server/server_job.py

"""
The main job wrapper for the server side.

This is the core infrastructure. Derived from the client side job.py

Copyright Martin J. Bligh, Andy Whitcroft 2007
"""

import getpass, os, sys, re, stat, tempfile, time, select, subprocess
import traceback, shutil, warnings, fcntl, pickle, logging, logging.config
from autotest_lib.client.bin import fd_stack, sysinfo
from autotest_lib.client.common_lib import error, log, utils, packages
from autotest_lib.server import test, subcommand, profilers
from autotest_lib.tko import db as tko_db, status_lib, utils as tko_utils


def _control_segment_path(name):
    """Get the pathname of the named control segment file."""
    server_dir = os.path.dirname(os.path.abspath(__file__))
    return os.path.join(server_dir, "control_segments", name)


CLIENT_CONTROL_FILENAME = 'control'
SERVER_CONTROL_FILENAME = 'control.srv'
MACHINES_FILENAME = '.machines'

CLIENT_WRAPPER_CONTROL_FILE = _control_segment_path('client_wrapper')
CRASHDUMPS_CONTROL_FILE = _control_segment_path('crashdumps')
CRASHINFO_CONTROL_FILE = _control_segment_path('crashinfo')
INSTALL_CONTROL_FILE = _control_segment_path('install')
CLEANUP_CONTROL_FILE = _control_segment_path('cleanup')

VERIFY_CONTROL_FILE = _control_segment_path('verify')
REPAIR_CONTROL_FILE = _control_segment_path('repair')


# by default provide a stub that generates no site data
def _get_site_job_data_dummy(job):
    return {}


# load up site-specific code for generating site-specific job data
get_site_job_data = utils.import_site_function(__file__,
    "autotest_lib.server.site_server_job", "get_site_job_data",
    _get_site_job_data_dummy)


class base_server_job(object):
    """
    The actual job against which we do everything.

    Properties:
            autodir
                    The top level autotest directory (/usr/local/autotest).
            serverdir
                    <autodir>/server/
            clientdir
                    <autodir>/client/
            conmuxdir
                    <autodir>/conmux/
            testdir
                    <autodir>/server/tests/
            site_testdir
                    <autodir>/server/site_tests/
            control
                    the control file for this job
            drop_caches_between_iterations
                    drop the pagecache between each iteration
    """

    STATUS_VERSION = 1


    def __init__(self, control, args, resultdir, label, user, machines,
                 client=False, parse_job='',
                 ssh_user='root', ssh_port=22, ssh_pass=''):
        """
            Server side job object.

            Parameters:
                control:        The control file (pathname of)
                args:           args to pass to the control file
                resultdir:      where to throw the results
                label:          label for the job
                user:           Username for the job (email address)
                client:         True if a client-side control file
        """
        path = os.path.dirname(__file__)
        self.autodir = os.path.abspath(os.path.join(path, '..'))
        self.serverdir = os.path.join(self.autodir, 'server')
        self.testdir   = os.path.join(self.serverdir, 'tests')
        self.site_testdir = os.path.join(self.serverdir, 'site_tests')
        self.tmpdir    = os.path.join(self.serverdir, 'tmp')
        self.conmuxdir = os.path.join(self.autodir, 'conmux')
        self.clientdir = os.path.join(self.autodir, 'client')
        self.toolsdir = os.path.join(self.autodir, 'client/tools')
        if control:
            self.control = self._load_control_file(control)
        else:
            self.control = ''
        self.resultdir = resultdir
        self.uncollected_log_file = os.path.join(resultdir, "uncollected_logs")
        self.debugdir = os.path.join(resultdir, 'debug')
        if resultdir:
            if not os.path.exists(resultdir):
                os.mkdir(resultdir)
            log_file = open(self.uncollected_log_file, "w")
            pickle.dump([], log_file)
            log_file.close()
            if not os.path.exists(self.debugdir):
                os.mkdir(self.debugdir)
            status_log = self.get_status_log_path()
            if os.path.exists(status_log):
                os.remove(status_log)
        self.label = label
        self.user = user
        self.args = args
        self.machines = machines
        self.client = client
        self.record_prefix = ''
        self.warning_loggers = set()
        self.warning_manager = warning_manager()
        self.ssh_user = ssh_user
        self.ssh_port = ssh_port
        self.ssh_pass = ssh_pass
        self.run_test_cleanup = True
        self.last_boot_tag = None
        self.hosts = set()
        self.drop_caches_between_iterations = False

