Added ability to wait for cache arrival in RequestCache

doc/basics/requestcache_tutorial_1.py

@@ -1,4 +1,4 @@
-from asyncio import create_task, run, sleep
+from asyncio import run
 
 from ipv8.requestcache import NumberCacheWithName, RequestCache
 
@@ -29,12 +29,10 @@ async def bar() -> None:
     """
     # Normally, you would add this to a network overlay instance.
     request_cache = RequestCache()
+    request_cache.register_anonymous_task("Add later", foo, request_cache, delay=1.23)
 
-    _ = create_task(foo(request_cache))
+    cache = await request_cache.wait_for(MyState, 0)
 
-    while not request_cache.has(MyState, 0):
-        await sleep(0.1)
-    cache = request_cache.pop(MyState, 0)
     print("I found a cache with the state:", cache.state)
 
 

ipv8/requestcache.py

@@ -7,11 +7,12 @@
 from contextlib import contextmanager, suppress
 from random import random
 from threading import Lock
-from typing import TYPE_CHECKING, TypeVar, overload
+from typing import TYPE_CHECKING, TypeVar, cast, overload
 
 from typing_extensions import Protocol
 
 from .taskmanager import TaskManager
+from .util import succeed
 
 if TYPE_CHECKING:
     from collections.abc import Generator, Iterable
@@ -156,6 +157,7 @@ def __init__(self) -> None:
         self._logger = logging.getLogger(self.__class__.__name__)
 
         self._identifiers: dict[str, NumberCache] = {}
+        self._waiters: dict[tuple[str, int], Future] = {}
         self.lock = Lock()
         self._shutdown = False
 
@@ -210,6 +212,9 @@ def add(self, cache: ACT) -> ACT | None:
                 timeout_delay = self._timeout_override
 
             self.register_task(cache, self._on_timeout, cache, delay=timeout_delay)
+            waiter = self._waiters.pop((cache.prefix, cache.number), None)
+            if waiter is not None and not waiter.done():
+                waiter.set_result(cache)
             return cache
 
     @overload
@@ -228,6 +233,42 @@ def has(self, prefix: str | type[CacheTypeVar], number: int) -> bool:
             return self._create_identifier(number, prefix) in self._identifiers
         return self.has(prefix.name, number)
 
+    def _watch_future(self, key: tuple[str, int]) -> None:
+        """
+        Ensure that a given future is killed after some timeout.
+        """
+        future = self._waiters.pop(key, None)
+        if future is not None and not future.done():
+            future.cancel()
+
+    @overload
+    def wait_for(self, prefix: str, number: int, timeout: float | None = None) -> Future[NumberCache]:
+        pass
+
+    @overload
+    def wait_for(self, prefix: type[CacheTypeVar], number: int, timeout: float | None = None) -> Future[CacheTypeVar]:
+        pass
+
+    def wait_for(self, prefix: str | type[CacheTypeVar], number: int,
+                 timeout: float | None = None) -> Future[CacheTypeVar] | Future[NumberCache]:
+        """
+        Returns a future that fires if or when the given cache is registered.
+        """
+        result = self.get(prefix, number)
+        if result is not None:
+            # This is just to please ``Mypy``: ``return succeed(result)`` is functionally equivalent in this block.
+            if isinstance(prefix, str):
+                return succeed(cast(NumberCache, result))
+            return succeed(cast(CacheTypeVar, result))
+        if isinstance(prefix, str):
+            fut: Future[NumberCache] = Future()
+            self._waiters[(prefix, number)] = fut
+            if timeout is not None:
+                self.register_anonymous_task(f"Watch RequestCache Future {fut}", self._watch_future, (prefix, number),
+                                             delay=timeout)
+            return self.register_anonymous_task(f"RequestCache wait for {prefix}", fut)
+        return cast(Future[CacheTypeVar], self.wait_for(prefix.name, number))
+
     @overload
     def get(self, prefix: str, number: int) -> NumberCache | None:
         pass

ipv8/test/test_requestcache.py

@@ -103,6 +103,14 @@ def on_timeout(self) -> None:
         """
 
 
+class MockNamedNumberCache(NumberCache):
+    """
+    A "normal" NumberCache that has a name.
+    """
+
+    name = "test"
+
+
 class TestRequestCache(TestBase):
     """
     Tests related to the request cache.
@@ -115,6 +123,13 @@ def setUp(self) -> None:
         super().setUp()
         self.request_cache = RequestCache()
 
+    async def tearDown(self) -> None:
+        """
+        Destroy the request cache.
+        """
+        await self.request_cache.shutdown()
+        await super().tearDown()
+
     async def test_shutdown(self) -> None:
         """
         Test if RequestCache does not allow new Caches after shutdown().
@@ -134,7 +149,6 @@ async def test_timeout(self) -> None:
         cache = MockCache(self.request_cache)
         self.request_cache.add(cache)
         await cache.timed_out
-        await self.request_cache.shutdown()
 
     async def test_add_duplicate(self) -> None:
         """
@@ -145,16 +159,13 @@ async def test_add_duplicate(self) -> None:
 
         self.assertIsNone(self.request_cache.add(cache))
 
