site_utils/gs_offloader.py

#!/usr/bin/python
#
# Copyright (c) 2012 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.

"""Script to archive old Autotest results to Google Storage.

Uses gsutil to archive files to the configured Google Storage bucket.
Upon successful copy, the local results directory is deleted.
"""

import base64
import datetime
import errno
import glob
import gzip
import logging
import logging.handlers
import os
import re
import shutil
import signal
import socket
import subprocess
import sys
import tempfile
import time

from optparse import OptionParser

import common
from autotest_lib.client.common_lib import error
from autotest_lib.client.common_lib import utils
from autotest_lib.site_utils import job_directories
from autotest_lib.tko import models

try:
    # Does not exist, nor is needed, on moblab.
    import psutil
except ImportError:
    psutil = None

import job_directories
import pubsub_utils
from autotest_lib.client.common_lib import global_config
from autotest_lib.client.common_lib.cros.graphite import autotest_stats
from autotest_lib.scheduler import email_manager
from chromite.lib import parallel


GS_OFFLOADING_ENABLED = global_config.global_config.get_config_value(
        'CROS', 'gs_offloading_enabled', type=bool, default=True)

STATS_KEY = 'gs_offloader.%s' % socket.gethostname().replace('.', '_')
METADATA_TYPE = 'result_dir_size'

timer = autotest_stats.Timer(STATS_KEY)

# Nice setting for process, the higher the number the lower the priority.
NICENESS = 10

# Maximum number of seconds to allow for offloading a single
# directory.
OFFLOAD_TIMEOUT_SECS = 60 * 60

# Sleep time per loop.
SLEEP_TIME_SECS = 5

# Minimum number of seconds between e-mail reports.
REPORT_INTERVAL_SECS = 60 * 60

# Location of Autotest results on disk.
RESULTS_DIR = '/usr/local/autotest/results'

# Hosts sub-directory that contains cleanup, verify and repair jobs.
HOSTS_SUB_DIR = 'hosts'

LOG_LOCATION = '/usr/local/autotest/logs/'
LOG_FILENAME_FORMAT = 'gs_offloader_%s_log_%s.txt'
LOG_TIMESTAMP_FORMAT = '%Y%m%d_%H%M%S'
LOGGING_FORMAT = '%(asctime)s - %(levelname)s - %(message)s'

# pylint: disable=E1120
NOTIFY_ADDRESS = global_config.global_config.get_config_value(
        'SCHEDULER', 'notify_email', default='')

ERROR_EMAIL_HELPER_URL = 'http://go/cros-triage-gsoffloader'
ERROR_EMAIL_SUBJECT_FORMAT = 'GS Offloader notifications from %s'
ERROR_EMAIL_REPORT_FORMAT = '''\
gs_offloader is failing to offload results directories.

Check %s to triage the issue.

First failure       Count   Directory name
=================== ======  ==============================
''' % ERROR_EMAIL_HELPER_URL
# --+----1----+----  ----+  ----+----1----+----2----+----3

ERROR_EMAIL_DIRECTORY_FORMAT = '%19s  %5d  %-1s\n'
ERROR_EMAIL_TIME_FORMAT = '%Y-%m-%d %H:%M:%S'

USE_RSYNC_ENABLED = global_config.global_config.get_config_value(
        'CROS', 'gs_offloader_use_rsync', type=bool, default=False)

# According to https://cloud.google.com/storage/docs/bucket-naming#objectnames
INVALID_GS_CHARS = ['[', ']', '*', '?', '#']
INVALID_GS_CHAR_RANGE = [(0x00, 0x1F), (0x7F, 0x84), (0x86, 0xFF)]

# Maximum number of files in the folder.
MAX_FILE_COUNT = 500
FOLDERS_NEVER_ZIP = ['debug', 'ssp_logs']
LIMIT_FILE_COUNT = global_config.global_config.get_config_value(
        'CROS', 'gs_offloader_limit_file_count', type=bool, default=False)

# Use multiprocessing for gsutil uploading.
GS_OFFLOADER_MULTIPROCESSING = global_config.global_config.get_config_value(
        'CROS', 'gs_offloader_multiprocessing', type=bool, default=False)