        self.stdout = fd_stack.fd_stack(1, sys.stdout)
        self.stderr = fd_stack.fd_stack(2, sys.stderr)

        if resultdir:
            self.sysinfo = sysinfo.sysinfo(self.resultdir)
        self.profilers = profilers.profilers(self)

        if not os.access(self.tmpdir, os.W_OK):
            try:
                os.makedirs(self.tmpdir, 0700)
            except os.error, e:
                # Thrown if the directory already exists, which it may.
                pass

        if not (os.access(self.tmpdir, os.W_OK) and os.path.isdir(self.tmpdir)):
            self.tmpdir = os.path.join(tempfile.gettempdir(),
                                       'autotest-' + getpass.getuser())
            try:
                os.makedirs(self.tmpdir, 0700)
            except os.error, e:
                # Thrown if the directory already exists, which it may.
                # If the problem was something other than the
                # directory already existing, this chmod should throw as well
                # exception.
                os.chmod(self.tmpdir, stat.S_IRWXU)

        job_data = {'label' : label, 'user' : user,
                    'hostname' : ','.join(machines),
                    'status_version' : str(self.STATUS_VERSION),
                    'job_started' : str(int(time.time()))}
        if self.resultdir:
            job_data.update(get_site_job_data(self))
            utils.write_keyval(self.resultdir, job_data)

        self.parse_job = parse_job
        if self.parse_job and len(machines) == 1:
            self.using_parser = True
            self.init_parser(resultdir)
        else:
            self.using_parser = False
        self.pkgmgr = packages.PackageManager(self.autodir,
                                             run_function_dargs={'timeout':600})
        self.pkgdir = os.path.join(self.autodir, 'packages')

        self.num_tests_run = 0
        self.num_tests_failed = 0

        self._register_subcommand_hooks()


    @staticmethod
    def _load_control_file(path):
        f = open(path)
        try:
            control_file = f.read()
        finally:
            f.close()
        return re.sub('\r', '', control_file)


    def _register_subcommand_hooks(self):
        """
        Register some hooks into the subcommand modules that allow us
        to properly clean up self.hosts created in forked subprocesses.
        """
        def on_fork(cmd):
            self._existing_hosts_on_fork = set(self.hosts)
        def on_join(cmd):
            new_hosts = self.hosts - self._existing_hosts_on_fork
            for host in new_hosts:
                host.close()
        subcommand.subcommand.register_fork_hook(on_fork)
        subcommand.subcommand.register_join_hook(on_join)


    def init_parser(self, resultdir):
        """
        Start the continuous parsing of resultdir. This sets up
        the database connection and inserts the basic job object into
        the database if necessary.
        """
        # redirect parser debugging to .parse.log
        parse_log = os.path.join(resultdir, '.parse.log')
        parse_log = open(parse_log, 'w', 0)
        tko_utils.redirect_parser_debugging(parse_log)
        # create a job model object and set up the db
        self.results_db = tko_db.db(autocommit=True)
        self.parser = status_lib.parser(self.STATUS_VERSION)
        self.job_model = self.parser.make_job(resultdir)
        self.parser.start(self.job_model)
        # check if a job already exists in the db and insert it if
        # it does not
        job_idx = self.results_db.find_job(self.parse_job)
        if job_idx is None:
            self.results_db.insert_job(self.parse_job, self.job_model)
        else:
            machine_idx = self.results_db.lookup_machine(self.job_model.machine)
            self.job_model.index = job_idx
            self.job_model.machine_idx = machine_idx


    def cleanup_parser(self):
        """
        This should be called after the server job is finished
        to carry out any remaining cleanup (e.g. flushing any
        remaining test results to the results db)
        """
        if not self.using_parser:
            return
        final_tests = self.parser.end()
        for test in final_tests:
            self.__insert_test(test)
        self.using_parser = False


