xref: /external/toolchain-utils/crosperf/results_cache.py

# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Module to deal with result cache."""

from __future__ import print_function

import glob
import hashlib
import os
import pickle
import re
import tempfile
import json
import sys

from cros_utils import command_executer
from cros_utils import misc

from image_checksummer import ImageChecksummer

import results_report
import test_flag

SCRATCH_DIR = os.path.expanduser('~/cros_scratch')
RESULTS_FILE = 'results.txt'
MACHINE_FILE = 'machine.txt'
AUTOTEST_TARBALL = 'autotest.tbz2'
PERF_RESULTS_FILE = 'perf-results.txt'
CACHE_KEYS_FILE = 'cache_keys.txt'


class Result(object):
  """Class for holding the results of a single test run.

  This class manages what exactly is stored inside the cache without knowing
  what the key of the cache is. For runs with perf, it stores perf.data,
  perf.report, etc. The key generation is handled by the ResultsCache class.
  """

  def __init__(self, logger, label, log_level, machine, cmd_exec=None):
    self.chromeos_root = label.chromeos_root
    self._logger = logger
    self.ce = cmd_exec or command_executer.GetCommandExecuter(
        self._logger,
        log_level=log_level)
    self.temp_dir = None
    self.label = label
    self.results_dir = None
    self.log_level = log_level
    self.machine = machine
    self.perf_data_files = []
    self.perf_report_files = []
    self.results_file = []
    self.chrome_version = ''
    self.err = None
    self.chroot_results_dir = ''
    self.test_name = ''
    self.keyvals = None
    self.board = None
    self.suite = None
    self.retval = None
    self.out = None

  def CopyFilesTo(self, dest_dir, files_to_copy):
    file_index = 0
    for file_to_copy in files_to_copy:
      if not os.path.isdir(dest_dir):
        command = 'mkdir -p %s' % dest_dir
        self.ce.RunCommand(command)
      dest_file = os.path.join(dest_dir,
                               ('%s.%s' % (os.path.basename(file_to_copy),
                                           file_index)))
      ret = self.ce.CopyFiles(file_to_copy, dest_file, recursive=False)
      if ret:
        raise IOError('Could not copy results file: %s' % file_to_copy)

  def CopyResultsTo(self, dest_dir):
    self.CopyFilesTo(dest_dir, self.perf_data_files)
    self.CopyFilesTo(dest_dir, self.perf_report_files)
    if len(self.perf_data_files) or len(self.perf_report_files):
      self._logger.LogOutput('Perf results files stored in %s.' % dest_dir)

  def GetNewKeyvals(self, keyvals_dict):
    # Initialize 'units' dictionary.
    units_dict = {}
    for k in keyvals_dict:
      units_dict[k] = ''
    results_files = self.GetDataMeasurementsFiles()
    for f in results_files:
      # Make sure we can find the results file
      if os.path.exists(f):
        data_filename = f
      else:
        # Otherwise get the base filename and create the correct
        # path for it.
        _, f_base = misc.GetRoot(f)
        data_filename = os.path.join(self.chromeos_root, 'chroot/tmp',
                                     self.temp_dir, f_base)
      if data_filename.find('.json') > 0:
        raw_dict = dict()
        if os.path.exists(data_filename):
          with open(data_filename, 'r') as data_file:
            raw_dict = json.load(data_file)

        if 'charts' in raw_dict:
          raw_dict = raw_dict['charts']
        for k1 in raw_dict:
          field_dict = raw_dict[k1]
          for k2 in field_dict:
            result_dict = field_dict[k2]
            key = k1 + '__' + k2
            if 'value' in result_dict:
              keyvals_dict[key] = result_dict['value']
            elif 'values' in result_dict:
              keyvals_dict[key] = result_dict['values']
            units_dict[key] = result_dict['units']
      else:
        if os.path.exists(data_filename):
          with open(data_filename, 'r') as data_file:
            lines = data_file.readlines()
            for line in lines:
              tmp_dict = json.loads(line)
              graph_name = tmp_dict['graph']
              graph_str = (graph_name + '__') if graph_name else ''
              key = graph_str + tmp_dict['description']
              keyvals_dict[key] = tmp_dict['value']
              units_dict[key] = tmp_dict['units']

    return keyvals_dict, units_dict

  def AppendTelemetryUnits(self, keyvals_dict, units_dict):
    """keyvals_dict is the dict of key-value used to generate Crosperf reports.