D = '[0-9][0-9]'
TIMESTAMP_PATTERN = '%s%s.%s.%s_%s.%s.%s' % (D, D, D, D, D, D, D)
CTS_RESULT_PATTERN = 'testResult.xml'
GTS_RESULT_PATTERN = 'xtsTestResult.xml'
# Google Storage bucket URI to store results in.
DEFAULT_CTS_RESULTS_GSURI = global_config.global_config.get_config_value(
        'CROS', 'cts_results_server', default='')
DEFAULT_CTS_APFE_GSURI = global_config.global_config.get_config_value(
        'CROS', 'cts_apfe_server', default='')

_PUBSUB_ENABLED = global_config.global_config.get_config_value(
        'CROS', 'cloud_notification_enabled:', type=bool, default=False)
_PUBSUB_TOPIC = global_config.global_config.get_config_value(
        'CROS', 'cloud_notification_topic::', type='string', default=None)

# the message data for new test result notification.
NEW_TEST_RESULT_MESSAGE = 'NEW_TEST_RESULT'


class TimeoutException(Exception):
    """Exception raised by the timeout_handler."""
    pass


def timeout_handler(_signum, _frame):
    """Handler for SIGALRM when the offloading process times out.

    @param _signum: Signal number of the signal that was just caught.
                    14 for SIGALRM.
    @param _frame: Current stack frame.

    @raise TimeoutException: Automatically raises so that the time out
                             is caught by the try/except surrounding the
                             Popen call.
    """
    raise TimeoutException('Process Timed Out')


def get_cmd_list(multiprocessing, dir_entry, gs_path):
    """Return the command to offload a specified directory.

    @param multiprocessing: True to turn on -m option for gsutil.
    @param dir_entry: Directory entry/path that which we need a cmd_list
                      to offload.
    @param gs_path: Location in google storage where we will
                    offload the directory.

    @return A command list to be executed by Popen.
    """
    cmd = ['gsutil']
    if multiprocessing:
        cmd.append('-m')
    if USE_RSYNC_ENABLED:
        cmd.append('rsync')
        target = os.path.join(gs_path, os.path.basename(dir_entry))
    else:
        cmd.append('cp')
        target = gs_path
    cmd += ['-eR', dir_entry, target]
    return cmd


def get_directory_size_kibibytes_cmd_list(directory):
    """Returns command to get a directory's total size."""
    # Having this in its own method makes it easier to mock in
    # unittests.
    return ['du', '-sk', directory]


def get_directory_size_kibibytes(directory):
    """Calculate the total size of a directory with all its contents.

    @param directory: Path to the directory

    @return Size of the directory in kibibytes.
    """
    cmd = get_directory_size_kibibytes_cmd_list(directory)
    process = subprocess.Popen(cmd,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE)
    stdout_data, stderr_data = process.communicate()

    if process.returncode != 0:
        # This function is used for statistics only, if it fails,
        # nothing else should crash.
        logging.warning('Getting size of %s failed. Stderr:', directory)
        logging.warning(stderr_data)
        return 0

    return int(stdout_data.split('\t', 1)[0])


def get_sanitized_name(name):
    """Get a string with all invalid characters in the name being replaced.

    @param name: Name to be processed.

    @return A string with all invalid characters in the name being
             replaced.
    """
    match_pattern = ''.join([re.escape(c) for c in INVALID_GS_CHARS])
    match_pattern += ''.join([r'\x%02x-\x%02x' % (r[0], r[1])
                              for r in INVALID_GS_CHAR_RANGE])
    invalid = re.compile('[%s]' % match_pattern)
    return invalid.sub(lambda x: '%%%02x' % ord(x.group(0)), name)


def sanitize_dir(dir_entry):
    """Replace all invalid characters in folder and file names with valid ones.

    @param dir_entry: Directory entry to be sanitized.
    """
    if not os.path.exists(dir_entry):
        return
    renames = []
    for root, dirs, files in os.walk(dir_entry):
        sanitized_root = get_sanitized_name(root)
        for name in dirs + files:
            sanitized_name = get_sanitized_name(name)
            if name != sanitized_name:
                orig_path = os.path.join(sanitized_root, name)
                rename_path = os.path.join(sanitized_root,
                                           sanitized_name)
                renames.append((orig_path, rename_path))
    for src, dest in renames:
        logging.warn('Invalid character found. Renaming %s to %s.',
                     src, dest)
        shutil.move(src, dest)


def _get_zippable_folders(dir_entry):
    folders_list = []
    for folder in os.listdir(dir_entry):
        folder_path = os.path.join(dir_entry, folder)
        if (not os.path.isfile(folder_path) and
                not folder in FOLDERS_NEVER_ZIP):
            folders_list.append(folder_path)
    return folders_list


def limit_file_count(dir_entry):
    """Limit the number of files in given directory.