    def verify(self):
        if not self.machines:
            raise error.AutoservError('No machines specified to verify')
        if self.resultdir:
            os.chdir(self.resultdir)
        try:
            namespace = {'machines' : self.machines, 'job' : self,
                         'ssh_user' : self.ssh_user,
                         'ssh_port' : self.ssh_port,
                         'ssh_pass' : self.ssh_pass}
            self._execute_code(VERIFY_CONTROL_FILE, namespace, protect=False)
        except Exception, e:
            msg = ('Verify failed\n' + str(e) + '\n' + traceback.format_exc())
            self.record('ABORT', None, None, msg)
            raise


    def repair(self, host_protection):
        if not self.machines:
            raise error.AutoservError('No machines specified to repair')
        if self.resultdir:
            os.chdir(self.resultdir)
        namespace = {'machines': self.machines, 'job': self,
                     'ssh_user': self.ssh_user, 'ssh_port': self.ssh_port,
                     'ssh_pass': self.ssh_pass,
                     'protection_level': host_protection}
        # no matter what happens during repair (except if it succeeded in
        # initiating hardware repair procedure), go on to try to reverify
        try:
            self._execute_code(REPAIR_CONTROL_FILE, namespace, protect=False)
        except error.AutoservHardwareRepairRequestedError:
            raise
        except Exception, exc:
            print 'Exception occured during repair'
            traceback.print_exc()

        self.verify()


    def precheck(self):
        """
        perform any additional checks in derived classes.
        """
        pass


    def enable_external_logging(self):
        """
        Start or restart external logging mechanism.
        """
        pass


    def disable_external_logging(self):
        """
        Pause or stop external logging mechanism.
        """
        pass


    def enable_test_cleanup(self):
        """
        By default tests run test.cleanup
        """
        self.run_test_cleanup = True


    def disable_test_cleanup(self):
        """
        By default tests do not run test.cleanup
        """
        self.run_test_cleanup = False


    def use_external_logging(self):
        """
        Return True if external logging should be used.
        """
        return False


    def parallel_simple(self, function, machines, log=True, timeout=None):
        """
        Run 'function' using parallel_simple, with an extra wrapper to handle
        the necessary setup for continuous parsing, if possible. If continuous
        parsing is already properly initialized then this should just work.
        """
        is_forking = not (len(machines) == 1 and self.machines == machines)
        if self.parse_job and is_forking and log:
            def wrapper(machine):
                self.parse_job += "/" + machine
                self.using_parser = True
                self.machines = [machine]
                self.resultdir = os.path.join(self.resultdir, machine)
                os.chdir(self.resultdir)
                utils.write_keyval(self.resultdir, {"hostname": machine})
                self.init_parser(self.resultdir)
                result = function(machine)
                self.cleanup_parser()
                return result
        elif len(machines) > 1 and log:
            def wrapper(machine):
                self.resultdir = os.path.join(self.resultdir, machine)
                os.chdir(self.resultdir)
                machine_data = {'hostname' : machine,
                                'status_version' : str(self.STATUS_VERSION)}
                utils.write_keyval(self.resultdir, machine_data)
                result = function(machine)
                return result
        else:
            wrapper = function
        subcommand.parallel_simple(wrapper, machines, log, timeout)


    USE_TEMP_DIR = object()
    def run(self, cleanup=False, install_before=False, install_after=False,
            collect_crashdumps=True, namespace={}, control=None,
            control_file_dir=None):
        # use a copy so changes don't affect the original dictionary
        namespace = namespace.copy()
        machines = self.machines
        if control is None:
            control = self.control
        if control_file_dir is None:
            control_file_dir = self.resultdir

        self.aborted = False
        namespace['machines'] = machines
        namespace['args'] = self.args
        namespace['job'] = self
        namespace['ssh_user'] = self.ssh_user
        namespace['ssh_port'] = self.ssh_port
        namespace['ssh_pass'] = self.ssh_pass
        test_start_time = int(time.time())

        if self.resultdir:
            os.chdir(self.resultdir)
            # touch status.log so that the parser knows a job is running here
            open(self.get_status_log_path(), 'w').close()
            self.enable_external_logging()

        collect_crashinfo = True
        temp_control_file_dir = None
        try:
            if install_before and machines:
                self._execute_code(INSTALL_CONTROL_FILE, namespace)

