run_isolated.py

#!/usr/bin/env python
# Copyright (c) 2012 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Reads a .isolated, creates a tree of hardlinks and runs the test.

Keeps a local cache.
"""

import ctypes
import hashlib
import httplib
import inspect
import json
import logging
import logging.handlers
import math
import optparse
import os
import Queue
import random
import re
import shutil
import stat
import subprocess
import sys
import tempfile
import threading
import time
import traceback
import urllib
import urllib2
import urlparse
import zlib


# Types of action accepted by link_file().
HARDLINK, SYMLINK, COPY = range(1, 4)

RE_IS_SHA1 = re.compile(r'^[a-fA-F0-9]{40}$')

# The file size to be used when we don't know the correct file size,
# generally used for .isolated files.
UNKNOWN_FILE_SIZE = None

# The size of each chunk to read when downloading and unzipping files.
ZIPPED_FILE_CHUNK = 16 * 1024

# The name of the log file to use.
RUN_ISOLATED_LOG_FILE = 'run_isolated.log'

# The base directory containing this file.
BASE_DIR = os.path.dirname(os.path.abspath(__file__))

# The name of the log to use for the run_test_cases.py command
RUN_TEST_CASES_LOG = os.path.join(BASE_DIR, 'run_test_cases.log')

# The delay (in seconds) to wait between logging statements when retrieving
# the required files. This is intended to let the user (or buildbot) know that
# the program is still running.
DELAY_BETWEEN_UPDATES_IN_SECS = 30

# The name of the key to store the count of url attempts.
COUNT_KEY = 'UrlOpenAttempt'

# The maximum number of attempts to trying opening a url before aborting.
MAX_URL_OPEN_ATTEMPTS = 20


class ConfigError(ValueError):
  """Generic failure to load a .isolated file."""
  pass


class MappingError(OSError):
  """Failed to recreate the tree."""
  pass


def get_flavor():
  """Returns the system default flavor. Copied from gyp/pylib/gyp/common.py."""
  flavors = {
    'cygwin': 'win',
    'win32': 'win',
    'darwin': 'mac',
    'sunos5': 'solaris',
    'freebsd7': 'freebsd',
    'freebsd8': 'freebsd',
  }
  return flavors.get(sys.platform, 'linux')


class Unbuffered(object):
  """Disable buffering on a file object."""
  def __init__(self, stream):
    self.stream = stream

  def write(self, data):
    self.stream.write(data)
    if '\n' in data:
      self.stream.flush()

  def __getattr__(self, attr):
    return getattr(self.stream, attr)


def disable_buffering():
  """Makes this process and child processes stdout unbuffered."""
  if not os.environ.get('PYTHONUNBUFFERED'):
    # Since sys.stdout is a C++ object, it's impossible to do
    # sys.stdout.write = lambda...
    sys.stdout = Unbuffered(sys.stdout)
    os.environ['PYTHONUNBUFFERED'] = 'x'


def os_link(source, link_name):
  """Add support for os.link() on Windows."""
  if sys.platform == 'win32':
    if not ctypes.windll.kernel32.CreateHardLinkW(
        unicode(link_name), unicode(source), 0):
      raise OSError()
  else:
    os.link(source, link_name)


def readable_copy(outfile, infile):
  """Makes a copy of the file that is readable by everyone."""
  shutil.copy(infile, outfile)
  read_enabled_mode = (os.stat(outfile).st_mode | stat.S_IRUSR |
                       stat.S_IRGRP | stat.S_IROTH)
  os.chmod(outfile, read_enabled_mode)


def link_file(outfile, infile, action):
  """Links a file. The type of link depends on |action|."""
  logging.debug('Mapping %s to %s' % (infile, outfile))
  if action not in (HARDLINK, SYMLINK, COPY):
    raise ValueError('Unknown mapping action %s' % action)
  if not os.path.isfile(infile):
    raise MappingError('%s is missing' % infile)
  if os.path.isfile(outfile):
    raise MappingError(
        '%s already exist; insize:%d; outsize:%d' %
        (outfile, os.stat(infile).st_size, os.stat(outfile).st_size))