    The method checks the total number of files in the given directory.
    If the number is greater than MAX_FILE_COUNT, the method will
    compress each folder in the given directory, except folders in
    FOLDERS_NEVER_ZIP.

    @param dir_entry: Directory entry to be checked.
    """
    count = utils.run('find "%s" | wc -l' % dir_entry,
                      ignore_status=True).stdout.strip()
    try:
        count = int(count)
    except ValueError, TypeError:
        logging.warn('Fail to get the file count in folder %s.',
                     dir_entry)
        return
    if count < MAX_FILE_COUNT:
        return

    # For test job, zip folders in a second level, e.g. 123-debug/host1.
    # This is to allow autoserv debug folder still be accessible.
    # For special task, it does not need to dig one level deeper.
    is_special_task = re.match(job_directories.SPECIAL_TASK_PATTERN,
                               dir_entry)

    folders = _get_zippable_folders(dir_entry)
    if not is_special_task:
        subfolders = []
        for folder in folders:
            subfolders.extend(_get_zippable_folders(folder))
        folders = subfolders

    for folder in folders:
        try:
            zip_name = '%s.tgz' % folder
            utils.run('tar -cz -C "%s" -f "%s" "%s"' %
                      (os.path.dirname(folder), zip_name,
                       os.path.basename(folder)))
        except error.CmdError as e:
            logging.error('Fail to compress folder %s. Error: %s',
                          folder, e)
            continue
        shutil.rmtree(folder)


def correct_results_folder_permission(dir_entry):
    """Make sure the results folder has the right permission settings.

    For tests running with server-side packaging, the results folder has
    the owner of root. This must be changed to the user running the
    autoserv process, so parsing job can access the results folder.

    @param dir_entry: Path to the results folder.
    """
    if not dir_entry:
        return
    try:
        subprocess.check_call(
                ['sudo', '-n', 'chown', '-R', str(os.getuid()), dir_entry])
        subprocess.check_call(
                ['sudo', '-n', 'chgrp', '-R', str(os.getgid()), dir_entry])
    except subprocess.CalledProcessError as e:
        logging.error('Failed to modify permission for %s: %s',
                      dir_entry, e)


def upload_testresult_files(dir_entry, multiprocessing):
    """Upload test results to separate gs buckets.

    Upload testResult.xml.gz/xtsTestResult.xml.gz file to cts_results_bucket.
    Upload timestamp.zip to cts_apfe_bucket.
    @param dir_entry: Path to the results folder.
    @param multiprocessing: True to turn on -m option for gsutil.
    """
    for host in glob.glob(os.path.join(dir_entry, '*')):
        cts_path = os.path.join(host, 'cheets_CTS.*', 'results', '*',
                                TIMESTAMP_PATTERN)
        gts_path = os.path.join(host, 'cheets_GTS.*', 'results', '*',
                                TIMESTAMP_PATTERN)
        for result_path, result_pattern in [(cts_path, CTS_RESULT_PATTERN),
                            (gts_path, GTS_RESULT_PATTERN)]:
            for path in glob.glob(result_path):
                try:
                    _upload_files(host, path, result_pattern, multiprocessing)
                except Exception as e:
                    logging.error('ERROR uploading test results %s to GS: %s',
                                  path, e)


def _is_release_build(build):
    """Check if it's a release build."""
    return re.match(r'(?!trybot-).*-release/.*', build)


def _upload_files(host, path, result_pattern, multiprocessing):
    keyval = models.test.parse_job_keyval(host)
    build = keyval['build']

    if not _is_release_build(build):
        # Only upload results for release builds.
        return

    parent_job_id = str(keyval['parent_job_id'])

    folders = path.split(os.sep)
    job_id = folders[-6]
    package = folders[-4]
    timestamp = folders[-1]

