Greatly improved peer host name resolution with caching

src/peerlistwidget.cpp

@@ -308,8 +308,14 @@ void PeerListWidget::loadPeers(const QTorrentHandle &h, bool force_hostname_reso
       updatePeer(peer_ip, peer);
       old_peers_set.remove(peer_ip);
       if(force_hostname_resolution) {
-        if(resolver)
-          resolver->resolve(peer.ip);
+        if(resolver) {
+          QString host = resolver->getHostFromCache(peer.ip);
+          if(host.isNull()) {
+            resolver->resolve(peer.ip);
+          } else {
+            peerItems.value(peer_ip)->setData(host);
+          }
+        }
       }
     } else {
       // Add new peer
@@ -332,10 +338,17 @@ QStandardItem* PeerListWidget::addPeer(QString ip, peer_info peer) {
   int row = listModel->rowCount();
   // Adding Peer to peer list
   listModel->insertRow(row);
-  listModel->setData(listModel->index(row, IP), ip);
+  QString host;
+  if(resolver) {
+    host = resolver->getHostFromCache(peer.ip);
+  }
+  if(host.isNull())
+    listModel->setData(listModel->index(row, IP), ip);
+  else
+    listModel->setData(listModel->index(row, IP), host);
   listModel->setData(listModel->index(row, IP_HIDDEN), ip);
   // Resolve peer host name is asked
-  if(resolver)
+  if(resolver && host.isNull())
     resolver->resolve(peer.ip);
   if(display_flags) {
     QString country_name;
@@ -381,6 +394,6 @@ void PeerListWidget::updatePeer(QString ip, peer_info peer) {
 void PeerListWidget::handleResolved(QString ip, QString hostname) {
   QStandardItem *item = peerItems.value(ip, 0);
   if(item) {
-    listModel->setData(listModel->indexFromItem(item), hostname);
+    item->setData(hostname);
   }
 }

src/peerlistwidget.h

@@ -55,17 +55,6 @@ class PropertiesWidget;
 class PeerListWidget : public QTreeView {
   Q_OBJECT
 
-private:
-  QStandardItemModel *listModel;
-  PeerListDelegate *listDelegate;
-  QSortFilterProxyModel * proxyModel;
-  QHash<QString, QStandardItem*> peerItems;
-  QHash<QString, libtorrent::asio::ip::tcp::endpoint> peerEndpoints;
-  QSet<QString> missingFlags;
-  QPointer<ReverseResolution> resolver;
-  PropertiesWidget* properties;
-  bool display_flags;
-
 public:
   PeerListWidget(PropertiesWidget *parent);
   ~PeerListWidget();
@@ -86,6 +75,17 @@ protected slots:
   void limitUpRateSelectedPeers(QStringList peer_ips);
   void limitDlRateSelectedPeers(QStringList peer_ips);
   void banSelectedPeers(QStringList peer_ips);
+
+private:
+  QStandardItemModel *listModel;
+  PeerListDelegate *listDelegate;
+  QSortFilterProxyModel * proxyModel;
+  QHash<QString, QStandardItem*> peerItems;
+  QHash<QString, libtorrent::asio::ip::tcp::endpoint> peerEndpoints;
+  QSet<QString> missingFlags;
+  QPointer<ReverseResolution> resolver;
+  PropertiesWidget* properties;
+  bool display_flags;
 };
 
 #endif // PEERLISTWIDGET_H

src/reverseresolution.h

@@ -36,6 +36,7 @@
 #include <QWaitCondition>
 #include <QMutex>
 #include <QList>
+#include <QCache>
 #include "misc.h"
 
 #include <boost/version.hpp>
@@ -47,7 +48,8 @@
 
 using namespace libtorrent;
 
-#define MAX_THREADS 20
+const int MAX_THREADS = 20;
+const int CACHE_SIZE = 500;
 
 class ReverseResolutionST: public QThread {
   Q_OBJECT
@@ -58,7 +60,8 @@ private:
   bool stopped;
 
 public:
-  ReverseResolutionST(libtorrent::asio::io_service &ios, QObject *parent=0): QThread(parent), resolver(ios), stopped(false) {
+  ReverseResolutionST(libtorrent::asio::io_service &ios, QObject *parent=0):
+    QThread(parent), resolver(ios), stopped(false) {
 
   }
 
@@ -93,18 +96,11 @@ protected:
 
 class ReverseResolution: public QThread {
   Q_OBJECT
-
-private:
-  QQueue<libtorrent::asio::ip::tcp::endpoint> ips;
-  QMutex mut;
-  QWaitCondition cond;
-  bool stopped;
-  libtorrent::asio::io_service ios;
-  QList<ReverseResolutionST*> subThreads;
-
+  Q_DISABLE_COPY(ReverseResolution)
 
 public:
-  ReverseResolution(QObject* parent): QThread(parent), stopped(false) {
+  explicit ReverseResolution(QObject* parent): QThread(parent), stopped(false) {
+    cache = new QCache<QString, QString>(CACHE_SIZE);
   }
 
   ~ReverseResolution() {
@@ -113,6 +109,7 @@ public:
       stopped = true;
       cond.wakeOne();
     }
+    delete cache;
     wait();
     qDebug("Host name resolver was deleted");
   }
@@ -124,8 +121,29 @@ public:
     cond.wakeOne();
   }
 
+  QString getHostFromCache(libtorrent::asio::ip::tcp::endpoint ip) {
+    mut.lock();
+    QString ip_str = misc::toQString(ip.address().to_string());
+    QString ret;
+    if(cache->contains(ip_str)) {
+      qDebug("Got host name from cache");
+      ret = *cache->object(ip_str);
+    } else {
+      ret = QString::null;
+    }
+    mut.unlock();
+    return ret;
+  }
+
   void resolve(libtorrent::asio::ip::tcp::endpoint ip) {
     mut.lock();
+    QString ip_str = misc::toQString(ip.address().to_string());
+    if(cache->contains(ip_str)) {
+      qDebug("Resolved host name using cache");
+      emit ip_resolved(ip_str, *cache->object(ip_str));
+      mut.unlock();
+      return;
+    }
     ips.enqueue(ip);
     if(subThreads.size() < MAX_THREADS)
       cond.wakeOne();
@@ -139,6 +157,7 @@ protected slots:
   void forwardSignal(QString ip, QString hostname) {
     emit ip_resolved(ip, hostname);
     mut.lock();
+    cache->insert(ip, new QString(hostname));
     subThreads.removeOne(static_cast<ReverseResolutionST*>(sender()));
     if(!ips.empty())
       cond.wakeOne();
@@ -168,6 +187,16 @@ protected:
     qDeleteAll(subThreads);
     mut.unlock();
   }
+
+private:
+  QQueue<libtorrent::asio::ip::tcp::endpoint> ips;
+  QMutex mut;
+  QWaitCondition cond;
+  bool stopped;
+  libtorrent::asio::io_service ios;
+  QCache<QString, QString> *cache;
+  QList<ReverseResolutionST*> subThreads;
 };
 
+
 #endif // REVERSERESOLUTION_H