wallet: ignore chainStateFlushed notifications while attaching chain

Author: mzumsande

src/wallet/wallet.cpp

@@ -523,6 +523,11 @@ bool CWallet::ChangeWalletPassphrase(const SecureString& strOldWalletPassphrase,
 
 void CWallet::chainStateFlushed(const CBlockLocator& loc)
 {
+    // Don't update the best block until the chain is attached so that in case of a shutdown,
+    // the rescan will be restarted at next startup.
+    if (m_attaching_chain) {
+        return;
+    }
     WalletBatch batch(GetDatabase());
     batch.WriteBestBlock(loc);
 }
@@ -2940,6 +2945,8 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
     // be pending on the validation-side until lock release. It's likely to have
     // block processing duplicata (if rescan block range overlaps with notification one)
     // but we guarantee at least than wallet state is correct after notifications delivery.
+    // However, chainStateFlushed notifications are ignored until the rescan is finished
+    // so that in case of a shutdown event, the rescan will be repeated at the next start.
     // This is temporary until rescan and notifications delivery are unified under same
     // interface.
     walletInstance->m_chain_notifications_handler = walletInstance->chain().handleNotifications(walletInstance);
@@ -2968,6 +2975,7 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
 
     if (tip_height && *tip_height != rescan_height)
     {
+        walletInstance->m_attaching_chain = true; //ignores chainStateFlushed notifications
         if (chain.havePruned()) {
             int block_height = *tip_height;
             while (block_height > 0 && chain.haveBlockOnDisk(block_height - 1) && rescan_height != block_height) {
@@ -3007,6 +3015,7 @@ bool CWallet::AttachChain(const std::shared_ptr<CWallet>& walletInstance, interf
                 return false;
             }
         }
+        walletInstance->m_attaching_chain = false;
         walletInstance->chainStateFlushed(chain.getTipLocator());
         walletInstance->GetDatabase().IncrementUpdateCounter();
     }

src/wallet/wallet.h

@@ -237,6 +237,7 @@ class CWallet final : public WalletStorage, public interfaces::Chain::Notificati
 
     std::atomic<bool> fAbortRescan{false};
     std::atomic<bool> fScanningWallet{false}; // controlled by WalletRescanReserver
+    std::atomic<bool> m_attaching_chain{false};
     std::atomic<int64_t> m_scanning_start{0};
     std::atomic<double> m_scanning_progress{0};
     friend class WalletRescanReserver;