            # determine the dir to write the control files to
            if control_file_dir and control_file_dir is not self.USE_TEMP_DIR:
                temp_control_file_dir = None
            else:
                temp_control_file_dir = control_file_dir = tempfile.mkdtemp(
                    suffix='temp_control_file_dir')
            server_control_file = os.path.join(control_file_dir,
                                               SERVER_CONTROL_FILENAME)
            client_control_file = os.path.join(control_file_dir,
                                               CLIENT_CONTROL_FILENAME)
            if self.client:
                namespace['control'] = control
                utils.open_write_close(client_control_file, control)
                shutil.copy(CLIENT_WRAPPER_CONTROL_FILE, server_control_file)
            else:
                namespace['utils'] = utils
                utils.open_write_close(server_control_file, control)
            self._execute_code(server_control_file, namespace)

            # disable crashinfo collection if we get this far without error
            collect_crashinfo = False
        finally:
            if temp_control_file_dir:
                # Clean up temp directory used for copies of the control files
                try:
                    shutil.rmtree(temp_control_file_dir)
                except Exception, e:
                    print 'Error %s removing dir %s' % (e,
                                                        temp_control_file_dir)

            if machines and (collect_crashdumps or collect_crashinfo):
                namespace['test_start_time'] = test_start_time
                if collect_crashinfo:
                    # includes crashdumps
                    self._execute_code(CRASHINFO_CONTROL_FILE, namespace)
                else:
                    self._execute_code(CRASHDUMPS_CONTROL_FILE, namespace)
            os.remove(self.uncollected_log_file)
            self.disable_external_logging()
            if cleanup and machines:
                self._execute_code(CLEANUP_CONTROL_FILE, namespace)
            if install_after and machines:
                self._execute_code(INSTALL_CONTROL_FILE, namespace)


    def run_test(self, url, *args, **dargs):
        """
        Summon a test object and run it.

        tag
                tag to add to testname
        url
                url of the test to run
        """

        (group, testname) = self.pkgmgr.get_package_name(url, 'test')

        tag = dargs.pop('tag', None)
        if tag:
            testname += '.' + str(tag)
        subdir = testname

        outputdir = os.path.join(self.resultdir, subdir)
        if os.path.exists(outputdir):
            msg = ("%s already exists, test <%s> may have"
                   " already run with tag <%s>" % (outputdir, testname, tag))
            raise error.TestError(msg)
        os.mkdir(outputdir)

        def group_func():
            try:
                test.runtest(self, url, tag, args, dargs)
            except error.TestBaseException, e:
                self.record(e.exit_status, subdir, testname, str(e))
                raise
            except Exception, e:
                info = str(e) + "\n" + traceback.format_exc()
                self.record('FAIL', subdir, testname, info)
                raise
            else:
                self.record('GOOD', subdir, testname, 'completed successfully')

        result, exc_info = self._run_group(testname, subdir, group_func)
        if exc_info and isinstance(exc_info[1], error.TestBaseException):
            return False
        elif exc_info:
            raise exc_info[0], exc_info[1], exc_info[2]
        else:
            return True


    def _run_group(self, name, subdir, function, *args, **dargs):
        """\
        Underlying method for running something inside of a group.
        """
        result, exc_info = None, None
        old_record_prefix = self.record_prefix
        try:
            self.record('START', subdir, name)
            self.record_prefix += '\t'
            try:
                result = function(*args, **dargs)
            finally:
                self.record_prefix = old_record_prefix
        except error.TestBaseException, e:
            self.record("END %s" % e.exit_status, subdir, name)
            exc_info = sys.exc_info()
        except Exception, e:
            err_msg = str(e) + '\n'
            err_msg += traceback.format_exc()
            self.record('END ABORT', subdir, name, err_msg)
            raise error.JobError(name + ' failed\n' + traceback.format_exc())
        else:
            self.record('END GOOD', subdir, name)

