fix(wallet): persist pending-observation coin locks once the record becomes readable - #7782
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… becomes readable Inputs added to the pending-observation set while the wallet record could not be read (or while no database transaction could be started) are only locked in memory. Once the record became readable again nothing wrote their locks to disk: CheckPendingObservations() only rewrites the record when an entry is released, and the next AddPendingObservation() rewrote the whole record but persisted the locks of its own new inputs only. A restart then read the missing lock as a manual unlock, dropped the entry and made the input selectable again. Track such entries with a dirty flag and persist the record together with the locks of all entries that are still locked in one transaction, both when adding entries and on the next check once the record is loaded. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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⛔ Final review complete — 1 blocking finding(s) (commit e774bab) · triage: normal |
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. WalkthroughThe client now writes pending observations and their still-locked inputs in one database transaction. If loading the stored record fails, Priority: ⬇️ Low Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🟡 Moderate · up to If saving a pending CoinJoin observation fails, the save is not reliably retried. After a restart, a coin that is still mixing could become spendable or selectable again. Retry handling should be fixed before merge. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The change improves restart protection for pending mixing inputs without establishing broader access or authority. Recovery remains incomplete after a further database failure, and the available security coverage is limited. Retained concerns Security review detailsSecurity Blast Radius
Trust Boundaries and Controls
Resilience and Maintainability Implications
Hardening Proposals
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 1🧪 Generate unit tests (beta)
🛠️ Fix failing CI checks 💡
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Final validation — Phase 2 only (queue backlog)
Verified the supplied review claims against head 56a3ae7 and the three-file PR diff; no actionable in-scope defects were found. The dirty flag and shared transactional persistence helper repair the recovery gap while preserving unreadable-record protection and manual unlock behavior, and the regression test checks persisted locks and wallet lock state after a database reload. No builds or tests were run in this static lane; the supplied CI snapshot shows lint and formatting passing, source builds pending, and PR-title validation failing because the workflow does not allow the coinjoin scope.
Review provenance
Source: reviewer 1: gpt-6.1-sol (agent: phase2-reviewer, role: general); reviewer 2: gpt-6.1-sol (agent: phase2-reviewer, role: dash-core-commit-history); final verifier: gpt-6.1-sol (agent: sol-verifier, role: final-verifier)
- Triage:
normalbygpt-6.1-sol(effort low) — The change updates pending-observation persistence and persistent coin-lock recovery across database failure and retry paths, warranting ordinary logic review but remaining too contained to meet the large-or-intricate requirement for critical. - Phase 1 reviewers: not run (skipped for throughput: 23 PRs queued, above the 10 limit)
- Fresh verifier:
gpt-6.1-sol— final-verifier; agentsol-verifier - Phase 2 reviewers:
gpt-6.1-sol— general (completed, effort high); agentphase2-reviewer,gpt-6.1-sol— dash-core-commit-history (completed, effort high); agentphase2-reviewer
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Actionable comments posted: 1
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Inline comments:
Review comments at @src/coinjoin/client.cpp:
- Line 795: Update `CheckPendingObservations` to include `m_pending_obs_dirty`
when deciding whether to retry persistence, and retain that dirty state when
`PersistPendingObservations` fails. Set the dirty flag when
`AddPendingObservation` changes the map, and clear it only after persistence
succeeds, including the initial write after record recovery.
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📒 Files selected for processing (2)
src/coinjoin/client.cppsrc/wallet/test/coinjoin_tests.cpp
Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 2 remain after this review.
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| // Entries added while the record could not be read are locked in memory only (see | ||
| // AddPendingObservation()), persist them once the record has been recovered | ||
| bool fChanged{!m_pending_obs_loaded && !m_pending_obs.empty()}; |
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🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win
🔎 Supported by static analysis
🏁 Script executed:
rg -n 'm_pending_obs_dirty|m_pending_obs_loaded|PersistPendingObservations|fChanged' src/coinjoin/client.cpp src/coinjoin/client.h
sed -n '675,880p' src/coinjoin/client.cppRepository: dashpay/dash
Length of output: 13243
🏁 Script executed:
rg -n -F -- 'm_pending_obs_dirty' src || test "$?" -eq 1
nl -ba src/coinjoin/client.h | sed -n '205,235p'
nl -ba src/coinjoin/client.cpp | sed -n '720,735p;790,878p'Repository: dashpay/dash
Length of output: 9687
Retry pending-observation writes after persistence failures.