  if action == COPY:
    readable_copy(outfile, infile)
  elif action == SYMLINK and sys.platform != 'win32':
    # On windows, symlink are converted to hardlink and fails over to copy.
    os.symlink(infile, outfile)  # pylint: disable=E1101
  else:
    try:
      os_link(infile, outfile)
    except OSError:
      # Probably a different file system.
      logging.warn(
          'Failed to hardlink, failing back to copy %s to %s' % (
            infile, outfile))
      readable_copy(outfile, infile)


def _set_write_bit(path, read_only):
  """Sets or resets the executable bit on a file or directory."""
  mode = os.lstat(path).st_mode
  if read_only:
    mode = mode & 0500
  else:
    mode = mode | 0200
  if hasattr(os, 'lchmod'):
    os.lchmod(path, mode)  # pylint: disable=E1101
  else:
    if stat.S_ISLNK(mode):
      # Skip symlink without lchmod() support.
      logging.debug('Can\'t change +w bit on symlink %s' % path)
      return

    # TODO(maruel): Implement proper DACL modification on Windows.
    os.chmod(path, mode)


def make_writable(root, read_only):
  """Toggle the writable bit on a directory tree."""
  assert os.path.isabs(root), root
  for dirpath, dirnames, filenames in os.walk(root, topdown=True):
    for filename in filenames:
      _set_write_bit(os.path.join(dirpath, filename), read_only)

    for dirname in dirnames:
      _set_write_bit(os.path.join(dirpath, dirname), read_only)


def rmtree(root):
  """Wrapper around shutil.rmtree() to retry automatically on Windows."""
  make_writable(root, False)
  if sys.platform == 'win32':
    for i in range(3):
      try:
        shutil.rmtree(root)
        break
      except WindowsError:  # pylint: disable=E0602
        delay = (i+1)*2
        print >> sys.stderr, (
            'The test has subprocess outliving it. Sleep %d seconds.' % delay)
        time.sleep(delay)
  else:
    shutil.rmtree(root)


def is_same_filesystem(path1, path2):
  """Returns True if both paths are on the same filesystem.

  This is required to enable the use of hardlinks.
  """
  assert os.path.isabs(path1), path1
  assert os.path.isabs(path2), path2
  if sys.platform == 'win32':
    # If the drive letter mismatches, assume it's a separate partition.
    # TODO(maruel): It should look at the underlying drive, a drive letter could
    # be a mount point to a directory on another drive.
    assert re.match(r'^[a-zA-Z]\:\\.*', path1), path1
    assert re.match(r'^[a-zA-Z]\:\\.*', path2), path2
    if path1[0].lower() != path2[0].lower():
      return False
  return os.stat(path1).st_dev == os.stat(path2).st_dev


def get_free_space(path):
  """Returns the number of free bytes."""
  if sys.platform == 'win32':
    free_bytes = ctypes.c_ulonglong(0)
    ctypes.windll.kernel32.GetDiskFreeSpaceExW(
        ctypes.c_wchar_p(path), None, None, ctypes.pointer(free_bytes))
    return free_bytes.value
  # For OSes other than Windows.
  f = os.statvfs(path)  # pylint: disable=E1101
  return f.f_bfree * f.f_frsize


def make_temp_dir(prefix, root_dir):
  """Returns a temporary directory on the same file system as root_dir."""
  base_temp_dir = None
  if not is_same_filesystem(root_dir, tempfile.gettempdir()):
    base_temp_dir = os.path.dirname(root_dir)
  return tempfile.mkdtemp(prefix=prefix, dir=base_temp_dir)


def load_isolated(content):
  """Verifies the .isolated file is valid and loads this object with the json
  data.
  """
  try:
    data = json.loads(content)
  except ValueError:
    raise ConfigError('Failed to parse: %s...' % content[:100])

  if not isinstance(data, dict):
    raise ConfigError('Expected dict, got %r' % data)

  for key, value in data.iteritems():
    if key == 'command':
      if not isinstance(value, list):
        raise ConfigError('Expected list, got %r' % value)
      if not value:
        raise ConfigError('Expected non-empty command')
      for subvalue in value:
        if not isinstance(subvalue, basestring):
          raise ConfigError('Expected string, got %r' % subvalue)

