Merge #17477: Remove the mempool's NotifyEntryAdded and NotifyEntryRemoved signals

e57980b473 [mempool] Remove NotifyEntryAdded and NotifyEntryRemoved callbacks (John Newbery)
2dd561f361 [validation] Remove pool member from ConnectTrace (John Newbery)
969b65f3f5 [validation] Remove NotifyEntryRemoved callback from ConnectTrace (John Newbery)
5613f9842b [validation] Remove conflictedTxs from PerBlockConnectTrace (John Newbery)
cdb893443c [validation interface] Remove vtxConflicted from BlockConnected (John Newbery)
1168394d75 [wallet] Notify conflicted transactions in TransactionRemovedFromMempool (John Newbery)

Pull request description:

  These boost signals were added in #9371, before we had a `TransactionRemovedFromMempool` method in the validation interface. The `NotifyEntryAdded` callback was used by validation to build a vector of conflicted transactions when connecting a block, which the wallet was notified of in the `BlockConnected` CValidationInterface callback.

  Now that we have a `TransactionRemovedFromMempool` callback, we can fire that signal directly from the mempool for conflicted transactions.

  Note that #9371 was implemented to ensure `-walletnotify` events were fired for these conflicted transaction. We inadvertently stopped sending these notifications in #16624 (Sep 2019 commit 7e89994). We should probably fix that, but in a different PR.

ACKs for top commit:
  jonatack:
    Re-ACK e57980b
  ryanofsky:
    Code review ACK e57980b473, no code changes since previous review, but helpful new code comments have been added and the PR description is now more clear about where the old code came from

Tree-SHA512: 3bdbaf1ef2731e788462d4756e69c42a1efdcf168691ce1bbfdaa4b7b55ac3c5b1fd4ab7b90bcdec653703600501b4224d252cfc086aef28f9ce0da3b0563a69

src/index/base.cpp

@@ -188,8 +188,7 @@ bool BaseIndex::Rewind(const CBlockIndex* current_tip, const CBlockIndex* new_ti
     return true;
 }
 
-void BaseIndex::BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex,
+void BaseIndex::BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex)
-                               const std::vector<CTransactionRef>& txn_conflicted)
 {
     if (!m_synced) {
         return;

src/index/base.h

@@ -64,8 +64,7 @@ private:
     bool Commit();
 
 protected:
-    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex,
+    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override;
-                        const std::vector<CTransactionRef>& txn_conflicted) override;
 
     void ChainStateFlushed(const CBlockLocator& locator) override;
 

src/init.cpp

@@ -73,6 +73,7 @@
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/algorithm/string/split.hpp>
+#include <boost/signals2/signal.hpp>
 #include <boost/thread.hpp>
 
 #if ENABLE_ZMQ

src/interfaces/chain.cpp

@@ -172,11 +172,9 @@ public:
     {
         m_notifications->TransactionRemovedFromMempool(tx);
     }
-    void BlockConnected(const std::shared_ptr<const CBlock>& block,
+    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* index) override
-        const CBlockIndex* index,
-        const std::vector<CTransactionRef>& tx_conflicted) override
     {
-        m_notifications->BlockConnected(*block, tx_conflicted, index->nHeight);
+        m_notifications->BlockConnected(*block, index->nHeight);
     }
     void BlockDisconnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* index) override
     {

src/interfaces/chain.h

@@ -219,7 +219,7 @@ public:
         virtual ~Notifications() {}
         virtual void TransactionAddedToMempool(const CTransactionRef& tx) {}
         virtual void TransactionRemovedFromMempool(const CTransactionRef& ptx) {}
-        virtual void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& tx_conflicted, int height) {}
+        virtual void BlockConnected(const CBlock& block, int height) {}
         virtual void BlockDisconnected(const CBlock& block, int height) {}
         virtual void UpdatedBlockTip() {}
         virtual void ChainStateFlushed(const CBlockLocator& locator) {}

src/interfaces/node.cpp

@@ -37,6 +37,8 @@
 
 #include <univalue.h>
 
+#include <boost/signals2/signal.hpp>
+
 class CWallet;
 fs::path GetWalletDir();
 std::vector<fs::path> ListWalletDir();

src/net_processing.cpp

@@ -1134,7 +1134,7 @@ PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn, BanMan* banman, CS
  * Evict orphan txn pool entries (EraseOrphanTx) based on a newly connected
  * block. Also save the time of the last tip update.
  */
-void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex, const std::vector<CTransactionRef>& vtxConflicted)
+void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex)
 {
     {
         LOCK(g_cs_orphans);

src/net_processing.h

@@ -35,7 +35,7 @@ public:
     /**
      * Overridden from CValidationInterface.
      */
-    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected, const std::vector<CTransactionRef>& vtxConflicted) override;
+    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override;
     void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) override;
     /**
      * Overridden from CValidationInterface.

