[WFS provider] Fix freeze when feature requests issued from main thre…

…ad and authentication manager triggers (fixes #37224)
qgis · Oct 23, 2020 · 571f3bd · 571f3bd
1 parent 2d99271
commit 571f3bd
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Showing 3 changed files with 58 additions and 4 deletions.
diff --git a/src/providers/wfs/qgswfsfeatureiterator.cpp b/src/providers/wfs/qgswfsfeatureiterator.cpp
@@ -33,6 +33,7 @@
 #include "qgsexception.h"
 #include "qgsfeedback.h"
 #include "qgssqliteutils.h"
+#include "qgsnetworkaccessmanager.h"
 
 #include <algorithm>
 #include <QDir>
@@ -84,7 +85,7 @@ QString QgsWFSFeatureHitsAsyncRequest::errorMessageWithReason( const QString &re
 
 // -------------------------
 
-QgsWFSFeatureDownloader::QgsWFSFeatureDownloader( QgsWFSSharedData *shared )
+QgsWFSFeatureDownloader::QgsWFSFeatureDownloader( QgsWFSSharedData *shared, bool requestMadeFromMainThread )
   : QgsWfsRequest( shared->mURI )
   , mShared( shared )
   , mStop( false )
@@ -97,6 +98,22 @@ QgsWFSFeatureDownloader::QgsWFSFeatureDownloader( QgsWFSSharedData *shared )
 {
   // Needed because used by a signal
   qRegisterMetaType< QVector<QgsWFSFeatureGmlIdPair> >( "QVector<QgsWFSFeatureGmlIdPair>" );
+
+  if ( requestMadeFromMainThread )
+  {
+    auto emitResumeMainThread = [this]()
+    {
+      emit resumeMainThread();
+    };
+    connect( QgsNetworkAccessManager::instance(), &QgsNetworkAccessManager::authRequestOccurred,
+             this, emitResumeMainThread, Qt::DirectConnection );
+    connect( QgsNetworkAccessManager::instance(), &QgsNetworkAccessManager::proxyAuthenticationRequired,
+             this, emitResumeMainThread, Qt::DirectConnection );
+#ifndef QT_NO_SSL
+    connect( QgsNetworkAccessManager::instance(), &QgsNetworkAccessManager::sslErrorsOccurred,
+             this, emitResumeMainThread, Qt::DirectConnection );
+#endif
+  }
 }
 
 QgsWFSFeatureDownloader::~QgsWFSFeatureDownloader()
@@ -893,6 +910,7 @@ QString QgsWFSFeatureDownloader::errorMessageWithReason( const QString &reason )
 
 QgsWFSThreadedFeatureDownloader::QgsWFSThreadedFeatureDownloader( QgsWFSSharedData *shared )
   : mShared( shared )
+  , mRequestMadeFromMainThread( QThread::currentThread() == QApplication::instance()->thread() )
 {
 }
 
@@ -926,7 +944,7 @@ void QgsWFSThreadedFeatureDownloader::startAndWait()
 void QgsWFSThreadedFeatureDownloader::run()
 {
   // We need to construct it in the run() method (i.e. in the new thread)
-  mDownloader = new QgsWFSFeatureDownloader( mShared );
+  mDownloader = new QgsWFSFeatureDownloader( mShared, mRequestMadeFromMainThread );
   {
     QMutexLocker locker( &mWaitMutex );
     mWaitCond.wakeOne();
@@ -1132,6 +1150,9 @@ void QgsWFSFeatureIterator::connectSignals( QgsWFSFeatureDownloader *downloader
 
   connect( downloader, &QgsWFSFeatureDownloader::endOfDownload,
            this, &QgsWFSFeatureIterator::endOfDownloadSynchronous, Qt::DirectConnection );
+
+  connect( downloader, &QgsWFSFeatureDownloader::resumeMainThread,
+           this, &QgsWFSFeatureIterator::resumeMainThreadSynchronous, Qt::DirectConnection );
 }
 
 void QgsWFSFeatureIterator::endOfDownloadSynchronous( bool )
@@ -1142,6 +1163,14 @@ void QgsWFSFeatureIterator::endOfDownloadSynchronous( bool )
   mWaitCond.wakeOne();
 }
 