    units_dict is a dictionary of the units for the return values in
    keyvals_dict.  We need to associate the units with the return values,
    for Telemetry tests, so that we can include the units in the reports.
    This function takes each value in keyvals_dict, finds the corresponding
    unit in the units_dict, and replaces the old value with a list of the
    old value and the units.  This later gets properly parsed in the
    ResultOrganizer class, for generating the reports.
    """

    results_dict = {}
    for k in keyvals_dict:
      # We don't want these lines in our reports; they add no useful data.
      if k == '' or k == 'telemetry_Crosperf':
        continue
      val = keyvals_dict[k]
      units = units_dict[k]
      new_val = [val, units]
      results_dict[k] = new_val
    return results_dict

  def GetKeyvals(self):
    results_in_chroot = os.path.join(self.chromeos_root, 'chroot', 'tmp')
    if not self.temp_dir:
      self.temp_dir = tempfile.mkdtemp(dir=results_in_chroot)
      command = 'cp -r {0}/* {1}'.format(self.results_dir, self.temp_dir)
      self.ce.RunCommand(command, print_to_console=False)

    command = ('python generate_test_report --no-color --csv %s' %
               (os.path.join('/tmp', os.path.basename(self.temp_dir))))
    _, out, _ = self.ce.ChrootRunCommandWOutput(self.chromeos_root,
                                                command,
                                                print_to_console=False)
    keyvals_dict = {}
    tmp_dir_in_chroot = misc.GetInsideChrootPath(self.chromeos_root,
                                                 self.temp_dir)
    for line in out.splitlines():
      tokens = re.split('=|,', line)
      key = tokens[-2]
      if key.startswith(tmp_dir_in_chroot):
        key = key[len(tmp_dir_in_chroot) + 1:]
      value = tokens[-1]
      keyvals_dict[key] = value

    # Check to see if there is a perf_measurements file and get the
    # data from it if so.
    keyvals_dict, units_dict = self.GetNewKeyvals(keyvals_dict)
    if self.suite == 'telemetry_Crosperf':
      # For telemtry_Crosperf results, append the units to the return
      # results, for use in generating the reports.
      keyvals_dict = self.AppendTelemetryUnits(keyvals_dict, units_dict)
    return keyvals_dict

  def GetResultsDir(self):
    mo = re.search(r'Results placed in (\S+)', self.out)
    if mo:
      result = mo.group(1)
      return result
    raise RuntimeError('Could not find results directory.')

  def FindFilesInResultsDir(self, find_args):
    if not self.results_dir:
      return None

    command = 'find %s %s' % (self.results_dir, find_args)
    ret, out, _ = self.ce.RunCommandWOutput(command, print_to_console=False)
    if ret:
      raise RuntimeError('Could not run find command!')
    return out

  def GetResultsFile(self):
    return self.FindFilesInResultsDir('-name results-chart.json').splitlines()

  def GetPerfDataFiles(self):
    return self.FindFilesInResultsDir('-name perf.data').splitlines()

  def GetPerfReportFiles(self):
    return self.FindFilesInResultsDir('-name perf.data.report').splitlines()

  def GetDataMeasurementsFiles(self):
    result = self.FindFilesInResultsDir('-name perf_measurements').splitlines()
    if not result:
      result = \
          self.FindFilesInResultsDir('-name results-chart.json').splitlines()
    return result

  def GeneratePerfReportFiles(self):
    perf_report_files = []
    for perf_data_file in self.perf_data_files:
      # Generate a perf.report and store it side-by-side with the perf.data
      # file.
      chroot_perf_data_file = misc.GetInsideChrootPath(self.chromeos_root,
                                                       perf_data_file)
      perf_report_file = '%s.report' % perf_data_file
      if os.path.exists(perf_report_file):
        raise RuntimeError('Perf report file already exists: %s' %
                           perf_report_file)
      chroot_perf_report_file = misc.GetInsideChrootPath(self.chromeos_root,
                                                         perf_report_file)
      perf_path = os.path.join(self.chromeos_root, 'chroot', 'usr/bin/perf')

      perf_file = '/usr/sbin/perf'
      if os.path.exists(perf_path):
        perf_file = '/usr/bin/perf'