src/test/validation_block_tests.cpp

@@ -42,7 +42,7 @@ struct TestSubscriber : public CValidationInterface {
         BOOST_CHECK_EQUAL(m_expected_tip, pindexNew->GetBlockHash());
     }
 
-    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex, const std::vector<CTransactionRef>& txnConflicted) override
+    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override
     {
         BOOST_CHECK_EQUAL(m_expected_tip, block->hashPrevBlock);
         BOOST_CHECK_EQUAL(m_expected_tip, pindex->pprev->GetBlockHash());

src/txmempool.cpp

@@ -355,7 +355,6 @@ void CTxMemPool::AddTransactionsUpdated(unsigned int n)
 
 void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAncestors, bool validFeeEstimate)
 {
-    NotifyEntryAdded(entry.GetSharedTx());
     // Add to memory pool without checking anything.
     // Used by AcceptToMemoryPool(), which DOES do
     // all the appropriate checks.
@@ -406,10 +405,12 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
 
 void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason)
 {
-    CTransactionRef ptx = it->GetSharedTx();
+    if (reason != MemPoolRemovalReason::BLOCK) {
-    NotifyEntryRemoved(ptx, reason);
+        // Notify clients that a transaction has been removed from the mempool
-    if (reason != MemPoolRemovalReason::BLOCK && reason != MemPoolRemovalReason::CONFLICT) {
+        // for any reason except being included in a block. Clients interested
-        GetMainSignals().TransactionRemovedFromMempool(ptx);
+        // in transactions included in blocks can subscribe to the BlockConnected
+        // notification.
+        GetMainSignals().TransactionRemovedFromMempool(it->GetSharedTx());
     }
 
     const uint256 hash = it->GetTx().GetHash();

src/txmempool.h

@@ -27,7 +27,6 @@
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/ordered_index.hpp>
 #include <boost/multi_index/sequenced_index.hpp>
-#include <boost/signals2/signal.hpp>
 
 class CBlockIndex;
 extern RecursiveMutex cs_main;
@@ -699,9 +698,6 @@ public:
 
     size_t DynamicMemoryUsage() const;
 
-    boost::signals2::signal<void (CTransactionRef)> NotifyEntryAdded;
-    boost::signals2::signal<void (CTransactionRef, MemPoolRemovalReason)> NotifyEntryRemoved;
-
 private:
     /** UpdateForDescendants is used by UpdateTransactionsFromBlock to update
      *  the descendants for a single transaction that has been added to the

src/validation.cpp

@@ -2504,35 +2504,21 @@ static int64_t nTimePostConnect = 0;
 struct PerBlockConnectTrace {
     CBlockIndex* pindex = nullptr;
     std::shared_ptr<const CBlock> pblock;
-    std::shared_ptr<std::vector<CTransactionRef>> conflictedTxs;
+    PerBlockConnectTrace() {}
-    PerBlockConnectTrace() : conflictedTxs(std::make_shared<std::vector<CTransactionRef>>()) {}
 };
 /**
  * Used to track blocks whose transactions were applied to the UTXO state as a
  * part of a single ActivateBestChainStep call.
  *
- * This class also tracks transactions that are removed from the mempool as
- * conflicts (per block) and can be used to pass all those transactions
- * through SyncTransaction.
- *
- * This class assumes (and asserts) that the conflicted transactions for a given
- * block are added via mempool callbacks prior to the BlockConnected() associated
- * with those transactions. If any transactions are marked conflicted, it is
- * assumed that an associated block will always be added.
- *
  * This class is single-use, once you call GetBlocksConnected() you have to throw
  * it away and make a new one.
  */
 class ConnectTrace {
 private:
     std::vector<PerBlockConnectTrace> blocksConnected;
-    CTxMemPool &pool;
-    boost::signals2::scoped_connection m_connNotifyEntryRemoved;
 
 public:
-    explicit ConnectTrace(CTxMemPool &_pool) : blocksConnected(1), pool(_pool) {
+    explicit ConnectTrace() : blocksConnected(1) {}
-        m_connNotifyEntryRemoved = pool.NotifyEntryRemoved.connect(std::bind(&ConnectTrace::NotifyEntryRemoved, this, std::placeholders::_1, std::placeholders::_2));
-    }
 
     void BlockConnected(CBlockIndex* pindex, std::shared_ptr<const CBlock> pblock) {
         assert(!blocksConnected.back().pindex);
@@ -2550,17 +2536,9 @@ public:
         // one waiting for the transactions from the next block. We pop
         // the last entry here to make sure the list we return is sane.
         assert(!blocksConnected.back().pindex);
-        assert(blocksConnected.back().conflictedTxs->empty());
         blocksConnected.pop_back();
         return blocksConnected;
     }
-
-    void NotifyEntryRemoved(CTransactionRef txRemoved, MemPoolRemovalReason reason) {
-        assert(!blocksConnected.back().pindex);
-        if (reason == MemPoolRemovalReason::CONFLICT) {
-            blocksConnected.back().conflictedTxs->emplace_back(std::move(txRemoved));
-        }
-    }
 };
 