        return result, exc_info


    def run_group(self, function, *args, **dargs):
        """\
        function:
                subroutine to run
        *args:
                arguments for the function
        """

        name = function.__name__

        # Allow the tag for the group to be specified.
        tag = dargs.pop('tag', None)
        if tag:
            name = tag

        return self._run_group(name, None, function, *args, **dargs)[0]


    def run_reboot(self, reboot_func, get_kernel_func):
        """\
        A specialization of run_group meant specifically for handling
        a reboot. Includes support for capturing the kernel version
        after the reboot.

        reboot_func: a function that carries out the reboot

        get_kernel_func: a function that returns a string
        representing the kernel version.
        """

        old_record_prefix = self.record_prefix
        try:
            self.record('START', None, 'reboot')
            self.record_prefix += '\t'
            reboot_func()
        except Exception, e:
            self.record_prefix = old_record_prefix
            err_msg = str(e) + '\n' + traceback.format_exc()
            self.record('END FAIL', None, 'reboot', err_msg)
        else:
            kernel = get_kernel_func()
            self.record_prefix = old_record_prefix
            self.record('END GOOD', None, 'reboot',
                        optional_fields={"kernel": kernel})


    def run_control(self, path):
        """Execute a control file found at path (relative to the autotest
        path). Intended for executing a control file within a control file,
        not for running the top-level job control file."""
        path = os.path.join(self.autodir, path)
        control_file = self._load_control_file(path)
        self.run(control=control_file, control_file_dir=self.USE_TEMP_DIR)


    def add_sysinfo_command(self, command, logfile=None, on_every_test=False):
        self._add_sysinfo_loggable(sysinfo.command(command, logf=logfile),
                                   on_every_test)


    def add_sysinfo_logfile(self, file, on_every_test=False):
        self._add_sysinfo_loggable(sysinfo.logfile(file), on_every_test)


    def _add_sysinfo_loggable(self, loggable, on_every_test):
        if on_every_test:
            self.sysinfo.test_loggables.add(loggable)
        else:
            self.sysinfo.boot_loggables.add(loggable)


    def record(self, status_code, subdir, operation, status='',
               optional_fields=None):
        """
        Record job-level status

        The intent is to make this file both machine parseable and
        human readable. That involves a little more complexity, but
        really isn't all that bad ;-)

        Format is <status code>\t<subdir>\t<operation>\t<status>

        status code: see common_lib.log.is_valid_status()
                     for valid status definition

        subdir: MUST be a relevant subdirectory in the results,
        or None, which will be represented as '----'

        operation: description of what you ran (e.g. "dbench", or
                                        "mkfs -t foobar /dev/sda9")

        status: error message or "completed sucessfully"

        ------------------------------------------------------------

        Initial tabs indicate indent levels for grouping, and is
        governed by self.record_prefix

        multiline messages have secondary lines prefaced by a double
        space ('  ')

        Executing this method will trigger the logging of all new
        warnings to date from the various console loggers.
        """
        # poll all our warning loggers for new warnings
        warnings = self._read_warnings()
        for timestamp, msg in warnings:
            self._record("WARN", None, None, msg, timestamp)

        # write out the actual status log line
        self._record(status_code, subdir, operation, status,
                      optional_fields=optional_fields)


    def _read_warnings(self):
        """Poll all the warning loggers and extract any new warnings that have
        been logged. If the warnings belong to a category that is currently
        disabled, this method will discard them and they will no longer be
        retrievable.

