qgstiledownloadmanager.cpp

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/***************************************************************************
                         qgstiledownloadmanager.cpp
                         --------------------------
    begin                : January 2021
    copyright            : (C) 2021 by Martin Dobias
    email                : wonder dot sk at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgstiledownloadmanager.h"
 
#include "qgslogger.h"
#include "qgsnetworkaccessmanager.h"
#include "qgsrangerequestcache.h"
 
#include <QElapsedTimer>
#include <QNetworkReply>
#include <QStandardPaths>
#include <QRegularExpression>
 
 
QgsTileDownloadManagerWorker::QgsTileDownloadManagerWorker( QgsTileDownloadManager *manager, QObject *parent )
  : QObject( parent )
  , mManager( manager )
  , mIdleTimer( this )
{
  connect( &mIdleTimer, &QTimer::timeout, this, &QgsTileDownloadManagerWorker::idleTimerTimeout );
}
 
void QgsTileDownloadManagerWorker::startIdleTimer()
{
  if ( !mIdleTimer.isActive() )
  {
    mIdleTimer.start( mManager->mIdleThreadTimeoutMs );
  }
}
 
void QgsTileDownloadManagerWorker::queueUpdated()
{
  const QMutexLocker locker( &mManager->mMutex );
 
  if ( mManager->mShuttingDown )
  {
    // here we HAVE to build up a list of replies from the queue before do anything
    // with them. Otherwise we can hit the situation where aborting the replies
    // triggers immediately their removal from the queue, and we'll be modifying
    // mQueue elsewhere while still trying to iterate over it here => crash
    // WARNING: there may be event loops/processEvents in play here, because in some circumstances
    // (authentication handling, ssl errors) QgsNetworkAccessManager will trigger these.
    std::vector< QNetworkReply * > replies;
    replies.reserve( mManager->mQueue.size() );
    for ( auto it = mManager->mQueue.begin(); it != mManager->mQueue.end(); ++it )
    {
      replies.emplace_back( it->networkReply );
    }
    // now abort all replies
    for ( QNetworkReply *reply : replies )
    {
      reply->abort();
    }
 
    quitThread();
    return;
  }
 
  if ( mIdleTimer.isActive() && !mManager->mQueue.empty() )
  {
    // if timer to kill thread is running: stop the timer, we have work to do
    mIdleTimer.stop();
  }
 
  // There's a potential race here -- if a reply finishes while we're still in the middle of iterating over the queue,
  // then the associated queue entry would get removed while we're iterating over the queue here.
  // So instead defer the actual queue removal until we've finished iterating over the queue.
  // WARNING: there may be event loops/processEvents in play here, because in some circumstances
  // (authentication handling, ssl errors) QgsNetworkAccessManager will trigger these.
  mManager->mStageQueueRemovals = true;
  for ( auto it = mManager->mQueue.begin(); it != mManager->mQueue.end(); ++it )
  {
    if ( !it->networkReply )
    {
      QgsDebugMsgLevel( QStringLiteral( "Tile download manager: starting request: " ) + it->request.url().toString(), 2 );
      // start entries which are not in progress
 
      it->networkReply = QgsNetworkAccessManager::instance()->get( it->request );
      connect( it->networkReply, &QNetworkReply::finished, it->objWorker, &QgsTileDownloadManagerReplyWorkerObject::replyFinished );
 
      ++mManager->mStats.networkRequestsStarted;
    }
  }
  mManager->mStageQueueRemovals = false;
  mManager->processStagedEntryRemovals();
}
 
void QgsTileDownloadManagerWorker::quitThread()
{
  QgsDebugMsgLevel( QStringLiteral( "Tile download manager: stopping worker thread" ), 2 );
 
  mManager->mWorker->deleteLater();
  mManager->mWorker = nullptr;
  // we signal to our worker thread it's time to go. Its finished() signal is connected
  // to deleteLater() call, so it will get deleted automatically
  mManager->mWorkerThread->quit();
  mManager->mWorkerThread = nullptr;
  mManager->mShuttingDown = false;
}
 
void QgsTileDownloadManagerWorker::idleTimerTimeout()
{
  const QMutexLocker locker( &mManager->mMutex );
  Q_ASSERT( mManager->mQueue.empty() );
  quitThread();
}
 