+void QgsWFSFeatureIterator::resumeMainThreadSynchronous()
+{
+  // Wake up waiting loop
+  QMutexLocker locker( &mMutex );
+  mProcessEvents = true;
+  mWaitCond.wakeOne();
+}
+
 void QgsWFSFeatureIterator::setInterruptionChecker( QgsFeedback *interruptionChecker )
 {
   mInterruptionChecker = interruptionChecker;
@@ -1267,6 +1296,8 @@ bool QgsWFSFeatureIterator::fetchFeature( QgsFeature &f )
     return true;
   }
 
+  const bool requestMadeFromMainThread = QThread::currentThread() == QApplication::instance()->thread();
+
   // Second step is to wait for features to be notified by the downloader
   while ( true )
   {
@@ -1400,6 +1431,11 @@ bool QgsWFSFeatureIterator::fetchFeature( QgsFeature &f )
         break;
       }
       mWaitCond.wait( &mMutex, timeout );
+      if ( requestMadeFromMainThread && mProcessEvents )
+      {
+        QgsApplication::instance()->processEvents();
+        mProcessEvents = false;
+      }
       if ( mInterruptionChecker && mInterruptionChecker->isCanceled() )
       {
         mTimeoutOrInterruptionOccurred = true;

diff --git a/src/providers/wfs/qgswfsfeatureiterator.h b/src/providers/wfs/qgswfsfeatureiterator.h
@@ -92,7 +92,7 @@ class QgsWFSFeatureDownloader: public QgsWfsRequest
 {
     Q_OBJECT
   public:
-    explicit QgsWFSFeatureDownloader( QgsWFSSharedData *shared );
+    explicit QgsWFSFeatureDownloader( QgsWFSSharedData *shared, bool requestMadeFromMainThread );
     ~QgsWFSFeatureDownloader() override;
 
     /**
@@ -118,6 +118,11 @@ class QgsWFSFeatureDownloader: public QgsWfsRequest
     //! Emitted when the download is finished (successful or not)
     void endOfDownload( bool success );
 
+    // Emitted when QgsNetworkAccessManager emit signals that require
+    // QgsBackgroundCachedFeatureIterator to process (authentication) events,
+    // if it was started from the main thread.
+    void resumeMainThread();
+
     //! Used internally by the stop() method
     void doStop();
 
@@ -187,6 +192,7 @@ class QgsWFSThreadedFeatureDownloader: public QThread
     QgsWFSFeatureDownloader *mDownloader = nullptr;
     QWaitCondition mWaitCond;
     QMutex mWaitMutex;
+    bool mRequestMadeFromMainThread = false;
 };
 
 class QgsWFSFeatureSource;
@@ -216,6 +222,7 @@ class QgsWFSFeatureIterator : public QObject,
   private slots:
     void featureReceivedSynchronous( const QVector<QgsWFSFeatureGmlIdPair> &list );
     void endOfDownloadSynchronous( bool success );
+    void resumeMainThreadSynchronous();
 
   private:
 
@@ -234,6 +241,7 @@ class QgsWFSFeatureIterator : public QObject,
 
     bool mNewFeaturesReceived = false;
     bool mDownloadFinished = false;
+    bool mProcessEvents = false;
     QgsFeatureIterator mCacheIterator;
     QgsFeedback *mInterruptionChecker = nullptr;
     bool mTimeoutOrInterruptionOccurred = false;

diff --git a/src/providers/wfs/qgswfsprovider.cpp b/src/providers/wfs/qgswfsprovider.cpp
@@ -118,9 +118,19 @@ QgsWFSProvider::QgsWFSProvider( const QString &uri, const ProviderOptions &optio
   //Failed to detect feature type from describeFeatureType -> get first feature from layer to detect type
   if ( mShared->mWKBType == QgsWkbTypes::Unknown )
   {
-    QgsWFSFeatureDownloader downloader( mShared.get() );
+    const bool requestMadeFromMainThread = QThread::currentThread() == QApplication::instance()->thread();
+    QgsWFSFeatureDownloader downloader( mShared.get(), requestMadeFromMainThread );
     connect( &downloader, static_cast<void ( QgsWFSFeatureDownloader::* )( QVector<QgsWFSFeatureGmlIdPair> )>( &QgsWFSFeatureDownloader::featureReceived ),
              this, &QgsWFSProvider::featureReceivedAnalyzeOneFeature );
+    if ( requestMadeFromMainThread )
+    {
+      auto processEvents = []()
+      {
+        QgsApplication::instance()->processEvents();
+      };
+      connect( &downloader, &QgsWFSFeatureDownloader::resumeMainThread,
+               this, processEvents );
+    }
     downloader.run( false, /* serialize features */
                     1 /* maxfeatures */ );
   }