      # The following is a hack, to use the perf.static binary that
      # was given to us by Stephane Eranian, until he can figure out
      # why "normal" perf cannot properly symbolize ChromeOS perf.data files.
      # Get the directory containing the 'crosperf' script.
      dirname, _ = misc.GetRoot(sys.argv[0])
      perf_path = os.path.join(dirname, '..', 'perf.static')
      if os.path.exists(perf_path):
        # copy the executable into the chroot so that it can be found.
        src_path = perf_path
        dst_path = os.path.join(self.chromeos_root, 'chroot',
                                'tmp/perf.static')
        command = 'cp %s %s' % (src_path, dst_path)
        self.ce.RunCommand(command)
        perf_file = '/tmp/perf.static'

      command = ('%s report '
                 '-n '
                 '--symfs /build/%s '
                 '--vmlinux /build/%s/usr/lib/debug/boot/vmlinux '
                 '--kallsyms /build/%s/boot/System.map-* '
                 '-i %s --stdio '
                 '> %s' % (perf_file, self.board, self.board, self.board,
                           chroot_perf_data_file, chroot_perf_report_file))
      self.ce.ChrootRunCommand(self.chromeos_root, command)

      # Add a keyval to the dictionary for the events captured.
      perf_report_files.append(misc.GetOutsideChrootPath(
          self.chromeos_root, chroot_perf_report_file))
    return perf_report_files

  def GatherPerfResults(self):
    report_id = 0
    for perf_report_file in self.perf_report_files:
      with open(perf_report_file, 'r') as f:
        report_contents = f.read()
        for group in re.findall(r'Events: (\S+) (\S+)', report_contents):
          num_events = group[0]
          event_name = group[1]
          key = 'perf_%s_%s' % (report_id, event_name)
          value = str(misc.UnitToNumber(num_events))
          self.keyvals[key] = value

  def PopulateFromRun(self, out, err, retval, test, suite):
    self.board = self.label.board
    self.out = out
    self.err = err
    self.retval = retval
    self.test_name = test
    self.suite = suite
    self.chroot_results_dir = self.GetResultsDir()
    self.results_dir = misc.GetOutsideChrootPath(self.chromeos_root,
                                                 self.chroot_results_dir)
    self.results_file = self.GetResultsFile()
    self.perf_data_files = self.GetPerfDataFiles()
    # Include all perf.report data in table.
    self.perf_report_files = self.GeneratePerfReportFiles()
    # TODO(asharif): Do something similar with perf stat.

    # Grab keyvals from the directory.
    self.ProcessResults()

  def ProcessJsonResults(self):
    # Open and parse the json results file generated by telemetry/test_that.
    if not self.results_file:
      raise IOError('No results file found.')
    filename = self.results_file[0]
    if not filename.endswith('.json'):
      raise IOError('Attempt to call json on non-json file: %s' % filename)

    if not os.path.exists(filename):
      return {}

    keyvals = {}
    with open(filename, 'r') as f:
      raw_dict = json.load(f)
      if 'charts' in raw_dict:
        raw_dict = raw_dict['charts']
      for k, field_dict in raw_dict.iteritems():
        for item in field_dict:
          keyname = k + "__" + item
          value_dict = field_dict[item]
          if 'value' in value_dict:
            result = value_dict['value']
          elif 'values' in value_dict:
            if not value_dict['values']:
              continue
            result = value_dict['values']
          units = value_dict['units']
          new_value = [result, units]
          keyvals[keyname] = new_value
    return keyvals

  def ProcessResults(self, use_cache=False):
    # Note that this function doesn't know anything about whether there is a
    # cache hit or miss. It should process results agnostic of the cache hit
    # state.
    if self.results_file and self.results_file[0].find('results_chart.json'):
      self.keyvals = self.ProcessJsonResults()
    else:
      if not use_cache:
        print('\n ** WARNING **: Had to use deprecated output-method to '
              'collect results.\n')
      self.keyvals = self.GetKeyvals()
    self.keyvals['retval'] = self.retval
    # Generate report from all perf.data files.
    # Now parse all perf report files and include them in keyvals.
    self.GatherPerfResults()

  def GetChromeVersionFromCache(self, cache_dir):
    # Read chrome_version from keys file, if present.
    chrome_version = ''
    keys_file = os.path.join(cache_dir, CACHE_KEYS_FILE)
    if os.path.exists(keys_file):
      with open(keys_file, 'r') as f:
        lines = f.readlines()
        for l in lines:
          if l.startswith('Google Chrome '):
            chrome_version = l
            if chrome_version.endswith('\n'):
              chrome_version = chrome_version[:-1]
            break
    return chrome_version

  def PopulateFromCacheDir(self, cache_dir, test, suite):
    self.test_name = test
    self.suite = suite
    # Read in everything from the cache directory.
    with open(os.path.join(cache_dir, RESULTS_FILE), 'r') as f:
      self.out = pickle.load(f)
      self.err = pickle.load(f)
      self.retval = pickle.load(f)

