STICKY_SERVERS = 4
NUM_RECENT_SERVERS = 20
MAX_RETRY_DELAY_FOR_SERVERS = 600 # sec
INIT_RETRY_DELAY_FOR_SERVERS = 15 # sec
@@ -551,20 +552,27 @@ class Network(Logger):
def _get_next_server_to_try(self) -> Optional[ServerAddr]:
now = time.time()
with self.interfaces_lock:
exclude_set = set(self.interfaces) | self.connecting
# first try from recent servers
connected_servers = set(self.interfaces) | self.connecting
# First try from recent servers. (which are persisted)
# As these are servers we successfully connected to recently, they are
# most likely to work. This also makes servers "sticky".
# Note: with sticky servers, it is more difficult for an attacker to eclipse the client,
# however if they succeed, the eclipsing would persist. To try to balance this,
# we only give priority to recent_servers up to NUM_STICKY_SERVERS.
with self.recent_servers_lock:
recent_servers = list(self._recent_servers)
recent_servers = [s for s in recent_servers if s.protocol == self.protocol]
for server in recent_servers:
if server in exclude_set:
continue
if not self._can_retry_server(server, now=now):
continue
return server
# try all servers we know about
if len(connected_servers & set(recent_servers)) < NUM_STICKY_SERVERS:
for server in recent_servers:
if server in connected_servers:
continue
if not self._can_retry_server(server, now=now):
continue
return server
# try all servers we know about, pick one at random
hostmap = self.get_servers()
servers = set(filter_protocol(hostmap, self.protocol)) - exclude_set
servers = list(set(filter_protocol(hostmap, self.protocol)) - connected_servers)
random.shuffle(servers)
for server in servers:
if not self._can_retry_server(server, now=now):
continue