lnworker: implement exponential backoff for retries

electrum/lnpeer.py

@@ -219,10 +219,7 @@ class Peer(Logger):
             if constants.net.rev_genesis_bytes() not in their_chains:
                 raise GracefulDisconnect(f"no common chain found with remote. (they sent: {their_chains})")
         # all checks passed
-        if self.channel_db and isinstance(self.transport, LNTransport):
-            self.channel_db.add_recent_peer(self.transport.peer_addr)
-            for chan in self.channels.values():
-                chan.add_or_update_peer_addr(self.transport.peer_addr)
+        self.lnworker.on_peer_successfully_established(self)
         self._received_init = True
         self.maybe_set_initialized()
 

electrum/lntransport.py

@@ -155,6 +155,8 @@ class LNTransportBase:
 
 
 class LNResponderTransport(LNTransportBase):
+    """Transport initiated by remote party."""
+
     def __init__(self, privkey: bytes, reader: StreamReader, writer: StreamWriter):
         LNTransportBase.__init__(self)
         self.reader = reader
@@ -211,7 +213,9 @@ class LNResponderTransport(LNTransportBase):
         self.init_counters(ck)
         return rs
 
+
 class LNTransport(LNTransportBase):
+    """Transport initiated by local party."""
 
     def __init__(self, privkey: bytes, peer_addr: LNPeerAddr):
         LNTransportBase.__init__(self)

electrum/lnworker.py

@@ -77,9 +77,11 @@ SAVED_PR_STATUS = [PR_PAID, PR_UNPAID, PR_INFLIGHT] # status that are persisted
 
 
 NUM_PEERS_TARGET = 4
-PEER_RETRY_INTERVAL = 600  # seconds
-PEER_RETRY_INTERVAL_FOR_CHANNELS = 30  # seconds
-GRAPH_DOWNLOAD_SECONDS = 600
+
+MAX_RETRY_DELAY_FOR_PEERS = 3600  # sec
+INIT_RETRY_DELAY_FOR_PEERS = 600  # sec
+MAX_RETRY_DELAY_FOR_CHANNEL_PEERS = 300  # sec
+INIT_RETRY_DELAY_FOR_CHANNEL_PEERS = 4  # sec
 
 FALLBACK_NODE_LIST_TESTNET = (
     LNPeerAddr(host='203.132.95.10', port=9735, pubkey=bfh('038863cf8ab91046230f561cd5b386cbff8309fa02e3f0c3ed161a3aeb64a643b9')),
@@ -156,6 +158,8 @@ class LNWorker(Logger):
         self.features |= LnFeatures.VAR_ONION_OPT
         self.features |= LnFeatures.PAYMENT_SECRET_OPT
 
+        self._last_tried_peer = {}  # type: Dict[LNPeerAddr, Tuple[float, int]]  # LNPeerAddr -> (unix ts, num_attempts)
+
     def channels_for_peer(self, node_id):
         return {}
 
@@ -204,8 +208,7 @@ class LNWorker(Logger):
                 continue
             peers = await self._get_next_peers_to_try()
             for peer in peers:
-                last_tried = self._last_tried_peer.get(peer, 0)
-                if last_tried + PEER_RETRY_INTERVAL < now:
+                if self._can_retry_peer(peer, now=now):
                     await self._add_peer(peer.host, peer.port, peer.pubkey)
 
     async def _add_peer(self, host, port, node_id) -> Peer:
@@ -214,7 +217,8 @@ class LNWorker(Logger):
         port = int(port)
         peer_addr = LNPeerAddr(host, port, node_id)
         transport = LNTransport(self.node_keypair.privkey, peer_addr)
-        self._last_tried_peer[peer_addr] = time.time()
+        last_time, num_attempts = self._last_tried_peer.get(peer_addr, (0, 0))
+        self._last_tried_peer[peer_addr] = time.time(), num_attempts + 1
         self.logger.info(f"adding peer {peer_addr}")
         peer = Peer(self, node_id, transport)
         await self.taskgroup.spawn(peer.main_loop())
@@ -233,7 +237,6 @@ class LNWorker(Logger):
         self.network = network
         self.config = network.config
         self.channel_db = self.network.channel_db
-        self._last_tried_peer = {}  # type: Dict[LNPeerAddr, float]  # LNPeerAddr -> unix timestamp
         self._add_peers_from_config()
         asyncio.run_coroutine_threadsafe(self.main_loop(), self.network.asyncio_loop)
 
