Add condition to -maxclients Xvfb option in run_web_tests

This is now only invoked where necessary (60+ cores).
Makes the test runner compatible with both modern machines and
linux-trusty-rel (which uses a very old Xvfb).

Bug: 1122100
Change-Id: Ib68f356efaa8fa361d0c377845bba165635d5362
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2385923
Commit-Queue: George Steel <gtsteel@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803900}

third_party/blink/tools/blinkpy/web_tests/port/linux.py

@@ -189,10 +189,7 @@ class LinuxPort(base.Port):
         self._xvfb_stdout = tempfile.NamedTemporaryFile(delete=False)
         self._xvfb_stderr = tempfile.NamedTemporaryFile(delete=False)
         self._xvfb_process = self.host.executive.popen(
-            [
-                'Xvfb', display, '-screen', '0', '1280x800x24', '-ac', '-dpi',
-                '96', '-maxclients', '512'
-            ],
+            ['Xvfb', display] + self.xvfb_flags(),
             stdout=self._xvfb_stdout,
             stderr=self._xvfb_stderr,
             env=env)
@@ -230,6 +227,16 @@ class LinuxPort(base.Port):
             display, retcode)
         return False
 
+    def xvfb_flags(self):
+        flags = ['-screen', '0', '1280x800x24', '-ac', '-dpi', '96']
+        # Raise the Xvfb connection limit if the default limit (256 connections)
+        # is in danger of being exceeded by 4 connections per test.
+        # This is conditional since the linux-trusty-rel build bot uses a very
+        # old version of Xvfb which does not recognise the flag.
+        if self.default_child_processes() > 60:
+            flags += ['-maxclients', '512']
+        return flags
+
     def _find_display(self):
         """Tries to find a free X display, looping if necessary."""
         # The "xvfb-run" command uses :99 by default.

third_party/blink/tools/blinkpy/web_tests/port/linux_unittest.py

@@ -137,6 +137,17 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertEqual(port.host.environ['HOME'], '/home/user')
         self.assertFalse(port.host.filesystem.exists(temp_home_dir))
 
+    def test_xvfb_flags(self):
+        port = self.make_port()
+        port.default_child_processes = lambda: 60
+        self.assertEqual(port.xvfb_flags(),
+                         ['-screen', '0', '1280x800x24', '-ac', '-dpi', '96'])
+        port.default_child_processes = lambda: 61
+        self.assertEqual(port.xvfb_flags(), [
+            '-screen', '0', '1280x800x24', '-ac', '-dpi', '96', '-maxclients',
+            '512'
+        ])
+
     def test_setup_test_run_starts_xvfb(self):
         def run_command_fake(args):
             if args[0:2] == ['xdpyinfo', '-display']:
@@ -149,10 +160,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertIsNone(port.setup_test_run())
         self.assertEqual(port.host.executive.calls, [
             ['xdpyinfo', '-display', ':99'],
-            [
-                'Xvfb', ':99', '-screen', '0', '1280x800x24', '-ac', '-dpi',
-                '96', '-maxclients', '512'
-            ],
+            ['Xvfb', ':99'] + port.xvfb_flags(),
             ['xdpyinfo'],
         ])
         env = port.setup_environ_for_server()
@@ -171,10 +179,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertIsNone(port.setup_test_run())
         self.assertEqual(port.host.executive.calls, [
             ['xdpyinfo', '-display', ':99'],
-            [
-                'Xvfb', ':99', '-screen', '0', '1280x800x24', '-ac', '-dpi',
-                '96', '-maxclients', '512'
-            ],
+            ['Xvfb', ':99'] + port.xvfb_flags(),
             ['xdpyinfo'],
         ])
         self.assertEqual(
@@ -201,10 +206,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
                 ['xdpyinfo', '-display', ':100'],
                 ['xdpyinfo', '-display', ':101'],
                 ['xdpyinfo', '-display', ':102'],
-                [
-                    'Xvfb', ':102', '-screen', '0', '1280x800x24', '-ac',
-                    '-dpi', '96', '-maxclients', '512'
-                ],
+                ['Xvfb', ':102'] + port.xvfb_flags(),
                 ['xdpyinfo'],
             ])
         env = port.setup_environ_for_server()
@@ -229,10 +231,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertIsNone(port.setup_test_run())
         self.assertEqual(port.host.executive.calls, [
             ['xdpyinfo', '-display', ':99'],
-            [
-                'Xvfb', ':99', '-screen', '0', '1280x800x24', '-ac', '-dpi',
-                '96', '-maxclients', '512'
-            ],
+            ['Xvfb', ':99'] + port.xvfb_flags(),
             ['xdpyinfo'],
             ['xdpyinfo'],
             ['xdpyinfo'],
@@ -255,10 +254,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertEqual(port.setup_test_run(), SYS_DEPS_EXIT_STATUS)
         self.assertEqual(port.host.executive.calls, [
             ['xdpyinfo', '-display', ':99'],
-            [
-                'Xvfb', ':99', '-screen', '0', '1280x800x24', '-ac', '-dpi',
-                '96', '-maxclients', '512'
-            ],
+            ['Xvfb', ':99'] + port.xvfb_flags(),
         ] + [['xdpyinfo']] * 51)
         env = port.setup_environ_for_server()
         self.assertEqual(env['DISPLAY'], ':99')
@@ -288,10 +284,7 @@ class LinuxPortTest(port_testcase.PortTestCase, LoggingTestCase):
         self.assertEqual(port.setup_test_run(), SYS_DEPS_EXIT_STATUS)
         self.assertEqual(port.host.executive.calls,
                          [['xdpyinfo', '-display', ':99'],
-                          [
-                              'Xvfb', ':99', '-screen', '0', '1280x800x24',
-                              '-ac', '-dpi', '96', '-maxclients', '512'
-                          ]])
+                          ['Xvfb', ':99'] + port.xvfb_flags()])
         self.assertLog([
             'DEBUG: Starting Xvfb with display ":99".\n',
             'CRITICAL: Failed to start Xvfb on display ":99" (xvfb retcode: 3).\n'