qt: mempool stats chart

Co-authored-by: Jonas Schnelli <dev@jonasschnelli.ch>
Co-authored-by: @RandyMcMillan <randy.lee.mcmillan@gmail.com>

Author: jonasschnelli

src/Makefile.qt.include

@@ -22,6 +22,7 @@ QT_FORMS_UI = \
   qt/forms/helpmessagedialog.ui \
   qt/forms/intro.ui \
   qt/forms/modaloverlay.ui \
+  qt/forms/mempoolstats.ui \
   qt/forms/openuridialog.ui \
   qt/forms/optionsdialog.ui \
   qt/forms/overviewpage.ui \
@@ -54,6 +55,7 @@ QT_MOC_CPP = \
   qt/moc_intro.cpp \
   qt/moc_macdockiconhandler.cpp \
   qt/moc_macnotificationhandler.cpp \
+  qt/moc_mempoolstats.cpp \
   qt/moc_modaloverlay.cpp \
   qt/moc_notificator.cpp \
   qt/moc_openuridialog.cpp \
@@ -126,6 +128,7 @@ BITCOIN_QT_H = \
   qt/macdockiconhandler.h \
   qt/macnotificationhandler.h \
   qt/macos_appnap.h \
+  qt/mempoolstats.h \
   qt/modaloverlay.h \
   qt/networkstyle.h \
   qt/notificator.h \
@@ -228,6 +231,7 @@ BITCOIN_QT_BASE_CPP = \
   qt/csvmodelwriter.cpp \
   qt/guiutil.cpp \
   qt/intro.cpp \
+  qt/mempoolstats.cpp \
   qt/modaloverlay.cpp \
   qt/networkstyle.cpp \
   qt/notificator.cpp \

src/interfaces/node.h

@@ -49,6 +49,24 @@ struct BlockAndHeaderTipInfo
     double verification_progress;
 };
 
+class mempool_feeinfo {
+public:
+    uint64_t total_size;
+    uint64_t total_fee;
+    uint64_t tx_count;
+    CAmount fee_from;
+    CAmount fee_to;
+
+    //TODO: remove
+    // added for storing and loading a mempool set during development to avoid waiting hours for collecting enought samples
+    SERIALIZE_METHODS(mempool_feeinfo, obj)
+    {
+        READWRITE(obj.total_size, obj.total_fee, obj.tx_count, obj.fee_from, obj.fee_to);
+    }
+};
+
+typedef std::vector<mempool_feeinfo> mempool_feehistogram;
+
 //! Top-level interface for a bitcoin node (bitcoind process).
 class Node
 {
@@ -122,6 +140,9 @@ class Node
     //! Get mempool dynamic usage.
     virtual size_t getMempoolDynamicUsage() = 0;
 
+    //! Get mempool fee histogram
+    virtual mempool_feehistogram getMempoolFeeHistogram() = 0;
+
     //! Get header tip height and time.
     virtual bool getHeaderTip(int& height, int64_t& block_time) = 0;
 