AddPendingObservation adds the observation before calling PersistPendingObservations. If TxnBegin() fails, the helper returns without writing it, and the caller only logs the failure. CheckPendingObservations does not read m_pending_obs_dirty. Once the record is loaded, it retries only if fChanged becomes true, such as when another observation is removed. The first write after record recovery has the same gap. If no later check triggers a write before restart, the input may become selectable while its mixing transaction is still in flight. Keep the state dirty after a failed write and clear it only after successful persistence.
Suggested fix
@@
for (const auto& outpoint : outpoints) {
m_pending_obs.emplace(outpoint, nNow);
@@
__func__, outpoint.ToStringShort());
}
+ m_pending_obs_dirty = true;
@@
__func__, outpoints.size());
+ } else {
+ m_pending_obs_dirty = false;
}
@@
- bool fChanged{!m_pending_obs_loaded && !m_pending_obs.empty()};
+ bool fChanged{m_pending_obs_dirty || (!m_pending_obs_loaded && !m_pending_obs.empty())};
@@
- if (fChanged && m_pending_obs_loaded && !PersistPendingObservations(*m_wallet, get_batch(), m_pending_obs)) {
- LogPrintf("CCoinJoinClientManager::%s -- ERROR: failed to persist %d pending observation(s)\n", __func__,
- m_pending_obs.size());
+ if (fChanged && m_pending_obs_loaded) {
+ if (!PersistPendingObservations(*m_wallet, get_batch(), m_pending_obs)) {
+ m_pending_obs_dirty = true;
+ LogPrintf("CCoinJoinClientManager::%s -- ERROR: failed to persist %d pending observation(s)\n", __func__,
+ m_pending_obs.size());
+ } else {
+ m_pending_obs_dirty = false;
+ }
}🤖 Prompt for AI Agents
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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
minimal, and validate.
Review comment at @src/coinjoin/client.cpp at line 795:
Update `CheckPendingObservations` to include `m_pending_obs_dirty` when deciding
whether to retry persistence, and retain that dirty state when
`PersistPendingObservations` fails. Set the dirty flag when
`AddPendingObservation` changes the map, and clear it only after persistence
succeeds, including the initial write after record recovery.
After applying the fix, consider running `coderabbit review --agent` for local
review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr
…the record was unreadable AddPendingObservation() locks its inputs in memory only when the pending-observation record cannot be read or no database transaction can be started. Once the record is readable again nothing ever writes those locks: CheckPendingObservations() writes only the record and only after a release, and the next AddPendingObservation() writes locks only for its own inputs. The record then lists inputs without a persistent lock. After a restart the missing lock reads as a manual unlock, the entry is dropped and the input becomes selectable again while the finalized mixing transaction spending it may still be in flight. Move the transactional write into PersistPendingObservations(), which writes the record together with the lock of every entry whose coin is still locked, and use it on both the add and the release path. CheckPendingObservations() also runs it when the record was recovered on this pass while entries were already held in memory. Rewriting a lock which is already persisted is idempotent and the set only holds the inputs of recent sessions. The existing unreadable-record test now re-adds an input before the record is made readable and checks that its lock is persisted by the recovering check pass.
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Re-review — Final validation — Phase 1 + Phase 2
Verified the combined reviewer findings against exact head e774bab. The transactional helper fixes successful recovery, but failed persistence loses the retry condition and can leave pending inputs protected only in memory after the database recovers. This was a static review only; the supplied CI snapshot shows successful lint and several builds, with wallet-enabled Linux tests and some additional builds still pending.