    # Untar the tarball to a temporary directory
    self.temp_dir = tempfile.mkdtemp(
        dir=os.path.join(self.chromeos_root, 'chroot', 'tmp'))

    command = ('cd %s && tar xf %s' %
               (self.temp_dir, os.path.join(cache_dir, AUTOTEST_TARBALL)))
    ret = self.ce.RunCommand(command, print_to_console=False)
    if ret:
      raise RuntimeError('Could not untar cached tarball')
    self.results_dir = self.temp_dir
    self.perf_data_files = self.GetPerfDataFiles()
    self.perf_report_files = self.GetPerfReportFiles()
    self.chrome_version = self.GetChromeVersionFromCache(cache_dir)
    self.ProcessResults(use_cache=True)

  def CleanUp(self, rm_chroot_tmp):
    if rm_chroot_tmp and self.results_dir:
      dirname, basename = misc.GetRoot(self.results_dir)
      if basename.find('test_that_results_') != -1:
        command = 'rm -rf %s' % self.results_dir
      else:
        command = 'rm -rf %s' % dirname
      self.ce.RunCommand(command)
    if self.temp_dir:
      command = 'rm -rf %s' % self.temp_dir
      self.ce.RunCommand(command)

  def StoreToCacheDir(self, cache_dir, machine_manager, key_list):
    # Create the dir if it doesn't exist.
    temp_dir = tempfile.mkdtemp()

    # Store to the temp directory.
    with open(os.path.join(temp_dir, RESULTS_FILE), 'w') as f:
      pickle.dump(self.out, f)
      pickle.dump(self.err, f)
      pickle.dump(self.retval, f)

    if not test_flag.GetTestMode():
      with open(os.path.join(temp_dir, CACHE_KEYS_FILE), 'w') as f:
        f.write('%s\n' % self.label.name)
        f.write('%s\n' % self.label.chrome_version)
        f.write('%s\n' % self.machine.checksum_string)
        for k in key_list:
          f.write(k)
          f.write('\n')

    if self.results_dir:
      tarball = os.path.join(temp_dir, AUTOTEST_TARBALL)
      command = ('cd %s && '
                 'tar '
                 '--exclude=var/spool '
                 '--exclude=var/log '
                 '-cjf %s .' % (self.results_dir, tarball))
      ret = self.ce.RunCommand(command)
      if ret:
        raise RuntimeError("Couldn't store autotest output directory.")
    # Store machine info.
    # TODO(asharif): Make machine_manager a singleton, and don't pass it into
    # this function.
    with open(os.path.join(temp_dir, MACHINE_FILE), 'w') as f:
      f.write(machine_manager.machine_checksum_string[self.label.name])

    if os.path.exists(cache_dir):
      command = 'rm -rf {0}'.format(cache_dir)
      self.ce.RunCommand(command)

    command = 'mkdir -p {0} && '.format(os.path.dirname(cache_dir))
    command += 'chmod g+x {0} && '.format(temp_dir)
    command += 'mv {0} {1}'.format(temp_dir, cache_dir)
    ret = self.ce.RunCommand(command)
    if ret:
      command = 'rm -rf {0}'.format(temp_dir)
      self.ce.RunCommand(command)
      raise RuntimeError('Could not move dir %s to dir %s' %
                         (temp_dir, cache_dir))

  @classmethod
  def CreateFromRun(cls,
                    logger,
                    log_level,
                    label,
                    machine,
                    out,
                    err,
                    retval,
                    test,
                    suite='telemetry_Crosperf'):
    if suite == 'telemetry':
      result = TelemetryResult(logger, label, log_level, machine)
    else:
      result = cls(logger, label, log_level, machine)
    result.PopulateFromRun(out, err, retval, test, suite)
    return result

  @classmethod
  def CreateFromCacheHit(cls,
                         logger,
                         log_level,
                         label,
                         machine,
                         cache_dir,
                         test,
                         suite='telemetry_Crosperf'):
    if suite == 'telemetry':
      result = TelemetryResult(logger, label, log_level, machine)
    else:
      result = cls(logger, label, log_level, machine)
    try:
      result.PopulateFromCacheDir(cache_dir, test, suite)

    except RuntimeError as e:
      logger.LogError('Exception while using cache: %s' % e)
      return None
    return result


class TelemetryResult(Result):
  """Class to hold the results of a single Telemetry run."""

