bugfix: pagination crash due to memory limitation

MongoDB sorts the results in memory, and the default mem limitation is
32M, if the sort operation consumes more than that it will return an
error:
OperationFailure: Executor error during find command: OperationFailed
Sort operation used more than the maximum 33554432 bytes of RAM. Add an
index, or specify a smaller limit.

To solve this problem, here we leverage aggregate() and
allowDiskUse=True, it is said will not be limited by memory

Change-Id: Id698ad1d02912e8b350a33a926fcccc390814fcc
Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>

3 files changed, 54 insertions, 19 deletions

diff --git a/testapi/opnfv_testapi/resources/handlers.py b/testapi/opnfv_testapi/resources/handlers.py
index 42372e8..0234c8a 100644
--- a/testapi/opnfv_testapi/resources/handlers.py
+++ b/testapi/opnfv_testapi/resources/handlers.py
@@ -105,21 +105,36 @@ class GenericApiHandler(web.RequestHandler):
             query = {}
         data = []
         sort = kwargs.get('sort')
-        page = kwargs.get('page')
-        last = kwargs.get('last')
-        per_page = kwargs.get('per_page')
+        page = kwargs.get('page', 0)
+        last = kwargs.get('last', 0)
+        per_page = kwargs.get('per_page', 0)
 
         cursor = self._eval_db(self.table, 'find', query)
+        records_count = yield cursor.count()
+        records_nr = records_count
+        if (records_count > last) and (last > 0):
+            records_nr = last
+
+        pipelines = list()
+        if query:
+            pipelines.append({'$match': query})
         if sort:
-            cursor = cursor.sort(sort)
-        if last and last != 0:
-            cursor = cursor.limit(last)
-        if page:
-            records_count = yield cursor.count()
-            total_pages, remainder = divmod(records_count, per_page)
+            pipelines.append({'$sort': sort})
+
+        if page > 0:
+            total_pages, remainder = divmod(records_nr, per_page)
             if remainder > 0:
                 total_pages += 1
-            cursor = cursor.skip((page - 1) * per_page).limit(per_page)
+            pipelines.append({'$skip': (page - 1) * per_page})
+            pipelines.append({'$limit': per_page})
+        else:
+            pipelines.append({'$limit': records_nr})
+
+        cursor = self._eval_db(self.table,
+                               'aggregate',
+                               pipelines,
+                               allowDiskUse=True)
+
         while (yield cursor.fetch_next):
             data.append(self.format_data(cursor.next_object()))
         if res_op is None:
diff --git a/testapi/opnfv_testapi/resources/result_handlers.py b/testapi/opnfv_testapi/resources/result_handlers.py
index 208af6d..1773216 100644
--- a/testapi/opnfv_testapi/resources/result_handlers.py
+++ b/testapi/opnfv_testapi/resources/result_handlers.py
@@ -147,13 +147,13 @@ class ResultsCLHandler(GenericResultHandler):
             @in trust_indicator: query
             @required trust_indicator: False
         """
-        limitations = {'sort': [('start_date', -1)]}
+        limitations = {'sort': {'start_date': -1}}
         last = self.get_query_argument('last', 0)
         if last is not None:
             last = self.get_int('last', last)
             limitations.update({'last': last})
 
-        page = self.get_query_argument('page', 1)
+        page = self.get_query_argument('page', None)
         if page is not None:
             page = self.get_int('page', page)
             limitations.update({'page': page,
diff --git a/testapi/opnfv_testapi/tests/unit/fake_pymongo.py b/testapi/opnfv_testapi/tests/unit/fake_pymongo.py
index b2564a6..adaf6f7 100644
--- a/testapi/opnfv_testapi/tests/unit/fake_pymongo.py
+++ b/testapi/opnfv_testapi/tests/unit/fake_pymongo.py
@@ -35,15 +35,14 @@ class MemCursor(object):
         return self.collection.pop()
 
     def sort(self, key_or_list):
-        key = key_or_list[0][0]
-        if key_or_list[0][1] == -1:
-            reverse = True
-        else:
-            reverse = False
+        for k, v in key_or_list.iteritems():
+            if v == -1:
+                reverse = True
+            else:
+                reverse = False
 
-        if key_or_list is not None:
             self.collection = sorted(self.collection,
-                                     key=itemgetter(key), reverse=reverse)
+                                     key=itemgetter(k), reverse=reverse)
         return self
 
     def limit(self, limit):
@@ -202,6 +201,27 @@ class MemDb(object):
     def find(self, *args):
         return MemCursor(self._find(*args))
 
+    def _aggregate(self, *args, **kwargs):
+        res = self.contents
+        print args
+        for arg in args[0]:
+            for k, v in arg.iteritems():
+                if k == '$match':
+                    res = self._find(v)
+        cursor = MemCursor(res)
+        for arg in args[0]:
+            for k, v in arg.iteritems():
+                if k == '$sort':
+                    cursor = cursor.sort(v)
+                elif k == '$skip':
+                    cursor = cursor.skip(v)
+                elif k == '$limit':
+                    cursor = cursor.limit(v)
+        return cursor
+
+    def aggregate(self, *args, **kwargs):
+        return self._aggregate(*args, **kwargs)
+
     def _update(self, spec, document, check_keys=True):
         updated = False