feestimator: encapsulate estimation file logic

This moves the fee_estimates file management to the CBlockPolicyEstimator
Flush() method.

Co-authored-by: John Newbery <john@johnnewbery.com>
Signed-off-by: Antoine Poinsot <darosior@protonmail.com>

src/init.cpp

@@ -98,8 +98,6 @@ static const bool DEFAULT_STOPAFTERBLOCKIMPORT = false;
 #define MIN_CORE_FILEDESCRIPTORS 150
 #endif
 
-static const char* FEE_ESTIMATES_FILENAME="fee_estimates.dat";
-
 static const char* DEFAULT_ASMAP_FILENAME="ip_asn.map";
 
 /**
@@ -235,17 +233,8 @@ void Shutdown(NodeContext& node)
         DumpMempool(*node.mempool);
     }
 
-    if (node.fee_estimator) {
-        node.fee_estimator->FlushUnconfirmed();
-        fs::path est_path = GetDataDir() / FEE_ESTIMATES_FILENAME;
-        CAutoFile est_fileout(fsbridge::fopen(est_path, "wb"), SER_DISK, CLIENT_VERSION);
-        if (!est_fileout.IsNull()) {
-            node.fee_estimator->Write(est_fileout);
-        } else {
-            LogPrintf("%s: Failed to write fee estimates to %s\n", __func__, est_path.string());
-        }
-    }
-
+    // Drop transactions we were still watching, and record fee estimations.
+    if (node.fee_estimator) node.fee_estimator->Flush();
 
     // FlushStateToDisk generates a ChainStateFlushed callback, which we should avoid missing
     if (node.chainman) {
@@ -1790,12 +1779,6 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
         return false;
     }
 
-    fs::path est_path = GetDataDir() / FEE_ESTIMATES_FILENAME;
-    CAutoFile est_filein(fsbridge::fopen(est_path, "rb"), SER_DISK, CLIENT_VERSION);
-    // Allowed to fail as this file IS missing on first startup.
-    if (node.fee_estimator && !est_filein.IsNull()) {
-        node.fee_estimator->Read(est_filein);
-    }
     // ********************************************************* Step 8: start indexers
     if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
         g_txindex = MakeUnique<TxIndex>(nTxIndexCache, false, fReindex);

src/policy/fees.cpp

@@ -10,6 +10,8 @@
 #include <txmempool.h>
 #include <util/system.h>
 
+static const char* FEE_ESTIMATES_FILENAME="fee_estimates.dat";
+
 static constexpr double INF_FEERATE = 1e99;
 
 std::string StringForFeeEstimateHorizon(FeeEstimateHorizon horizon) {
@@ -489,6 +491,7 @@ CBlockPolicyEstimator::CBlockPolicyEstimator()
 {
     static_assert(MIN_BUCKET_FEERATE > 0, "Min feerate must be nonzero");
     size_t bucketIndex = 0;
+
     for (double bucketBoundary = MIN_BUCKET_FEERATE; bucketBoundary <= MAX_BUCKET_FEERATE; bucketBoundary *= FEE_SPACING, bucketIndex++) {
         buckets.push_back(bucketBoundary);
         bucketMap[bucketBoundary] = bucketIndex;
@@ -500,6 +503,13 @@ CBlockPolicyEstimator::CBlockPolicyEstimator()
     feeStats = std::unique_ptr<TxConfirmStats>(new TxConfirmStats(buckets, bucketMap, MED_BLOCK_PERIODS, MED_DECAY, MED_SCALE));
     shortStats = std::unique_ptr<TxConfirmStats>(new TxConfirmStats(buckets, bucketMap, SHORT_BLOCK_PERIODS, SHORT_DECAY, SHORT_SCALE));
     longStats = std::unique_ptr<TxConfirmStats>(new TxConfirmStats(buckets, bucketMap, LONG_BLOCK_PERIODS, LONG_DECAY, LONG_SCALE));
+
+    // If the fee estimation file is present, read recorded estimations
+    fs::path est_filepath = GetDataDir() / FEE_ESTIMATES_FILENAME;
+    CAutoFile est_file(fsbridge::fopen(est_filepath, "rb"), SER_DISK, CLIENT_VERSION);
+    if (est_file.IsNull() || !Read(est_file)) {
+        LogPrintf("Failed to read fee estimates from %s. Continue anyway.\n", est_filepath.string());
+    }
 }
 
 CBlockPolicyEstimator::~CBlockPolicyEstimator()
@@ -856,6 +866,15 @@ CFeeRate CBlockPolicyEstimator::estimateSmartFee(int confTarget, FeeCalculation
     return CFeeRate(llround(median));
 }
 
+void CBlockPolicyEstimator::Flush() {
+    FlushUnconfirmed();
+
+    fs::path est_filepath = GetDataDir() / FEE_ESTIMATES_FILENAME;
+    CAutoFile est_file(fsbridge::fopen(est_filepath, "wb"), SER_DISK, CLIENT_VERSION);
+    if (est_file.IsNull() || !Write(est_file)) {
+        LogPrintf("Failed to write fee estimates to %s\n", est_filepath.string());
+    }
+}
 
 bool CBlockPolicyEstimator::Write(CAutoFile& fileout) const
 {

src/policy/fees.h

@@ -215,6 +215,9 @@ public:
     /** Calculation of highest target that estimates are tracked for */
     unsigned int HighestTargetTracked(FeeEstimateHorizon horizon) const;
 
+    /** Drop still unconfirmed transactions and record current estimations, if the fee estimation file is present. */
+    void Flush();
+
 private:
     mutable RecursiveMutex m_cs_fee_estimator;