Merge #17135: gui: Make polling in ClientModel asynchronous

6b6be41 gui: Make polling in ClientModel asynchronous (João Barbosa)

Pull request description:

  After #14193 `ClientModel::updateTimer` can take some time, as such the GUI hangs, like #17112.

  Fixes this by polling in a background thread and updating the GUI asynchronously.

ACKs for top commit:
  laanwj:
    ACK 6b6be41
  Sjors:
    Code review re-ACK 6b6be41; only replaced the scary cast with `{ timer->start(); }`

Tree-SHA512: fd98b0c6535441aee3ee03c48b58b4b1f9bdd172ec6b8150da883022f719df34cabfd4c133412bf410e7f709f7bf1e9ef16dca05ef1f3689d526ceaeee51de38

Author: laanwj

src/qt/clientmodel.cpp

@@ -19,6 +19,7 @@
 #include <stdint.h>
 
 #include <QDebug>
+#include <QThread>
 #include <QTimer>
 
 static int64_t nLastHeaderTipUpdateNotification = 0;
@@ -30,22 +31,36 @@ ClientModel::ClientModel(interfaces::Node& node, OptionsModel *_optionsModel, QO
     optionsModel(_optionsModel),
     peerTableModel(nullptr),
     banTableModel(nullptr),
-    pollTimer(nullptr)
+    m_thread(new QThread(this))
 {
     cachedBestHeaderHeight = -1;
     cachedBestHeaderTime = -1;
     peerTableModel = new PeerTableModel(m_node, this);
     banTableModel = new BanTableModel(m_node, this);
-    pollTimer = new QTimer(this);
-    connect(pollTimer, &QTimer::timeout, this, &ClientModel::updateTimer);
-    pollTimer->start(MODEL_UPDATE_DELAY);
+
+    QTimer* timer = new QTimer;
+    timer->setInterval(MODEL_UPDATE_DELAY);
+    connect(timer, &QTimer::timeout, [this] {
+        // no locking required at this point
+        // the following calls will acquire the required lock
+        Q_EMIT mempoolSizeChanged(m_node.getMempoolSize(), m_node.getMempoolDynamicUsage());
+        Q_EMIT bytesChanged(m_node.getTotalBytesRecv(), m_node.getTotalBytesSent());
+    });
+    connect(m_thread, &QThread::finished, timer, &QObject::deleteLater);
+    connect(m_thread, &QThread::started, [timer] { timer->start(); });
+    // move timer to thread so that polling doesn't disturb main event loop
+    timer->moveToThread(m_thread);
+    m_thread->start();
 
     subscribeToCoreSignals();
 }
 
 ClientModel::~ClientModel()
 {
     unsubscribeFromCoreSignals();
+
+    m_thread->quit();
+    m_thread->wait();
 }
 
 int ClientModel::getNumConnections(unsigned int flags) const
@@ -90,14 +105,6 @@ int64_t ClientModel::getHeaderTipTime() const
     return cachedBestHeaderTime;
 }
 
-void ClientModel::updateTimer()
-{
-    // no locking required at this point
-    // the following calls will acquire the required lock
-    Q_EMIT mempoolSizeChanged(m_node.getMempoolSize(), m_node.getMempoolDynamicUsage());
-    Q_EMIT bytesChanged(m_node.getTotalBytesRecv(), m_node.getTotalBytesSent());
-}
-
 void ClientModel::updateNumConnections(int numConnections)
 {
     Q_EMIT numConnectionsChanged(numConnections);

src/qt/clientmodel.h

@@ -90,7 +90,8 @@ class ClientModel : public QObject
     PeerTableModel *peerTableModel;
     BanTableModel *banTableModel;
 
-    QTimer *pollTimer;
+    //! A thread to interact with m_node asynchronously
+    QThread* const m_thread;
 
     void subscribeToCoreSignals();
     void unsubscribeFromCoreSignals();
@@ -110,7 +111,6 @@ class ClientModel : public QObject
     void showProgress(const QString &title, int nProgress);
 
 public Q_SLOTS:
-    void updateTimer();
     void updateNumConnections(int numConnections);
     void updateNetworkActive(bool networkActive);
     void updateAlert();