 /**
@@ -2854,7 +2832,7 @@ bool CChainState::ActivateBestChain(BlockValidationState &state, const CChainPar
             do {
                 // We absolutely may not unlock cs_main until we've made forward progress
                 // (with the exception of shutdown due to hardware issues, low disk space, etc).
-                ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+                ConnectTrace connectTrace; // Destructed before cs_main is unlocked
 
                 if (pindexMostWork == nullptr) {
                     pindexMostWork = FindMostWorkChain();
@@ -2881,7 +2859,7 @@ bool CChainState::ActivateBestChain(BlockValidationState &state, const CChainPar
 
                 for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
                     assert(trace.pblock && trace.pindex);
-                    GetMainSignals().BlockConnected(trace.pblock, trace.pindex, trace.conflictedTxs);
+                    GetMainSignals().BlockConnected(trace.pblock, trace.pindex);
                 }
             } while (!m_chain.Tip() || (starting_tip && CBlockIndexWorkComparator()(m_chain.Tip(), starting_tip)));
             if (!blocks_connected) return true;

src/validationinterface.cpp

@@ -32,7 +32,7 @@ struct ValidationInterfaceConnections {
 struct MainSignalsInstance {
     boost::signals2::signal<void (const CBlockIndex *, const CBlockIndex *, bool fInitialDownload)> UpdatedBlockTip;
     boost::signals2::signal<void (const CTransactionRef &)> TransactionAddedToMempool;
-    boost::signals2::signal<void (const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::vector<CTransactionRef>&)> BlockConnected;
+    boost::signals2::signal<void (const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex)> BlockConnected;
     boost::signals2::signal<void (const std::shared_ptr<const CBlock>&, const CBlockIndex* pindex)> BlockDisconnected;
     boost::signals2::signal<void (const CTransactionRef &)> TransactionRemovedFromMempool;
     boost::signals2::signal<void (const CBlockLocator &)> ChainStateFlushed;
@@ -79,7 +79,7 @@ void RegisterValidationInterface(CValidationInterface* pwalletIn) {
     ValidationInterfaceConnections& conns = g_signals.m_internals->m_connMainSignals[pwalletIn];
     conns.UpdatedBlockTip = g_signals.m_internals->UpdatedBlockTip.connect(std::bind(&CValidationInterface::UpdatedBlockTip, pwalletIn, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
     conns.TransactionAddedToMempool = g_signals.m_internals->TransactionAddedToMempool.connect(std::bind(&CValidationInterface::TransactionAddedToMempool, pwalletIn, std::placeholders::_1));
-    conns.BlockConnected = g_signals.m_internals->BlockConnected.connect(std::bind(&CValidationInterface::BlockConnected, pwalletIn, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
+    conns.BlockConnected = g_signals.m_internals->BlockConnected.connect(std::bind(&CValidationInterface::BlockConnected, pwalletIn, std::placeholders::_1, std::placeholders::_2));
     conns.BlockDisconnected = g_signals.m_internals->BlockDisconnected.connect(std::bind(&CValidationInterface::BlockDisconnected, pwalletIn, std::placeholders::_1, std::placeholders::_2));
     conns.TransactionRemovedFromMempool = g_signals.m_internals->TransactionRemovedFromMempool.connect(std::bind(&CValidationInterface::TransactionRemovedFromMempool, pwalletIn, std::placeholders::_1));
     conns.ChainStateFlushed = g_signals.m_internals->ChainStateFlushed.connect(std::bind(&CValidationInterface::ChainStateFlushed, pwalletIn, std::placeholders::_1));
@@ -163,9 +163,9 @@ void CMainSignals::TransactionRemovedFromMempool(const CTransactionRef &ptx) {
                           ptx->GetWitnessHash().ToString());
 }
 
-void CMainSignals::BlockConnected(const std::shared_ptr<const CBlock> &pblock, const CBlockIndex *pindex, const std::shared_ptr<const std::vector<CTransactionRef>>& pvtxConflicted) {
+void CMainSignals::BlockConnected(const std::shared_ptr<const CBlock> &pblock, const CBlockIndex *pindex) {
-    auto event = [pblock, pindex, pvtxConflicted, this] {
+    auto event = [pblock, pindex, this] {
-        m_internals->BlockConnected(pblock, pindex, *pvtxConflicted);
+        m_internals->BlockConnected(pblock, pindex);
     };
     ENQUEUE_AND_LOG_EVENT(event, "%s: block hash=%s block height=%d", __func__,
                           pblock->GetHash().ToString(),

