fixed priority handling on the new scheduler so that it's backwards compatible (ie. bigger priorities are higher). also fixed a few documentation bugs related to requests priority

docs/topics/request-response.rst

@@ -77,11 +77,10 @@ Request objects
        body to ``str`` (if given as ``unicode``).
     :type encoding: string
 
-    :param priority: the priority of this request (defaults to ``0.0``).
-       The priority is used by the scheduler to define the order used to return
-       requests. It can also be used to feed priorities externally, for
-       example, using an offline long-term scheduler.
-    :type encoding: int or float
+    :param priority: the priority of this request (defaults to ``0``).
+       The priority is used by the scheduler to define the order used to process
+       requests.
+    :type priority: int
 
     :param dont_filter: indicates that this request should not be filtered by
        the scheduler. This is used when you want to perform an identical

docs/topics/settings.rst

@@ -338,7 +338,7 @@ DEPTH_PRIORITY
 
 Default: ``1``
 
-An integer that is used to set the request priority based on request depth.
+An integer that is used to adjust the request priority based on its depth.
 
 To crawl in `breadth-first order`_, set :setting:`DEPTH_PRIORITY` to ``1``.
 

scrapy/contrib/spidermiddleware/depth.py

@@ -47,7 +47,7 @@ class DepthMiddleware(object):
                 depth = response.request.meta['depth'] + 1
                 request.meta['depth'] = depth
                 if self.prio:
-                    request.priority += depth * self.prio
+                    request.priority -= depth * self.prio
                 if self.maxdepth and depth > self.maxdepth:
                     log.msg("Ignoring link (depth > %d): %s " % (self.maxdepth, request.url), \
                         level=log.DEBUG, spider=spider)

scrapy/core/scheduler.py

@@ -58,7 +58,7 @@ class Scheduler(object):
             return
         try:
             reqd = request_to_dict(request, self.spider)
-            self.dqs.push(reqd, request.priority)
+            self.dqs.push(reqd, -request.priority)
         except ValueError: # non serializable request
             return
         else:
@@ -67,7 +67,7 @@ class Scheduler(object):
 
     def _mqpush(self, request):
         stats.inc_value('scheduler/memory_enqueued', spider=self.spider)
-        self.mqs.push(request, request.priority)
+        self.mqs.push(request, -request.priority)
 
     def _dqpop(self):
         if self.dqs: