Merge #18766: Disable fee estimation in blocksonly mode (by removing the fee estimates global)

4e28753f60613ecd35cdef87bef5f99c302c3fbd feestimator: encapsulate estimation file logic (Antoine Poinsot)
e8ea6ad9c16997bdc7e22a20eca16e234290b7ff init: don't create a CBlockPolicyEstimator if we don't relay transactions (Antoine Poinsot)
86ff2cf202bfb9d9b50800b8ffe3fead3f77f5fa Remove the remaining fee estimation globals (Antoine Poinsot)
03bfeee957ab7e3b6aece82b9561774648094f54 interface: remove unused estimateSmartFee method from node (Antoine Poinsot)

Pull request description:

  If the `blocksonly` mode is turned on after running with transaction
  relay enabled for a while, the fee estimation will serve outdated data
  to both the internal wallet and to external applications that might be
  feerate-sensitive and make use of `estimatesmartfee` (for example a
  Lightning Network node).

  This has already caused issues (for example https://github.com/bitcoin/bitcoin/issues/16840 (C-lightning), or https://github.com/lightningnetwork/lnd/issues/2562 (LND)) and it seems prudent to fail rather than to give inaccurate values.

  This fixes #16840, and closes #16890 which tried to fix the symptoms (RPC) but not the cause as mentioned by sdaftuar :
  > If this is a substantial problem, then I would think we should take action to protect our own wallet users as well (rather than hide the results of what our fee estimation would do!).

ACKs for top commit:
  MarcoFalke:
    re-ACK 4e28753f60 👋
  jnewbery:
    utACK 4e28753f60613ecd35cdef87bef5f99c302c3fbd

Tree-SHA512: c869cf03b86d8194002970bbc84662dae76874967949b9be0d9a4511a1eabcb1627c38aca3154da9dcece1a4c49ec02bd4f9fcca2ec310986e07904559e63ba8

13 files changed, 69 insertions, 52 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 9756a7dfb3..371399de9e 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -85,7 +85,6 @@
 #include <zmq/zmqrpc.h>
 #endif
 
-static bool fFeeEstimatesInitialized = false;
 static const bool DEFAULT_PROXYRANDOMIZE = true;
 static const bool DEFAULT_REST_ENABLE = false;
 static const bool DEFAULT_STOPAFTERBLOCKIMPORT = false;
@@ -99,8 +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";
 
 /**
@@ -236,17 +233,8 @@ void Shutdown(NodeContext& node)
         DumpMempool(*node.mempool);
     }
 
-    if (fFeeEstimatesInitialized)
-    {
-        ::feeEstimator.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())
-            ::feeEstimator.Write(est_fileout);
-        else
-            LogPrintf("%s: Failed to write fee estimates to %s\n", __func__, est_path.string());
-        fFeeEstimatesInitialized = false;
-    }
+    // 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) {
@@ -304,6 +292,7 @@ void Shutdown(NodeContext& node)
     globalVerifyHandle.reset();
     ECC_Stop();
     node.mempool.reset();
+    node.fee_estimator.reset();
     node.chainman = nullptr;
     node.scheduler.reset();
 
@@ -1384,14 +1373,24 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
     // is not yet setup and may end up being set up twice if we
     // need to reindex later.
 
+    // see Step 2: parameter interactions for more information about these
+    fListen = args.GetBoolArg("-listen", DEFAULT_LISTEN);
+    fDiscover = args.GetBoolArg("-discover", true);
+    g_relay_txes = !args.GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY);
+
     assert(!node.banman);
     node.banman = MakeUnique<BanMan>(GetDataDir() / "banlist.dat", &uiInterface, args.GetArg("-bantime", DEFAULT_MISBEHAVING_BANTIME));
     assert(!node.connman);
     node.connman = MakeUnique<CConnman>(GetRand(std::numeric_limits<uint64_t>::max()), GetRand(std::numeric_limits<uint64_t>::max()), args.GetBoolArg("-networkactive", true));
 
+    assert(!node.fee_estimator);
+    // Don't initialize fee estimation with old data if we don't relay transactions,
+    // as they would never get updated.
+    if (g_relay_txes) node.fee_estimator = std::make_unique<CBlockPolicyEstimator>();
+
     assert(!node.mempool);
     int check_ratio = std::min<int>(std::max<int>(args.GetArg("-checkmempool", chainparams.DefaultConsistencyChecks() ? 1 : 0), 0), 1000000);
-    node.mempool = MakeUnique<CTxMemPool>(&::feeEstimator, check_ratio);
+    node.mempool = std::make_unique<CTxMemPool>(node.fee_estimator.get(), check_ratio);
 
     assert(!node.chainman);
     node.chainman = &g_chainman;
@@ -1473,11 +1472,6 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
         }
     }
 
