frontend/afe/site_rpc_interface.py

# pylint: disable-msg=C0111

# 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.

__author__ = 'cmasone@chromium.org (Chris Masone)'

# The boto module is only available/used in Moblab for validation of cloud
# storage access. The module is not available in the test lab environment,
# and the import error is handled.
try:
    import boto
except ImportError:
    boto = None
import common
import ConfigParser
import datetime
import logging
import os
import re
import shutil
import socket

from autotest_lib.frontend.afe import models
from autotest_lib.client.common_lib import control_data
from autotest_lib.client.common_lib import error
from autotest_lib.client.common_lib import global_config
from autotest_lib.client.common_lib import priorities
from autotest_lib.client.common_lib import time_utils
from autotest_lib.client.common_lib.cros import dev_server
from autotest_lib.client.common_lib.cros.graphite import autotest_stats
from autotest_lib.frontend.afe import rpc_utils
from autotest_lib.server import utils
from autotest_lib.server.cros import provision
from autotest_lib.server.cros.dynamic_suite import constants
from autotest_lib.server.cros.dynamic_suite import control_file_getter
from autotest_lib.server.cros.dynamic_suite import tools
from autotest_lib.server.cros.dynamic_suite.suite import Suite
from autotest_lib.server.hosts import moblab_host
from autotest_lib.site_utils import host_history
from autotest_lib.site_utils import job_history
from autotest_lib.site_utils import server_manager_utils
from autotest_lib.site_utils import stable_version_utils


_CONFIG = global_config.global_config
MOBLAB_BOTO_LOCATION = '/home/moblab/.boto'

# Google Cloud Storage bucket url regex pattern. The pattern is used to extract
# the bucket name from the bucket URL. For example, "gs://image_bucket/google"
# should result in a bucket name "image_bucket".
GOOGLE_STORAGE_BUCKET_URL_PATTERN = re.compile(
        r'gs://(?P<bucket>[a-zA-Z][a-zA-Z0-9-_]*)/?.*')

# Constants used in JSON RPC field names.
_USE_EXISTING_BOTO_FILE = 'use_existing_boto_file'
_GS_ACCESS_KEY_ID = 'gs_access_key_id'
_GS_SECRETE_ACCESS_KEY = 'gs_secret_access_key'
_IMAGE_STORAGE_SERVER = 'image_storage_server'
_RESULT_STORAGE_SERVER = 'results_storage_server'


# Relevant CrosDynamicSuiteExceptions are defined in client/common_lib/error.py.


def canonicalize_suite_name(suite_name):
    # Do not change this naming convention without updating
    # site_utils.parse_job_name.
    return 'test_suites/control.%s' % suite_name


def formatted_now():
    return datetime.datetime.now().strftime(time_utils.TIME_FMT)


def _get_control_file_contents_by_name(build, ds, suite_name):
    """Return control file contents for |suite_name|.

    Query the dev server at |ds| for the control file |suite_name|, included
    in |build| for |board|.

    @param build: unique name by which to refer to the image from now on.
    @param ds: a dev_server.DevServer instance to fetch control file with.
    @param suite_name: canonicalized suite name, e.g. test_suites/control.bvt.
    @raises ControlFileNotFound if a unique suite control file doesn't exist.
    @raises NoControlFileList if we can't list the control files at all.
    @raises ControlFileEmpty if the control file exists on the server, but
                             can't be read.

    @return the contents of the desired control file.
    """
    getter = control_file_getter.DevServerGetter.create(build, ds)
    timer = autotest_stats.Timer('control_files.parse.%s.%s' %
                                 (ds.get_server_name(ds.url()
                                                     ).replace('.', '_'),
                                  suite_name.rsplit('.')[-1]))
    # Get the control file for the suite.
    try:
        with timer:
            control_file_in = getter.get_control_file_contents_by_name(
                    suite_name)
    except error.CrosDynamicSuiteException as e:
        raise type(e)("%s while testing %s." % (e, build))
    if not control_file_in:
        raise error.ControlFileEmpty(
                "Fetching %s returned no data." % suite_name)
    # Force control files to only contain ascii characters.
    try:
        control_file_in.encode('ascii')
    except UnicodeDecodeError as e:
        raise error.ControlFileMalformed(str(e))

    return control_file_in


def _stage_build_artifacts(build):
    """
    Ensure components of |build| necessary for installing images are staged.

    @param build image we want to stage.

    @raises StageControlFileFailure: if the dev server throws 500 while staging
        suite control files.