    elif key == 'files':
      if not isinstance(value, dict):
        raise ConfigError('Expected dict, got %r' % value)
      for subkey, subvalue in value.iteritems():
        if not isinstance(subkey, basestring):
          raise ConfigError('Expected string, got %r' % subkey)
        if not isinstance(subvalue, dict):
          raise ConfigError('Expected dict, got %r' % subvalue)
        for subsubkey, subsubvalue in subvalue.iteritems():
          if subsubkey == 'l':
            if not isinstance(subsubvalue, basestring):
              raise ConfigError('Expected string, got %r' % subsubvalue)
          elif subsubkey == 'm':
            if not isinstance(subsubvalue, int):
              raise ConfigError('Expected int, got %r' % subsubvalue)
          elif subsubkey == 'h':
            if not RE_IS_SHA1.match(subsubvalue):
              raise ConfigError('Expected sha-1, got %r' % subsubvalue)
          elif subsubkey == 's':
            if not isinstance(subsubvalue, int):
              raise ConfigError('Expected int, got %r' % subsubvalue)
          else:
            raise ConfigError('Unknown subsubkey %s' % subsubkey)
        if bool('h' in subvalue) and bool('l' in subvalue):
          raise ConfigError(
              'Did not expect both \'h\' (sha-1) and \'l\' (link), got: %r' %
              subvalue)

    elif key == 'includes':
      if not isinstance(value, list):
        raise ConfigError('Expected list, got %r' % value)
      if not value:
        raise ConfigError('Expected non-empty includes list')
      for subvalue in value:
        if not RE_IS_SHA1.match(subvalue):
          raise ConfigError('Expected sha-1, got %r' % subvalue)

    elif key == 'read_only':
      if not isinstance(value, bool):
        raise ConfigError('Expected bool, got %r' % value)

    elif key == 'relative_cwd':
      if not isinstance(value, basestring):
        raise ConfigError('Expected string, got %r' % value)

    elif key == 'os':
      if value != get_flavor():
        raise ConfigError(
            'Expected \'os\' to be \'%s\' but got \'%s\'' %
            (get_flavor(), value))

    else:
      raise ConfigError('Unknown key %s' % key)

  return data


def fix_python_path(cmd):
  """Returns the fixed command line to call the right python executable."""
  out = cmd[:]
  if out[0] == 'python':
    out[0] = sys.executable
  elif out[0].endswith('.py'):
    out.insert(0, sys.executable)
  return out


def url_open(url, data=None, retry_404=False, content_type=None):
  """Attempts to open the given url multiple times.

  |data| can be either:
    -None for a GET request
    -str for pre-encoded data
    -list for data to be encoded
    -dict for data to be encoded (COUNT_KEY will be added in this case)

  If no wait_duration is given, the default wait time will exponentially
  increase between each retry.

  Returns a file-like object, where the response may be read from, or None
  if it was unable to connect.
  """
  method = 'GET' if data is None else 'POST'

  if isinstance(data, dict) and COUNT_KEY in data:
    logging.error('%s already existed in the data passed into UlrOpen. It '
                  'would be overwritten. Aborting UrlOpen', COUNT_KEY)
    return None

  assert not ((method != 'POST') and content_type), (
      'Can\'t use content_type on GET')

  def make_request(extra):
    """Returns a urllib2.Request instance for this specific retry."""
    if isinstance(data, str) or data is None:
      payload = data
    else:
      if isinstance(data, dict):
        payload = data.items()
      else:
        payload = data[:]
      payload.extend(extra.iteritems())
      payload = urllib.urlencode(payload)

    new_url = url
    if isinstance(data, str) or data is None:
      # In these cases, add the extra parameter to the query part of the url.
      url_parts = list(urlparse.urlparse(new_url))
      # Append the query parameter.
      if url_parts[4] and extra:
        url_parts[4] += '&'
      url_parts[4] += urllib.urlencode(extra)
      new_url = urlparse.urlunparse(url_parts)

    request = urllib2.Request(new_url, data=payload)
    if payload is not None:
      if content_type:
        request.add_header('Content-Type', content_type)
      request.add_header('Content-Length', len(payload))
    return request

  return url_open_request(make_request, retry_404)


def url_open_request(make_request, retry_404=False):
  """Internal version of url_open() for users that need special handling.
  """
  last_error = None
  for attempt in range(MAX_URL_OPEN_ATTEMPTS):
    extra = {COUNT_KEY: attempt} if attempt else {}
    request = make_request(extra)
    try:
      url_response = urllib2.urlopen(request)
      logging.debug('url_open(%s) succeeded', request.get_full_url())
      return url_response
    except urllib2.HTTPError as e:
      if e.code < 500 and not (retry_404 and e.code == 404):
        # This HTTPError means we reached the server and there was a problem
        # with the request, so don't retry.
        logging.error(
            'Able to connect to %s but an exception was thrown.\n%s\n%s',
            request.get_full_url(), e, e.read())
        return None