src/validationinterface.h

@@ -92,10 +92,32 @@ protected:
     /**
      * Notifies listeners of a transaction leaving mempool.
      *
-     * This only fires for transactions which leave mempool because of expiry,
+     * This notification fires for transactions that are removed from the
-     * size limiting, reorg (changes in lock times/coinbase maturity), or
+     * mempool for the following reasons:
-     * replacement. This does not include any transactions which are included
+     *
-     * in BlockConnectedDisconnected either in block->vtx or in txnConflicted.
+     * - EXPIRY (expired from mempool after -mempoolexpiry hours)
+     * - SIZELIMIT (removed in size limiting if the mempool exceeds -maxmempool megabytes)
+     * - REORG (removed during a reorg)
+     * - CONFLICT (removed because it conflicts with in-block transaction)
+     * - REPLACED (removed due to RBF replacement)
+     *
+     * This does not fire for transactions that are removed from the mempool
+     * because they have been included in a block. Any client that is interested
+     * in transactions removed from the mempool for inclusion in a block can learn
+     * about those transactions from the BlockConnected notification.
+     *
+     * Transactions that are removed from the mempool because they conflict
+     * with a transaction in the new block will have
+     * TransactionRemovedFromMempool events fired *before* the BlockConnected
+     * event is fired. If multiple blocks are connected in one step, then the
+     * ordering could be:
+     *
+     * - TransactionRemovedFromMempool(tx1 from block A)
+     * - TransactionRemovedFromMempool(tx2 from block A)
+     * - TransactionRemovedFromMempool(tx1 from block B)
+     * - TransactionRemovedFromMempool(tx2 from block B)
+     * - BlockConnected(A)
+     * - BlockConnected(B)
      *
      * Called on a background thread.
      */
@@ -106,7 +128,7 @@ protected:
      *
      * Called on a background thread.
      */
-    virtual void BlockConnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex, const std::vector<CTransactionRef> &txnConflicted) {}
+    virtual void BlockConnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex) {}
     /**
      * Notifies listeners of a block being disconnected
      *
@@ -170,7 +192,7 @@ public:
     void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
     void TransactionAddedToMempool(const CTransactionRef &);
     void TransactionRemovedFromMempool(const CTransactionRef &);
-    void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::shared_ptr<const std::vector<CTransactionRef>> &);
+    void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex);
     void BlockDisconnected(const std::shared_ptr<const CBlock> &, const CBlockIndex* pindex);
     void ChainStateFlushed(const CBlockLocator &);
     void BlockChecked(const CBlock&, const BlockValidationState&);

src/wallet/wallet.cpp

@@ -1109,7 +1109,7 @@ void CWallet::TransactionRemovedFromMempool(const CTransactionRef &ptx) {
     }
 }
 
-void CWallet::BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted, int height)
+void CWallet::BlockConnected(const CBlock& block, int height)
 {
     const uint256& block_hash = block.GetHash();
     auto locked_chain = chain().lock();
@@ -1122,9 +1122,6 @@ void CWallet::BlockConnected(const CBlock& block, const std::vector<CTransaction
         SyncTransaction(block.vtx[index], confirm);
         TransactionRemovedFromMempool(block.vtx[index]);
     }
-    for (const CTransactionRef& ptx : vtxConflicted) {
-        TransactionRemovedFromMempool(ptx);
-    }
 }
 
 void CWallet::BlockDisconnected(const CBlock& block, int height)

src/wallet/wallet.h

@@ -876,7 +876,7 @@ public:
     bool AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose=true);
     void LoadToWallet(CWalletTx& wtxIn) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void TransactionAddedToMempool(const CTransactionRef& tx) override;
-    void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& vtxConflicted, int height) override;
+    void BlockConnected(const CBlock& block, int height) override;
     void BlockDisconnected(const CBlock& block, int height) override;
     void UpdatedBlockTip() override;
     int64_t RescanFromTime(int64_t startTime, const WalletRescanReserver& reserver, bool update);

src/zmq/zmqnotificationinterface.cpp

@@ -177,7 +177,7 @@ void CZMQNotificationInterface::TransactionAddedToMempool(const CTransactionRef&
     }
 }
 
-void CZMQNotificationInterface::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected, const std::vector<CTransactionRef>& vtxConflicted)
+void CZMQNotificationInterface::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected)
 {
     for (const CTransactionRef& ptx : pblock->vtx) {
         // Do a normal notify for each transaction added in the block

src/zmq/zmqnotificationinterface.h

@@ -26,7 +26,7 @@ protected:
 
     // CValidationInterface
     void TransactionAddedToMempool(const CTransactionRef& tx) override;
-    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected, const std::vector<CTransactionRef>& vtxConflicted) override;
+    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override;
     void BlockDisconnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexDisconnected) override;
     void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override;