🔴 1 blocking
1 finding(s) not shown inline (the lines are not part of this PR's diff)
🔴 Blocking: Retain pending persistence state until the recovery write succeeds
src/coinjoin/client.cpp:793-799
The recovery write has only one opportunity to succeed. fChanged starts true when memory-only observations exist and the record is unloaded, but LoadPendingObservations() sets m_pending_obs_loaded = true before the persistence attempt at line 874. If TxnBegin(), a write, or the commit fails, the caller only logs the error. On the next periodic check, fChanged starts false; with the inputs still locked and no spend, manual unlock, or timeout release, no write is attempted even after database availability returns. The same missing retry follows a failed AddPendingObservation() write when the record is already loaded. Consequently, an input can remain absent from both the persisted observation record and persistent locks until another add or release triggers a write, and a restart before then makes it selectable while its finalized mixing transaction may still be in flight. This is within the PR's stated recovery goal, which explicitly includes transient transaction-start failures. Retain a dirty/pending-write flag across calls, set it whenever observations cannot be persisted, and clear it only after the complete transaction succeeds. Add a regression covering a failed persistence attempt followed by an otherwise idle successful check, verifying that the record and lock survive wallet reload.
source: muse-spark-1.3-contributor (phase1-reviewer: general); gpt-6.1-sol (phase2-reviewer: general)
Review provenance
Source: reviewer 1: muse-spark-1.3-contributor (agent: phase1-reviewer, role: general); reviewer 2: gpt-6.1-sol (agent: phase2-reviewer, role: general); reviewer 3: gpt-6.1-sol (agent: phase2-reviewer, role: dash-core-commit-history); final verifier: gpt-6.1-sol (agent: sol-verifier, role: final-verifier)
- Triage:
normalbygpt-6.1-sol(effort low) — The diff changes transactional persistence and recovery of CoinJoin input locks in src/coinjoin/client.cpp, requiring reasoning about failure paths and manual unlocks, but remains a contained fix rather than a large or intricate critical-surface change. - Phase 1 reviewers:
muse-spark-1.3-contributor— general (completed, effort xhigh); agentphase1-reviewer - Phase 1 model:
muse-spark-1.3-contributor— not quota-gated; passed overgemini-3.8-flash-high(antigravity below 15% reserve: weekly 15% left, 5h 100% left),glm-5.3-flash(not used above high effort; tier asks max) - Fresh verifier:
gpt-6.1-sol— final-verifier; agentsol-verifier - Phase 2 reviewers:
gpt-6.1-sol— general (completed, effort high); agentphase2-reviewer,gpt-6.1-sol— dash-core-commit-history (completed, effort high); agentphase2-reviewer
🤖 Prompt for all review comments with AI agents
These findings are from an automated code review. Verify each finding against the current code and only fix it if needed.
In `src/coinjoin/client.cpp`:
- [BLOCKING] src/coinjoin/client.cpp:793-799: Retain pending persistence state until the recovery write succeeds
The recovery write has only one opportunity to succeed. `fChanged` starts true when memory-only observations exist and the record is unloaded, but `LoadPendingObservations()` sets `m_pending_obs_loaded = true` before the persistence attempt at line 874. If `TxnBegin()`, a write, or the commit fails, the caller only logs the error. On the next periodic check, `fChanged` starts false; with the inputs still locked and no spend, manual unlock, or timeout release, no write is attempted even after database availability returns. The same missing retry follows a failed `AddPendingObservation()` write when the record is already loaded. Consequently, an input can remain absent from both the persisted observation record and persistent locks until another add or release triggers a write, and a restart before then makes it selectable while its finalized mixing transaction may still be in flight. This is within the PR's stated recovery goal, which explicitly includes transient transaction-start failures. Retain a dirty/pending-write flag across calls, set it whenever observations cannot be persisted, and clear it only after the complete transaction succeeds. Add a regression covering a failed persistence attempt followed by an otherwise idle successful check, verifying that the record and lock survive wallet reload.