src/node/interfaces.cpp

@@ -174,6 +174,58 @@ class NodeImpl : public Node
     int64_t getTotalBytesSent() override { return m_context->connman ? m_context->connman->GetTotalBytesSent() : 0; }
     size_t getMempoolSize() override { return m_context->mempool ? m_context->mempool->size() : 0; }
     size_t getMempoolDynamicUsage() override { return m_context->mempool ? m_context->mempool->DynamicMemoryUsage() : 0; }
+    interfaces::mempool_feehistogram getMempoolFeeHistogram() override {
+         /* TODO: define log scale formular for dynamically creating the
+          * feelimits but with the property of not constantly changing
+          * (and thus screw up client implementations) */
+         static const std::vector<CAmount> feelimits{1, 2, 3, 4, 5, 6, 7, 8, 10,
+          12, 14, 17, 20, 25, 30, 40, 50, 60, 70, 80, 100,
+          120, 140, 170, 200, 250, 300, 400, 500, 600, 700, 800, 1000,
+          1200, 1400, 1700, 2000, 2500, 3000, 4000, 5000, 6000, 7000, 8000, 10000};
+
+         /* keep histogram per...
+          * ... cumulated tx sizes
+          * ... txns (count)
+          * ... cumulated fees */
+         std::vector<uint64_t> sizes(feelimits.size(), 0);
+         std::vector<uint64_t> count(feelimits.size(), 0);
+         std::vector<uint64_t> fees(feelimits.size(), 0);
+
+         {
+             LOCK(m_context->mempool->cs);
+             for (const CTxMemPoolEntry& e : m_context->mempool->mapTx) {
+                 int size = (int)e.GetTxSize();
+                 CAmount fee = e.GetFee();
+                 uint64_t asize = e.GetSizeWithAncestors();
+                 CAmount afees = e.GetModFeesWithAncestors();
+                 uint64_t dsize = e.GetSizeWithDescendants();
+                 CAmount dfees = e.GetModFeesWithDescendants();
+
+                 CAmount fpb = fee / size; //fee per byte
+                 CAmount afpb = afees / asize; //fee per byte including ancestors
+                 CAmount dfpb = dfees / dsize; //fee per byte including descendants
+                 CAmount tfpb = (afees + dfees - fee) / (asize + dsize - size);
+                 CAmount feeperbyte = std::max(std::min(dfpb, tfpb), std::min(fpb, afpb));
+
+                 // distribute feerates into feelimits
+                 for (size_t i = 0; i < feelimits.size(); i++) {
+                     if (feeperbyte >= feelimits[i] && (i == feelimits.size() - 1 || feeperbyte < feelimits[i + 1])) {
+                         sizes[i] += size;
+                         count[i]++;
+                         fees[i] += fee;
+                         break;
+                     }
+                 }
+             }
+         }
+         interfaces::mempool_feehistogram feeinfo;
+         for (size_t i = 0; i < feelimits.size(); i++) {
+             feeinfo.push_back({sizes[i], fees[i], count[i], feelimits[i], (i == feelimits.size() - 1 ? std::numeric_limits<int64_t>::max() : feelimits[i + 1])});
+         }
+
+         return feeinfo;
+     }
+
     bool getHeaderTip(int& height, int64_t& block_time) override
     {
         LOCK(::cs_main);

src/qt/clientmodel.cpp

@@ -13,6 +13,7 @@
 #include <clientversion.h>
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
+#include <memusage.h>
 #include <net.h>
 #include <netbase.h>
 #include <util/system.h>
@@ -23,6 +24,7 @@
 #include <functional>
 
 #include <QDebug>
+#include <QMutexLocker>
 #include <QThread>
 #include <QTimer>
 
@@ -51,6 +53,19 @@ ClientModel::ClientModel(interfaces::Node& node, OptionsModel *_optionsModel, QO
     connect(timer, &QTimer::timeout, [this] {
         // no locking required at this point
         // the following calls will acquire the required lock
+
+        int64_t now = GetTime();
+        if (m_mempool_feehist_last_sample_timestamp == 0 || static_cast<uint64_t>(m_mempool_feehist_last_sample_timestamp)+static_cast<uint64_t>(m_mempool_collect_intervall) < static_cast<uint64_t>(now)) {
+            QMutexLocker locker(&m_mempool_locker);
+            interfaces::mempool_feehistogram fee_histogram = m_node.getMempoolFeeHistogram();
+            m_mempool_feehist.push_back({now, fee_histogram});
+            if (m_mempool_feehist.size() > m_mempool_max_samples) {
+                m_mempool_feehist.erase(m_mempool_feehist.begin(), m_mempool_feehist.begin()+1);
+            }
+            m_mempool_feehist_last_sample_timestamp = now;
+            Q_EMIT mempoolFeeHistChanged();
+        }
+
         Q_EMIT mempoolSizeChanged(m_node.getMempoolSize(), m_node.getMempoolDynamicUsage());
         Q_EMIT bytesChanged(m_node.getTotalBytesRecv(), m_node.getTotalBytesSent());
     });

src/qt/clientmodel.h

@@ -5,6 +5,7 @@
 #ifndef BITCOIN_QT_CLIENTMODEL_H
 #define BITCOIN_QT_CLIENTMODEL_H
 
+#include <QMutex>
 #include <QObject>
 #include <QDateTime>
 
@@ -13,18 +14,15 @@
 #include <sync.h>
 #include <uint256.h>
 
+#include <interfaces/node.h>
+
 class BanTableModel;
 class CBlockIndex;
 class OptionsModel;
 class PeerTableModel;
 class PeerTableSortProxy;
 enum class SynchronizationState;
 
