Synnefo » snf-ganeti

#

#

# Copyright (C) 2006, 2007 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Module dealing with command line parsing"""

import sys

import textwrap

import os.path

import copy

import time

import logging

from cStringIO import StringIO

from ganeti import utils

from ganeti import errors

from ganeti import constants

from ganeti import opcodes

from ganeti import luxi

from ganeti import ssconf

from ganeti import rpc

from optparse import (OptionParser, make_option, TitledHelpFormatter,

                      Option, OptionValueError)

__all__ = ["DEBUG_OPT", "NOHDR_OPT", "SEP_OPT", "GenericMain",

           "SubmitOpCode", "GetClient",

           "cli_option", "ikv_option", "keyval_option",

           "GenerateTable", "AskUser",

           "ARGS_NONE", "ARGS_FIXED", "ARGS_ATLEAST", "ARGS_ANY", "ARGS_ONE",

           "USEUNITS_OPT", "FIELDS_OPT", "FORCE_OPT", "SUBMIT_OPT",

           "ListTags", "AddTags", "RemoveTags", "TAG_SRC_OPT",

           "FormatError", "SplitNodeOption", "SubmitOrSend",

           "JobSubmittedException", "FormatTimestamp", "ParseTimespec",

           "ToStderr", "ToStdout", "UsesRPC",

           "GetOnlineNodes", "JobExecutor", "SYNC_OPT", "CONFIRM_OPT",

           ]

NO_PREFIX = "no_"

UN_PREFIX = "-"

def _ExtractTagsObject(opts, args):

  """Extract the tag type object.

  Note that this function will modify its args parameter.

  """

  if not hasattr(opts, "tag_type"):

    raise errors.ProgrammerError("tag_type not passed to _ExtractTagsObject")

  kind = opts.tag_type

  if kind == constants.TAG_CLUSTER:

    retval = kind, kind

  elif kind == constants.TAG_NODE or kind == constants.TAG_INSTANCE:

    if not args:

      raise errors.OpPrereqError("no arguments passed to the command")

    name = args.pop(0)

    retval = kind, name

  else:

    raise errors.ProgrammerError("Unhandled tag type '%s'" % kind)

  return retval

def _ExtendTags(opts, args):

  """Extend the args if a source file has been given.

  This function will extend the tags with the contents of the file

  passed in the 'tags_source' attribute of the opts parameter. A file

  named '-' will be replaced by stdin.

  """

  fname = opts.tags_source

  if fname is None:

    return

  if fname == "-":

    new_fh = sys.stdin

  else:

    new_fh = open(fname, "r")

  new_data = []

  try:

    # we don't use the nice 'new_data = [line.strip() for line in fh]'

    # because of python bug 1633941

    while True:

      line = new_fh.readline()

      if not line:

        break

      new_data.append(line.strip())

  finally:

    new_fh.close()

  args.extend(new_data)

def ListTags(opts, args):

  """List the tags on a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  op = opcodes.OpGetTags(kind=kind, name=name)

  result = SubmitOpCode(op)

  result = list(result)

  result.sort()

  for tag in result:

    ToStdout(tag)

def AddTags(opts, args):

  """Add tags on a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  _ExtendTags(opts, args)

  if not args:

    raise errors.OpPrereqError("No tags to be added")

  op = opcodes.OpAddTags(kind=kind, name=name, tags=args)

  SubmitOpCode(op)

def RemoveTags(opts, args):

  """Remove tags from a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  _ExtendTags(opts, args)

  if not args:

    raise errors.OpPrereqError("No tags to be removed")

  op = opcodes.OpDelTags(kind=kind, name=name, tags=args)

  SubmitOpCode(op)

DEBUG_OPT = make_option("-d", "--debug", default=False,

                        action="store_true",

                        help="Turn debugging on")

NOHDR_OPT = make_option("--no-headers", default=False,

                        action="store_true", dest="no_headers",

                        help="Don't display column headers")

SEP_OPT = make_option("--separator", default=None,

                      action="store", dest="separator",

                      help="Separator between output fields"

                      " (defaults to one space)")

USEUNITS_OPT = make_option("--units", default=None,

                           dest="units", choices=('h', 'm', 'g', 't'),

                           help="Specify units for output (one of hmgt)")