    @return: dev_server.ImageServer instance to use with this build.
    @return: timings dictionary containing staging start/end times.
    """
    timings = {}
    # Ensure components of |build| necessary for installing images are staged
    # on the dev server. However set synchronous to False to allow other
    # components to be downloaded in the background.
    ds = dev_server.resolve(build)
    timings[constants.DOWNLOAD_STARTED_TIME] = formatted_now()
    timer = autotest_stats.Timer('control_files.stage.%s' % (
            ds.get_server_name(ds.url()).replace('.', '_')))
    try:
        with timer:
            ds.stage_artifacts(image=build, artifacts=['test_suites'])
    except dev_server.DevServerException as e:
        raise error.StageControlFileFailure(
                "Failed to stage %s: %s" % (build, e))
    timings[constants.PAYLOAD_FINISHED_TIME] = formatted_now()
    return (ds, timings)


@rpc_utils.route_rpc_to_master
def create_suite_job(name='', board='', build='', pool='', control_file='',
                     check_hosts=True, num=None, file_bugs=False, timeout=24,
                     timeout_mins=None, priority=priorities.Priority.DEFAULT,
                     suite_args=None, wait_for_results=True, job_retry=False,
                     max_retries=None, max_runtime_mins=None, suite_min_duts=0,
                     offload_failures_only=False, builds={},
                     test_source_build=None, run_prod_code=False,
                     delay_minutes=0, **kwargs):
    """
    Create a job to run a test suite on the given device with the given image.

    When the timeout specified in the control file is reached, the
    job is guaranteed to have completed and results will be available.

    @param name: The test name if control_file is supplied, otherwise the name
                 of the test suite to run, e.g. 'bvt'.
    @param board: the kind of device to run the tests on.
    @param build: unique name by which to refer to the image from now on.
    @param builds: the builds to install e.g.
                   {'cros-version:': 'x86-alex-release/R18-1655.0.0',
                    'fw-version:':  'x86-alex-firmware/R36-5771.50.0',
                    'fwro-version:':  'x86-alex-firmware/R36-5771.49.0'}
                   If builds is given a value, it overrides argument build.
    @param test_source_build: Build that contains the server-side test code.
    @param pool: Specify the pool of machines to use for scheduling
            purposes.
    @param check_hosts: require appropriate live hosts to exist in the lab.
    @param num: Specify the number of machines to schedule across (integer).
                Leave unspecified or use None to use default sharding factor.
    @param file_bugs: File a bug on each test failure in this suite.
    @param timeout: The max lifetime of this suite, in hours.
    @param timeout_mins: The max lifetime of this suite, in minutes. Takes
                         priority over timeout.
    @param priority: Integer denoting priority. Higher is more important.
    @param suite_args: Optional arguments which will be parsed by the suite
                       control file. Used by control.test_that_wrapper to
                       determine which tests to run.
    @param wait_for_results: Set to False to run the suite job without waiting
                             for test jobs to finish. Default is True.
    @param job_retry: Set to True to enable job-level retry. Default is False.
    @param max_retries: Integer, maximum job retries allowed at suite level.
                        None for no max.
    @param max_runtime_mins: Maximum amount of time a job can be running in
                             minutes.
    @param suite_min_duts: Integer. Scheduler will prioritize getting the
                           minimum number of machines for the suite when it is
                           competing with another suite that has a higher
                           priority but already got minimum machines it needs.
    @param offload_failures_only: Only enable gs_offloading for failed jobs.
    @param run_prod_code: If True, the suite will run the test code that
                          lives in prod aka the test code currently on the
                          lab servers. If False, the control files and test
                          code for this suite run will be retrieved from the
                          build artifacts.
    @param delay_minutes: Delay the creation of test jobs for a given number of
                          minutes.
    @param kwargs: extra keyword args. NOT USED.

    @raises ControlFileNotFound: if a unique suite control file doesn't exist.
    @raises NoControlFileList: if we can't list the control files at all.
    @raises StageControlFileFailure: If the dev server throws 500 while
                                     staging test_suites.
    @raises ControlFileEmpty: if the control file exists on the server, but
                              can't be read.

    @return: the job ID of the suite; -1 on error.
    """
    if type(num) is not int and num is not None:
        raise error.SuiteArgumentException('Ill specified num argument %r. '
                                           'Must be an integer or None.' % num)
    if num == 0:
        logging.warning("Can't run on 0 hosts; using default.")
        num = None

    # TODO(dshi): crbug.com/496782 Remove argument build and its reference after
    # R45 falls out of stable channel.
    if build and not builds:
        builds = {provision.CROS_VERSION_PREFIX: build}

