Merge #8448: Store mempool and prioritization data to disk

582068a Add mempool.dat to doc/files.md (Pieter Wuille)
3f78562 Add DumpMempool and LoadMempool (Pieter Wuille)
ced7c94 Add AcceptToMemoryPoolWithTime function (Pieter Wuille)
c3efb58 Add feedelta to TxMempoolInfo (Pieter Wuille)

6 files changed, 147 insertions, 7 deletions

diff --git a/doc/files.md b/doc/files.md
index f7eca57dcb..928977143b 100644
--- a/doc/files.md
+++ b/doc/files.md
@@ -10,6 +10,7 @@
 * db.log: wallet database log file
 * debug.log: contains debug information and general logging generated by bitcoind or bitcoin-qt
 * fee_estimates.dat: stores statistics used to estimate minimum transaction fees and priorities required for confirmation; since 0.10.0
+* mempool.dat: dump of the mempool's transactions; since 0.14.0.
 * peers.dat: peer IP address database (custom format); since 0.7.0
 * wallet.dat: personal wallet (BDB) with keys and transactions
 * .cookie: session RPC authentication cookie (written at start when cookie authentication is used, deleted on shutdown): since 0.12.0
diff --git a/src/init.cpp b/src/init.cpp
index 84b0108ea8..efaf821f4f 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -207,6 +207,7 @@ void Shutdown()
 
     StopTorControl();
     UnregisterNodeSignals(GetNodeSignals());
+    DumpMempool();
 
     if (fFeeEstimatesInitialized)
     {
@@ -659,6 +660,8 @@ void ThreadImport(std::vector<boost::filesystem::path> vImportFiles)
         LogPrintf("Stopping after block import\n");
         StartShutdown();
     }
+
+    LoadMempool();
 }
 
 /** Sanity checks
diff --git a/src/main.cpp b/src/main.cpp
index 5e17ec6251..11abc0d175 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1135,7 +1135,7 @@ std::string FormatStateMessage(const CValidationState &state)
 }
 
 bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const CTransaction& tx, bool fLimitFree,
-                              bool* pfMissingInputs, bool fOverrideMempoolLimit, const CAmount& nAbsurdFee,
+                              bool* pfMissingInputs, int64_t nAcceptTime, bool fOverrideMempoolLimit, const CAmount& nAbsurdFee,
                               std::vector<uint256>& vHashTxnToUncache)
 {
     const uint256 hash = tx.GetHash();
@@ -1308,7 +1308,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
             }
         }
 
-        CTxMemPoolEntry entry(tx, nFees, GetTime(), dPriority, chainActive.Height(), pool.HasNoInputsOf(tx), inChainInputValue, fSpendsCoinbase, nSigOpsCost, lp);
+        CTxMemPoolEntry entry(tx, nFees, nAcceptTime, dPriority, chainActive.Height(), pool.HasNoInputsOf(tx), inChainInputValue, fSpendsCoinbase, nSigOpsCost, lp);
         unsigned int nSize = entry.GetTxSize();
 
         // Check that the transaction doesn't have an excessive number of
@@ -1572,11 +1572,11 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
     return true;
 }
 
-bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
-                        bool* pfMissingInputs, bool fOverrideMempoolLimit, const CAmount nAbsurdFee)
+bool AcceptToMemoryPoolWithTime(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
+                        bool* pfMissingInputs, int64_t nAcceptTime, bool fOverrideMempoolLimit, const CAmount nAbsurdFee)
 {
     std::vector<uint256> vHashTxToUncache;
-    bool res = AcceptToMemoryPoolWorker(pool, state, tx, fLimitFree, pfMissingInputs, fOverrideMempoolLimit, nAbsurdFee, vHashTxToUncache);
+    bool res = AcceptToMemoryPoolWorker(pool, state, tx, fLimitFree, pfMissingInputs, nAcceptTime, fOverrideMempoolLimit, nAbsurdFee, vHashTxToUncache);
     if (!res) {
         BOOST_FOREACH(const uint256& hashTx, vHashTxToUncache)
             pcoinsTip->Uncache(hashTx);
@@ -1584,6 +1584,12 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     return res;
 }
 
+bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
+                        bool* pfMissingInputs, bool fOverrideMempoolLimit, const CAmount nAbsurdFee)
+{
+    return AcceptToMemoryPoolWithTime(pool, state, tx, fLimitFree, pfMissingInputs, GetTime(), fOverrideMempoolLimit, nAbsurdFee);
+}
+
 /** Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock */
 bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
 {
@@ -6929,6 +6935,119 @@ int VersionBitsTipStateSinceHeight(const Consensus::Params& params, Consensus::D
     return VersionBitsStateSinceHeight(chainActive.Tip(), params, pos, versionbitscache);
 }
 
+static const uint64_t MEMPOOL_DUMP_VERSION = 1;
+
+bool LoadMempool(void)
+{
+    int64_t nExpiryTimeout = GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
+    FILE* filestr = fopen((GetDataDir() / "mempool.dat").string().c_str(), "r");
+    CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
+    if (file.IsNull()) {
+        LogPrintf("Failed to open mempool file from disk. Continuing anyway.\n");
+        return false;
+    }
+
+    int64_t count = 0;
+    int64_t skipped = 0;
+    int64_t failed = 0;
+    int64_t nNow = GetTime();
+
+    try {
+        uint64_t version;
+        file >> version;
+        if (version != MEMPOOL_DUMP_VERSION) {
+            return false;
+        }
+        uint64_t num;
+        file >> num;
+        double prioritydummy = 0;
+        while (num--) {
+            CTransaction tx;
+            int64_t nTime;
+            int64_t nFeeDelta;
+            file >> tx;
+            file >> nTime;
+            file >> nFeeDelta;
+
+            CAmount amountdelta = nFeeDelta;
+            if (amountdelta) {
+                mempool.PrioritiseTransaction(tx.GetHash(), tx.GetHash().ToString(), prioritydummy, amountdelta);
+            }
+            CValidationState state;
+            if (nTime + nExpiryTimeout > nNow) {
+                LOCK(cs_main);
+                AcceptToMemoryPoolWithTime(mempool, state, tx, true, NULL, nTime);
+                if (state.IsValid()) {
+                    ++count;
+                } else {
+                    ++failed;
+                }
+            } else {
+                ++skipped;
+            }
+        }
+        std::map<uint256, CAmount> mapDeltas;
+        file >> mapDeltas;
+
+        for (const auto& i : mapDeltas) {
+            mempool.PrioritiseTransaction(i.first, i.first.ToString(), prioritydummy, i.second);
+        }
+    } catch (const std::exception& e) {
+        LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
+        return false;
+    }
+
+    LogPrintf("Imported mempool transactions from disk: %i successes, %i failed, %i expired\n", count, failed, skipped);
+    return true;
+}
+
+void DumpMempool(void)
+{
+    int64_t start = GetTimeMicros();
+
+    std::map<uint256, CAmount> mapDeltas;
+    std::vector<TxMempoolInfo> vinfo;
+
+    {
+        LOCK(mempool.cs);
+        for (const auto &i : mempool.mapDeltas) {
+            mapDeltas[i.first] = i.second.first;
+        }
+        vinfo = mempool.infoAll();
+    }
+
+    int64_t mid = GetTimeMicros();
+
+    try {
+        FILE* filestr = fopen((GetDataDir() / "mempool.dat.new").string().c_str(), "w");
+        if (!filestr) {
+            return;
+        }
+
+        CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
+
+        uint64_t version = MEMPOOL_DUMP_VERSION;
+        file << version;
+
+        file << (uint64_t)vinfo.size();
+        for (const auto& i : vinfo) {
+            file << *(i.tx);
+            file << (int64_t)i.nTime;
+            file << (int64_t)i.nFeeDelta;
+            mapDeltas.erase(i.tx->GetHash());
+        }
+
+        file << mapDeltas;
+        FileCommit(file.Get());
+        file.fclose();
+        RenameOver(GetDataDir() / "mempool.dat.new", GetDataDir() / "mempool.dat");
+        int64_t last = GetTimeMicros();
+        LogPrintf("Dumped mempool: %gs to copy, %gs to dump\n", (mid-start)*0.000001, (last-mid)*0.000001);
+    } catch (const std::exception& e) {
+        LogPrintf("Failed to dump mempool: %s. Continuing anyway.\n", e.what());
+    }
+}
+
 class CMainCleanup
 {
 public:
diff --git a/src/main.h b/src/main.h
index 3eab9b89da..4c6af95142 100644
--- a/src/main.h
+++ b/src/main.h
@@ -291,6 +291,10 @@ void PruneAndFlush();
 bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                         bool* pfMissingInputs, bool fOverrideMempoolLimit=false, const CAmount nAbsurdFee=0);
 