3 participants
Issue being fixed or feature implemented
After a successful mixing session the client keeps the session's inputs locked until the wallet sees the finalized transaction spending them (
m_pending_obs). The set is mirrored to the wallet database as thecj_pending_obsrecord, and each input also gets a persistentlockedutxoentry, so the protection survives a restart. Both are written in one database transaction.When the record exists but can't be read, or no transaction can be started,
AddPendingObservation()deliberately persists nothing. It locks the new inputs in memory only and logs that they "will not survive a restart".LoadPendingObservations()keeps retrying the read. When a retry succeeds it merges the record into the in-memory set, but nothing ever writes the locks of the memory-only entries to disk:CheckPendingObservations()only writes when an entry was released, and even then it writes only the record, not the locks.AddPendingObservation()rewrites the whole record, including the earlier memory-only entries, but writeslockedutxoonly for the inputs it is adding itself.After a restart the record therefore lists inputs that have no persistent lock. The first check reads the missing lock as a manual
lockunspentrelease, drops the entry and makes the input selectable again, even though the finalized mixing transaction spending it may still be in flight. A transientTxnBegin()failure inAddPendingObservation()ends in the same state: the next add persists the record but not the earlier lock.Why this is a real problem
The code path at c14104b:
m_pending_obs_loadedis unset, sofTxn/fPersistedare false andLockCoin()gets a null batch, which is a memory-only lock: src/coinjoin/client.cpp#L707-L714fChanged, and only the record: src/coinjoin/client.cpp#L865The new unit test
coinjoin_pending_observation_recovered_testswalks through this sequence:Here it is against the unfixed code:
Test run without the fix
After the restart, the input added while the record was unreadable has no
lockedutxoentry, so the reloaded wallet doesn't consider it locked. It isn't in the persisted record either. The input that was already persisted before is still locked, which is why each per-outpoint check fails exactly once.Why it matters
The trigger is narrow. It needs a pending-observation record that fails to read and later reads fine, or a transient failure to start a database transaction, followed by a restart before the wallet sees the finalized mixing transaction. When it happens, though, the protection this code exists for is silently lost, despite the code having recovered the record. The input can be picked for another mixing session that conflicts with the in-flight transaction. That session then fails, and a collateral may be charged. No funds are lost.
This code is in v24.0.0-rc.1/rc.2, so this should also go to the v24.0.x release branch.
What was done?
m_pending_obs_dirtytoCCoinJoinClientManager. It is set whenever entries were added without being persisted, and cleared once a full persist succeeds.AddPendingObservation()intoPersistPendingObservations(WalletBatch&). In one transaction it writes the record pluslockedutxofor every entry whose coin is still locked, not only the entries just added. It still refuses to write while the record is unread, and aborts the whole transaction on any failure, exactly as before.AddPendingObservation()locks the new inputs in memory as before, then calls the helper.CheckPendingObservations(), once the record is loaded, calls the helper if the set is dirty. Otherwise it keeps the existing record-only write when something was released.Why this is the correct minimal fix
The root cause is that "this entry's lock isn't on disk yet" was never remembered once the record became readable. The dirty flag remembers it. The next opportunity to persist (an add, or the periodic check right after the record loads) then writes the record and the locks together, in the same single transaction the code already uses to avoid partial states.
Two smaller alternatives aren't enough:
AddPendingObservation()would leave the gap open until the next mixing session completes, which may be after the restart.Rewriting
lockedutxofor entries that are already persisted is idempotent, and the set only holds the inputs of recent sessions. Tracking which entries are memory-only would add state without benefit.Behavior intentionally left unchanged:
How Has This Been Tested?
macOS arm64, debug build (
--enable-debug --enable-werror, depends prefix).coinjoin_tests/coinjoin_pending_observation_recovered_testsinsrc/wallet/test/coinjoin_tests.cpp, next to the existing reload/unreadable-record tests. It reloads a copy of the wallet database and checks the persisted lock, the reloaded wallet's lock state and the persisted record.*** No errors detected.src/test/test_dash --run_test=coinjoin_tests,wallet_tests,walletdb_tests,walletload_tests,coinjoin_inouts_tests,coinjoin_dstxmanager_tests,coinjoin_queue_tests: 115 test cases, no errors.test/functional/test_runner.py rpc_coinjoin.py p2p_dstx.py: both passed.git diff -U0 | contrib/devtools/clang-format-diff.py -p1: no changes in the touched code. The only suggestion is a pre-existing include-order nit in the test file.Breaking Changes
None.
Checklist:
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