    # Default test source build to CrOS build if it's not specified and
    # run_prod_code is set to False.
    if not run_prod_code:
        test_source_build = Suite.get_test_source_build(
                builds, test_source_build=test_source_build)

    suite_name = canonicalize_suite_name(name)
    if run_prod_code:
        ds = dev_server.resolve(build)
        keyvals = {}
        getter = control_file_getter.FileSystemGetter(
                [_CONFIG.get_config_value('SCHEDULER',
                                          'drone_installation_directory')])
        control_file = getter.get_control_file_contents_by_name(suite_name)
    else:
        (ds, keyvals) = _stage_build_artifacts(test_source_build)
    keyvals[constants.SUITE_MIN_DUTS_KEY] = suite_min_duts

    if not control_file:
        # No control file was supplied so look it up from the build artifacts.
        suite_name = canonicalize_suite_name(name)
        control_file = _get_control_file_contents_by_name(test_source_build,
                                                          ds, suite_name)
    # Do not change this naming convention without updating
    # site_utils.parse_job_name.
    if not run_prod_code:
        name = '%s-%s' % (test_source_build, suite_name)
    else:
        # If run_prod_code is True, test_source_build is not set, use the
        # first build in the builds list for the sutie job name.
        name = '%s-%s' % (builds.values()[0], suite_name)

    timeout_mins = timeout_mins or timeout * 60
    max_runtime_mins = max_runtime_mins or timeout * 60

    if not board:
        board = utils.ParseBuildName(builds[provision.CROS_VERSION_PREFIX])[0]

    # TODO(dshi): crbug.com/496782 Remove argument build and its reference after
    # R45 falls out of stable channel.
    # Prepend build and board to the control file.
    inject_dict = {'board': board,
                   'build': builds.get(provision.CROS_VERSION_PREFIX),
                   'builds': builds,
                   'check_hosts': check_hosts,
                   'pool': pool,
                   'num': num,
                   'file_bugs': file_bugs,
                   'timeout': timeout,
                   'timeout_mins': timeout_mins,
                   'devserver_url': ds.url(),
                   'priority': priority,
                   'suite_args' : suite_args,
                   'wait_for_results': wait_for_results,
                   'job_retry': job_retry,
                   'max_retries': max_retries,
                   'max_runtime_mins': max_runtime_mins,
                   'offload_failures_only': offload_failures_only,
                   'test_source_build': test_source_build,
                   'run_prod_code': run_prod_code,
                   'delay_minutes': delay_minutes,
                   }

    control_file = tools.inject_vars(inject_dict, control_file)

    return rpc_utils.create_job_common(name,
                                       priority=priority,
                                       timeout_mins=timeout_mins,
                                       max_runtime_mins=max_runtime_mins,
                                       control_type='Server',
                                       control_file=control_file,
                                       hostless=True,
                                       keyvals=keyvals)


# TODO: hide the following rpcs under is_moblab
def moblab_only(func):
    """Ensure moblab specific functions only run on Moblab devices."""
    def verify(*args, **kwargs):
        if not utils.is_moblab():
            raise error.RPCException('RPC: %s can only run on Moblab Systems!',
                                     func.__name__)
        return func(*args, **kwargs)
    return verify


@moblab_only
def get_config_values():
    """Returns all config values parsed from global and shadow configs.

    Config values are grouped by sections, and each section is composed of
    a list of name value pairs.
    """
    sections =_CONFIG.get_sections()
    config_values = {}
    for section in sections:
        config_values[section] = _CONFIG.config.items(section)
    return rpc_utils.prepare_for_serialization(config_values)


def _write_config_file(config_file, config_values, overwrite=False):
    """Writes out a configuration file.

    @param config_file: The name of the configuration file.
    @param config_values: The ConfigParser object.
    @param ovewrite: Flag on if overwriting is allowed.
    """
    if not config_file:
        raise error.RPCException('Empty config file name.')
    if not overwrite and os.path.exists(config_file):
        raise error.RPCException('Config file already exists.')

    if config_values:
        with open(config_file, 'w') as config_file:
            config_values.write(config_file)


def _read_original_config():
    """Reads the orginal configuratino without shadow.

    @return: A configuration object, see global_config_class.
    """
    original_config = global_config.global_config_class()
    original_config.set_config_files(shadow_file='')
    return original_config


def _read_raw_config(config_file):
    """Reads the raw configuration from a configuration file.

    @param: config_file: The path of the configuration file.

    @return: A ConfigParser object.
    """
    shadow_config = ConfigParser.RawConfigParser()
    shadow_config.read(config_file)
    return shadow_config


def _get_shadow_config_from_partial_update(config_values):
    """Finds out the new shadow configuration based on a partial update.

    Since the input is only a partial config, we should not lose the config
    data inside the existing shadow config file. We also need to distinguish
    if the input config info overrides with a new value or reverts back to
    an original value.

    @param config_values: See get_moblab_settings().

    @return: The new shadow configuration as ConfigParser object.
    """
    original_config = _read_original_config()
    existing_shadow = _read_raw_config(_CONFIG.shadow_file)
    for section, config_value_list in config_values.iteritems():
        for key, value in config_value_list:
            if original_config.get_config_value(section, key,
                                                default='',
                                                allow_blank=True) != value:
                if not existing_shadow.has_section(section):
                    existing_shadow.add_section(section)
                existing_shadow.set(section, key, value)
            elif existing_shadow.has_option(section, key):
                existing_shadow.remove_option(section, key)
    return existing_shadow


def _update_partial_config(config_values):
    """Updates the shadow configuration file with a partial config udpate.

