[Android] Add logging of active device_forwarders

build/android/pylib/forwarder.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.
 
 # pylint: disable=W0212
 
 import fcntl
 import logging
 import os
 import psutil
@@ skipping 78 matching lines @@
         try:
           (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
               [instance._host_forwarder_path] + redirection_command)
         except OSError as e:
           if e.errno == 2:
             raise Exception('Unable to start host forwarder. Make sure you have'
                             ' built host_forwarder.')
           else: raise
         if exit_code != 0:
           Forwarder._KillDeviceLocked(device, tool)
+          # Log alive forwarders
+          ps_out = device.RunShellCommand(['ps'])
+          logging.info('Currently running device_forwarders:')
+          for line in ps_out:
+            if 'device_forwarder' in line:
+              logging.info('    %s', line)
           raise Exception('%s exited with %d:\n%s' % (
               instance._host_forwarder_path, exit_code, '\n'.join(output)))
         tokens = output.split(':')
         if len(tokens) != 2:
           raise Exception('Unexpected host forwarder output "%s", '
                           'expected "device_port:host_port"' % output)
         device_port = int(tokens[0])
         host_port = int(tokens[1])
         serial_with_port = (device_serial, device_port)
         instance._device_to_host_port_map[serial_with_port] = host_port
@@ skipping 203 matching lines @@
     logging.info('Killing device_forwarder.')
     Forwarder._instance._initialized_devices.discard(str(device))
     if not device.FileExists(Forwarder._DEVICE_FORWARDER_PATH):
       return
 
     cmd = '%s %s --kill-server' % (tool.GetUtilWrapper(),
                                    Forwarder._DEVICE_FORWARDER_PATH)
     device.RunShellCommand(
         cmd, env={'LD_LIBRARY_PATH': Forwarder._DEVICE_FORWARDER_FOLDER},
         check_return=True)