    # Path: bucket/build/parent_job_id/cheets_CTS.*/job_id_timestamp/
    # or bucket/build/parent_job_id/cheets_GTS.*/job_id_timestamp/
    cts_apfe_gs_path = os.path.join(
            DEFAULT_CTS_APFE_GSURI, build, parent_job_id,
            package, job_id + '_' + timestamp) + '/'

    # Path: bucket/cheets_CTS.*/job_id_timestamp/
    # or bucket/cheets_GTS.*/job_id_timestamp/
    test_result_gs_path = os.path.join(
            DEFAULT_CTS_RESULTS_GSURI, package,
            job_id + '_' + timestamp) + '/'

    for zip_file in glob.glob(os.path.join('%s.zip' % path)):
        utils.run(' '.join(get_cmd_list(
                multiprocessing, zip_file, cts_apfe_gs_path)))
        logging.debug('Upload %s to %s ', zip_file, cts_apfe_gs_path)

    for test_result_file in glob.glob(os.path.join(path, result_pattern)):
        # gzip test_result_file(testResult.xml/xtsTestResult.xml)
        test_result_file_gz =  '%s.gz' % test_result_file
        with open(test_result_file, 'r') as f_in, (
                gzip.open(test_result_file_gz, 'w')) as f_out:
            shutil.copyfileobj(f_in, f_out)
        utils.run(' '.join(get_cmd_list(
                multiprocessing, test_result_file_gz, test_result_gs_path)))
        logging.debug('Zip and upload %s to %s',
                      test_result_file_gz, test_result_gs_path)
        # Remove test_result_file_gz(estResult.xml.gz/xtsTestResult.xml.gz)
        os.remove(test_result_file_gz)


def _create_test_result_notification(gs_path):
    """Construct a test result notification.

    @param gs_path: The test result Google Cloud Storage URI.

    @returns The notification message.
    """
    data = base64.b64encode(NEW_TEST_RESULT_MESSAGE)
    msg_payload = {'data': data}
    msg_attributes = {}
    msg_attributes['gcs_uri'] = gs_path
    msg_payload['attributes'] = msg_attributes

    return msg_payload


def get_offload_dir_func(gs_uri, multiprocessing, pubsub_topic=None):
    """Returns the offload directory function for the given gs_uri

    @param gs_uri: Google storage bucket uri to offload to.
    @param multiprocessing: True to turn on -m option for gsutil.
    @param pubsub_topic: The pubsub topic to publish notificaitons. If None,
          pubsub is not enabled.

    @return offload_dir function to perform the offload.
    """
    @timer.decorate
    def offload_dir(dir_entry, dest_path):
        """Offload the specified directory entry to Google storage.

        @param dir_entry: Directory entry to offload.
        @param dest_path: Location in google storage where we will
                          offload the directory.

        """
        try:
            counter = autotest_stats.Counter(STATS_KEY)
            counter.increment('jobs_offload_started')

            sanitize_dir(dir_entry)
            if DEFAULT_CTS_RESULTS_GSURI:
                upload_testresult_files(dir_entry, multiprocessing)

            if LIMIT_FILE_COUNT:
                limit_file_count(dir_entry)

            error = False
            stdout_file = tempfile.TemporaryFile('w+')
            stderr_file = tempfile.TemporaryFile('w+')
            process = None
            signal.alarm(OFFLOAD_TIMEOUT_SECS)
            gs_path = '%s%s' % (gs_uri, dest_path)
            process = subprocess.Popen(
                    get_cmd_list(multiprocessing, dir_entry, gs_path),
                    stdout=stdout_file, stderr=stderr_file)
            process.wait()
            signal.alarm(0)

            if process.returncode == 0:
                dir_size = get_directory_size_kibibytes(dir_entry)

                counter.increment('kibibytes_transferred_total',
                                  dir_size)
                metadata = {
                    '_type': METADATA_TYPE,
                    'size_KB': dir_size,
                    'result_dir': dir_entry,
                    'drone': socket.gethostname().replace('.', '_')
                }
                autotest_stats.Gauge(STATS_KEY, metadata=metadata).send(
                        'kibibytes_transferred', dir_size)
                counter.increment('jobs_offloaded')

                if pubsub_topic:
                    message = _create_test_result_notification(gs_path)
                    msg_ids = pubsub_utils.publish_notifications(
                            pubsub_topic, [message])
                    if not msg_ids:
                        error = True