    @param config_values: See get_moblab_settings().
    """
    existing_config = _get_shadow_config_from_partial_update(config_values)
    _write_config_file(_CONFIG.shadow_file, existing_config, True)


@moblab_only
def update_config_handler(config_values):
    """Update config values and override shadow config.

    @param config_values: See get_moblab_settings().
    """
    original_config = _read_original_config()
    new_shadow = ConfigParser.RawConfigParser()
    for section, config_value_list in config_values.iteritems():
        for key, value in config_value_list:
            if original_config.get_config_value(section, key,
                                                default='',
                                                allow_blank=True) != value:
                if not new_shadow.has_section(section):
                    new_shadow.add_section(section)
                new_shadow.set(section, key, value)

    if not _CONFIG.shadow_file or not os.path.exists(_CONFIG.shadow_file):
        raise error.RPCException('Shadow config file does not exist.')
    _write_config_file(_CONFIG.shadow_file, new_shadow, True)

    # TODO (sbasi) crbug.com/403916 - Remove the reboot command and
    # instead restart the services that rely on the config values.
    os.system('sudo reboot')


@moblab_only
def reset_config_settings():
    with open(_CONFIG.shadow_file, 'w') as config_file:
        pass
    os.system('sudo reboot')


@moblab_only
def set_boto_key(boto_key):
    """Update the boto_key file.

    @param boto_key: File name of boto_key uploaded through handle_file_upload.
    """
    if not os.path.exists(boto_key):
        raise error.RPCException('Boto key: %s does not exist!' % boto_key)
    shutil.copyfile(boto_key, moblab_host.MOBLAB_BOTO_LOCATION)


@moblab_only
def set_launch_control_key(launch_control_key):
    """Update the launch_control_key file.

    @param launch_control_key: File name of launch_control_key uploaded through
            handle_file_upload.
    """
    if not os.path.exists(launch_control_key):
        raise error.RPCException('Launch Control key: %s does not exist!' %
                                 launch_control_key)
    shutil.copyfile(launch_control_key,
                    moblab_host.MOBLAB_LAUNCH_CONTROL_KEY_LOCATION)
    # Restart the devserver service.
    os.system('sudo restart moblab-devserver-init')


###########Moblab Config Wizard RPCs #######################
def _get_public_ip_address(socket_handle):
    """Gets the public IP address.

    Connects to Google DNS server using a socket and gets the preferred IP
    address from the connection.

    @param: socket_handle: a unix socket.

    @return: public ip address as string.
    """
    try:
        socket_handle.settimeout(1)
        socket_handle.connect(('8.8.8.8', 53))
        socket_name = socket_handle.getsockname()
        if socket_name is not None:
            logging.info('Got socket name from UDP socket.')
            return socket_name[0]
        logging.warn('Created UDP socket but with no socket_name.')
    except socket.error:
        logging.warn('Could not get socket name from UDP socket.')
    return None


def _get_network_info():
    """Gets the network information.

    TCP socket is used to test the connectivity. If there is no connectivity, try to
    get the public IP with UDP socket.

    @return: a tuple as (public_ip_address, connected_to_internet).
    """
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    ip = _get_public_ip_address(s)
    if ip is not None:
        logging.info('Established TCP connection with well known server.')
        return (ip, True)
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return (_get_public_ip_address(s), False)


@moblab_only
def get_network_info():
    """Returns the server ip addresses, and if the server connectivity.

    The server ip addresses as an array of strings, and the connectivity as a
    flag.
    """
    network_info = {}
    info = _get_network_info()
    if info[0] is not None:
        network_info['server_ips'] = [info[0]]
    network_info['is_connected'] = info[1]

    return rpc_utils.prepare_for_serialization(network_info)


# Gets the boto configuration.
def _get_boto_config():
    """Reads the boto configuration from the boto file.

    @return: Boto configuration as ConfigParser object.
    """
    boto_config = ConfigParser.ConfigParser()
    boto_config.read(MOBLAB_BOTO_LOCATION)
    return boto_config


