Add rudimentary benchmarking code and a couple of benchmarks

This commit implements a '--bench' argument for runtests.py. When
specified, this runs a couple of special "benchmark" tests that are
specifically created for testing performance of the explorer page.

It's very rudimentary at the moment as I needed something quickly to
implement the performance improvement in this PR. It gets the job done
though.

runtests.py

@@ -18,6 +18,7 @@ def make_parser():
     parser.add_argument('--elasticsearch2', action='store_true')
     parser.add_argument('--elasticsearch5', action='store_true')
     parser.add_argument('--elasticsearch6', action='store_true')
+    parser.add_argument('--bench', action='store_true')
     return parser
 
 
@@ -61,7 +62,15 @@ def runtests():
         # forcibly delete the ELASTICSEARCH_URL setting to skip those tests
         del os.environ['ELASTICSEARCH_URL']
 
-    argv = [sys.argv[0], 'test'] + rest
+    if args.bench:
+        benchmarks = [
+            'wagtail.admin.tests.benches',
+        ]
+
+        argv = [sys.argv[0], 'test', '-v2'] + benchmarks + rest
+    else:
+        argv = [sys.argv[0], 'test'] + rest
+
     try:
         execute_from_command_line(argv)
     finally:

wagtail/admin/tests/benches.py

@@ -0,0 +1,86 @@
+from __future__ import absolute_import, unicode_literals
+
+from django.test import TestCase
+from django.urls import reverse
+from django.utils import timezone
+
+from wagtail.core.models import Page, Site
+from wagtail.tests.benchmark import Benchmark
+from wagtail.tests.testapp.models import SingleEventPage, StreamPage
+from wagtail.tests.utils import WagtailTestUtils
+
+
+class BenchPageExplorerWith50LargePages(Benchmark, WagtailTestUtils, TestCase):
+    """
+    Creates 50 pages with large body content and benches the explorer.
+    This will be slow if the body content is being loaded from the database.
+    """
+
+    def setUp(self):
+        self.root_page = Page.objects.get(id=1)
+
+        # Add a site so the URLs render correctly
+        Site.objects.create(is_default_site=True, root_page=self.root_page)
+
+        # Create a large piece of body text
+        body = '[' + ','.join(['{"type": "text", "value": "%s"}' % ('foo' * 2000)] * 100) + ']'
+
+        # Create 50 simple pages with long content fields
+        for i in range(50):
+            self.root_page.add_child(instance=StreamPage(
+                title="Page {}".format(i + 1),
+                slug=str(i + 1),
+                body=body,
+            ))
+
+        self.login()
+
+    def bench(self):
+        response = self.client.get(reverse('wagtailadmin_explore', args=(self.root_page.id, )))
+
+        # Check the response was good
+        self.assertEqual(response.status_code, 200)
+
+        # Check every single page was rendered
+        self.assertContains(response, "Page 1")
+        self.assertContains(response, "Page 49")
+
+
+class BenchPageExplorerWithCustomURLPages(Benchmark, WagtailTestUtils, TestCase):
+    """
+    Creates 50 pages of a class with a customised the .url property.
+    This will check how long it takes to generate URLs for all of these
+    pages.
+    """
+
+    def setUp(self):
+        self.root_page = Page.objects.get(id=1)
+
+        # Add a site so the URLs render correctly
+        Site.objects.create(is_default_site=True, root_page=self.root_page)
+
+        # Create 50 blog pages
+        for i in range(50):
+            self.root_page.add_child(instance=SingleEventPage(
+                title="Event {}".format(i + 1),
+                slug=str(i + 1),
+                date_from=timezone.now(),
+                audience="public",
+                location="reykjavik",
+                cost="cost",
+            ))
+
+        self.login()
+
+    def bench(self):
+        response = self.client.get(reverse('wagtailadmin_explore', args=(self.root_page.id, )))
+
+        # Check the response was good
+        self.assertEqual(response.status_code, 200)
+
+        # Check every single page was rendered
+        self.assertContains(response, "Event 1")
+        self.assertContains(response, "Event 49")
+
+        # Check the URLs were rendered correctly
+        self.assertContains(response, 'a href="http:///49/pointless-suffix/"')

wagtail/tests/benchmark.py

@@ -0,0 +1,27 @@
+from __future__ import absolute_import, unicode_literals
+
+import time
+import tracemalloc
+
+
+class Benchmark():
+    repeat = 10
+
+    def test(self):
+        timings = []
+        memory_usage = []
+        tracemalloc.start()
+
+        for i in range(self.repeat):
+            before_memory = tracemalloc.take_snapshot()
+            start_time = time.time()
+
+            self.bench()
+
+            end_time = time.time()
+            after_memory = tracemalloc.take_snapshot()
+            timings.append(end_time - start_time)
+            memory_usage.append(sum([t.size for t in after_memory.compare_to(before_memory, 'filename')]))
+
+        print("time min:", min(timings), "max:", max(timings), "avg:", sum(timings) / len(timings))
+        print("memory min:", min(memory_usage), "max:", max(memory_usage), "avg:", sum(memory_usage) / len(memory_usage))