Add script to run a test in a separate read-only directory.

isolate/xvfb.py

+# 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.
+
+"""Helper tools to manage a Virtual X buffer with Xvfb."""
+
+import commands
+import logging
+import os
+import signal
+import subprocess
+import tempfile
+
+
+def _XvfbPidFilename(unique_name):
+  """Returns the filename to the Xvfb pid file.  This name is unique for each
+  builder. This is used by the linux builders."""
+  return os.path.join(tempfile.gettempdir(), 'xvfb-%s.pid' % unique_name)
+
+
+def start_virtualx(unique_name, path=None, display=':9'):
+  """Start a virtual X server and set the DISPLAY environment variable so sub
+  processes will use the virtual X server.  Also start icewm. This only works
+  on Linux and assumes that xvfb and icewm are installed.
+
+  Args:
+    unique_name: A unique name to identify this X session that is used for the
+        pid file.
+        E.g., webkit-rel-linux.
+    path: (optional) the path where build outputs are generated, xdisplaycheck
+          will be executed to verify Xvfb correctly started.
+  """
+  # We use a pid file to make sure we don't have any xvfb processes running
+  # from a previous test run.
+  stop_virtualx(unique_name)
+
+  # Start a virtual X server that we run the tests in.  This makes it so we can
+  # run the tests even if we didn't start the tests from an X session.
+  proc = subprocess.Popen(
+      ['Xvfb', display, '-screen', '0', '1024x768x24', '-ac'],
+      stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+  xvfb_pid_filename = _XvfbPidFilename(unique_name)
+  open(xvfb_pid_filename, 'w').write(str(proc.pid))
+  if path:
+    # Verifies that Xvfb has started by using xdisplaycheck.
+    xdisplaycheck_path = os.path.join(path, 'xdisplaycheck')
+    if not os.path.exists(xdisplaycheck_path):
+      raise Exception('%s doesn\'t exist.' % xdisplaycheck_path)
+    logging.info('Verifying Xvfb has started...')
+    status, output = commands.getstatusoutput(xdisplaycheck_path)
+    if status != 0:
+      logging.info('Xvfb return code (None if still running): %s' % proc.poll())
+      logging.info('Xvfb stdout and stderr:%s' % proc.communicate())
+      raise Exception(output)
+    logging.info('...OK')
+  # Some ChromeOS tests need a window manager.
+  subprocess.Popen("icewm", stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+  return display
+
+
+def stop_virtualx(unique_name):
+  """Try and stop the virtual X server if one was started with StartVirtualX.
+  When the X server dies, it takes down the window manager with it.
+  If a virtual x server is not running, this method does nothing."""
+  xvfb_pid_filename = _XvfbPidFilename(unique_name)
+  if os.path.exists(xvfb_pid_filename):
+    # If the process doesn't exist, we raise an exception that we can ignore.
+    try:
+      os.kill(int(open(xvfb_pid_filename).read()), signal.SIGKILL)
+    except OSError:
+      pass
+    os.remove(xvfb_pid_filename)
+
+
+class Xvfb(object):
+  def __init__(self, unique_name):
+    self.unique_name = unique_name
+
+  def start(self, build=None):
+    start_virtualx(self.unique_name, build)
+
+  def stop(self):
+    stop_virtualx(self.unique_name)