FIELDS_OPT = make_option("-o", "--output", dest="output", action="store",

                         type="string", help="Comma separated list of"

                         " output fields",

                         metavar="FIELDS")

FORCE_OPT = make_option("-f", "--force", dest="force", action="store_true",

                        default=False, help="Force the operation")

CONFIRM_OPT = make_option("--yes", dest="confirm", action="store_true",

                          default=False, help="Do not require confirmation")

TAG_SRC_OPT = make_option("--from", dest="tags_source",

                          default=None, help="File with tag names")

SUBMIT_OPT = make_option("--submit", dest="submit_only",

                         default=False, action="store_true",

                         help="Submit the job and return the job ID, but"

                         " don't wait for the job to finish")

SYNC_OPT = make_option("--sync", dest="do_locking",

                       default=False, action="store_true",

                       help="Grab locks while doing the queries"

                       " in order to ensure more consistent results")

_DRY_RUN_OPT = make_option("--dry-run", default=False,

                          action="store_true",

                          help="Do not execute the operation, just run the"

                          " check steps and verify it it could be executed")

def ARGS_FIXED(val):

  """Macro-like function denoting a fixed number of arguments"""

  return -val

def ARGS_ATLEAST(val):

  """Macro-like function denoting a minimum number of arguments"""

  return val

ARGS_NONE = None

ARGS_ONE = ARGS_FIXED(1)

ARGS_ANY = ARGS_ATLEAST(0)

def check_unit(option, opt, value):

  """OptParsers custom converter for units.

  """

  try:

    return utils.ParseUnit(value)

  except errors.UnitParseError, err:

    raise OptionValueError("option %s: %s" % (opt, err))

class CliOption(Option):

  """Custom option class for optparse.

  """

  TYPES = Option.TYPES + ("unit",)

  TYPE_CHECKER = copy.copy(Option.TYPE_CHECKER)

  TYPE_CHECKER["unit"] = check_unit

def _SplitKeyVal(opt, data):

  """Convert a KeyVal string into a dict.

  This function will convert a key=val[,...] string into a dict. Empty

  values will be converted specially: keys which have the prefix 'no_'

  will have the value=False and the prefix stripped, the others will

  have value=True.

  @type opt: string

  @param opt: a string holding the option name for which we process the

      data, used in building error messages

  @type data: string

  @param data: a string of the format key=val,key=val,...

  @rtype: dict

  @return: {key=val, key=val}

  @raises errors.ParameterError: if there are duplicate keys

  """

  kv_dict = {}

  if data:

    for elem in data.split(","):

      if "=" in elem:

        key, val = elem.split("=", 1)

      else:

        if elem.startswith(NO_PREFIX):

          key, val = elem[len(NO_PREFIX):], False

        elif elem.startswith(UN_PREFIX):

          key, val = elem[len(UN_PREFIX):], None

        else:

          key, val = elem, True

      if key in kv_dict:

        raise errors.ParameterError("Duplicate key '%s' in option %s" %

                                    (key, opt))

      kv_dict[key] = val

  return kv_dict

def check_ident_key_val(option, opt, value):

  """Custom parser for the IdentKeyVal option type.

  """

  if ":" not in value:

    ident, rest = value, ''

  else:

    ident, rest = value.split(":", 1)

  if ident.startswith(NO_PREFIX):

    if rest:

      msg = "Cannot pass options when removing parameter groups: %s" % value

      raise errors.ParameterError(msg)

    retval = (ident[len(NO_PREFIX):], False)

  elif ident.startswith(UN_PREFIX):

    if rest:

      msg = "Cannot pass options when removing parameter groups: %s" % value

      raise errors.ParameterError(msg)

    retval = (ident[len(UN_PREFIX):], None)

  else:

    kv_dict = _SplitKeyVal(opt, rest)

    retval = (ident, kv_dict)

  return retval

class IdentKeyValOption(Option):

  """Custom option class for ident:key=val,key=val options.

  This will store the parsed values as a tuple (ident, {key: val}). As

  such, multiple uses of this option via action=append is possible.

