Retry failed tile loads 5 times (with exp backoff) before giving up

This allows us to fetch tiles over unreliable network links a bit
better -- burst errors of only a few seconds will no longer drop
tiles.

Change-Id: I00c33424b58e032b1fb74c89052ea7f5cbd97d30
Reviewed-by: Thomas Lowe <thomas.lowe@nokia.com>
Reviewed-by: Ian Chen <ian.1.chen@nokia.com>
Reviewed-by: Alex Wilson <alex.wilson@nokia.com>

7 files changed, 123 insertions, 0 deletions

diff --git a/src/location/maps/qgeomapimages.cpp b/src/location/maps/qgeomapimages.cpp
index 3f38a898..3997865a 100644
--- a/src/location/maps/qgeomapimages.cpp
+++ b/src/location/maps/qgeomapimages.cpp
@@ -40,6 +40,7 @@
 ****************************************************************************/
 #include "qgeomapimages_p.h"
 
+#include <QSharedPointer>
 #include "qgeotilespec.h"
 #include "qgeotiledmapdata_p.h"
 #include "qgeotiledmappingmanagerengine.h"
@@ -47,6 +48,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class RetryFuture;
+
 class QGeoMapImagesPrivate
 {
 public:
@@ -58,7 +61,10 @@ public:
 
     void setVisibleTiles(const QSet<QGeoTileSpec> &tiles);
     void tileFetched(const QGeoTileSpec &tile);
+    void tileError(const QGeoTileSpec &tile, const QString &errorString);
 
+    QHash<QGeoTileSpec, int> retries_;
+    QHash<QGeoTileSpec, QSharedPointer<RetryFuture> > futures_;
     QSet<QGeoTileSpec> visible_;
     QList<QSharedPointer<QGeoTileTexture> > cachedTex_;
     QSet<QGeoTileSpec> requested_;
@@ -78,6 +84,12 @@ void QGeoMapImages::setVisibleTiles(const QSet<QGeoTileSpec> &tiles)
     d->setVisibleTiles(tiles);
 }
 
+void QGeoMapImages::tileError(const QGeoTileSpec &tile, const QString &errorString)
+{
+    Q_D(QGeoMapImages);
+    d->tileError(tile, errorString);
+}
+
 QList<QSharedPointer<QGeoTileTexture> > QGeoMapImages::cachedTiles() const
 {
     Q_D(const QGeoMapImages);
@@ -132,6 +144,71 @@ void QGeoMapImagesPrivate::setVisibleTiles(const QSet<QGeoTileSpec> &tiles)
     if (!requestTiles.isEmpty() || !cancelTiles.isEmpty()) {
         if (map_) {
             map_->updateTileRequests(requestTiles, cancelTiles);
+
+            // Remove any cancelled tiles from the error retry hash to avoid
+            // re-using the numbers for a totally different request cycle.
+            iter i = cancelTiles.constBegin();
+            iter end = cancelTiles.constEnd();
+            for (; i != end; ++i) {
+                retries_.remove(*i);
+                futures_.remove(*i);
+            }
+        }
+    }
+}
+
+// Represents a tile that needs to be retried after a certain period of time
+class RetryFuture : public QObject
+{
+    Q_OBJECT
+public:
+    RetryFuture(const QGeoTileSpec &tile, QGeoTiledMapData *map, QObject *parent=0);
+
+public slots:
+    void retry();
+
+private:
+    QGeoTileSpec tile_;
+    QGeoTiledMapData *map_;
+};
+
+RetryFuture::RetryFuture(const QGeoTileSpec &tile, QGeoTiledMapData *map, QObject *parent)
+    : QObject(parent), tile_(tile), map_(map)
+{}
+
+void RetryFuture::retry()
+{
+    QSet<QGeoTileSpec> requestTiles;
+    QSet<QGeoTileSpec> cancelTiles;
+    requestTiles.insert(tile_);
+    if (map_)
+        map_->updateTileRequests(requestTiles, cancelTiles);
+}
+
+void QGeoMapImagesPrivate::tileError(const QGeoTileSpec &tile, const QString &errorString)
+{
+    if (requested_.contains(tile)) {
+        int count = retries_.value(tile, 0);
+        retries_.insert(tile, count + 1);
+
+        if (count >= 5) {
+            qWarning("QGeoMapImages: Failed to fetch tile (%d,%d,%d) 5 times, giving up. "
+                     "Last error message was: '%s'",
+                     tile.x(), tile.y(), tile.zoom(), qPrintable(errorString));
+            requested_.remove(tile);
+            retries_.remove(tile);
+            futures_.remove(tile);
+
+        } else {
+            // Exponential time backoff when retrying
+            int delay = (1 << count) * 500;
+
+            QSharedPointer<RetryFuture> future(new RetryFuture(tile, map_));
+            futures_.insert(tile, future);
+
+            QTimer::singleShot(delay, future.data(), SLOT(retry()));
+            // Passing .data() to singleShot is ok -- Qt will clean up the
+            // connection if the target qobject is deleted
         }
     }
 }
@@ -139,6 +216,10 @@ void QGeoMapImagesPrivate::setVisibleTiles(const QSet<QGeoTileSpec> &tiles)
 void QGeoMapImagesPrivate::tileFetched(const QGeoTileSpec &tile)
 {
     requested_.remove(tile);
+    retries_.remove(tile);
+    futures_.remove(tile);
 }
 