@moblab_only
def get_cloud_storage_info():
    """RPC handler to get the cloud storage access information.
    """
    cloud_storage_info = {}
    value =_CONFIG.get_config_value('CROS', _IMAGE_STORAGE_SERVER)
    if value is not None:
        cloud_storage_info[_IMAGE_STORAGE_SERVER] = value
    value =_CONFIG.get_config_value('CROS', _RESULT_STORAGE_SERVER)
    if value is not None:
        cloud_storage_info[_RESULT_STORAGE_SERVER] = value

    boto_config = _get_boto_config()
    sections = boto_config.sections()

    if sections:
        cloud_storage_info[_USE_EXISTING_BOTO_FILE] = True
    else:
        cloud_storage_info[_USE_EXISTING_BOTO_FILE] = False
    if 'Credentials' in sections:
        options = boto_config.options('Credentials')
        if _GS_ACCESS_KEY_ID in options:
            value = boto_config.get('Credentials', _GS_ACCESS_KEY_ID)
            cloud_storage_info[_GS_ACCESS_KEY_ID] = value
        if _GS_SECRETE_ACCESS_KEY in options:
            value = boto_config.get('Credentials', _GS_SECRETE_ACCESS_KEY)
            cloud_storage_info[_GS_SECRETE_ACCESS_KEY] = value

    return rpc_utils.prepare_for_serialization(cloud_storage_info)


def _get_bucket_name_from_url(bucket_url):
    """Gets the bucket name from a bucket url.

    @param: bucket_url: the bucket url string.
    """
    if bucket_url:
        match = GOOGLE_STORAGE_BUCKET_URL_PATTERN.match(bucket_url)
        if match:
            return match.group('bucket')
    return None


def _is_valid_boto_key(key_id, key_secret):
    """Checks if the boto key is valid.

    @param: key_id: The boto key id string.
    @param: key_secret: The boto key string.

    @return: A tuple as (valid_boolean, details_string).
    """
    if not key_id or not key_secret:
        return (False, "Empty key id or secret.")
    conn = boto.connect_gs(key_id, key_secret)
    try:
        buckets = conn.get_all_buckets()
        return (True, None)
    except boto.exception.GSResponseError:
        details = "The boto access key is not valid"
        return (False, details)
    finally:
        conn.close()


def _is_valid_bucket(key_id, key_secret, bucket_name):
    """Checks if a bucket is valid and accessible.

    @param: key_id: The boto key id string.
    @param: key_secret: The boto key string.
    @param: bucket name string.

    @return: A tuple as (valid_boolean, details_string).
    """
    if not key_id or not key_secret or not bucket_name:
        return (False, "Server error: invalid argument")
    conn = boto.connect_gs(key_id, key_secret)
    bucket = conn.lookup(bucket_name)
    conn.close()
    if bucket:
        return (True, None)
    return (False, "Bucket %s does not exist." % bucket_name)


def _is_valid_bucket_url(key_id, key_secret, bucket_url):
    """Validates the bucket url is accessible.

    @param: key_id: The boto key id string.
    @param: key_secret: The boto key string.
    @param: bucket url string.

    @return: A tuple as (valid_boolean, details_string).
    """
    bucket_name = _get_bucket_name_from_url(bucket_url)
    if bucket_name:
        return _is_valid_bucket(key_id, key_secret, bucket_name)
    return (False, "Bucket url %s is not valid" % bucket_url)


def _validate_cloud_storage_info(cloud_storage_info):
    """Checks if the cloud storage information is valid.

    @param: cloud_storage_info: The JSON RPC object for cloud storage info.

    @return: A tuple as (valid_boolean, details_string).
    """
    valid = True
    details = None
    if not cloud_storage_info[_USE_EXISTING_BOTO_FILE]:
        key_id = cloud_storage_info[_GS_ACCESS_KEY_ID]
        key_secret = cloud_storage_info[_GS_SECRETE_ACCESS_KEY]
        valid, details = _is_valid_boto_key(key_id, key_secret)

        if valid:
            valid, details = _is_valid_bucket_url(
                key_id, key_secret, cloud_storage_info[_IMAGE_STORAGE_SERVER])

        if valid:
            valid, details = _is_valid_bucket_url(
                key_id, key_secret, cloud_storage_info[_RESULT_STORAGE_SERVER])
    return (valid, details)


def _create_operation_status_response(is_ok, details):
    """Helper method to create a operation status reponse.

    @param: is_ok: Boolean for if the operation is ok.
    @param: details: A detailed string.

    @return: A serialized JSON RPC object.
    """
    status_response = {'status_ok': is_ok}
    if details:
        status_response['status_details'] = details
    return rpc_utils.prepare_for_serialization(status_response)


@moblab_only
def validate_cloud_storage_info(cloud_storage_info):
    """RPC handler to check if the cloud storage info is valid.
    """
    valid, details = _validate_cloud_storage_info(cloud_storage_info)
    return _create_operation_status_response(valid, details)


