Chrome Endure tests forcefully clear ChromeDriver's node cache on each test iteration.

chrome/test/functional/perf_endure.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Performance tests for Chrome Endure (long-running perf tests on Chrome).
 
 This module accepts the following environment variable inputs:
   TEST_LENGTH: The number of seconds in which to run each test.
   PERF_STATS_INTERVAL: The number of seconds to wait in-between each sampling
@@ skipping 184 matching lines @@
 
     if event_info['type'] == 'GCEvent':
       self._events_to_output.append({
         'type': 'GarbageCollection',
         'time': elapsed_time,
         'data':
             {'collected_bytes': event_info['data']['usedHeapSizeDelta']},
       })
 
   def _RunEndureTest(self, webapp_name, tab_title_substring, test_description,
-                     do_scenario):
+                     do_scenario, frame_xpath=''):
     """The main test harness function to run a general Chrome Endure test.
 
     After a test has performed any setup work and has navigated to the proper
     starting webpage, this function should be invoked to run the endurance test.
 
     Args:
       webapp_name: A string name for the webapp being tested.  Should not
           include spaces.  For example, 'Gmail', 'Docs', or 'Plus'.
       tab_title_substring: A unique substring contained within the title of
           the tab to use, for identifying the appropriate tab.
       test_description: A string description of what the test does, used for
           outputting results to be graphed.  Should not contain spaces.  For
           example, 'ComposeDiscard' for Gmail.
       do_scenario: A callable to be invoked that implements the scenario to be
           performed by this test.  The callable is invoked iteratively for the
           duration of the test.
+      frame_xpath: The string xpath of the frame in which to inject javascript
+          to clear chromedriver's cache (a temporary workaround until the
+          WebDriver team changes how they handle their DOM node cache).
     """
     self._num_errors = 0
     self._test_start_time = time.time()
     last_perf_stats_time = time.time()
     self._GetPerformanceStats(
         webapp_name, test_description, tab_title_substring)
     self._iteration_num = 0  # Available to |do_scenario| if needed.
 
     self._remote_inspector_client.StartTimelineEventMonitoring(
         self._OnTimelineEvent)
@@ skipping 15 matching lines @@
         self._GetPerformanceStats(
             webapp_name, test_description, tab_title_substring)
 
       if self._iteration_num % 10 == 0:
         remaining_time = self._test_length_sec - (time.time() -
                                                   self._test_start_time)
         logging.info('Chrome interaction #%d. Time remaining in test: %d sec.' %
                      (self._iteration_num, remaining_time))
 
       do_scenario()
+      # Clear ChromeDriver's DOM node cache so its growth doesn't affect the
+      # results of Chrome Endure.
+      # TODO(dennisjeffrey): Once the WebDriver team implements changes to
+      # handle their DOM node cache differently, we need to revisit this.  It
+      # may no longer be necessary at that point to forcefully delete the cache.
+      # Additionally, the Javascript below relies on an internal property of
+      # WebDriver that may change at any time.  This is only a temporary
+      # workaround to stabilize the Chrome Endure test results.
+      js = """
+        (function() {
+          delete document.$wdc_;
+          window.domAutomationController.send('done');
+        })();
+      """
+      self.ExecuteJavascript(js, frame_xpath=frame_xpath)
 
     self._remote_inspector_client.StopTimelineEventMonitoring()
     # TODO(dmikurube): Call HeapProfilerDump when PyAuto supports dumping for
     # renderer processes.
 
     self._GetPerformanceStats(
         webapp_name, test_description, tab_title_substring, is_last=True)
 
   def _GetProcessInfo(self, tab_title_substring):
     """Gets process info associated with an open browser/tab.
@@ skipping 449 matching lines @@
       discard_button = self._GetElement(self._driver.find_element_by_xpath,
                                         discard_xpath)
       discard_button.click()
 
       # Wait for the message to be discarded, assumed to be true after the
       # "To" field is removed from the webpage DOM.
       self._wait.until(lambda _: not self._GetElement(
                            self._driver.find_element_by_name, 'to'))
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
-                        test_description, scenario)
+                        test_description, scenario,
+                        frame_xpath=self._FRAME_XPATH)
 
   # TODO(dennisjeffrey): Remove this test once the Gmail team is done analyzing
   # the results after the test runs for a period of time.
   def testGmailComposeDiscardSleep(self):
     """Like testGmailComposeDiscard, but sleeps for 30s between iterations.
 
