MBSResolver: improve efficiency of querying latest version

Only get 5 results at a time, and if we see that we're already
retrieving an old versions, stop requesting more pages.

module_build_service/resolver/MBSResolver.py

@@ -66,7 +66,7 @@ class MBSResolver(KojiResolver):
         """
         query = self._query_from_nsvc(name, stream, version, context, states)
         query["page"] = 1
-        query["per_page"] = 10
+        query["per_page"] = 5
         query.update(kwargs)
         modules = []
 
@@ -81,6 +81,11 @@ class MBSResolver(KojiResolver):
             if not data["meta"]["next"]:
                 break
 
+            if version is None and "stream_version_lte" not in kwargs:
+                # Stop querying when we've gotten a different version
+                if modules_per_page[-1]["version"] != modules[0]["version"]:
+                    break
+
             query["page"] += 1
 
         # Error handling

tests/test_resolver/test_mbs.py

@@ -56,11 +56,12 @@ class FakeMBS(object):
     def __init__(self, session_mock):
         session_mock.get = self.get
         self.items = test_items
+        self.request_count = 0
         self.required_params = {
             'order_desc_by': 'version',
             'state': ['ready'],
             'verbose': True,
-            'per_page': 10,
+            'per_page': 5,
         }
 
     def item_matches(self, item, params):
@@ -86,6 +87,8 @@ class FakeMBS(object):
             self.items.append(item)
 
     def get(self, url, params={}):
+        self.request_count += 1
+
         for k, v in self.required_params.items():
             if v == ABSENT:
                 assert k not in params
@@ -153,15 +156,18 @@ class TestMBSModule:
     ):
         """ Test for querying MBS without the version of a module """
 
-        version = formatted_testmodule_mmd.get_version()
-
         fake_mbs.items = []
 
-        for i in range(0, 6):
-            for context in ("00000000", "00000001"):
+        # First page has version1.context[0..4]
+        # Second page has version1.context5, version2.context[0..3]
+        # Third page has version2.context[4..5]
+        # We should only query the first two pages
+        for i in range(0, 2):
+            for context in range(0, 6):
+                context_string = "{0:08d}".format(context)
                 m = formatted_testmodule_mmd.copy()
                 m.set_version(20180205135154 - i)
-                m.set_context(context)
+                m.set_context(context_string)
                 add_item(fake_mbs.items, mmd=m)
 
         ret = resolver.get_module_modulemds("testmodule", "master")
@@ -169,8 +175,13 @@ class TestMBSModule:
         expected = {
             "testmodule:master:20180205135154:00000000",
             "testmodule:master:20180205135154:00000001",
+            "testmodule:master:20180205135154:00000002",
+            "testmodule:master:20180205135154:00000003",
+            "testmodule:master:20180205135154:00000004",
+            "testmodule:master:20180205135154:00000005",
         }
         assert nsvcs == expected
+        assert fake_mbs.request_count == 2
 
     @pytest.mark.parametrize('strict', (False, True))
     def test_get_module_modulemds_not_found(self, resolver, fake_mbs, strict):