 
 
 
void QgsTileDownloadManagerReplyWorkerObject::replyFinished()
{
  const QMutexLocker locker( &mManager->mMutex );
 
  QgsDebugMsgLevel( QStringLiteral( "Tile download manager: internal reply finished: " ) + mRequest.url().toString(), 2 );
 
  QNetworkReply *reply = qobject_cast<QNetworkReply *>( sender() );
  QByteArray data;
 
  if ( reply->error() == QNetworkReply::NoError )
  {
    ++mManager->mStats.networkRequestsOk;
    data = reply->readAll();
  }
  else
  {
    ++mManager->mStats.networkRequestsFailed;
    const QString contentType = reply->header( QNetworkRequest::ContentTypeHeader ).toString();
    if ( contentType.startsWith( QLatin1String( "text/plain" ) ) )
      data = reply->readAll();
  }
 
  QMap<QNetworkRequest::Attribute, QVariant> attributes;
  attributes.insert( QNetworkRequest::SourceIsFromCacheAttribute, reply->attribute( QNetworkRequest::SourceIsFromCacheAttribute ) );
  attributes.insert( QNetworkRequest::RedirectionTargetAttribute, reply->attribute( QNetworkRequest::RedirectionTargetAttribute ) );
  attributes.insert( QNetworkRequest::HttpStatusCodeAttribute, reply->attribute( QNetworkRequest::HttpStatusCodeAttribute ) );
  attributes.insert( QNetworkRequest::HttpReasonPhraseAttribute, reply->attribute( QNetworkRequest::HttpReasonPhraseAttribute ) );
 
  QMap<QNetworkRequest::KnownHeaders, QVariant> headers;
  headers.insert( QNetworkRequest::ContentTypeHeader, reply->header( QNetworkRequest::ContentTypeHeader ) );
 
  // Save loaded data to cache
  int httpStatusCode = reply->attribute( QNetworkRequest::Attribute::HttpStatusCodeAttribute ).toInt();
  if ( httpStatusCode == 206 && mManager->isRangeRequest( mRequest ) )
  {
    mManager->mRangesCache->registerEntry( mRequest, data );
  }
 
  emit finished( data, reply->url(), attributes, headers, reply->rawHeaderPairs(), reply->error(), reply->errorString() );
 
  reply->deleteLater();
 
  // kill the worker obj
  deleteLater();
 
  mManager->removeEntry( mRequest );
 
  if ( mManager->mQueue.empty() )
  {
    // if this was the last thing in the queue, start a timer to kill thread after X seconds
    mManager->mWorker->startIdleTimer();
  }
}
 
 
 
 
QgsTileDownloadManager::QgsTileDownloadManager()
{
  mRangesCache.reset( new QgsRangeRequestCache );
 
  const QgsSettings settings;
  QString cacheDirectory = settings.value( QStringLiteral( "cache/directory" ) ).toString();
  if ( cacheDirectory.isEmpty() )
    cacheDirectory = QStandardPaths::writableLocation( QStandardPaths::CacheLocation );
  if ( !cacheDirectory.endsWith( QDir::separator() ) )
  {
    cacheDirectory.push_back( QDir::separator() );
  }
  cacheDirectory += QLatin1String( "http-ranges" );
  const qint64 cacheSize = settings.value( QStringLiteral( "cache/size" ), 256 * 1024 * 1024 ).toLongLong();
 
  mRangesCache->setCacheDirectory( cacheDirectory );
  mRangesCache->setCacheSize( cacheSize );
}
 
QgsTileDownloadManager::~QgsTileDownloadManager()
{
  // make sure the worker thread is gone and any pending requests are canceled
  shutdown();
}
 
QgsTileDownloadManagerReply *QgsTileDownloadManager::get( const QNetworkRequest &request )
{
  const QMutexLocker locker( &mMutex );
 
  if ( isCachedRangeRequest( request ) )
  {
    QgsTileDownloadManagerReply *reply = new QgsTileDownloadManagerReply( this, request ); // lives in the same thread as the caller
    QTimer::singleShot( 0, reply, &QgsTileDownloadManagerReply::cachedRangeRequestFinished );
    return reply;
  }
 
  if ( !mWorker )
  {
    QgsDebugMsgLevel( QStringLiteral( "Tile download manager: starting worker thread" ), 2 );
    mWorkerThread = new QThread;
    mWorker = new QgsTileDownloadManagerWorker( this );
    mWorker->moveToThread( mWorkerThread );
    QObject::connect( mWorkerThread, &QThread::finished, mWorker, &QObject::deleteLater );
    mWorkerThread->start();
  }
 
  QgsTileDownloadManagerReply *reply = new QgsTileDownloadManagerReply( this, request ); // lives in the same thread as the caller
 
  ++mStats.requestsTotal;
 
  QgsTileDownloadManager::QueueEntry entry = findEntryForRequest( request );
  if ( !entry.isValid() )
  {
    QgsDebugMsgLevel( QStringLiteral( "Tile download manager: get (new entry): " ) + request.url().toString(), 2 );
    // create a new entry and add it to queue
    entry.request = request;
    entry.objWorker = new QgsTileDownloadManagerReplyWorkerObject( this, request );
    entry.objWorker->moveToThread( mWorkerThread );
 
    QObject::connect( entry.objWorker, &QgsTileDownloadManagerReplyWorkerObject::finished, reply, &QgsTileDownloadManagerReply::requestFinished );  // should be queued connection
 
    addEntry( entry );
  }
  else
  {
    QgsDebugMsgLevel( QStringLiteral( "Tile download manager: get (existing entry): " ) + request.url().toString(), 2 );
 
    QObject::connect( entry.objWorker, &QgsTileDownloadManagerReplyWorkerObject::finished, reply, &QgsTileDownloadManagerReply::requestFinished );  // should be queued connection
 
    ++mStats.requestsMerged;
  }
 
  signalQueueModified();
 
  return reply;
}
 
bool QgsTileDownloadManager::hasPendingRequests() const
{
  const QMutexLocker locker( &mMutex );
 
  return !mQueue.empty();
}
 
bool QgsTileDownloadManager::waitForPendingRequests( int msec ) const
{
  QElapsedTimer t;
  t.start();
 
  while ( msec == -1 || t.elapsed() < msec )
  {
    {
      const QMutexLocker locker( &mMutex );
      if ( mQueue.empty() )
        return true;
    }
    QThread::usleep( 1000 );
  }
 
  return false;
}
 
void QgsTileDownloadManager::shutdown()
{
  {
    const QMutexLocker locker( &mMutex );
    if ( !mWorkerThread )
      return;  // nothing to stop
 
    // let's signal to the thread
    mShuttingDown = true;
    signalQueueModified();
  }
 
  // wait until the thread is gone
  while ( 1 )
  {
    {
      const QMutexLocker locker( &mMutex );
      if ( !mWorkerThread )
        return;  // the thread has stopped
    }
 
    QThread::usleep( 1000 );
  }
}
 
bool QgsTileDownloadManager::hasWorkerThreadRunning() const
{
  return mWorkerThread && mWorkerThread->isRunning();
}
 
void QgsTileDownloadManager::resetStatistics()
{
  const QMutexLocker locker( &mMutex );
  mStats = QgsTileDownloadManager::Stats();
}
 
QgsTileDownloadManager::QueueEntry QgsTileDownloadManager::findEntryForRequest( const QNetworkRequest &request )
{
  for ( auto it = mQueue.begin(); it != mQueue.end(); ++it )
  {
    if ( it->request.url() == request.url() && it->request.rawHeader( "Range" ) == request.rawHeader( "Range" ) )
      return *it;
  }
  return QgsTileDownloadManager::QueueEntry();
}
 
void QgsTileDownloadManager::addEntry( const QgsTileDownloadManager::QueueEntry &entry )
{
  for ( auto it = mQueue.begin(); it != mQueue.end(); ++it )
  {
    Q_ASSERT( entry.request.url() != it->request.url() || entry.request.rawHeader( "Range" ) != it->request.rawHeader( "Range" ) );
  }
 
  mQueue.emplace_back( entry );
}
 
void QgsTileDownloadManager::updateEntry( const QgsTileDownloadManager::QueueEntry &entry )
{
  for ( auto it = mQueue.begin(); it != mQueue.end(); ++it )
  {
    if ( entry.request.url() == it->request.url() && entry.request.rawHeader( "Range" ) == it->request.rawHeader( "Range" ) )
    {
      *it = entry;
      return;
    }
  }
  Q_ASSERT( false );
}
 