-namespace interfaces {
-class Handler;
-class Node;
-}
-
 QT_BEGIN_NAMESPACE
 class QTimer;
 QT_END_NAMESPACE
@@ -87,6 +85,13 @@ class ClientModel : public QObject
     Mutex m_cached_tip_mutex;
     uint256 m_cached_tip_blocks GUARDED_BY(m_cached_tip_mutex){};
 
+    typedef std::pair<int64_t, std::vector<interfaces::mempool_feeinfo>> mempool_feehist_sample; //!< sample plus timestamp
+    mutable QMutex m_mempool_locker;
+    const static size_t m_mempool_max_samples{540};
+    const static size_t m_mempool_collect_intervall{20}; // 540*20 = 3h of sample window
+    std::vector<mempool_feehist_sample> m_mempool_feehist;
+    std::atomic<int64_t> m_mempool_feehist_last_sample_timestamp{0};
+
 private:
     interfaces::Node& m_node;
     std::unique_ptr<interfaces::Handler> m_handler_show_progress;
@@ -111,6 +116,7 @@ class ClientModel : public QObject
     void numConnectionsChanged(int count);
     void numBlocksChanged(int count, const QDateTime& blockDate, double nVerificationProgress, bool header, SynchronizationState sync_state);
     void mempoolSizeChanged(long count, size_t mempoolSizeInBytes);
+    void mempoolFeeHistChanged();
     void networkActiveChanged(bool networkActive);
     void alertsChanged(const QString &warnings);
     void bytesChanged(quint64 totalBytesIn, quint64 totalBytesOut);

src/qt/forms/debugwindow.ui

@@ -891,6 +891,44 @@
        </item>
       </layout>
      </widget>
+     <widget class="QWidget" name="tab_mempool">
+      <property name="minimumSize">
+       <size>
+        <width>747</width>
+        <height>0</height>
+       </size>
+      </property>
+      <attribute name="title">
+       <string>Mempool</string>
+      </attribute>
+      <layout class="QVBoxLayout" name="verticalLayout_9" stretch="0">
+       <property name="leftMargin">
+        <number>0</number>
+       </property>
+       <property name="topMargin">
+        <number>0</number>
+       </property>
+       <property name="rightMargin">
+        <number>0</number>
+       </property>
+       <property name="bottomMargin">
+        <number>0</number>
+       </property>
+       <item>
+        <widget class="MempoolStats" name="mempool_graph" native="true">
+         <property name="sizePolicy">
+          <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
+           <horstretch>0</horstretch>
+           <verstretch>0</verstretch>
+          </sizepolicy>
+         </property>
+         <property name="styleSheet">
+          <string notr="true">QScrollBar {height:0px;}</string>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </widget>
      <widget class="QWidget" name="tab_peers">
       <attribute name="title">
        <string>&amp;Peers</string>
@@ -1655,6 +1693,12 @@
     <slot>clear()</slot>
    </slots>
   </customwidget>
+  <customwidget>
+   <class>MempoolStats</class>
+   <extends>QWidget</extends>
+   <header>qt/mempoolstats.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <resources>
   <include location="../bitcoin.qrc"/>

src/qt/forms/mempoolstats.ui

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>MempoolStats</class>
+ <widget class="QWidget" name="MempoolStats">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>800</width>
+    <height>640</height>
+   </rect>
+  </property>
+  <property name="minimumSize">
+   <size>
+    <width>800</width>
+    <height>640</height>
+   </size>
+  </property>
+  <property name="windowTitle">
+   <string>Mempool Stats</string>
+  </property>
+  <layout class="QHBoxLayout" name="horizontalLayout">
+   <property name="leftMargin">
+    <number>0</number>
+   </property>
+   <property name="topMargin">
+    <number>0</number>
+   </property>
+   <property name="rightMargin">
+    <number>0</number>
+   </property>
+   <property name="bottomMargin">
+    <number>0</number>
+   </property>
+   <item>
+    <widget class="QGraphicsView" name="graphicsView">
+     <property name="horizontalScrollBarPolicy">
+      <enum>Qt::ScrollBarAlwaysOff</enum>
+     </property>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>