fix(platform-wallet): never drop a wallet event on the wallets-map lock - #4557
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romchornyi wants to merge 2 commits into
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fix(platform-wallet): never drop a wallet event on the wallets-map lock#4557romchornyi wants to merge 2 commits into
romchornyi wants to merge 2 commits into
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The manager's `wallets` map was a `tokio::sync::RwLock`, and the two synchronous event handlers that resolve a wallet through it cannot await: `BalanceUpdateHandler` probed with `try_read()` and dropped the event's balance snapshot whenever a manager lifecycle write (create / remove / load) was in flight, and `SpendObservationHandler` carried a whole deferral queue to survive the same probe failing. The bus neither retries nor coalesces, so a dropped snapshot leaves superseded totals on screen until some later balance-bearing event happens to arrive, and nothing guarantees one does. Convert the map to `arc_swap::ArcSwap` (already this crate's idiom for rare-write / hot-read state): readers take a wait-free snapshot that can never fail or block, so the drop window no longer exists rather than being papered over. The rare lifecycle writers publish via `rcu`, preserving the generation-checked removal's check-and-remove atomicity, and the sync-context accessors that used `blocking_read()` become wait-free loads, removing their panic-inside-runtime hazard. With the read infallible, `SpendObservationHandler`'s pending queue loses its premise: there is no contention outcome left to defer, so the queue, its 4096-outpoint cap and the shedding warning go, and the handler applies every observation at delivery. Its regression test keeps `#4309` pinned against the closest window the new type admits — a lifecycle writer parked mid-`rcu` across the delivery — as does the balance handler's own test, which asserts the snapshot lands before that writer commits.
romchornyi
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August 31, 2026 15:56
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📝 WalkthroughWalkthroughThe wallet map changes from an ChangesWallet map synchronization
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to A failed wallet load can currently roll back a newer wallet generation that reused the same ID, potentially removing valid wallet state. The PR should not merge until rollback is generation-aware. Sequence Diagram(s)sequenceDiagram
participant Lifecycle
participant ArcSwapWallets
participant BalanceUpdateHandler
participant PlatformWallet
Lifecycle->>ArcSwapWallets: start rcu map update
BalanceUpdateHandler->>ArcSwapWallets: load wallet snapshot
ArcSwapWallets-->>BalanceUpdateHandler: return current snapshot
BalanceUpdateHandler->>PlatformWallet: update balance atomics
ArcSwapWallets-->>Lifecycle: commit updated map
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In `@packages/rs-platform-wallet/src/manager/load.rs`:
- Line 228: The load_from_persistor rollback currently tracks only WalletId,
allowing a newer wallet generation to be removed after concurrent replacement.
Track each inserted wallet’s generation, and during both wallets rollback and
wm.remove_wallet rollback remove only when the current entry still matches that
generation. Add a regression test covering removal, same-ID re-registration, and
a subsequent load failure.
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📒 Files selected for processing (10)
packages/rs-platform-wallet/src/manager/accessors.rspackages/rs-platform-wallet/src/manager/dashpay_sync.rspackages/rs-platform-wallet/src/manager/dpns_sync.rspackages/rs-platform-wallet/src/manager/load.rspackages/rs-platform-wallet/src/manager/mod.rspackages/rs-platform-wallet/src/manager/platform_address_sync.rspackages/rs-platform-wallet/src/manager/wallet_lifecycle.rspackages/rs-platform-wallet/src/wallet/core/balance_handler.rspackages/rs-platform-wallet/src/wallet/core/broadcast.rspackages/rs-platform-wallet/src/wallet/core/spend_observer.rs
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…shed Two follow-ups on the review of this PR. `cargo fmt` on the `wallets_map` test helper, whose return type the ArcSwap change left wrapped. And the rollback in `load_from_persistor` tracked only `WalletId`, so it removed by id alone. That is safe while nothing else touches the map, and this is the interleaving where something does: this load publishes a generation under an id, a concurrent `remove_wallet` frees that id, a registration publishes a NEW generation under it, and only then does a later iteration fail and reach the rollback. Removing by id would delete that new registration — a live wallet this call never created and whose owner is still using it — and the inner-manager unwind that follows would strip its backing too. The rollback is now generation-checked, the same rule `remove_wallet` applies to its own removal: an entry is reclaimed only while it still holds the `Arc<WalletGeneration>` this load inserted, and the inner-manager unwind keys off that same answer. An id that never reached `self.wallets` — this call failed between the two inserts — has no such owner and unwinds as before. The decision is a pure `rollback_targets`, so the invariant is pinned without racing a real load against a real re-registration: `rollback_only_reclaims_the_generation_this_load_published` asserts both halves — reclaimed while ours, refused once superseded. Pre-existing: the id-only removal predates the ArcSwap change, which altered how the map is written, not what the rollback matched on.
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Issue being fixed or feature implemented
The manager's
walletsmap is atokio::sync::RwLock, and the two event handlers that resolve a wallet through it are synchronous and cannot await:BalanceUpdateHandlerprobed it withtry_read()and dropped the event's balance snapshot whenever a lifecycle write (wallet create / remove / load) was in flight. The event bus neither retries nor coalesces, so a dropped snapshot leaves superseded totals on screen until some later balance-bearing event happens to arrive — and nothing guarantees one does.SpendObservationHandlercarries an entire deferral queue whose only reason to exist is that sametry_read()failing (dashpay/platform#4309).Extracted from #4406, where it was one commit among many. It is independent of that PR's subject and is a live fix on its own.
What was done?
PlatformWalletManager::walletsbecomesarc_swap::ArcSwap— already this crate's idiom for rare-write / hot-read state. Readers take a wait-free snapshot that can never fail or block, so the drop window no longer exists rather than being papered over.rcu, preserving the generation-checked removal's check-and-remove atomicity (wallet_lifecycle.rs,load.rs).blocking_read()become wait-free loads, removing their panic-inside-runtime hazard (accessors.rs).SpendObservationHandler's pending queue loses its premise: there is no contention outcome left to defer. The queue, itsMAX_QUEUED_SPEND_OBSERVATIONScap and the shedding warning are removed, and the handler applies every observation at delivery (spend_observer.rs, −181 lines).How Has This Been Tested?
cargo test -p platform-wallet— 928 tests pass.Two regression tests pin the behaviour against the closest window the new type admits — a lifecycle writer parked mid-
rcuacross the delivery:manager::tests::balance_snapshot_survives_wallets_map_write_contention— the snapshot must land in the wallet's balance atomics before that writer commits.wallet::core::broadcast::tests::a_wallets_map_write_in_flight_does_not_cost_a_spend_observation— the in-broadcast fence must clear anyway (replaces the old contention/deferral test, whose scenario is now unreachable).Breaking Changes
None.
walletsis not part of the public API surface;get_wallet_blockingkeeps its name and signature (it is simply no longer blocking).Checklist:
For repository code-owners and collaborators only
Summary by CodeRabbit
Performance Improvements
Reliability