@moblab_only
def submit_wizard_config_info(cloud_storage_info):
    """RPC handler to submit the cloud storage info.
    """
    valid, details = _validate_cloud_storage_info(cloud_storage_info)
    if not valid:
        return _create_operation_status_response(valid, details)
    config_update = {}
    config_update['CROS'] = [
        (_IMAGE_STORAGE_SERVER, cloud_storage_info[_IMAGE_STORAGE_SERVER]),
        (_RESULT_STORAGE_SERVER, cloud_storage_info[_RESULT_STORAGE_SERVER])
    ]
    _update_partial_config(config_update)

    if not cloud_storage_info[_USE_EXISTING_BOTO_FILE]:
        boto_config = ConfigParser.RawConfigParser()
        boto_config.add_section('Credentials')
        boto_config.set('Credentials', _GS_ACCESS_KEY_ID,
                        cloud_storage_info[_GS_ACCESS_KEY_ID])
        boto_config.set('Credentials', _GS_SECRETE_ACCESS_KEY,
                        cloud_storage_info[_GS_SECRETE_ACCESS_KEY])
        _write_config_file(MOBLAB_BOTO_LOCATION, boto_config, True)

    _CONFIG.parse_config_file()

    return _create_operation_status_response(True, None)


def get_job_history(**filter_data):
    """Get history of the job, including the special tasks executed for the job

    @param filter_data: filter for the call, should at least include
                        {'job_id': [job id]}
    @returns: JSON string of the job's history, including the information such
              as the hosts run the job and the special tasks executed before
              and after the job.
    """
    job_id = filter_data['job_id']
    job_info = job_history.get_job_info(job_id)
    return rpc_utils.prepare_for_serialization(job_info.get_history())


def get_host_history(start_time, end_time, hosts=None, board=None, pool=None):
    """Get history of a list of host.

    The return is a JSON string of host history for each host, for example,
    {'172.22.33.51': [{'status': 'Resetting'
                       'start_time': '2014-08-07 10:02:16',
                       'end_time': '2014-08-07 10:03:16',
                       'log_url': 'http://autotest/reset-546546/debug',
                       'dbg_str': 'Task: Special Task 19441991 (host ...)'},
                       {'status': 'Running'
                       'start_time': '2014-08-07 10:03:18',
                       'end_time': '2014-08-07 10:13:00',
                       'log_url': 'http://autotest/reset-546546/debug',
                       'dbg_str': 'HQE: 15305005, for job: 14995562'}
                     ]
    }
    @param start_time: start time to search for history, can be string value or
                       epoch time.
    @param end_time: end time to search for history, can be string value or
                     epoch time.
    @param hosts: A list of hosts to search for history. Default is None.
    @param board: board type of hosts. Default is None.
    @param pool: pool type of hosts. Default is None.
    @returns: JSON string of the host history.
    """
    return rpc_utils.prepare_for_serialization(
            host_history.get_history_details(
                    start_time=start_time, end_time=end_time,
                    hosts=hosts, board=board, pool=pool,
                    process_pool_size=4))


def shard_heartbeat(shard_hostname, jobs=(), hqes=(), known_job_ids=(),
                    known_host_ids=(), known_host_statuses=()):
    """Receive updates for job statuses from shards and assign hosts and jobs.

    @param shard_hostname: Hostname of the calling shard
    @param jobs: Jobs in serialized form that should be updated with newer
                 status from a shard.
    @param hqes: Hostqueueentries in serialized form that should be updated with
                 newer status from a shard. Note that for every hostqueueentry
                 the corresponding job must be in jobs.
    @param known_job_ids: List of ids of jobs the shard already has.
    @param known_host_ids: List of ids of hosts the shard already has.
    @param known_host_statuses: List of statuses of hosts the shard already has.

    @returns: Serialized representations of hosts, jobs, suite job keyvals
              and their dependencies to be inserted into a shard's database.
    """
    # The following alternatives to sending host and job ids in every heartbeat
    # have been considered:
    # 1. Sending the highest known job and host ids. This would work for jobs:
    #    Newer jobs always have larger ids. Also, if a job is not assigned to a
    #    particular shard during a heartbeat, it never will be assigned to this
    #    shard later.
    #    This is not true for hosts though: A host that is leased won't be sent
    #    to the shard now, but might be sent in a future heartbeat. This means
    #    sometimes hosts should be transfered that have a lower id than the
    #    maximum host id the shard knows.
    # 2. Send the number of jobs/hosts the shard knows to the master in each
    #    heartbeat. Compare these to the number of records that already have
    #    the shard_id set to this shard. In the normal case, they should match.
    #    In case they don't, resend all entities of that type.
    #    This would work well for hosts, because there aren't that many.
    #    Resending all jobs is quite a big overhead though.
    #    Also, this approach might run into edge cases when entities are
    #    ever deleted.
    # 3. Mixtures of the above: Use 1 for jobs and 2 for hosts.
    #    Using two different approaches isn't consistent and might cause
    #    confusion. Also the issues with the case of deletions might still
    #    occur.
    #
    # The overhead of sending all job and host ids in every heartbeat is low:
    # At peaks one board has about 1200 created but unfinished jobs.
    # See the numbers here: http://goo.gl/gQCGWH
    # Assuming that job id's have 6 digits and that json serialization takes a
    # comma and a space as overhead, the traffic per id sent is about 8 bytes.
    # If 5000 ids need to be sent, this means 40 kilobytes of traffic.
    # A NOT IN query with 5000 ids took about 30ms in tests made.
    # These numbers seem low enough to outweigh the disadvantages of the
    # solutions described above.
    timer = autotest_stats.Timer('shard_heartbeat')
    with timer:
        shard_obj = rpc_utils.retrieve_shard(shard_hostname=shard_hostname)
        rpc_utils.persist_records_sent_from_shard(shard_obj, jobs, hqes)
        assert len(known_host_ids) == len(known_host_statuses)
        for i in range(len(known_host_ids)):
            host_model = models.Host.objects.get(pk=known_host_ids[i])
            if host_model.status != known_host_statuses[i]:
                host_model.status = known_host_statuses[i]
                host_model.save()