                if not error:
                    shutil.rmtree(dir_entry)
            else:
                error = True
        except TimeoutException:
            # If we finished the call to Popen(), we may need to
            # terminate the child process.  We don't bother calling
            # process.poll(); that inherently races because the child
            # can die any time it wants.
            if process:
                try:
                    process.terminate()
                except OSError:
                    # We don't expect any error other than "No such
                    # process".
                    pass
            logging.error('Offloading %s timed out after waiting %d '
                          'seconds.', dir_entry, OFFLOAD_TIMEOUT_SECS)
            error = True
        except OSError as e:
            # The wrong file permission can lead call
            # `shutil.rmtree(dir_entry)` to raise OSError with message
            # 'Permission denied'. Details can be found in
            # crbug.com/536151
            if e.errno == errno.EACCES:
                logging.warn('Try to correct file permission of %s.', dir_entry)
                correct_results_folder_permission(dir_entry)
        finally:
            signal.alarm(0)
            if error:
                # Rewind the log files for stdout and stderr and log
                # their contents.
                stdout_file.seek(0)
                stderr_file.seek(0)
                stderr_content = stderr_file.read()
                logging.error('Error occurred when offloading %s:',
                              dir_entry)
                logging.error('Stdout:\n%s \nStderr:\n%s',
                              stdout_file.read(), stderr_content)
                # Some result files may have wrong file permission. Try
                # to correct such error so later try can success.
                # TODO(dshi): The code is added to correct result files
                # with wrong file permission caused by bug 511778. After
                # this code is pushed to lab and run for a while to
                # clean up these files, following code and function
                # correct_results_folder_permission can be deleted.
                if 'CommandException: Error opening file' in stderr_content:
                    logging.warn('Try to correct file permission of %s.',
                                 dir_entry)
                    correct_results_folder_permission(dir_entry)
            stdout_file.close()
            stderr_file.close()
    return offload_dir


def delete_files(dir_entry, dest_path):
    """Simply deletes the dir_entry from the filesystem.

    Uses same arguments as offload_dir so that it can be used in replace
    of it on systems that only want to delete files instead of
    offloading them.

    @param dir_entry: Directory entry to offload.
    @param dest_path: NOT USED.
    """
    shutil.rmtree(dir_entry)


def report_offload_failures(joblist):
    """Generate e-mail notification for failed offloads.

    The e-mail report will include data from all jobs in `joblist`.

    @param joblist List of jobs to be reported in the message.
    """
    def _format_job(job):
        d = datetime.datetime.fromtimestamp(job.get_failure_time())
        data = (d.strftime(ERROR_EMAIL_TIME_FORMAT),
                job.get_failure_count(),
                job.get_job_directory())
        return ERROR_EMAIL_DIRECTORY_FORMAT % data
    joblines = [_format_job(job) for job in joblist]
    joblines.sort()
    email_subject = ERROR_EMAIL_SUBJECT_FORMAT % socket.gethostname()
    email_message = ERROR_EMAIL_REPORT_FORMAT + ''.join(joblines)
    email_manager.manager.send_email(NOTIFY_ADDRESS, email_subject,
                                     email_message)


def wait_for_gs_write_access(gs_uri):
    """Verify and wait until we have write access to Google Storage.

    @param gs_uri: The Google Storage URI we are trying to offload to.
    """
    # TODO (sbasi) Try to use the gsutil command to check write access.
    # Ensure we have write access to gs_uri.
    dummy_file = tempfile.NamedTemporaryFile()
    test_cmd = get_cmd_list(False, dummy_file.name, gs_uri)
    while True:
        try:
            subprocess.check_call(test_cmd)
            subprocess.check_call(
                    ['gsutil', 'rm',
                     os.path.join(gs_uri,
                                  os.path.basename(dummy_file.name))])
            break
        except subprocess.CalledProcessError:
            logging.debug('Unable to offload to %s, sleeping.', gs_uri)
            time.sleep(120)


class Offloader(object):
    """State of the offload process.