  """

  TYPES = Option.TYPES + ("identkeyval",)

  TYPE_CHECKER = copy.copy(Option.TYPE_CHECKER)

  TYPE_CHECKER["identkeyval"] = check_ident_key_val

def check_key_val(option, opt, value):

  """Custom parser for the KeyVal option type.

  """

  return _SplitKeyVal(opt, value)

class KeyValOption(Option):

  """Custom option class for key=val,key=val options.

  This will store the parsed values as a dict {key: val}.

  """

  TYPES = Option.TYPES + ("keyval",)

  TYPE_CHECKER = copy.copy(Option.TYPE_CHECKER)

  TYPE_CHECKER["keyval"] = check_key_val

# optparse.py sets make_option, so we do it for our own option class, too

cli_option = CliOption

ikv_option = IdentKeyValOption

keyval_option = KeyValOption

def _ParseArgs(argv, commands, aliases):

  """Parser for the command line arguments.

  This function parses the arguments and returns the function which

  must be executed together with its (modified) arguments.

  @param argv: the command line

  @param commands: dictionary with special contents, see the design

      doc for cmdline handling

  @param aliases: dictionary with command aliases {'alias': 'target, ...}

  """

  if len(argv) == 0:

    binary = "<command>"

  else:

    binary = argv[0].split("/")[-1]

  if len(argv) > 1 and argv[1] == "--version":

    ToStdout("%s (ganeti) %s", binary, constants.RELEASE_VERSION)

    # Quit right away. That way we don't have to care about this special

    # argument. optparse.py does it the same.

    sys.exit(0)

  if len(argv) < 2 or not (argv[1] in commands or

                           argv[1] in aliases):

    # let's do a nice thing

    sortedcmds = commands.keys()

    sortedcmds.sort()

    ToStdout("Usage: %s {command} [options...] [argument...]", binary)

    ToStdout("%s <command> --help to see details, or man %s", binary, binary)

    ToStdout("")

    # compute the max line length for cmd + usage

    mlen = max([len(" %s" % cmd) for cmd in commands])

    mlen = min(60, mlen) # should not get here...

    # and format a nice command list

    ToStdout("Commands:")

    for cmd in sortedcmds:

      cmdstr = " %s" % (cmd,)

      help_text = commands[cmd][4]

      help_lines = textwrap.wrap(help_text, 79 - 3 - mlen)

      ToStdout("%-*s - %s", mlen, cmdstr, help_lines.pop(0))

      for line in help_lines:

        ToStdout("%-*s   %s", mlen, "", line)

    ToStdout("")

    return None, None, None

  # get command, unalias it, and look it up in commands

  cmd = argv.pop(1)

  if cmd in aliases:

    if cmd in commands:

      raise errors.ProgrammerError("Alias '%s' overrides an existing"

                                   " command" % cmd)

    if aliases[cmd] not in commands:

      raise errors.ProgrammerError("Alias '%s' maps to non-existing"

                                   " command '%s'" % (cmd, aliases[cmd]))

    cmd = aliases[cmd]

  func, nargs, parser_opts, usage, description = commands[cmd]

  parser = OptionParser(option_list=parser_opts + [_DRY_RUN_OPT],

                        description=description,

                        formatter=TitledHelpFormatter(),

                        usage="%%prog %s %s" % (cmd, usage))

  parser.disable_interspersed_args()

  options, args = parser.parse_args()

  if nargs is None:

    if len(args) != 0:

      ToStderr("Error: Command %s expects no arguments", cmd)

      return None, None, None

  elif nargs < 0 and len(args) != -nargs:

    ToStderr("Error: Command %s expects %d argument(s)", cmd, -nargs)

    return None, None, None

  elif nargs >= 0 and len(args) < nargs:

    ToStderr("Error: Command %s expects at least %d argument(s)", cmd, nargs)

    return None, None, None

  return func, options, args

def SplitNodeOption(value):

  """Splits the value of a --node option.

  """

  if value and ':' in value:

    return value.split(':', 1)

  else:

    return (value, None)

def UsesRPC(fn):

  def wrapper(*args, **kwargs):

    rpc.Init()

    try:

      return fn(*args, **kwargs)

    finally:

      rpc.Shutdown()

  return wrapper

def AskUser(text, choices=None):

  """Ask the user a question.