-    // see Step 2: parameter interactions for more information about these
-    fListen = args.GetBoolArg("-listen", DEFAULT_LISTEN);
-    fDiscover = args.GetBoolArg("-discover", true);
-    g_relay_txes = !args.GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY);
-
     for (const std::string& strAddr : args.GetArgs("-externalip")) {
         CService addrLocal;
         if (Lookup(strAddr, addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
@@ -1785,13 +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 (!est_filein.IsNull())
-        ::feeEstimator.Read(est_filein);
-    fFeeEstimatesInitialized = true;
-
     // ********************************************************* Step 8: start indexers
     if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
         g_txindex = MakeUnique<TxIndex>(nTxIndexCache, false, fReindex);
diff --git a/src/interfaces/node.h b/src/interfaces/node.h
index 5079be038e..36f76aeb4f 100644
--- a/src/interfaces/node.h
+++ b/src/interfaces/node.h
@@ -151,9 +151,6 @@ public:
     //! Get network active.
     virtual bool getNetworkActive() = 0;
 
-    //! Estimate smart fee.
-    virtual CFeeRate estimateSmartFee(int num_blocks, bool conservative, int* returned_target = nullptr) = 0;
-
     //! Get dust relay fee.
     virtual CFeeRate getDustRelayFee() = 0;
 
diff --git a/src/node/context.cpp b/src/node/context.cpp
index 49d0c37235..958221a913 100644
--- a/src/node/context.cpp
+++ b/src/node/context.cpp
@@ -8,6 +8,7 @@
 #include <interfaces/chain.h>
 #include <net.h>
 #include <net_processing.h>
+#include <policy/fees.h>
 #include <scheduler.h>
 #include <txmempool.h>
 
diff --git a/src/node/context.h b/src/node/context.h
index 3228831ed1..9b611bf8f5 100644
--- a/src/node/context.h
+++ b/src/node/context.h
@@ -12,6 +12,7 @@
 
 class ArgsManager;
 class BanMan;
+class CBlockPolicyEstimator;
 class CConnman;
 class CScheduler;
 class CTxMemPool;
@@ -36,6 +37,7 @@ class WalletClient;
 struct NodeContext {
     std::unique_ptr<CConnman> connman;
     std::unique_ptr<CTxMemPool> mempool;
+    std::unique_ptr<CBlockPolicyEstimator> fee_estimator;
     std::unique_ptr<PeerManager> peerman;
     ChainstateManager* chainman{nullptr}; // Currently a raw pointer because the memory is not managed by this struct
     std::unique_ptr<BanMan> banman;
diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index a8c8be05fb..da3e759e38 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -221,15 +221,6 @@ public:
         }
     }
     bool getNetworkActive() override { return m_context->connman && m_context->connman->GetNetworkActive(); }
-    CFeeRate estimateSmartFee(int num_blocks, bool conservative, int* returned_target = nullptr) override
-    {
-        FeeCalculation fee_calc;
-        CFeeRate result = ::feeEstimator.estimateSmartFee(num_blocks, &fee_calc, conservative);
-        if (returned_target) {
-            *returned_target = fee_calc.returnedTarget;
-        }
-        return result;
-    }
     CFeeRate getDustRelayFee() override { return ::dustRelayFee; }
     UniValue executeRpc(const std::string& command, const UniValue& params, const std::string& uri) override
     {
@@ -601,11 +592,13 @@ public:
     }
     CFeeRate estimateSmartFee(int num_blocks, bool conservative, FeeCalculation* calc) override
     {
-        return ::feeEstimator.estimateSmartFee(num_blocks, calc, conservative);
+        if (!m_node.fee_estimator) return {};
+        return m_node.fee_estimator->estimateSmartFee(num_blocks, calc, conservative);
     }
     unsigned int estimateMaxBlocks() override
     {
-        return ::feeEstimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
+        if (!m_node.fee_estimator) return 0;
+        return m_node.fee_estimator->HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
     }
     CFeeRate mempoolMinFee() override
     {
diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index 0f31093dbb..f6e378866c 100644
--- a/src/policy/fees.cpp
+++ b/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
 {
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 8ea8816dc3..dd9f530c99 100644
--- a/src/policy/fees.h
+++ b/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;
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 392073d047..57327e6004 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -17,6 +17,7 @@
 #include <node/coinstats.h>
 #include <node/context.h>
 #include <node/utxo_snapshot.h>
+#include <policy/fees.h>
 #include <policy/feerate.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
@@ -81,6 +82,15 @@ ChainstateManager& EnsureChainman(const util::Ref& context)
     return *node.chainman;
 }
 
+CBlockPolicyEstimator& EnsureFeeEstimator(const util::Ref& context)
+{
+    NodeContext& node = EnsureNodeContext(context);
+    if (!node.fee_estimator) {
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "Fee estimation disabled");
+    }
+    return *node.fee_estimator;
+}
+
 /* Calculate the difficulty for a given block index.
  */
 double GetDifficulty(const CBlockIndex* blockindex)
diff --git a/src/rpc/blockchain.h b/src/rpc/blockchain.h
index 5b362bf211..91766aacc9 100644
--- a/src/rpc/blockchain.h
+++ b/src/rpc/blockchain.h
@@ -15,6 +15,7 @@ extern RecursiveMutex cs_main;
 
 class CBlock;
 class CBlockIndex;
+class CBlockPolicyEstimator;
 class CTxMemPool;
 class ChainstateManager;
 class UniValue;
@@ -54,5 +55,6 @@ void CalculatePercentilesByWeight(CAmount result[NUM_GETBLOCKSTATS_PERCENTILES],
 NodeContext& EnsureNodeContext(const util::Ref& context);
 CTxMemPool& EnsureMemPool(const util::Ref& context);
 ChainstateManager& EnsureChainman(const util::Ref& context);
+CBlockPolicyEstimator& EnsureFeeEstimator(const util::Ref& context);
 
