util: add NetworkRetryManager, a baseclass for LNWorker and Network

electrum/util.py

@@ -23,7 +23,8 @@
 import binascii
 import os, sys, re, json
 from collections import defaultdict, OrderedDict
-from typing import NamedTuple, Union, TYPE_CHECKING, Tuple, Optional, Callable, Any, Sequence
+from typing import (NamedTuple, Union, TYPE_CHECKING, Tuple, Optional, Callable, Any,
+                    Sequence, Dict, Generic, TypeVar)
 from datetime import datetime
 import decimal
 from decimal import Decimal
@@ -1342,3 +1343,53 @@ callback_mgr = CallbackManager()
 trigger_callback = callback_mgr.trigger_callback
 register_callback = callback_mgr.register_callback
 unregister_callback = callback_mgr.unregister_callback
+
+
+_NetAddrType = TypeVar("_NetAddrType")
+
+
+class NetworkRetryManager(Generic[_NetAddrType]):
+    """Truncated Exponential Backoff for network connections."""
+
+    def __init__(
+            self, *,
+            max_retry_delay_normal: float,
+            init_retry_delay_normal: float,
+            max_retry_delay_urgent: float = None,
+            init_retry_delay_urgent: float = None,
+    ):
+        self._last_tried_addr = {}  # type: Dict[_NetAddrType, Tuple[float, int]]  # (unix ts, num_attempts)
+
+        # note: these all use "seconds" as unit
+        if max_retry_delay_urgent is None:
+            max_retry_delay_urgent = max_retry_delay_normal
+        if init_retry_delay_urgent is None:
+            init_retry_delay_urgent = init_retry_delay_normal
+        self._max_retry_delay_normal = max_retry_delay_normal
+        self._init_retry_delay_normal = init_retry_delay_normal
+        self._max_retry_delay_urgent = max_retry_delay_urgent
+        self._init_retry_delay_urgent = init_retry_delay_urgent
+
+    def _trying_addr_now(self, addr: _NetAddrType) -> None:
+        last_time, num_attempts = self._last_tried_addr.get(addr, (0, 0))
+        self._last_tried_addr[addr] = time.time(), num_attempts + 1
+
+    def _on_connection_successfully_established(self, addr: _NetAddrType) -> None:
+        self._last_tried_addr[addr] = time.time(), 0
+
+    def _can_retry_addr(self, peer: _NetAddrType, *,
+                        now: float = None, urgent: bool = False) -> bool:
+        if now is None:
+            now = time.time()
+        last_time, num_attempts = self._last_tried_addr.get(peer, (0, 0))
+        if urgent:
+            delay = min(self._max_retry_delay_urgent,
+                        self._init_retry_delay_urgent * 2 ** num_attempts)
+        else:
+            delay = min(self._max_retry_delay_normal,
+                        self._init_retry_delay_normal * 2 ** num_attempts)
+        next_time = last_time + delay
+        return next_time < now
+
+    def _clear_addr_retry_times(self) -> None:
+        self._last_tried_addr.clear()