+/** (try to) add transaction to memory pool with a specified acceptance time **/
+bool AcceptToMemoryPoolWithTime(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
+                        bool* pfMissingInputs, int64_t nAcceptTime, bool fOverrideMempoolLimit=false, const CAmount nAbsurdFee=0);
+
 /** Convert CValidationState to a human-readable message for logging */
 std::string FormatStateMessage(const CValidationState &state);
 
@@ -529,6 +533,12 @@ static const unsigned int REJECT_ALREADY_KNOWN = 0x101;
 /** Transaction conflicts with a transaction already known */
 static const unsigned int REJECT_CONFLICT = 0x102;
 
+/** Dump the mempool to disk. */
+void DumpMempool();
+
+/** Load the mempool from disk. */
+bool LoadMempool();
+
 // The following things handle network-processing logic
 // (and should be moved to a separate file)
 
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index e5d28ac2ea..313d33507f 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -833,6 +833,10 @@ void CTxMemPool::queryHashes(vector<uint256>& vtxid)
     }
 }
 
+static TxMempoolInfo GetInfo(CTxMemPool::indexed_transaction_set::const_iterator it) {
+    return TxMempoolInfo{it->GetSharedTx(), it->GetTime(), CFeeRate(it->GetFee(), it->GetTxSize()), it->GetModifiedFee() - it->GetFee()};
+}
+
 std::vector<TxMempoolInfo> CTxMemPool::infoAll() const
 {
     LOCK(cs);
@@ -841,7 +845,7 @@ std::vector<TxMempoolInfo> CTxMemPool::infoAll() const
     std::vector<TxMempoolInfo> ret;
     ret.reserve(mapTx.size());
     for (auto it : iters) {
-        ret.push_back(TxMempoolInfo{it->GetSharedTx(), it->GetTime(), CFeeRate(it->GetFee(), it->GetTxSize())});
+        ret.push_back(GetInfo(it));
     }
 
     return ret;
@@ -862,7 +866,7 @@ TxMempoolInfo CTxMemPool::info(const uint256& hash) const
     indexed_transaction_set::const_iterator i = mapTx.find(hash);
     if (i == mapTx.end())
         return TxMempoolInfo();
-    return TxMempoolInfo{i->GetSharedTx(), i->GetTime(), CFeeRate(i->GetFee(), i->GetTxSize())};
+    return GetInfo(i);
 }
 
 CFeeRate CTxMemPool::estimateFee(int nBlocks) const
diff --git a/src/txmempool.h b/src/txmempool.h
index bb2638c3b7..9b0ca4655e 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -329,6 +329,9 @@ struct TxMempoolInfo
 
     /** Feerate of the transaction. */
     CFeeRate feeRate;
+
+    /** The fee delta. */
+    int64_t nFeeDelta;
 };
 
 /**