-        await self.request_cache.shutdown()
-
     async def test_timeout_future_default_value(self) -> None:
         """
         Test if a registered future gets set to None on timeout.
         """
         cache = MockRegisteredCache(self.request_cache)
         self.request_cache.add(cache)
         self.assertEqual(None, (await cache.timed_out))
-        await self.request_cache.shutdown()
 
     async def test_timeout_future_custom_value(self) -> None:
         """
@@ -166,8 +177,6 @@ async def test_timeout_future_custom_value(self) -> None:
         cache.managed_futures[0] = (cache.managed_futures[0][0], 123)
         self.assertEqual(123, (await cache.timed_out))
 
-        await self.request_cache.shutdown()
-
     async def test_timeout_future_exception(self) -> None:
         """
         Test if a registered future raises an exception on timeout.
@@ -179,8 +188,6 @@ async def test_timeout_future_exception(self) -> None:
         with self.assertRaises(RuntimeError):
             await cache.timed_out
 
-        await self.request_cache.shutdown()
-
     async def test_cancel_future_after_shutdown(self) -> None:
         """
         Test if a registered future is cancelled when the RequestCache has shutdown.
@@ -211,8 +218,6 @@ async def test_passthrough_noargs(self) -> None:
 
         self.assertTrue(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_timeout(self) -> None:
         """
         Test if passthrough respects the timeout value.
@@ -225,8 +230,6 @@ async def test_passthrough_timeout(self) -> None:
 
         self.assertFalse(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_filter_one_match(self) -> None:
         """
         Test if passthrough filters correctly with one filter, that matches.
@@ -239,8 +242,6 @@ async def test_passthrough_filter_one_match(self) -> None:
 
         self.assertTrue(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_filter_one_mismatch(self) -> None:
         """
         Test if passthrough filters correctly with one filter, that doesn't match.
@@ -253,8 +254,6 @@ async def test_passthrough_filter_one_mismatch(self) -> None:
 
         self.assertFalse(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_filter_many_match(self) -> None:
         """
         Test if passthrough filters correctly with many filters, that all match.
@@ -267,8 +266,6 @@ async def test_passthrough_filter_many_match(self) -> None:
 
         self.assertTrue(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_filter_some_match(self) -> None:
         """
         Test if passthrough filters correctly with many filters, for which some match.
@@ -281,8 +278,6 @@ async def test_passthrough_filter_some_match(self) -> None:
 
         self.assertTrue(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_passthrough_filter_no_match(self) -> None:
         """
         Test if passthrough filters correctly with many filters, for which none match.
@@ -295,8 +290,6 @@ async def test_passthrough_filter_no_match(self) -> None:
 
         self.assertFalse(cache.timed_out)
 
-        await self.request_cache.shutdown()
-
     async def test_has_by_class(self) -> None:
         """
         Check if we can call ``.has()`` by cache class.
@@ -307,7 +300,52 @@ async def test_has_by_class(self) -> None:
 
         self.assertTrue(self.request_cache.has(MockNamedCache, added.number))
 
-        await self.request_cache.shutdown()
+    async def test_wait_for_by_name(self) -> None:
+        """
+        Check if we can call ``.wait_for()`` by cache name.
+        """
+        cache = MockNamedNumberCache(self.request_cache, MockNamedNumberCache.name, 1337)
+        fut = self.request_cache.wait_for(MockNamedNumberCache.name, 1337)
+
+        added = self.request_cache.add(cache)
+        result = await fut
+
+        self.assertEqual(added, result)
+
+    async def test_wait_for_by_class(self) -> None:
+        """
+        Check if we can call ``.wait_for()`` by cache class.
+        """
+        cache = MockNamedNumberCache(self.request_cache, MockNamedNumberCache.name, 1337)
+        fut = self.request_cache.wait_for(MockNamedNumberCache, 1337)
+
+        added = self.request_cache.add(cache)
+        result = await fut
+
+        self.assertEqual(added, result)
+
+    async def test_wait_for_already_added(self) -> None:
+        """
+        Check if we can ``.wait_for()`` returns when a cache is already available.
+        """
+        cache = MockNamedNumberCache(self.request_cache, MockNamedNumberCache.name, 1337)
+        added = self.request_cache.add(cache)
+        fut = self.request_cache.wait_for(MockNamedNumberCache.name, 1337)
+
+        result = await fut
+
+        self.assertEqual(added, result)
+
+    async def test_wait_for_timeout(self) -> None:
+        """
+        Check if ``.wait_for()`` cancels its future when a timeout occurs.
+        """
+        fut = self.request_cache.wait_for(MockNamedNumberCache.name, 1337, timeout=0.0)
+
+        await sleep(0)
+
+        self.assertTrue(fut.done())
+        self.assertTrue(fut.cancelled())
 
     async def test_get_by_class(self) -> None:
         """
@@ -318,8 +356,6 @@ async def test_get_by_class(self) -> None:
 
         self.assertEqual(added, self.request_cache.get(MockNamedCache, added.number))
 
-        await self.request_cache.shutdown()
-
     async def test_pop_by_class(self) -> None:
         """
         Check if we can call ``.pop()`` by cache class.
@@ -328,5 +364,3 @@ async def test_pop_by_class(self) -> None:
         added = self.request_cache.add(cache)
 
         self.assertEqual(added, self.request_cache.pop(MockNamedCache, added.number))
-
-        await self.request_cache.shutdown()