  @param text: the question to ask

  @param choices: list with elements tuples (input_char, return_value,

      description); if not given, it will default to: [('y', True,

      'Perform the operation'), ('n', False, 'Do no do the operation')];

      note that the '?' char is reserved for help

  @return: one of the return values from the choices list; if input is

      not possible (i.e. not running with a tty, we return the last

      entry from the list

  """

  if choices is None:

    choices = [('y', True, 'Perform the operation'),

               ('n', False, 'Do not perform the operation')]

  if not choices or not isinstance(choices, list):

    raise errors.ProgrammerError("Invalid choices argument to AskUser")

  for entry in choices:

    if not isinstance(entry, tuple) or len(entry) < 3 or entry[0] == '?':

      raise errors.ProgrammerError("Invalid choices element to AskUser")

  answer = choices[-1][1]

  new_text = []

  for line in text.splitlines():

    new_text.append(textwrap.fill(line, 70, replace_whitespace=False))

  text = "\n".join(new_text)

  try:

    f = file("/dev/tty", "a+")

  except IOError:

    return answer

  try:

    chars = [entry[0] for entry in choices]

    chars[-1] = "[%s]" % chars[-1]

    chars.append('?')

    maps = dict([(entry[0], entry[1]) for entry in choices])

    while True:

      f.write(text)

      f.write('\n')

      f.write("/".join(chars))

      f.write(": ")

      line = f.readline(2).strip().lower()

      if line in maps:

        answer = maps[line]

        break

      elif line == '?':

        for entry in choices:

          f.write(" %s - %s\n" % (entry[0], entry[2]))

        f.write("\n")

        continue

  finally:

    f.close()

  return answer

class JobSubmittedException(Exception):

  """Job was submitted, client should exit.

  This exception has one argument, the ID of the job that was

  submitted. The handler should print this ID.

  This is not an error, just a structured way to exit from clients.

  """

def SendJob(ops, cl=None):

  """Function to submit an opcode without waiting for the results.

  @type ops: list

  @param ops: list of opcodes

  @type cl: luxi.Client

  @param cl: the luxi client to use for communicating with the master;

             if None, a new client will be created

  """

  if cl is None:

    cl = GetClient()

  job_id = cl.SubmitJob(ops)

  return job_id

def PollJob(job_id, cl=None, feedback_fn=None):

  """Function to poll for the result of a job.

  @type job_id: job identified

  @param job_id: the job to poll for results

  @type cl: luxi.Client

  @param cl: the luxi client to use for communicating with the master;

             if None, a new client will be created

  """

  if cl is None:

    cl = GetClient()

  prev_job_info = None

  prev_logmsg_serial = None

  while True:

    result = cl.WaitForJobChange(job_id, ["status"], prev_job_info,

                                 prev_logmsg_serial)

    if not result:

      # job not found, go away!

      raise errors.JobLost("Job with id %s lost" % job_id)

    # Split result, a tuple of (field values, log entries)

    (job_info, log_entries) = result

    (status, ) = job_info

    if log_entries:

      for log_entry in log_entries:

        (serial, timestamp, _, message) = log_entry

        if callable(feedback_fn):

          feedback_fn(log_entry[1:])

        else:

          encoded = utils.SafeEncode(message)

          ToStdout("%s %s", time.ctime(utils.MergeTime(timestamp)), encoded)

        prev_logmsg_serial = max(prev_logmsg_serial, serial)

    # TODO: Handle canceled and archived jobs

    elif status in (constants.JOB_STATUS_SUCCESS,

                    constants.JOB_STATUS_ERROR,

                    constants.JOB_STATUS_CANCELING,

                    constants.JOB_STATUS_CANCELED):

      break

    prev_job_info = job_info

  jobs = cl.QueryJobs([job_id], ["status", "opstatus", "opresult"])

  if not jobs:

    raise errors.JobLost("Job with id %s lost" % job_id)

  status, opstatus, result = jobs[0]

  if status == constants.JOB_STATUS_SUCCESS:

    return result

  elif status in (constants.JOB_STATUS_CANCELING,

                  constants.JOB_STATUS_CANCELED):

    raise errors.OpExecError("Job was canceled")

  else:

    has_ok = False

    for idx, (status, msg) in enumerate(zip(opstatus, result)):

      if status == constants.OP_STATUS_SUCCESS:

        has_ok = True

      elif status == constants.OP_STATUS_ERROR:

        if has_ok:

          raise errors.OpExecError("partial failure (opcode %d): %s" %

                                   (idx, msg))

        else:

          raise errors.OpExecError(str(msg))

    # default failure mode

    raise errors.OpExecError(result)

def SubmitOpCode(op, cl=None, feedback_fn=None):

  """Legacy function to submit an opcode.