        Returns a list of (timestamp, message) tuples, where timestamp is an
        integer epoch timestamp."""
        warnings = []
        while True:
            # pull in a line of output from every logger that has
            # output ready to be read
            loggers, _, _ = select.select(self.warning_loggers, [], [], 0)
            closed_loggers = set()
            for logger in loggers:
                line = logger.readline()
                # record any broken pipes (aka line == empty)
                if len(line) == 0:
                    closed_loggers.add(logger)
                    continue
                # parse out the warning
                timestamp, msgtype, msg = line.split('\t', 2)
                timestamp = int(timestamp)
                # if the warning is valid, add it to the results
                if self.warning_manager.is_valid(timestamp, msgtype):
                    warnings.append((timestamp, msg.strip()))

            # stop listening to loggers that are closed
            self.warning_loggers -= closed_loggers

            # stop if none of the loggers have any output left
            if not loggers:
                break

        # sort into timestamp order
        warnings.sort()
        return warnings


    def disable_warnings(self, warning_type, record=True):
        self.warning_manager.disable_warnings(warning_type)
        if record:
            self.record("INFO", None, None,
                        "disabling %s warnings" % warning_type,
                        {"warnings.disable": warning_type})


    def enable_warnings(self, warning_type, record=True):
        self.warning_manager.enable_warnings(warning_type)
        if record:
            self.record("INFO", None, None,
                        "enabling %s warnings" % warning_type,
                        {"warnings.enable": warning_type})


    def get_status_log_path(self, subdir=None):
        """Return the path to the job status log.

        @param subdir - Optional paramter indicating that you want the path
            to a subdirectory status log.

        @returns The path where the status log should be.
        """
        if subdir:
            return os.path.join(self.resultdir, subdir, "status.log")
        else:
            return os.path.join(self.resultdir, "status.log")


    def _update_uncollected_logs_list(self, update_func):
        """Updates the uncollected logs list in a multi-process safe manner.

        @param update_func - a function that updates the list of uncollected
            logs. Should take one parameter, the list to be updated.
        """
        log_file = open(self.uncollected_log_file, "r+")
        fcntl.flock(log_file, fcntl.LOCK_EX)
        try:
            uncollected_logs = pickle.load(log_file)
            update_func(uncollected_logs)
            log_file.seek(0)
            log_file.truncate()
            pickle.dump(uncollected_logs, log_file)
        finally:
            fcntl.flock(log_file, fcntl.LOCK_UN)
            log_file.close()


    def add_client_log(self, hostname, remote_path, local_path):
        """Adds a new set of client logs to the list of uncollected logs,
        to allow for future log recovery.

        @param host - the hostname of the machine holding the logs
        @param remote_path - the directory on the remote machine holding logs
        @param local_path - the local directory to copy the logs into
        """
        def update_func(logs_list):
            logs_list.append((hostname, remote_path, local_path))
        self._update_uncollected_logs_list(update_func)


    def remove_client_log(self, hostname, remote_path, local_path):
        """Removes a set of client logs from the list of uncollected logs,
        to allow for future log recovery.

        @param host - the hostname of the machine holding the logs
        @param remote_path - the directory on the remote machine holding logs
        @param local_path - the local directory to copy the logs into
        """
        def update_func(logs_list):
            logs_list.remove((hostname, remote_path, local_path))
        self._update_uncollected_logs_list(update_func)


    def _render_record(self, status_code, subdir, operation, status='',
                       epoch_time=None, record_prefix=None,
                       optional_fields=None):
        """
        Internal Function to generate a record to be written into a
        status log. For use by server_job.* classes only.
        """
        if subdir:
            if re.match(r'[\n\t]', subdir):
                raise ValueError('Invalid character in subdir string')
            substr = subdir
        else:
            substr = '----'

        if not log.is_valid_status(status_code):
            raise ValueError('Invalid status code supplied: %s' % status_code)
        if not operation:
            operation = '----'
        if re.match(r'[\n\t]', operation):
            raise ValueError('Invalid character in operation string')
        operation = operation.rstrip()
        status = status.rstrip()
        status = re.sub(r"\t", "  ", status)
        # Ensure any continuation lines are marked so we can
        # detect them in the status file to ensure it is parsable.
        status = re.sub(r"\n", "\n" + self.record_prefix + "  ", status)