void QgsTileDownloadManager::removeEntry( const QNetworkRequest &request )
{
  if ( mStageQueueRemovals )
  {
    mStagedQueueRemovals.emplace_back( request );
  }
  else
  {
    for ( auto it = mQueue.begin(); it != mQueue.end(); ++it )
    {
      if ( it->request.url() == request.url() && it->request.rawHeader( "Range" ) == request.rawHeader( "Range" ) )
      {
        mQueue.erase( it );
        return;
      }
    }
    Q_ASSERT( false );
  }
}
 
void QgsTileDownloadManager::processStagedEntryRemovals()
{
  Q_ASSERT( !mStageQueueRemovals );
  for ( const QNetworkRequest &request : mStagedQueueRemovals )
  {
    removeEntry( request );
  }
  mStagedQueueRemovals.clear();
}
 
void QgsTileDownloadManager::signalQueueModified()
{
  QMetaObject::invokeMethod( mWorker, &QgsTileDownloadManagerWorker::queueUpdated, Qt::QueuedConnection );
}
 
bool QgsTileDownloadManager::isRangeRequest( const QNetworkRequest &request )
{
  if ( request.rawHeader( "Range" ).isEmpty() )
    return false;
  QRegularExpression regex( "^bytes=\\d+-\\d+$" );
  QRegularExpressionMatch match = regex.match( QString::fromUtf8( request.rawHeader( "Range" ) ) );
  return match.hasMatch();
}
 
bool QgsTileDownloadManager::isCachedRangeRequest( const QNetworkRequest &request )
{
  QNetworkRequest::CacheLoadControl loadControl = ( QNetworkRequest::CacheLoadControl ) request.attribute( QNetworkRequest::CacheLoadControlAttribute ).toInt();
  bool saveControl = request.attribute( QNetworkRequest::CacheSaveControlAttribute ).toBool();
  return isRangeRequest( request ) && saveControl && loadControl != QNetworkRequest::AlwaysNetwork && mRangesCache->hasEntry( request );
}
 
 
 
QgsTileDownloadManagerReply::QgsTileDownloadManagerReply( QgsTileDownloadManager *manager, const QNetworkRequest &request )
  : mManager( manager )
  , mRequest( request )
{
}
 
QgsTileDownloadManagerReply::~QgsTileDownloadManagerReply()
{
  const QMutexLocker locker( &mManager->mMutex );
 
  if ( !mHasFinished )
  {
    QgsDebugMsgLevel( QStringLiteral( "Tile download manager: reply deleted before finished: " ) + mRequest.url().toString(), 2 );
 
    ++mManager->mStats.requestsEarlyDeleted;
  }
}
 
void QgsTileDownloadManagerReply::requestFinished( QByteArray data, QUrl url, const QMap<QNetworkRequest::Attribute, QVariant> &attributes, const QMap<QNetworkRequest::KnownHeaders, QVariant> &headers, const QList<QNetworkReply::RawHeaderPair> rawHeaderPairs, QNetworkReply::NetworkError error, const QString &errorString )
{
  QgsDebugMsgLevel( QStringLiteral( "Tile download manager: reply finished: " ) + mRequest.url().toString(), 2 );
 
  mHasFinished = true;
  mData = data;
  mUrl = url;
  mAttributes = attributes;
  mHeaders = headers;
  mRawHeaderPairs = rawHeaderPairs;
  mError = error;
  mErrorString = errorString;
  emit finished();
}
 
void QgsTileDownloadManagerReply::cachedRangeRequestFinished()
{
  QgsDebugMsgLevel( QStringLiteral( "Tile download manager: internal range request reply loaded from cache: " ) + mRequest.url().toString(), 2 );
  mHasFinished = true;
  mData = mManager->mRangesCache->entry( mRequest );
  mUrl = mRequest.url();
  emit finished();
}
 
QVariant QgsTileDownloadManagerReply::attribute( QNetworkRequest::Attribute code )
{
  return mAttributes.contains( code ) ? mAttributes.value( code ) : QVariant();
}
 
QVariant QgsTileDownloadManagerReply::header( QNetworkRequest::KnownHeaders header )
{
  return mHeaders.contains( header ) ? mHeaders.value( header ) : QVariant();
}