Remove circular reference in GossipVerifier
#4294
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Rather than `match`ing on on several optional objects (with another one to come in a future commit), build an iterator over the futures using the fact that an `Option` is an iterator.
TheBlueMatt
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`P2PGossipSync` is a rather poor design. It currently basically requires two circular `Arc` references, leaving `NetworkGraph`s to leak if LDK is un-loaded: * `P2PGossipSync` owns/holds a reference to the `GossipVerifier` and `GossipVerifier` holds an `Arc` to the `P2PGossipSync` and * `PeerManager` holds a reference to the `P2PGossipSync` (as the gossip message handler) which owns/holds a reference to the `GossipVerifier`, which has a `Deref` (likely an `Arc` in practice) to the `PeerManager`. Instead, we should move towards the same design we have elsewhere - hold a `Notifier` and expose waiting on it to the background processor then poll for completion from there (in this case, as in others by checking for completion when handling `get_and_clear_pending_msg_events` calls). Here we take the first step towards this, adding a shared `Notifier` to `PendingChecks` and piping it through to `UtxoFuture`s so that they can be simply resolved and wake the background processor (once it waits on the new `Notifier`).
`P2PGossipSync` is a rather poor design. It currently basically requires two circular `Arc` references, leaving `NetworkGraph`s to leak if LDK is un-loaded: * `P2PGossipSync` owns/holds a reference to the `GossipVerifier` and `GossipVerifier` holds an `Arc` to the `P2PGossipSync` and * `PeerManager` holds a reference to the `P2PGossipSync` (as the gossip message handler) which owns/holds a reference to the `GossipVerifier`, which has a `Deref` (likely an `Arc` in practice) to the `PeerManager`. Instead, we should move towards the same design we have elsewhere - hold a `Notifier` and expose waiting on it to the background processor then poll for completion from there (in this case, as in others by checking for completion when handling `get_and_clear_pending_msg_events` calls). Here we do the bulk of this work, moving `UtxoFuture` resolution to a simple function that signals the `Notifier` and stores the result. We then poll to convert the result into forwarded messages in `P2PGossipSync::get_and_clear_pending_message_events`. Note that we still rely on manual wakeups from the gossip validator, but that will be fixed in the next commit.
`P2PGossipSync` is a rather poor design. It currently basically requires two circular `Arc` references, leaving `NetworkGraph`s to leak if LDK is un-loaded: * `P2PGossipSync` owns/holds a reference to the `GossipVerifier` and `GossipVerifier` holds an `Arc` to the `P2PGossipSync` and * `PeerManager` holds a reference to the `P2PGossipSync` (as the gossip message handler) which owns/holds a reference to the `GossipVerifier`, which has a `Deref` (likely an `Arc` in practice) to the `PeerManager`. Instead, we should move towards the same design we have elsewhere - hold a `Notifier` and expose waiting on it to the background processor then poll for completion from there (in this case, as in others by checking for completion when handling `get_and_clear_pending_msg_events` calls). After the last few commits of setup, here we finally switch to waking the background processor directly when we detect async gossip validation completion, allowing us to drop the circular references in `P2PGossipSync`/`GossipVerifier` entirely. Fixes lightningdevkit#3369
Now that we do not rely on circular references for `P2PGossipSync` validation, we no longer need the hacky `P2PGossipSync::add_utxo_lookup` method to add the gossip validator after building the `P2PGossipSync` first. Thus, we remove it here, updating some tests that relied on it.
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #4294 +/- ##
==========================================
- Coverage 89.38% 86.60% -2.78%
==========================================
Files 180 158 -22
Lines 139834 101863 -37971
Branches 139834 101863 -37971
==========================================
- Hits 124985 88222 -36763
+ Misses 12262 11224 -1038
+ Partials 2587 2417 -170
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P2PGossipSyncis a rather poor design. It currently basicallyrequires two circular
Arcreferences, leavingNetworkGraphs toleak if LDK is un-loaded:
P2PGossipSyncowns/holds a reference to theGossipVerifierandGossipVerifierholds anArcto theP2PGossipSyncandPeerManagerholds a reference to theP2PGossipSync(as thegossip message handler) which owns/holds a reference to the
GossipVerifier, which has aDeref(likely anArcinpractice) to the
PeerManager.Instead, we should move towards the same design we have elsewhere -
hold a
Notifierand expose waiting on it to the backgroundprocessor then poll for completion from there (in this case, as in
others by checking for completion when handling
get_and_clear_pending_msg_eventscalls).Fixes #3369