        if not optional_fields:
            optional_fields = {}

        # Generate timestamps for inclusion in the logs
        if epoch_time is None:
            epoch_time = int(time.time())
        local_time = time.localtime(epoch_time)
        optional_fields["timestamp"] = str(epoch_time)
        optional_fields["localtime"] = time.strftime("%b %d %H:%M:%S",
                                                     local_time)

        fields = [status_code, substr, operation]
        fields += ["%s=%s" % x for x in optional_fields.iteritems()]
        fields.append(status)

        if record_prefix is None:
            record_prefix = self.record_prefix

        msg = '\t'.join(str(x) for x in fields)
        return record_prefix + msg + '\n'


    def _record_prerendered(self, msg):
        """
        Record a pre-rendered msg into the status logs. The only
        change this makes to the message is to add on the local
        indentation. Should not be called outside of server_job.*
        classes. Unlike _record, this does not write the message
        to standard output.
        """
        lines = []
        status_file = self.get_status_log_path()
        status_log = open(status_file, 'a')
        for line in msg.splitlines():
            line = self.record_prefix + line + '\n'
            lines.append(line)
            status_log.write(line)
        status_log.close()
        self.__parse_status(lines)


    def _fill_server_control_namespace(self, namespace, protect=True):
        """
        Prepare a namespace to be used when executing server control files.

        This sets up the control file API by importing modules and making them
        available under the appropriate names within namespace.

        For use by _execute_code().

        Args:
          namespace: The namespace dictionary to fill in.
          protect: Boolean.  If True (the default) any operation that would
              clobber an existing entry in namespace will cause an error.
        Raises:
          error.AutoservError: When a name would be clobbered by import.
        """
        def _import_names(module_name, names=()):
            """
            Import a module and assign named attributes into namespace.

            Args:
                module_name: The string module name.
                names: A limiting list of names to import from module_name.  If
                    empty (the default), all names are imported from the module
                    similar to a "from foo.bar import *" statement.
            Raises:
                error.AutoservError: When a name being imported would clobber
                    a name already in namespace.
            """
            module = __import__(module_name, {}, {}, names)

            # No names supplied?  Import * from the lowest level module.
            # (Ugh, why do I have to implement this part myself?)
            if not names:
                for submodule_name in module_name.split('.')[1:]:
                    module = getattr(module, submodule_name)
                if hasattr(module, '__all__'):
                    names = getattr(module, '__all__')
                else:
                    names = dir(module)

            # Install each name into namespace, checking to make sure it
            # doesn't override anything that already exists.
            for name in names:
                # Check for conflicts to help prevent future problems.
                if name in namespace and protect:
                    if namespace[name] is not getattr(module, name):
                        raise error.AutoservError('importing name '
                                '%s from %s %r would override %r' %
                                (name, module_name, getattr(module, name),
                                 namespace[name]))
                    else:
                        # Encourage cleanliness and the use of __all__ for a
                        # more concrete API with less surprises on '*' imports.
                        warnings.warn('%s (%r) being imported from %s for use '
                                      'in server control files is not the '
                                      'first occurrance of that import.' %
                                      (name, namespace[name], module_name))

                namespace[name] = getattr(module, name)


        # This is the equivalent of prepending a bunch of import statements to
        # the front of the control script.
        namespace.update(os=os, sys=sys)
        _import_names('autotest_lib.server',
                ('hosts', 'autotest', 'kvm', 'git', 'standalone_profiler',
                 'source_kernel', 'rpm_kernel', 'deb_kernel', 'git_kernel'))
        _import_names('autotest_lib.server.subcommand',
                      ('parallel', 'parallel_simple', 'subcommand'))
        _import_names('autotest_lib.server.utils',
                      ('run', 'get_tmp_dir', 'sh_escape', 'parse_machine'))
        _import_names('autotest_lib.client.common_lib.error')
        _import_names('autotest_lib.client.common_lib.barrier', ('barrier',))

        # Inject ourself as the job object into other classes within the API.
        # (Yuck, this injection is a gross thing be part of a public API. -gps)
        #
        # XXX Base & SiteAutotest do not appear to use .job.  Who does?
        namespace['autotest'].Autotest.job = self
        # server.hosts.base_classes.Host uses .job.
        namespace['hosts'].Host.job = self


    def _execute_code(self, code_file, namespace, protect=True):
        """
        Execute code using a copy of namespace as a server control script.

