devserver: add ongoing au process number check in check_health.

This CL mainly does:
1. Add checking the number of current background au processes in
check_healthy devserver call.
2. Force kill_au_proc to kill the au process if the process's pid is
passed.

BUG=chromium:696606
TEST=Run local devserver and call check_health & kill_au_proc.

Change-Id: I4fe44407b85659bd3aab309ac8efe11b0b457f68
Reviewed-on: https://chromium-review.googlesource.com/447821
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Commit-Queue: Xixuan Wu <xixuan@chromium.org>
Tested-by: Xixuan Wu <xixuan@chromium.org>
diff --git a/cros_update_progress.py b/cros_update_progress.py
index f7c6b8e..72b872a 100644
--- a/cros_update_progress.py
+++ b/cros_update_progress.py
@@ -20,21 +20,36 @@
 
 from __future__ import print_function
 
+import datetime
 import glob
 import logging
 import os
+import re
+
+import log_util
+
+# Module-local log function.
+def _Log(message, *args):
+  return log_util.LogWithTag('CROS_UPDATE_PROGRESS', message, *args)
 
 # only import setup_chromite before chromite import.
 import setup_chromite # pylint: disable=unused-import
 try:
   from chromite.lib import osutils
 except ImportError as e:
-  logging.debug('chromite cannot be imported: %r', e)
+  _Log('chromite cannot be imported: %r', e)
   osutils = None
 
+
 # Path for status tracking log.
 _TRACK_LOG_FILE_PATH = '/tmp/auto-update/tracking_log/%s_%s.log'
 
+# Pattern for status tracking log filename.
+_TRACK_LOG_FILE_NAME_PATTERN = r'([^_]+)_([^_]+).log'
+
+# The gap hour used in checking AU processes' count.
+AU_PROCESS_HOUR_GAP = 3
+
 # Path for executing log.
 _EXECUTE_LOG_FILE_PATH = '/tmp/auto-update/executing_log/%s_%s.log'
 
@@ -90,11 +105,73 @@
   return _TRACK_LOG_FILE_PATH % (host_name, pid)
 
 
+def GetAllTrackStatusFileByTime():
+  """Return all track status files existing in TRACK_LOG_FILE_PATH.
+
+  Returns:
+    A track status file list ordered by created time reversely.
+  """
+  return sorted(glob.glob(_TRACK_LOG_FILE_PATH % ('*', '*')),
+                key=os.path.getctime, reverse=True)
+
+
+def ParsePidFromTrackLogFileName(track_log_filename):
+  """Parse pid from a given track log file's name.
+
+  The track log file's name for auto-update is fixed:
+      hostname_pid.log
+
+  This func is used to parse pid from a given track log file.
+
+  Args:
+    track_log_filename: the filename of the track log to be parsed.
+
+  Returns:
+    the parsed pid (int).
+  """
+  match = re.match(_TRACK_LOG_FILE_NAME_PATTERN, track_log_filename)
+  try:
+    return int(match.groups()[1])
+  except (AttributeError, IndexError, ValueError) as e:
+    _Log('Cannot parse pid from track log file %s: %s', track_log_filename, e)
+    return None
+
+
 def GetAllTrackStatusFileByHostName(host_name):
   """Return a list of existing track status files generated for a host."""
   return glob.glob(_TRACK_LOG_FILE_PATH % (host_name, '*'))
 
 
+def GetAllRunningAUProcess():
+  """Get all the ongoing AU processes' pids from tracking logs.
+
+  This func only checks the tracking logs generated in latest several hours,
+  which is for avoiding the case that 'there's a running process whose id is
+  as the same as a previous AU process'.
+
+  Returns:
+    A list of background AU processes' pids.
+  """
+  pids = []
+  now = datetime.datetime.now()
+  track_log_list = GetAllTrackStatusFileByTime()
+  # Only check log file created in 3 hours.
+  for track_log in track_log_list:
+    try:
+      created_time = datetime.datetime.fromtimestamp(
+          os.path.getctime(track_log))
+      if now - created_time >= datetime.timedelta(hours=AU_PROCESS_HOUR_GAP):
+        break
+
+      pid = ParsePidFromTrackLogFileName(os.path.basename(track_log))
+      if pid and IsProcessAlive(pid):
+        pids.append(pid)
+    except (ValueError, os.error) as e:
+      _Log('Error happened in getting pid from %s: %s', track_log, e)
+
+  return pids
+
+
 def GetAUTempDirectory(host_name, pid):
   """Return the temp dir for storing codes and logs during auto-update."""
   au_tempdir = _CROS_UPDATE_TEMP_PATH % (host_name, pid)