  def __init__(self, logger, label, log_level, machine, cmd_exec=None):
    super(TelemetryResult, self).__init__(logger, label, log_level, machine,
                                          cmd_exec)

  def PopulateFromRun(self, out, err, retval, test, suite):
    self.out = out
    self.err = err
    self.retval = retval

    self.ProcessResults()

  def ProcessResults(self):
    # The output is:
    # url,average_commit_time (ms),...
    # www.google.com,33.4,21.2,...
    # We need to convert to this format:
    # {"www.google.com:average_commit_time (ms)": "33.4",
    #  "www.google.com:...": "21.2"}
    # Added note:  Occasionally the output comes back
    # with "JSON.stringify(window.automation.GetResults())" on
    # the first line, and then the rest of the output as
    # described above.

    lines = self.out.splitlines()
    self.keyvals = {}

    if lines:
      if lines[0].startswith('JSON.stringify'):
        lines = lines[1:]

    if not lines:
      return
    labels = lines[0].split(',')
    for line in lines[1:]:
      fields = line.split(',')
      if len(fields) != len(labels):
        continue
      for i in xrange(1, len(labels)):
        key = '%s %s' % (fields[0], labels[i])
        value = fields[i]
        self.keyvals[key] = value
    self.keyvals['retval'] = self.retval

  def PopulateFromCacheDir(self, cache_dir, test, suite):
    self.test_name = test
    self.suite = suite
    with open(os.path.join(cache_dir, RESULTS_FILE), 'r') as f:
      self.out = pickle.load(f)
      self.err = pickle.load(f)
      self.retval = pickle.load(f)

    self.chrome_version = \
        super(TelemetryResult, self).GetChromeVersionFromCache(cache_dir)
    self.ProcessResults()


class CacheConditions(object):
  """Various Cache condition values, for export."""

  # Cache hit only if the result file exists.
  CACHE_FILE_EXISTS = 0

  # Cache hit if the checksum of cpuinfo and totalmem of
  # the cached result and the new run match.
  MACHINES_MATCH = 1

  # Cache hit if the image checksum of the cached result and the new run match.
  CHECKSUMS_MATCH = 2

  # Cache hit only if the cached result was successful
  RUN_SUCCEEDED = 3

  # Never a cache hit.
  FALSE = 4

  # Cache hit if the image path matches the cached image path.
  IMAGE_PATH_MATCH = 5

  # Cache hit if the uuid of hard disk mataches the cached one

  SAME_MACHINE_MATCH = 6


class ResultsCache(object):
  """Class to handle the cache for storing/retrieving test run results.

  This class manages the key of the cached runs without worrying about what
  is exactly stored (value). The value generation is handled by the Results
  class.
  """
  CACHE_VERSION = 6

  def __init__(self):
    # Proper initialization happens in the Init function below.
    self.chromeos_image = None
    self.chromeos_root = None
    self.test_name = None
    self.iteration = None
    self.test_args = None
    self.profiler_args = None
    self.board = None
    self.cache_conditions = None
    self.machine_manager = None
    self.machine = None
    self._logger = None
    self.ce = None
    self.label = None
    self.share_cache = None
    self.suite = None
    self.log_level = None
    self.show_all = None
    self.run_local = None


  def Init(self, chromeos_image, chromeos_root, test_name, iteration, test_args,
           profiler_args, machine_manager, machine, board, cache_conditions,
           logger_to_use, log_level, label, share_cache, suite,
           show_all_results, run_local):
    self.chromeos_image = chromeos_image
    self.chromeos_root = chromeos_root
    self.test_name = test_name
    self.iteration = iteration
    self.test_args = test_args
    self.profiler_args = profiler_args
    self.board = board
    self.cache_conditions = cache_conditions
    self.machine_manager = machine_manager
    self.machine = machine
    self._logger = logger_to_use
    self.ce = command_executer.GetCommandExecuter(self._logger,
                                                  log_level=log_level)
    self.label = label
    self.share_cache = share_cache
    self.suite = suite
    self.log_level = log_level
    self.show_all = show_all_results
    self.run_local = run_local

  def GetCacheDirForRead(self):
    matching_dirs = []
    for glob_path in self.FormCacheDir(self.GetCacheKeyList(True)):
      matching_dirs += glob.glob(glob_path)