+#include "qgeomapimages.moc"
+
 QT_END_NAMESPACE
diff --git a/src/location/maps/qgeomapimages_p.h b/src/location/maps/qgeomapimages_p.h
index 02ceb15e..f5adea20 100644
--- a/src/location/maps/qgeomapimages_p.h
+++ b/src/location/maps/qgeomapimages_p.h
@@ -55,6 +55,7 @@
 #include <QSet>
 #include <QList>
 #include <QSharedPointer>
+#include <QString>
 
 QT_BEGIN_NAMESPACE
 
@@ -76,6 +77,7 @@ public:
     QList<QSharedPointer<QGeoTileTexture> > cachedTiles() const;
 
     void tileFetched(const QGeoTileSpec &tile);
+    void tileError(const QGeoTileSpec &tile, const QString &errorString);
 
 private:
     QGeoMapImagesPrivate *d_ptr;
diff --git a/src/location/maps/qgeotiledmapdata.cpp b/src/location/maps/qgeotiledmapdata.cpp
index 89eec6c4..4e9eec29 100644
--- a/src/location/maps/qgeotiledmapdata.cpp
+++ b/src/location/maps/qgeotiledmapdata.cpp
@@ -150,6 +150,12 @@ void QGeoTiledMapData::tileFetched(const QGeoTileSpec &spec)
     d->tileFetched(spec);
 }
 
+void QGeoTiledMapData::tileError(const QGeoTileSpec &spec, const QString &errorString)
+{
+    Q_D(QGeoTiledMapData);
+    d->tileError(spec, errorString);
+}
+
 QGeoTileCache* QGeoTiledMapData::tileCache()
 {
     Q_D(QGeoTiledMapData);
@@ -349,6 +355,11 @@ void QGeoTiledMapDataPrivate::tileFetched(const QGeoTileSpec &spec)
     map_->update();
 }
 
+void QGeoTiledMapDataPrivate::tileError(const QGeoTileSpec &spec, const QString &errorString)
+{
+    mapImages_->tileError(spec, errorString);
+}
+
 QSet<QGeoTileSpec> QGeoTiledMapDataPrivate::visibleTiles()
 {
     return visibleTiles_;
diff --git a/src/location/maps/qgeotiledmapdata_p.h b/src/location/maps/qgeotiledmapdata_p.h
index 4313f1c1..521c5131 100644
--- a/src/location/maps/qgeotiledmapdata_p.h
+++ b/src/location/maps/qgeotiledmapdata_p.h
@@ -53,6 +53,7 @@
 //
 