    Contains the following member fields:
      * _offload_func:  Function to call for each attempt to offload
        a job directory.
      * _jobdir_classes:  List of classes of job directory to be
        offloaded.
      * _processes:  Maximum number of outstanding offload processes
        to allow during an offload cycle.
      * _age_limit:  Minimum age in days at which a job may be
        offloaded.
      * _open_jobs: a dictionary mapping directory paths to Job
        objects.
      * _next_report_time:  Earliest time that we should send e-mail
        if there are failures to be reported.
    """

    def __init__(self, options):
        self._pubsub_topic = None
        if options.delete_only:
            self._offload_func = delete_files
        else:
            self.gs_uri = utils.get_offload_gsuri()
            logging.debug('Offloading to: %s', self.gs_uri)
            multiprocessing = False
            if options.multiprocessing:
                multiprocessing = True
            elif options.multiprocessing is None:
                multiprocessing = GS_OFFLOADER_MULTIPROCESSING
            logging.info(
                    'Offloader multiprocessing is set to:%r', multiprocessing)
            if options.pubsub_topic_for_job_upload:
              self._pubsub_topic = options.pubsub_topic_for_job_upload
            elif _PUBSUB_ENABLED:
              self._pubsub_topic = _PUBSUB_TOPIC
            self._offload_func = get_offload_dir_func(
                    self.gs_uri, multiprocessing, self._pubsub_topic)
        classlist = []
        if options.process_hosts_only or options.process_all:
            classlist.append(job_directories.SpecialJobDirectory)
        if not options.process_hosts_only:
            classlist.append(job_directories.RegularJobDirectory)
        self._jobdir_classes = classlist
        assert self._jobdir_classes
        self._processes = options.parallelism
        self._age_limit = options.days_old
        self._open_jobs = {}
        self._next_report_time = time.time()
        self._pusub_topic = None


    def _add_new_jobs(self):
        """Find new job directories that need offloading.

        Go through the file system looking for valid job directories
        that are currently not in `self._open_jobs`, and add them in.

        """
        new_job_count = 0
        for cls in self._jobdir_classes:
            for resultsdir in cls.get_job_directories():
                if resultsdir in self._open_jobs:
                    continue
                self._open_jobs[resultsdir] = cls(resultsdir)
                new_job_count += 1
        logging.debug('Start of offload cycle - found %d new jobs',
                      new_job_count)


    def _remove_offloaded_jobs(self):
        """Removed offloaded jobs from `self._open_jobs`."""
        removed_job_count = 0
        for jobkey, job in self._open_jobs.items():
            if job.is_offloaded():
                del self._open_jobs[jobkey]
                removed_job_count += 1
        logging.debug('End of offload cycle - cleared %d new jobs, '
                      'carrying %d open jobs',
                      removed_job_count, len(self._open_jobs))


    def _have_reportable_errors(self):
        """Return whether any jobs need reporting via e-mail.

        @return True if there are reportable jobs in `self._open_jobs`,
                or False otherwise.
        """
        for job in self._open_jobs.values():
            if job.is_reportable():
                return True
        return False


    def _update_offload_results(self):
        """Check and report status after attempting offload.

        This function processes all jobs in `self._open_jobs`, assuming
        an attempt has just been made to offload all of them.

        Any jobs that have been successfully offloaded are removed.

        If any jobs have reportable errors, and we haven't generated
        an e-mail report in the last `REPORT_INTERVAL_SECS` seconds,
        send new e-mail describing the failures.

        """
        self._remove_offloaded_jobs()
        if self._have_reportable_errors():
            # N.B. We include all jobs that have failed at least once,
            # which may include jobs that aren't otherwise reportable.
            failed_jobs = [j for j in self._open_jobs.values()
                           if j.get_failure_time()]
            logging.debug('Currently there are %d jobs with offload '
                          'failures', len(failed_jobs))
            if time.time() >= self._next_report_time:
                logging.debug('Reporting failures by e-mail')
                report_offload_failures(failed_jobs)
                self._next_report_time = (
                        time.time() + REPORT_INTERVAL_SECS)


    def offload_once(self):
        """Perform one offload cycle.

        Find all job directories for new jobs that we haven't seen
        before.  Then, attempt to offload the directories for any
        jobs that have finished running.  Offload of multiple jobs
        is done in parallel, up to `self._processes` at a time.

        After we've tried uploading all directories, go through the list
        checking the status of all uploaded directories.  If necessary,
        report failures via e-mail.