  This is just a simple wrapper over the construction of the processor

  instance. It should be extended to better handle feedback and

  interaction functions.

  """

  if cl is None:

    cl = GetClient()

  job_id = SendJob([op], cl)

  op_results = PollJob(job_id, cl=cl, feedback_fn=feedback_fn)

  return op_results[0]

def SubmitOrSend(op, opts, cl=None, feedback_fn=None):

  """Wrapper around SubmitOpCode or SendJob.

  This function will decide, based on the 'opts' parameter, whether to

  submit and wait for the result of the opcode (and return it), or

  whether to just send the job and print its identifier. It is used in

  order to simplify the implementation of the '--submit' option.

  It will also add the dry-run parameter from the options passed, if true.

  """

  if opts and opts.dry_run:

    op.dry_run = opts.dry_run

  if opts and opts.submit_only:

    job_id = SendJob([op], cl=cl)

    raise JobSubmittedException(job_id)

  else:

    return SubmitOpCode(op, cl=cl, feedback_fn=feedback_fn)

def GetClient():

  # TODO: Cache object?

  try:

    client = luxi.Client()

  except luxi.NoMasterError:

    master, myself = ssconf.GetMasterAndMyself()

    if master != myself:

      raise errors.OpPrereqError("This is not the master node, please connect"

                                 " to node '%s' and rerun the command" %

                                 master)

    else:

      raise

  return client

def FormatError(err):

  """Return a formatted error message for a given error.

  This function takes an exception instance and returns a tuple

  consisting of two values: first, the recommended exit code, and

  second, a string describing the error message (not

  newline-terminated).

  """

  retcode = 1

  obuf = StringIO()

  msg = str(err)

  if isinstance(err, errors.ConfigurationError):

    txt = "Corrupt configuration file: %s" % msg

    logging.error(txt)

    obuf.write(txt + "\n")

    obuf.write("Aborting.")

    retcode = 2

  elif isinstance(err, errors.HooksAbort):

    obuf.write("Failure: hooks execution failed:\n")

    for node, script, out in err.args[0]:

      if out:

        obuf.write("  node: %s, script: %s, output: %s\n" %

                   (node, script, out))

      else:

        obuf.write("  node: %s, script: %s (no output)\n" %

                   (node, script))

  elif isinstance(err, errors.HooksFailure):

    obuf.write("Failure: hooks general failure: %s" % msg)

  elif isinstance(err, errors.ResolverError):

    this_host = utils.HostInfo.SysName()

    if err.args[0] == this_host:

      msg = "Failure: can't resolve my own hostname ('%s')"

    else:

      msg = "Failure: can't resolve hostname '%s'"

    obuf.write(msg % err.args[0])

  elif isinstance(err, errors.OpPrereqError):

    obuf.write("Failure: prerequisites not met for this"

               " operation:\n%s" % msg)

  elif isinstance(err, errors.OpExecError):

    obuf.write("Failure: command execution error:\n%s" % msg)

  elif isinstance(err, errors.TagError):

    obuf.write("Failure: invalid tag(s) given:\n%s" % msg)

  elif isinstance(err, errors.JobQueueDrainError):

    obuf.write("Failure: the job queue is marked for drain and doesn't"

               " accept new requests\n")

  elif isinstance(err, errors.JobQueueFull):

    obuf.write("Failure: the job queue is full and doesn't accept new"