    if matching_dirs:
      # Cache file found.
      return matching_dirs[0]
    return None

  def GetCacheDirForWrite(self, get_keylist=False):
    cache_path = self.FormCacheDir(self.GetCacheKeyList(False))[0]
    if get_keylist:
      args_str = '%s_%s_%s' % (self.test_args, self.profiler_args,
                               self.run_local)
      version, image = results_report.ParseChromeosImage(
          self.label.chromeos_image)
      keylist = [version, image, self.label.board, self.machine.name,
                 self.test_name, str(self.iteration), args_str]
      return cache_path, keylist
    return cache_path

  def FormCacheDir(self, list_of_strings):
    cache_key = ' '.join(list_of_strings)
    cache_dir = misc.GetFilenameFromString(cache_key)
    if self.label.cache_dir:
      cache_home = os.path.abspath(os.path.expanduser(self.label.cache_dir))
      cache_path = [os.path.join(cache_home, cache_dir)]
    else:
      cache_path = [os.path.join(SCRATCH_DIR, cache_dir)]

    if len(self.share_cache):
      for path in [x.strip() for x in self.share_cache.split(',')]:
        if os.path.exists(path):
          cache_path.append(os.path.join(path, cache_dir))
        else:
          self._logger.LogFatal('Unable to find shared cache: %s' % path)

    return cache_path

  def GetCacheKeyList(self, read):
    if read and CacheConditions.MACHINES_MATCH not in self.cache_conditions:
      machine_checksum = '*'
    else:
      machine_checksum = self.machine_manager.machine_checksum[self.label.name]
    if read and CacheConditions.CHECKSUMS_MATCH not in self.cache_conditions:
      checksum = '*'
    elif self.label.image_type == 'trybot':
      checksum = hashlib.md5(self.label.chromeos_image).hexdigest()
    elif self.label.image_type == 'official':
      checksum = '*'
    else:
      checksum = ImageChecksummer().Checksum(self.label, self.log_level)

    if read and CacheConditions.IMAGE_PATH_MATCH not in self.cache_conditions:
      image_path_checksum = '*'
    else:
      image_path_checksum = hashlib.md5(self.chromeos_image).hexdigest()

    machine_id_checksum = ''
    if read and CacheConditions.SAME_MACHINE_MATCH not in self.cache_conditions:
      machine_id_checksum = '*'
    else:
      if self.machine and self.machine.name in self.label.remote:
        machine_id_checksum = self.machine.machine_id_checksum
      else:
        for machine in self.machine_manager.GetMachines(self.label):
          if machine.name == self.label.remote[0]:
            machine_id_checksum = machine.machine_id_checksum
            break

    temp_test_args = '%s %s %s' % (self.test_args, self.profiler_args,
                                   self.run_local)
    test_args_checksum = hashlib.md5(temp_test_args).hexdigest()
    return (image_path_checksum, self.test_name, str(self.iteration),
            test_args_checksum, checksum, machine_checksum, machine_id_checksum,
            str(self.CACHE_VERSION))

  def ReadResult(self):
    if CacheConditions.FALSE in self.cache_conditions:
      cache_dir = self.GetCacheDirForWrite()
      command = 'rm -rf %s' % (cache_dir, )
      self.ce.RunCommand(command)
      return None
    cache_dir = self.GetCacheDirForRead()

    if not cache_dir:
      return None

    if not os.path.isdir(cache_dir):
      return None

    if self.log_level == 'verbose':
      self._logger.LogOutput('Trying to read from cache dir: %s' % cache_dir)
    result = Result.CreateFromCacheHit(self._logger, self.log_level, self.label,
                                       self.machine, cache_dir,
                                       self.test_name, self.suite)
    if not result:
      return None

    if (result.retval == 0 or
        CacheConditions.RUN_SUCCEEDED not in self.cache_conditions):
      return result

    return None

  def StoreResult(self, result):
    cache_dir, keylist = self.GetCacheDirForWrite(get_keylist=True)
    result.StoreToCacheDir(cache_dir, self.machine_manager, keylist)


class MockResultsCache(ResultsCache):
  """Class for mock testing, corresponding to ResultsCache class."""

  def Init(self, *args):
    pass

  def ReadResult(self):
    return None

  def StoreResult(self, result):
    pass


class MockResult(Result):
  """Class for mock testing, corresponding to Result class."""

  def PopulateFromRun(self, out, err, retval, test, suite):
    self.out = out
    self.err = err
    self.retval = retval