        """
        self._add_new_jobs()
        with parallel.BackgroundTaskRunner(
                self._offload_func, processes=self._processes) as queue:
            for job in self._open_jobs.values():
                job.enqueue_offload(queue, self._age_limit)
        self._update_offload_results()


def parse_options():
    """Parse the args passed into gs_offloader."""
    defaults = 'Defaults:\n  Destination: %s\n  Results Path: %s' % (
            utils.DEFAULT_OFFLOAD_GSURI, RESULTS_DIR)
    usage = 'usage: %prog [options]\n' + defaults
    parser = OptionParser(usage)
    parser.add_option('-a', '--all', dest='process_all',
                      action='store_true',
                      help='Offload all files in the results directory.')
    parser.add_option('-s', '--hosts', dest='process_hosts_only',
                      action='store_true',
                      help='Offload only the special tasks result files '
                      'located in the results/hosts subdirectory')
    parser.add_option('-p', '--parallelism', dest='parallelism',
                      type='int', default=1,
                      help='Number of parallel workers to use.')
    parser.add_option('-o', '--delete_only', dest='delete_only',
                      action='store_true',
                      help='GS Offloader will only the delete the '
                      'directories and will not offload them to google '
                      'storage. NOTE: If global_config variable '
                      'CROS.gs_offloading_enabled is False, --delete_only '
                      'is automatically True.',
                      default=not GS_OFFLOADING_ENABLED)
    parser.add_option('-d', '--days_old', dest='days_old',
                      help='Minimum job age in days before a result can be '
                      'offloaded.', type='int', default=0)
    parser.add_option('-t', '--pubsub_topic_for_job_upload',
                      dest='pubsub_topic_for_job_upload',
                      help='The pubsub topic to send notifciations for '
                      'new job upload',
                      action='store', type='string', default=None)
    parser.add_option('-l', '--log_size', dest='log_size',
                      help='Limit the offloader logs to a specified '
                      'number of Mega Bytes.', type='int', default=0)
    parser.add_option('-m', dest='multiprocessing', action='store_true',
                      help='Turn on -m option for gsutil. If not set, the '
                      'global config setting gs_offloader_multiprocessing '
                      'under CROS section is applied.')
    options = parser.parse_args()[0]
    if options.process_all and options.process_hosts_only:
        parser.print_help()
        print ('Cannot process all files and only the hosts '
               'subdirectory. Please remove an argument.')
        sys.exit(1)
    return options


def main():
    """Main method of gs_offloader."""
    options = parse_options()

    if options.process_all:
        offloader_type = 'all'
    elif options.process_hosts_only:
        offloader_type = 'hosts'
    else:
        offloader_type = 'jobs'

    log_timestamp = time.strftime(LOG_TIMESTAMP_FORMAT)
    if options.log_size > 0:
        log_timestamp = ''
    log_basename = LOG_FILENAME_FORMAT % (offloader_type, log_timestamp)
    log_filename = os.path.join(LOG_LOCATION, log_basename)
    log_formatter = logging.Formatter(LOGGING_FORMAT)
    # Replace the default logging handler with a RotatingFileHandler. If
    # options.log_size is 0, the file size will not be limited. Keeps
    # one backup just in case.
    handler = logging.handlers.RotatingFileHandler(
            log_filename, maxBytes=1024 * options.log_size, backupCount=1)
    handler.setFormatter(log_formatter)
    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)
    logger.addHandler(handler)

    # Nice our process (carried to subprocesses) so we don't overload
    # the system.
    logging.debug('Set process to nice value: %d', NICENESS)
    os.nice(NICENESS)
    if psutil:
        proc = psutil.Process()
        logging.debug('Set process to ionice IDLE')
        proc.ionice(psutil.IOPRIO_CLASS_IDLE)

    # os.listdir returns relative paths, so change to where we need to
    # be to avoid an os.path.join on each loop.
    logging.debug('Offloading Autotest results in %s', RESULTS_DIR)
    os.chdir(RESULTS_DIR)

    signal.signal(signal.SIGALRM, timeout_handler)

    offloader = Offloader(options)
    if not options.delete_only:
        wait_for_gs_write_access(offloader.gs_uri)
    while True:
        offloader.offload_once()
        time.sleep(SLEEP_TIME_SECS)


if __name__ == '__main__':
    main()