        Unless protect_namespace is explicitly set to False, the dict will not
        be modified.

        Args:
          code_file: The filename of the control file to execute.
          namespace: A dict containing names to make available during execution.
          protect: Boolean.  If True (the default) a copy of the namespace dict
              is used during execution to prevent the code from modifying its
              contents outside of this function.  If False the raw dict is
              passed in and modifications will be allowed.
        """
        if protect:
            namespace = namespace.copy()
        self._fill_server_control_namespace(namespace, protect=protect)
        # TODO: Simplify and get rid of the special cases for only 1 machine.
        if len(self.machines) > 1:
            machines_text = '\n'.join(self.machines) + '\n'
            # Only rewrite the file if it does not match our machine list.
            try:
                machines_f = open(MACHINES_FILENAME, 'r')
                existing_machines_text = machines_f.read()
                machines_f.close()
            except EnvironmentError:
                existing_machines_text = None
            if machines_text != existing_machines_text:
                utils.open_write_close(MACHINES_FILENAME, machines_text)
        execfile(code_file, namespace, namespace)


    def _record(self, status_code, subdir, operation, status='',
                 epoch_time=None, optional_fields=None):
        """
        Actual function for recording a single line into the status
        logs. Should never be called directly, only by job.record as
        this would bypass the console monitor logging.
        """

        msg = self._render_record(status_code, subdir, operation, status,
                                  epoch_time, optional_fields=optional_fields)

        status_file = self.get_status_log_path()
        sys.stdout.write(msg)
        open(status_file, "a").write(msg)
        if subdir:
            sub_status_file = self.get_status_log_path(subdir)
            open(sub_status_file, "a").write(msg)
        self.__parse_status(msg.splitlines())


    def __parse_status(self, new_lines):
        if not self.using_parser:
            return
        new_tests = self.parser.process_lines(new_lines)
        for test in new_tests:
            self.__insert_test(test)


    def __insert_test(self, test):
        """
        An internal method to insert a new test result into the
        database. This method will not raise an exception, even if an
        error occurs during the insert, to avoid failing a test
        simply because of unexpected database issues."""
        self.num_tests_run += 1
        if status_lib.is_worse_than_or_equal_to(test.status, 'FAIL'):
            self.num_tests_failed += 1
        try:
            self.results_db.insert_test(self.job_model, test)
        except Exception:
            msg = ("WARNING: An unexpected error occured while "
                   "inserting test results into the database. "
                   "Ignoring error.\n" + traceback.format_exc())
            print >> sys.stderr, msg


site_server_job = utils.import_site_class(
    __file__, "autotest_lib.server.site_server_job", "site_server_job",
    base_server_job)

class server_job(site_server_job, base_server_job):
    pass


class warning_manager(object):
    """Class for controlling warning logs. Manages the enabling and disabling
    of warnings."""
    def __init__(self):
        # a map of warning types to a list of disabled time intervals
        self.disabled_warnings = {}


    def is_valid(self, timestamp, warning_type):
        """Indicates if a warning (based on the time it occured and its type)
        is a valid warning. A warning is considered "invalid" if this type of
        warning was marked as "disabled" at the time the warning occured."""
        disabled_intervals = self.disabled_warnings.get(warning_type, [])
        for start, end in disabled_intervals:
            if timestamp >= start and (end is None or timestamp < end):
                return False
        return True


    def disable_warnings(self, warning_type, current_time_func=time.time):
        """As of now, disables all further warnings of this type."""
        intervals = self.disabled_warnings.setdefault(warning_type, [])
        if not intervals or intervals[-1][1] is not None:
            intervals.append((current_time_func(), None))


    def enable_warnings(self, warning_type, current_time_func=time.time):
        """As of now, enables all further warnings of this type."""
        intervals = self.disabled_warnings.get(warning_type, [])
        if intervals and intervals[-1][1] is None:
            intervals[-1] = (intervals[-1][0], current_time_func())