Auto merge of #4343 - oxarbitrage:issue3083, r=str4d

Add expired transaction notifications

Closes https://github.com/zcash/zcash/issues/3083

src/init.cpp

@@ -368,6 +368,7 @@ std::string HelpMessage(HelpMessageMode mode)
 #ifndef WIN32
     strUsage += HelpMessageOpt("-sysperms", _("Create new files with system default permissions, instead of umask 077 (only effective with disabled wallet functionality)"));
 #endif
+    strUsage += HelpMessageOpt("-txexpirynotify=<cmd>", _("Execute command when transaction expires (%s in cmd is replaced by transaction id)"));
     strUsage += HelpMessageOpt("-txindex", strprintf(_("Maintain a full transaction index, used by the getrawtransaction rpc call (default: %u)"), DEFAULT_TXINDEX));
 
     strUsage += HelpMessageGroup(_("Connection options:"));
@@ -529,6 +530,14 @@ static void BlockNotifyCallback(const uint256& hashNewTip)
     boost::thread t(runCommand, strCmd); // thread runs free
 }
 
+static void TxExpiryNotifyCallback(const uint256& txid)
+{
+    std::string strCmd = GetArg("-txexpirynotify", "");
+
+    boost::replace_all(strCmd, "%s", txid.GetHex());
+    boost::thread t(runCommand, strCmd); // thread runs free
+}
+
 struct CImportingNow
 {
     CImportingNow() {
@@ -1569,6 +1578,9 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (mapArgs.count("-blocknotify"))
         uiInterface.NotifyBlockTip.connect(BlockNotifyCallback);
 
+    if (mapArgs.count("-txexpirynotify"))
+        uiInterface.NotifyTxExpiration.connect(TxExpiryNotifyCallback);
+
     uiInterface.InitMessage(_("Activating best chain..."));
     // scan for better chains in the block chain database, that are not yet connected in the active best chain
     CValidationState state;

src/main.cpp

@@ -3161,7 +3161,11 @@ bool static ConnectTip(CValidationState& state, const CChainParams& chainparams,
     mempool.removeForBlock(pblock->vtx, pindexNew->nHeight, txConflicted, !IsInitialBlockDownload(chainparams));
 
     // Remove transactions that expire at new block height from mempool
-    mempool.removeExpired(pindexNew->nHeight);
+    auto ids = mempool.removeExpired(pindexNew->nHeight);
+
+    for (auto id : ids) {
+        uiInterface.NotifyTxExpiration(id);
+    }
 
     // Update chainActive & related variables.
     UpdateTip(pindexNew, chainparams);

src/txmempool.cpp

@@ -406,7 +406,7 @@ void CTxMemPool::removeConflicts(const CTransaction &tx, std::list<CTransaction>
     }
 }
 
-void CTxMemPool::removeExpired(unsigned int nBlockHeight)
+std::vector<uint256> CTxMemPool::removeExpired(unsigned int nBlockHeight)
 {
     // Remove expired txs from the mempool
     LOCK(cs);
@@ -418,11 +418,14 @@ void CTxMemPool::removeExpired(unsigned int nBlockHeight)
             transactionsToRemove.push_back(tx);
         }
     }
+    std::vector<uint256> ids;
     for (const CTransaction& tx : transactionsToRemove) {
         list<CTransaction> removed;
         remove(tx, removed, true);
+        ids.push_back(tx.GetHash());
         LogPrint("mempool", "Removing expired txid: %s\n", tx.GetHash().ToString());
     }
+    return ids;
 }
 
 /**

src/txmempool.h

@@ -203,7 +203,7 @@ public:
     void removeWithAnchor(const uint256 &invalidRoot, ShieldedType type);
     void removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight, int flags);
     void removeConflicts(const CTransaction &tx, std::list<CTransaction>& removed);
-    void removeExpired(unsigned int nBlockHeight);
+    std::vector<uint256> removeExpired(unsigned int nBlockHeight);
     void removeForBlock(const std::vector<CTransaction>& vtx, unsigned int nBlockHeight,
                         std::list<CTransaction>& conflicts, bool fCurrentEstimate = true);
     void removeWithoutBranchId(uint32_t nMemPoolBranchId);

src/ui_interface.h

@@ -98,6 +98,9 @@ public:
 
     /** New block has been accepted */
     boost::signals2::signal<void (const uint256& hash)> NotifyBlockTip;
+
+    /** Transaction expired */
+    boost::signals2::signal<void (const uint256& txid)> NotifyTxExpiration;
 };
 
 extern CClientUIInterface uiInterface;