               " job submissions until old jobs are archived\n")

  elif isinstance(err, errors.TypeEnforcementError):

    obuf.write("Parameter Error: %s" % msg)

  elif isinstance(err, errors.ParameterError):

    obuf.write("Failure: unknown/wrong parameter name '%s'" % msg)

  elif isinstance(err, errors.GenericError):

    obuf.write("Unhandled Ganeti error: %s" % msg)

  elif isinstance(err, luxi.NoMasterError):

    obuf.write("Cannot communicate with the master daemon.\nIs it running"

               " and listening for connections?")

  elif isinstance(err, luxi.TimeoutError):

    obuf.write("Timeout while talking to the master daemon. Error:\n"

               "%s" % msg)

  elif isinstance(err, luxi.ProtocolError):

    obuf.write("Unhandled protocol error while talking to the master daemon:\n"

               "%s" % msg)

  elif isinstance(err, JobSubmittedException):

    obuf.write("JobID: %s\n" % err.args[0])

    retcode = 0

  else:

    obuf.write("Unhandled exception: %s" % msg)

  return retcode, obuf.getvalue().rstrip('\n')

def GenericMain(commands, override=None, aliases=None):

  """Generic main function for all the gnt-* commands.

  Arguments:

    - commands: a dictionary with a special structure, see the design doc

                for command line handling.

    - override: if not None, we expect a dictionary with keys that will

                override command line options; this can be used to pass

                options from the scripts to generic functions

    - aliases: dictionary with command aliases {'alias': 'target, ...}

  """

  # save the program name and the entire command line for later logging

  if sys.argv:

    binary = os.path.basename(sys.argv[0]) or sys.argv[0]

    if len(sys.argv) >= 2:

      binary += " " + sys.argv[1]

      old_cmdline = " ".join(sys.argv[2:])

    else:

      old_cmdline = ""

  else:

    binary = "<unknown program>"

    old_cmdline = ""

  if aliases is None:

    aliases = {}

  try:

    func, options, args = _ParseArgs(sys.argv, commands, aliases)

  except errors.ParameterError, err:

    result, err_msg = FormatError(err)

    ToStderr(err_msg)

    return 1

  if func is None: # parse error

    return 1

  if override is not None:

    for key, val in override.iteritems():

      setattr(options, key, val)

  utils.SetupLogging(constants.LOG_COMMANDS, debug=options.debug,

                     stderr_logging=True, program=binary)

  if old_cmdline:

    logging.info("run with arguments '%s'", old_cmdline)

  else:

    logging.info("run with no arguments")

  try:

    result = func(options, args)

  except (errors.GenericError, luxi.ProtocolError,

          JobSubmittedException), err:

    result, err_msg = FormatError(err)

    logging.exception("Error during command processing")

    ToStderr(err_msg)

  return result

def GenerateTable(headers, fields, separator, data,

                  numfields=None, unitfields=None,

                  units=None):

  """Prints a table with headers and different fields.

  @type headers: dict

  @param headers: dictionary mapping field names to headers for

      the table

  @type fields: list

  @param fields: the field names corresponding to each row in

      the data field

  @param separator: the separator to be used; if this is None,

      the default 'smart' algorithm is used which computes optimal

      field width, otherwise just the separator is used between

      each field

  @type data: list

  @param data: a list of lists, each sublist being one row to be output

  @type numfields: list

  @param numfields: a list with the fields that hold numeric

      values and thus should be right-aligned

  @type unitfields: list

  @param unitfields: a list with the fields that hold numeric

      values that should be formatted with the units field

  @type units: string or None

  @param units: the units we should use for formatting, or None for

      automatic choice (human-readable for non-separator usage, otherwise

      megabytes); this is a one-letter string

  """

  if units is None:

    if separator:

      units = "m"

    else:

      units = "h"

  if numfields is None:

    numfields = []

  if unitfields is None:

    unitfields = []

  numfields = utils.FieldSet(*numfields)

  unitfields = utils.FieldSet(*unitfields)

  format_fields = []

  for field in fields:

    if headers and field not in headers:

      # TODO: handle better unknown fields (either revert to old

      # style of raising exception, or deal more intelligently with

      # variable fields)

      headers[field] = field

    if separator is not None:

      format_fields.append("%s")

    elif numfields.Matches(field):

      format_fields.append("%*s")

    else:

      format_fields.append("%-*s")

  if separator is None:

    mlens = [0 for name in fields]

    format = ' '.join(format_fields)

  else:

    format = separator.replace("%", "%%").join(format_fields)

  for row in data:

    if row is None:

      continue

    for idx, val in enumerate(row):

      if unitfields.Matches(fields[idx]):

        try:

          val = int(val)

        except ValueError:

          pass

        else:

          val = row[idx] = utils.FormatUnit(val, units)

      val = row[idx] = str(val)

      if separator is None:

        mlens[idx] = max(mlens[idx], len(val))

  result = []

  if headers:

    args = []

    for idx, name in enumerate(fields):

      hdr = headers[name]

      if separator is None:

        mlens[idx] = max(mlens[idx], len(hdr))

        args.append(mlens[idx])

      args.append(hdr)

    result.append(format % tuple(args))

  for line in data:

    args = []

    if line is None:

      line = ['-' for _ in fields]

    for idx in xrange(len(fields)):

      if separator is None:

        args.append(mlens[idx])

      args.append(line[idx])

    result.append(format % tuple(args))

  return result

def FormatTimestamp(ts):

  """Formats a given timestamp.

  @type ts: timestamp

  @param ts: a timeval-type timestamp, a tuple of seconds and microseconds

  @rtype: string

  @return: a string with the formatted timestamp

  """

  if not isinstance (ts, (tuple, list)) or len(ts) != 2:

    return '?'

  sec, usec = ts

  return time.strftime("%F %T", time.localtime(sec)) + ".%06d" % usec

def ParseTimespec(value):

  """Parse a time specification.

  The following suffixed will be recognized:

    - s: seconds

    - m: minutes

    - h: hours

    - d: day

    - w: weeks

  Without any suffix, the value will be taken to be in seconds.

  """

  value = str(value)

  if not value:

    raise errors.OpPrereqError("Empty time specification passed")

  suffix_map = {

    's': 1,

    'm': 60,

    'h': 3600,

    'd': 86400,

    'w': 604800,

    }

  if value[-1] not in suffix_map:

    try:

      value = int(value)

    except ValueError:

      raise errors.OpPrereqError("Invalid time specification '%s'" % value)

  else:

    multiplier = suffix_map[value[-1]]

    value = value[:-1]

    if not value: # no data left after stripping the suffix

      raise errors.OpPrereqError("Invalid time specification (only"

                                 " suffix passed)")

    try:

      value = int(value) * multiplier

    except ValueError:

      raise errors.OpPrereqError("Invalid time specification '%s'" % value)

  return value

def GetOnlineNodes(nodes, cl=None, nowarn=False):

  """Returns the names of online nodes.

  This function will also log a warning on stderr with the names of

  the online nodes.

  @param nodes: if not empty, use only this subset of nodes (minus the

      offline ones)

  @param cl: if not None, luxi client to use

  @type nowarn: boolean

  @param nowarn: by default, this function will output a note with the

      offline nodes that are skipped; if this parameter is True the

      note is not displayed

  """

  if cl is None:

    cl = GetClient()

  result = cl.QueryNodes(names=nodes, fields=["name", "offline"],

                         use_locking=False)

  offline = [row[0] for row in result if row[1]]

  if offline and not nowarn:

    ToStderr("Note: skipping offline node(s): %s" % ", ".join(offline))

  return [row[0] for row in result if not row[1]]

def _ToStream(stream, txt, *args):

  """Write a message to a stream, bypassing the logging system

  @type stream: file object

  @param stream: the file to which we should write

  @type txt: str

  @param txt: the message

  """

  if args:

    args = tuple(args)

    stream.write(txt % args)

  else:

    stream.write(txt)

  stream.write('\n')

  stream.flush()

def ToStdout(txt, *args):

  """Write a message to stdout only, bypassing the logging system

  This is just a wrapper over _ToStream.

  @type txt: str

  @param txt: the message

  """

  _ToStream(sys.stdout, txt, *args)

def ToStderr(txt, *args):

  """Write a message to stderr only, bypassing the logging system

  This is just a wrapper over _ToStream.

  @type txt: str

  @param txt: the message

  """

  _ToStream(sys.stderr, txt, *args)

class JobExecutor(object):

  """Class which manages the submission and execution of multiple jobs.