don't download image in db session

oml/item/models.py

@@ -437,30 +437,6 @@ class Item(db.Model):
                     if state.nodes.download_preview(u.id, self.id):
                         break
 
-    def update_cover(self):
-        logger.debug('%s update cover', self.id)
-        key = 'cover:%s' % self.id
-        cover = None
-        if 'cover' in self.meta and self.meta['cover']:
-            logger.debug('download cover %s %s', self.id, self.meta['cover'])
-            try:
-                cover = ox.cache.read_url(self.meta['cover'])
-            except:
-                logger.debug('unable to read cover url %s', self.meta['cover'])
-                cover = None
-            if cover:
-                icons[key] = cover
-                self.info['coverRatio'] = get_ratio(cover)
-        else:
-            del icons[key]
-        if not cover:
-            if 'previewRatio' in self.info:
-                self.info['coverRatio'] = self.info['previewRatio']
-            elif 'coverRatio' in self.info:
-                del self.info['coverRatio']
-        icons.clear('cover:%s:' % self.id)
-        logger.debug('%s update_cover done', self.id)
-
     def get_preview(self):
         key = 'preview:%s' % self.id
         data = icons[key]
@@ -490,11 +466,14 @@ class Item(db.Model):
         icons.clear('preview:%s:' % self.id)
         logger.debug('%s update_preview done', self.id)
 
-    def update_icons(self):
+    def update_cover(self):
         if state.online:
-            self.update_cover()
+            download_cover(self.id)
         elif state.tasks:
             state.tasks.queue('getcover', self.id)
+
+    def update_icons(self):
+        self.update_cover()
         self.update_preview()
 
     def load_metadata(self):
@@ -856,15 +835,47 @@ def update_sort_table():
                 s.connection().execute(q)
             s.commit()
 
+def download_cover(id):
+    key = 'cover:%s' % id
+    with db.session():
+        i = Item.get(id)
+        if i:
+            url = i.meta.get('cover')
+        else:
+            url = None
+
+    logger.debug('download cover %s %s', self.id, url)
+    ratio = None
+    try:
+        cover = ox.net.read_url(url)
+        ratio = get_ratio(cover)
+    except:
+        logger.debug('unable to read cover url %s', url)
+        cover = None
+    with db.session():
+        i = Item.get(id, for_update=True)
+        if i:
+            if cover:
+                i.info['coverRatio'] = get_ratio(cover)
+            else:
+                if 'previewRatio' in i.info:
+                    i.info['coverRatio'] = i.info['previewRatio']
+                elif 'coverRatio' in i.info:
+                    del i.info['coverRatio']
+            i.save()
+
+    if cover:
+        icons[key] = cover
+    else:
+        del icons[key]
+    icons.clear('cover:%s:' % id)
+    logger.debug('%s update_cover done', id)
 
 def get_cover(id):
     delay = 60
     if state.online:
         # logger.debug('get_cover(%s)', id)
-        with db.session():
-            i = Item.get(id)
-            if i:
-                i.update_cover()
+        download_cover(id)
     else:
         state.main.call_later(delay, lambda: state.tasks.queue('getcover', id))