@@ -259,20 +262,43 @@ class LNWorker(Logger):
         #self.logger.info(f'is_good {peer.host}')
         return True
 
+    def on_peer_successfully_established(self, peer: Peer) -> None:
+        if isinstance(peer.transport, LNTransport):
+            peer_addr = peer.transport.peer_addr
+            # reset connection attempt count
+            self._last_tried_peer[peer_addr] = time.time(), 0
+            # add into channel db
+            if self.channel_db:
+                self.channel_db.add_recent_peer(peer_addr)
+            # save network address into channels we might have with peer
+            for chan in peer.channels.values():
+                chan.add_or_update_peer_addr(peer_addr)
+
+    def _can_retry_peer(self, peer: LNPeerAddr, *,
+                        now: float = None, for_channel: bool = False) -> bool:
+        if now is None:
+            now = time.time()
+        last_time, num_attempts = self._last_tried_peer.get(peer, (0, 0))
+        if for_channel:
+            delay = min(MAX_RETRY_DELAY_FOR_CHANNEL_PEERS,
+                        INIT_RETRY_DELAY_FOR_CHANNEL_PEERS * 2 ** num_attempts)
+        else:
+            delay = min(MAX_RETRY_DELAY_FOR_PEERS,
+                        INIT_RETRY_DELAY_FOR_PEERS * 2 ** num_attempts)
+        next_time = last_time + delay
+        return next_time < now
+
     async def _get_next_peers_to_try(self) -> Sequence[LNPeerAddr]:
         now = time.time()
         await self.channel_db.data_loaded.wait()
-        recent_peers = self.channel_db.get_recent_peers()
-        # maintenance for last tried times
-        # due to this, below we can just test membership in _last_tried_peer
-        for peer in list(self._last_tried_peer):
-            if now >= self._last_tried_peer[peer] + PEER_RETRY_INTERVAL:
-                del self._last_tried_peer[peer]
         # first try from recent peers
+        recent_peers = self.channel_db.get_recent_peers()
         for peer in recent_peers:
+            if not peer:
+                continue
             if peer.pubkey in self.peers:
                 continue
-            if peer in self._last_tried_peer:
+            if not self._can_retry_peer(peer, now=now):
                 continue
             if not self.is_good_peer(peer):
                 continue
@@ -289,7 +315,7 @@ class LNWorker(Logger):
                     peer = LNPeerAddr(host, port, node_id)
                 except ValueError:
                     continue
-                if peer in self._last_tried_peer:
+                if not self._can_retry_peer(peer, now=now):
                     continue
                 if not self.is_good_peer(peer):
                     continue
@@ -304,7 +330,7 @@ class LNWorker(Logger):
         else:
             return []  # regtest??
 
-        fallback_list = [peer for peer in fallback_list if peer not in self._last_tried_peer]
+        fallback_list = [peer for peer in fallback_list if self._can_retry_peer(peer, now=now)]
         if fallback_list:
             return [random.choice(fallback_list)]
 
@@ -1269,18 +1295,10 @@ class LNWallet(LNWorker):
             peer_addresses.append(LNPeerAddr(host, port, chan.node_id))
         # will try addresses stored in channel storage
         peer_addresses += list(chan.get_peer_addresses())
+        # Done gathering addresses.
         # Now select first one that has not failed recently.
-        # Use long retry interval to check. This ensures each address we gathered gets a chance.
-        for peer in peer_addresses:
-            last_tried = self._last_tried_peer.get(peer, 0)
-            if last_tried + PEER_RETRY_INTERVAL < now:
-                await self._add_peer(peer.host, peer.port, peer.pubkey)
-                return
-        # Still here? That means all addresses failed ~recently.
-        # Use short retry interval now.
         for peer in peer_addresses:
-            last_tried = self._last_tried_peer.get(peer, 0)
-            if last_tried + PEER_RETRY_INTERVAL_FOR_CHANNELS < now:
+            if self._can_retry_peer(peer, for_channel=True, now=now):
                 await self._add_peer(peer.host, peer.port, peer.pubkey)
                 return