 #include <QObject>
+#include <QString>
 
 #include "qgeomapdata_p.h"
 #include "qgeocameradata_p.h"
@@ -80,6 +81,7 @@ public:
     void paintGL(QGLPainter *painter);
 
     void tileFetched(const QGeoTileSpec &spec);
+    void tileError(const QGeoTileSpec &spec, const QString &errorString);
 
     QGeoCoordinate screenPositionToCoordinate(const QPointF &pos, bool clipToViewport = true) const;
     QPointF coordinateToScreenPosition(const QGeoCoordinate &coordinate, bool clipToViewport = true) const;
diff --git a/src/location/maps/qgeotiledmapdata_p_p.h b/src/location/maps/qgeotiledmapdata_p_p.h
index 97f83949..f2091667 100644
--- a/src/location/maps/qgeotiledmapdata_p_p.h
+++ b/src/location/maps/qgeotiledmapdata_p_p.h
@@ -78,6 +78,9 @@ class QGeoProjection;
 class QGeoCameraTiles;
 class QGeoMapImages;
 class QGeoMapGeometry;
+class QGeoTiledMapData;
+class QGeoTiledMappingManagerEngine;
+class QGLPainter;
 
 class QGLSceneNode;
 
@@ -99,6 +102,7 @@ public:
     QPointF coordinateToScreenPosition(const QGeoCoordinate &coordinate) const;
 
     void tileFetched(const QGeoTileSpec &spec);
+    void tileError(const QGeoTileSpec &spec, const QString &errorString);
     QSet<QGeoTileSpec> visibleTiles();
 
     QGeoTiledMappingManagerEngine *engine() const;
diff --git a/src/location/maps/qgeotiledmappingmanagerengine.cpp b/src/location/maps/qgeotiledmappingmanagerengine.cpp
index 4d05951e..1f44d640 100644
--- a/src/location/maps/qgeotiledmappingmanagerengine.cpp
+++ b/src/location/maps/qgeotiledmappingmanagerengine.cpp
@@ -264,6 +264,27 @@ void QGeoTiledMappingManagerEngine::engineTileFinished(const QGeoTileSpec &spec,
 
 void QGeoTiledMappingManagerEngine::engineTileError(const QGeoTileSpec &spec, const QString &errorString)
 {
+    Q_D(QGeoTiledMappingManagerEngine);
+
+    QSet<QGeoTiledMapData*> maps = d->tileHash_.value(spec);
+    typedef QSet<QGeoTiledMapData*>::const_iterator map_iter;
+    map_iter map = maps.constBegin();
+    map_iter mapEnd = maps.constEnd();
+    for (; map != mapEnd; ++map) {
+        QSet<QGeoTileSpec> tileSet = d->mapHash_.value(*map);
+
+        tileSet.remove(spec);
+        if (tileSet.isEmpty())
+            d->mapHash_.remove(*map);
+        else
+            d->mapHash_.insert(*map, tileSet);
+    }
+    d->tileHash_.remove(spec);
+
+    for (map = maps.constBegin(); map != mapEnd; ++map) {
+        (*map)->tileError(spec, errorString);
+    }
+
     emit tileError(spec, errorString);
 }
 
diff --git a/src/location/maps/qgeotilefetcher.cpp b/src/location/maps/qgeotilefetcher.cpp
index 8080706c..5f9fc479 100644
--- a/src/location/maps/qgeotilefetcher.cpp
+++ b/src/location/maps/qgeotilefetcher.cpp
@@ -130,6 +130,8 @@ void QGeoTileFetcher::cancelTileRequests(const QSet<QGeoTileSpec> &tiles)
         if (reply) {
             d->invmap_.remove(*tile);
             reply->abort();
+            if (reply->isFinished())
+                reply->deleteLater();
         }
         d->queue_.removeAll(*tile);
     }