Retry browser startup in desktop_browser_finder.

telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py

 # Copyright 2013 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.
 """Finds desktop browsers that can be controlled by telemetry."""
 
 import logging
 import os
 import sys
 
 import dependency_manager  # pylint: disable=import-error
@@ skipping 42 matching lines @@
   def Create(self, finder_options):
     if self._flash_path and not os.path.exists(self._flash_path):
       logging.warning(
           'Could not find Flash at %s. Continuing without Flash.\n'
           'To run with Flash, check it out via http://go/read-src-internal',
           self._flash_path)
       self._flash_path = None
 
     self._InitPlatformIfNeeded()
 
-    browser_backend = desktop_browser_backend.DesktopBrowserBackend(
-        self._platform_backend,
-        finder_options.browser_options, self._local_executable,
-        self._flash_path, self._is_content_shell, self._browser_directory)
-    return browser.Browser(
-        browser_backend, self._platform_backend, self._credentials_path)
+    num_retries = 3
+    for x in range(0, num_retries):
+      returned_browser = None
+      try:
+        returned_browser = None
+        restart = 'Starting browser, attempt %d of %d' % ((x + 1), num_retries)

[nednguyen, 2017/05/07 23:47:43]

Can you remove this the line below. We shouldn't add logging in case there is no
retry.

[Ken Russell (switch to Gerrit), 2017/05/08 20:44:11]

Yes, done.

+        logging.warning(restart)
+
+        browser_backend = desktop_browser_backend.DesktopBrowserBackend(
+            self._platform_backend,
+            finder_options.browser_options, self._local_executable,
+            self._flash_path, self._is_content_shell, self._browser_directory)
+
+        returned_browser = browser.Browser(
+            browser_backend, self._platform_backend, self._credentials_path)
+
+        # Try fetching the zeroth tab. If this works, then the browser
+        # appears to be working.
+        _ = returned_browser.tabs[0]
+
+        logging.warning('Started browser successfully.')

[nednguyen, 2017/05/07 23:47:43]

I think this log is not needed.

[Ken Russell (switch to Gerrit), 2017/05/08 20:44:11]

OK, removed.

+        return returned_browser
+      except Exception:
+        logging.warning('Browser creation failed, retrying')

[nednguyen, 2017/05/07 23:47:43]

logging.warning('Browser creation failed, retrying (attempt %d of %d)', x + 1,
num_retries)

[Ken Russell (switch to Gerrit), 2017/05/08 20:44:11]

Done, slightly rephrased.

+        # Attempt to clean up things left over from the failed browser startup.
+        try:
+          if returned_browser:
+            returned_browser.Close()
+        except Exception:
+          pass
+        # Re-raise the exception the last time through.
+        if x == num_retries - 1:
+          raise
 
   def SupportsOptions(self, browser_options):
     if ((len(browser_options.extensions_to_load) != 0)
         and self._is_content_shell):
       return False
     return True
 
   def UpdateExecutableIfNeeded(self):
     pass
 
@@ skipping 200 matching lines @@
     if "--ozone-platform" in arg:
       has_ozone_platform = True
 
   if len(browsers) and not has_x11_display and not has_ozone_platform:
     logging.warning(
       'Found (%s), but you do not have a DISPLAY environment set.' %
       ','.join([b.browser_type for b in browsers]))
     return []
 
   return browsers