 #endif
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 7d45ad9434..798973850f 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -1059,7 +1059,10 @@ static RPCHelpMan estimatesmartfee()
 {
     RPCTypeCheck(request.params, {UniValue::VNUM, UniValue::VSTR});
     RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
-    unsigned int max_target = ::feeEstimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
+
+    CBlockPolicyEstimator& fee_estimator = EnsureFeeEstimator(request.context);
+
+    unsigned int max_target = fee_estimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
     unsigned int conf_target = ParseConfirmTarget(request.params[0], max_target);
     bool conservative = true;
     if (!request.params[1].isNull()) {
@@ -1073,7 +1076,7 @@ static RPCHelpMan estimatesmartfee()
     UniValue result(UniValue::VOBJ);
     UniValue errors(UniValue::VARR);
     FeeCalculation feeCalc;
-    CFeeRate feeRate = ::feeEstimator.estimateSmartFee(conf_target, &feeCalc, conservative);
+    CFeeRate feeRate = fee_estimator.estimateSmartFee(conf_target, &feeCalc, conservative);
     if (feeRate != CFeeRate(0)) {
         result.pushKV("feerate", ValueFromAmount(feeRate.GetFeePerK()));
     } else {
@@ -1144,7 +1147,10 @@ static RPCHelpMan estimaterawfee()
 {
     RPCTypeCheck(request.params, {UniValue::VNUM, UniValue::VNUM}, true);
     RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
-    unsigned int max_target = ::feeEstimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
+
+    CBlockPolicyEstimator& fee_estimator = EnsureFeeEstimator(request.context);
+
+    unsigned int max_target = fee_estimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
     unsigned int conf_target = ParseConfirmTarget(request.params[0], max_target);
     double threshold = 0.95;
     if (!request.params[1].isNull()) {
@@ -1161,9 +1167,9 @@ static RPCHelpMan estimaterawfee()
         EstimationResult buckets;
 
         // Only output results for horizons which track the target
-        if (conf_target > ::feeEstimator.HighestTargetTracked(horizon)) continue;
+        if (conf_target > fee_estimator.HighestTargetTracked(horizon)) continue;
 
-        feeRate = ::feeEstimator.estimateRawFee(conf_target, threshold, horizon, &buckets);
+        feeRate = fee_estimator.estimateRawFee(conf_target, threshold, horizon, &buckets);
         UniValue horizon_result(UniValue::VOBJ);
         UniValue errors(UniValue::VARR);
         UniValue passbucket(UniValue::VOBJ);
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index adf5970206..fffa29a1d3 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -16,6 +16,7 @@
 #include <net.h>
 #include <net_processing.h>
 #include <noui.h>
+#include <policy/fees.h>
 #include <pow.h>
 #include <rpc/blockchain.h>
 #include <rpc/register.h>
@@ -141,7 +142,8 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
 
     pblocktree.reset(new CBlockTreeDB(1 << 20, true));
 
-    m_node.mempool = MakeUnique<CTxMemPool>(&::feeEstimator, 1);
+    m_node.fee_estimator = std::make_unique<CBlockPolicyEstimator>();
+    m_node.mempool = std::make_unique<CTxMemPool>(m_node.fee_estimator.get(), 1);
 
     m_node.chainman = &::g_chainman;
     m_node.chainman->InitializeChainstate(*m_node.mempool);
diff --git a/src/validation.cpp b/src/validation.cpp
index 3aec96bc5a..2585345dee 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -22,7 +22,6 @@
 #include <logging/timer.h>
 #include <node/ui_interface.h>
 #include <optional.h>
-#include <policy/fees.h>
 #include <policy/policy.h>
 #include <policy/settings.h>
 #include <pow.h>
@@ -148,8 +147,6 @@ arith_uint256 nMinimumChainWork;
 
 CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE);
 
-CBlockPolicyEstimator feeEstimator;
-
 // Internal stuff
 namespace {
     CBlockIndex* pindexBestInvalid = nullptr;
diff --git a/src/validation.h b/src/validation.h
index ffb038ad75..6d8c6d431a 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -42,7 +42,6 @@ class CChainParams;
 class CInv;
 class CConnman;
 class CScriptCheck;
-class CBlockPolicyEstimator;
 class CTxMemPool;
 class ChainstateManager;
 class TxValidationState;
@@ -110,7 +109,6 @@ enum class SynchronizationState {
 };
 
 extern RecursiveMutex cs_main;
-extern CBlockPolicyEstimator feeEstimator;
 typedef std::unordered_map<uint256, CBlockIndex*, BlockHasher> BlockMap;
 extern Mutex g_best_block_mutex;
 extern std::condition_variable g_best_block_cv;