        hosts, jobs, suite_keyvals = rpc_utils.find_records_for_shard(
                shard_obj, known_job_ids=known_job_ids,
                known_host_ids=known_host_ids)
        return {
            'hosts': [host.serialize() for host in hosts],
            'jobs': [job.serialize() for job in jobs],
            'suite_keyvals': [kv.serialize() for kv in suite_keyvals],
        }


def get_shards(**filter_data):
    """Return a list of all shards.

    @returns A sequence of nested dictionaries of shard information.
    """
    shards = models.Shard.query_objects(filter_data)
    serialized_shards = rpc_utils.prepare_rows_as_nested_dicts(shards, ())
    for serialized, shard in zip(serialized_shards, shards):
        serialized['labels'] = [label.name for label in shard.labels.all()]

    return serialized_shards


def add_shard(hostname, labels):
    """Add a shard and start running jobs on it.

    @param hostname: The hostname of the shard to be added; needs to be unique.
    @param labels: Board labels separated by a comma. Jobs of one of the labels
                   will be assigned to the shard.

    @raises error.RPCException: If label provided doesn't start with `board:`
    @raises model_logic.ValidationError: If a shard with the given hostname
            already exists.
    @raises models.Label.DoesNotExist: If the label specified doesn't exist.
    """
    labels = labels.split(',')
    label_models = []
    for label in labels:
        if not label.startswith('board:'):
            raise error.RPCException('Sharding only supports for `board:.*` '
                                     'labels.')
        # Fetch label first, so shard isn't created when label doesn't exist.
        label_models.append(models.Label.smart_get(label))

    shard = models.Shard.add_object(hostname=hostname)
    for label in label_models:
        shard.labels.add(label)
    return shard.id


def delete_shard(hostname):
    """Delete a shard and reclaim all resources from it.

    This claims back all assigned hosts from the shard. To ensure all DUTs are
    in a sane state, a Reboot task with highest priority is scheduled for them.
    This reboots the DUTs and then all left tasks continue to run in drone of
    the master.

    The procedure for deleting a shard:
        * Lock all unlocked hosts on that shard.
        * Remove shard information .
        * Assign a reboot task with highest priority to these hosts.
        * Unlock these hosts, then, the reboot tasks run in front of all other
        tasks.

    The status of jobs that haven't been reported to be finished yet, will be
    lost. The master scheduler will pick up the jobs and execute them.

    @param hostname: Hostname of the shard to delete.
    """
    shard = rpc_utils.retrieve_shard(shard_hostname=hostname)
    hostnames_to_lock = [h.hostname for h in
                         models.Host.objects.filter(shard=shard, locked=False)]

    # TODO(beeps): Power off shard
    # For ChromeOS hosts, a reboot test with the highest priority is added to
    # the DUT. After a reboot it should be ganranteed that no processes from
    # prior tests that were run by a shard are still running on.

    # Lock all unlocked hosts.
    dicts = {'locked': True, 'lock_time': datetime.datetime.now()}
    models.Host.objects.filter(hostname__in=hostnames_to_lock).update(**dicts)

    # Remove shard information.
    models.Host.objects.filter(shard=shard).update(shard=None)
    models.Job.objects.filter(shard=shard).update(shard=None)
    shard.labels.clear()
    shard.delete()

    # Assign a reboot task with highest priority: Super.
    t = models.Test.objects.get(name='platform_BootPerfServer:shard')
    c = utils.read_file(os.path.join(common.autotest_dir, t.path))
    if hostnames_to_lock:
        rpc_utils.create_job_common(
                'reboot_dut_for_shard_deletion',
                priority=priorities.Priority.SUPER,
                control_type='Server',
                control_file=c, hosts=hostnames_to_lock)

    # Unlock these shard-related hosts.
    dicts = {'locked': False, 'lock_time': None}
    models.Host.objects.filter(hostname__in=hostnames_to_lock).update(**dicts)


def get_servers(hostname=None, role=None, status=None):
    """Get a list of servers with matching role and status.