     This is a temporary test requested by the Gmail team to compare against the
     results from testGmailComposeDiscard above.
     """
     test_description = 'ComposeDiscardSleep'
@@ skipping 34 matching lines @@
       # "To" field is removed from the webpage DOM.
       self._wait.until(lambda _: not self._GetElement(
                            self._driver.find_element_by_name, 'to'))
 
       # Sleep 2 minutes after every batch of 500 compose/discard iterations.
       if self._iteration_num % 500 == 0:
         logging.info('Sleeping 2 minutes.')
         time.sleep(120)
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
-                        test_description, scenario)
+                        test_description, scenario,
+                        frame_xpath=self._FRAME_XPATH)
 
   def testGmailAlternateThreadlistConversation(self):
     """Alternates between threadlist view and conversation view.
 
     This test continually clicks between the threadlist (Inbox) and the
     conversation view (e-mail message view), and periodically gathers
     performance stats that may reveal memory bloat.
     """
     test_description = 'ThreadConversation'
 
@@ skipping 22 matching lines @@
       self.WaitForDomNode(inbox_xpath, frame_xpath=self._FRAME_XPATH)
       inbox = self._GetElement(self._driver.find_element_by_xpath, inbox_xpath)
       self._ClickElementAndRecordLatency(inbox, test_description, 'Threadlist')
       self._wait.until(
           lambda _: not self._GetElement(
               self._driver.find_element_by_xpath,
               '//div[text()="Click here to "]'))
       time.sleep(1)
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
-                        test_description, scenario)
+                        test_description, scenario,
+                        frame_xpath=self._FRAME_XPATH)
 
   def testGmailAlternateTwoLabels(self):
     """Continuously alternates between two labels.
 
     This test continually clicks between the "Inbox" and "Sent Mail" labels,
     and periodically gathers performance stats that may reveal memory bloat.
     """
     test_description = 'AlternateLabels'
 
     def scenario():
@@ skipping 18 matching lines @@
       self.WaitForDomNode(inbox_xpath, frame_xpath=self._FRAME_XPATH)
       inbox = self._GetElement(self._driver.find_element_by_xpath, inbox_xpath)
       self._ClickElementAndRecordLatency(inbox, test_description, 'Inbox')
       self.assertTrue(
           self.WaitUntil(lambda: 'Inbox' in self.GetActiveTabTitle(),
                          timeout=60, expect_retval=True, retry_sleep=1),
           msg='Timed out waiting for Inbox to appear.')
       time.sleep(1)
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
-                        test_description, scenario)
+                        test_description, scenario,
+                        frame_xpath=self._FRAME_XPATH)
 
   def testGmailExpandCollapseConversation(self):
     """Continuously expands/collapses all messages in a conversation.
 
     This test opens up a conversation (e-mail thread) with several messages,
     then continually alternates between the "Expand all" and "Collapse all"
     views, while periodically gathering performance stats that may reveal memory
     bloat.
     """
     test_description = 'ExpandCollapse'
@@ skipping 30 matching lines @@
       collapse = self._GetElement(self._driver.find_element_by_xpath,
                                   collapse_xpath)
       collapse.click()
       self.WaitForDomNode(
           '//img[@alt="Collapse all"]/parent::*/parent::*/parent::*'
           '[@style="display: none; "]',
           frame_xpath=self._FRAME_XPATH)
       time.sleep(1)
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
-                        test_description, scenario)
+                        test_description, scenario,
+                        frame_xpath=self._FRAME_XPATH)
 
 
 class ChromeEndureDocsTest(ChromeEndureBaseTest):
   """Long-running performance tests for Chrome using Google Docs."""
 
   _WEBAPP_NAME = 'Docs'
   _TAB_TITLE_SUBSTRING = 'Google Drive'
 
   def setUp(self):
     ChromeEndureBaseTest.setUp(self)
@@ skipping 171 matching lines @@
         self._num_errors += 1
 
       time.sleep(1)
 
     self._RunEndureTest(self._WEBAPP_NAME, self._TAB_TITLE_SUBSTRING,
                         test_description, scenario)
 
 
 if __name__ == '__main__':
   pyauto_functional.Main()