Retry browser startup in desktop_browser_finder.

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

Index: telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py
diff --git a/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py b/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py
index e2cedb744857bbd6886669a9f69166f38ed0d018..438febd164cf2aef02fd04bea85d2bc75222d846 100644
--- a/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py
+++ b/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py
@@ -60,12 +60,39 @@ class PossibleDesktopBrowser(possible_browser.PossibleBrowser):
 
     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)