    @param hostname: FQDN of the server.
    @param role: Name of the server role, e.g., drone, scheduler. Default to
                 None to match any role.
    @param status: Status of the server, e.g., primary, backup, repair_required.
                   Default to None to match any server status.

    @raises error.RPCException: If server database is not used.
    @return: A list of server names for servers with matching role and status.
    """
    if not server_manager_utils.use_server_db():
        raise error.RPCException('Server database is not enabled. Please try '
                                 'retrieve servers from global config.')
    servers = server_manager_utils.get_servers(hostname=hostname, role=role,
                                               status=status)
    return [s.get_details() for s in servers]


@rpc_utils.route_rpc_to_master
def get_stable_version(board=stable_version_utils.DEFAULT, android=False):
    """Get stable version for the given board.

    @param board: Name of the board.
    @param android: If True, the given board is an Android-based device. If
                    False, assume its a Chrome OS-based device.

    @return: Stable version of the given board. Return global configure value
             of CROS.stable_cros_version if stable_versinos table does not have
             entry of board DEFAULT.
    """
    return stable_version_utils.get(board=board, android=android)


@rpc_utils.route_rpc_to_master
def get_all_stable_versions():
    """Get stable versions for all boards.

    @return: A dictionary of board:version.
    """
    return stable_version_utils.get_all()


@rpc_utils.route_rpc_to_master
def set_stable_version(version, board=stable_version_utils.DEFAULT):
    """Modify stable version for the given board.

    @param version: The new value of stable version for given board.
    @param board: Name of the board, default to value `DEFAULT`.
    """
    stable_version_utils.set(version=version, board=board)


@rpc_utils.route_rpc_to_master
def delete_stable_version(board):
    """Modify stable version for the given board.

    Delete a stable version entry in afe_stable_versions table for a given
    board, so default stable version will be used.

    @param board: Name of the board.
    """
    stable_version_utils.delete(board=board)


def get_tests_by_build(build):
    """Get the tests that are available for the specified build.

    @param build: unique name by which to refer to the image.

    @return: A sorted list of all tests that are in the build specified.
    """
    # Stage the test artifacts.
    try:
        ds = dev_server.ImageServer.resolve(build)
        build = ds.translate(build)
    except dev_server.DevServerException as e:
        raise ValueError('Could not resolve build %s: %s' % (build, e))

    try:
        ds.stage_artifacts(image=build, artifacts=['test_suites'])
    except dev_server.DevServerException as e:
        raise error.StageControlFileFailure(
                'Failed to stage %s: %s' % (build, e))

    # Collect the control files specified in this build
    cfile_getter = control_file_getter.DevServerGetter.create(build, ds)
    control_file_list = cfile_getter.get_control_file_list()

    test_objects = []
    _id = 0
    for control_file_path in control_file_list:
        # Read and parse the control file
        control_file = cfile_getter.get_control_file_contents(
                control_file_path)
        control_obj = control_data.parse_control_string(control_file)

        # Extract the values needed for the AFE from the control_obj.
        # The keys list represents attributes in the control_obj that
        # are required by the AFE
        keys = ['author', 'doc', 'name', 'time', 'test_type', 'experimental',
                'test_category', 'test_class', 'dependencies', 'run_verify',
                'sync_count', 'job_retries', 'retries', 'path']

        test_object = {}
        for key in keys:
            test_object[key] = getattr(control_obj, key) if hasattr(
                    control_obj, key) else ''

        # Unfortunately, the AFE expects different key-names for certain
        # values, these must be corrected to avoid the risk of tests
        # being omitted by the AFE.
        # The 'id' is an additional value used in the AFE.
        # The control_data parsing does not reference 'run_reset', but it
        # is also used in the AFE and defaults to True.
        test_object['id'] = _id
        test_object['run_reset'] = True
        test_object['description'] = test_object.get('doc', '')
        test_object['test_time'] = test_object.get('time', 0)
        test_object['test_retry'] = test_object.get('retries', 0)

        # Fix the test name to be consistent with the current presentation
        # of test names in the AFE.
        testpath, subname = os.path.split(control_file_path)
        testname = os.path.basename(testpath)
        subname = subname.split('.')[1:]
        if subname:
            testname = '%s:%s' % (testname, ':'.join(subname))

        test_object['name'] = testname

        # Correct the test path as parse_control_string sets an empty string.
        test_object['path'] = control_file_path

        _id += 1
        test_objects.append(test_object)

    test_objects = sorted(test_objects, key=lambda x: x.get('name'))
    return rpc_utils.prepare_for_serialization(test_objects)