      # The HTTPError was due to a server error, so retry the attempt.
      logging.warning('Able to connect to %s on attempt %d.\nException: %s ',
                      request.get_full_url(), attempt, e)
      last_error = e

    except (urllib2.URLError, httplib.HTTPException) as e:
      logging.warning('Unable to open url %s on attempt %d.\nException: %s',
                      request.get_full_url(), attempt, e)
      last_error = e

    # Only sleep if we are going to try again.
    if attempt != MAX_URL_OPEN_ATTEMPTS - 1:
      duration = random.random() * 3 + math.pow(1.5, (attempt + 1))
      duration = min(10, max(0.1, duration))
      time.sleep(duration)

  logging.error('Unable to open given url, %s, after %d attempts.\n%s',
                request.get_full_url(), MAX_URL_OPEN_ATTEMPTS, last_error)
  return None


class ThreadPool(object):
  """Implements a multithreaded worker pool oriented for mapping jobs with
  thread-local result storage.

  Arguments:
  - initial_threads: Number of threads to start immediately. Can be 0 if it is
    uncertain that threads will be needed.
  - max_threads: Maximum number of threads that will be started when all the
                 threads are busy working. Often the number of CPU cores.
  - queue_size: Maximum number of tasks to buffer in the queue. 0 for unlimited
                queue. A non-zero value may make add_task() blocking.
  """
  QUEUE_CLASS = Queue.PriorityQueue

  def __init__(self, initial_threads, max_threads, queue_size):
    logging.debug(
        'ThreadPool(%d, %d, %d)', initial_threads, max_threads, queue_size)
    assert initial_threads <= max_threads
    # Update this check once 256 cores CPU are common.
    assert max_threads <= 256

    self.tasks = self.QUEUE_CLASS(queue_size)
    self._max_threads = max_threads

    # Mutables.
    self._num_of_added_tasks_lock = threading.Lock()
    self._num_of_added_tasks = 0
    self._outputs_exceptions_cond = threading.Condition()
    self._outputs = []
    self._exceptions = []
    # Number of threads in wait state.
    self._ready_lock = threading.Lock()
    self._ready = 0
    self._workers_lock = threading.Lock()
    self._workers = []
    for _ in range(initial_threads):
      self._add_worker()

  def _add_worker(self):
    """Adds one worker thread if there isn't too many. Thread-safe."""
    # Better to take the lock two times than hold it for too long.
    with self._workers_lock:
      if len(self._workers) >= self._max_threads:
        return False
    worker = threading.Thread(target=self._run)
    with self._workers_lock:
      if len(self._workers) >= self._max_threads:
        return False
      self._workers.append(worker)
    worker.daemon = True
    worker.start()

  def add_task(self, priority, func, *args, **kwargs):
    """Adds a task, a function to be executed by a worker.

    |priority| can adjust the priority of the task versus others. Lower priority
    takes precedence.

    |func| can either return a return value to be added to the output list or
    be a generator which can emit multiple values.

    Returns the index of the item added, e.g. the total number of enqueued items
    up to now.
    """
    assert isinstance(priority, int)
    assert callable(func)
    with self._ready_lock:
      start_new_worker = not self._ready
    with self._num_of_added_tasks_lock:
      self._num_of_added_tasks += 1
      index = self._num_of_added_tasks
    self.tasks.put((priority, index, func, args, kwargs))
    if start_new_worker:
      self._add_worker()
    return index

  def _run(self):
    """Worker thread loop. Runs until a None task is queued."""
    while True:
      try:
        with self._ready_lock:
          self._ready += 1
        task = self.tasks.get()
      finally:
        with self._ready_lock:
          self._ready -= 1
      try:
        if task is None:
          # We're done.
          return
        _priority, _index, func, args, kwargs = task
        if inspect.isgeneratorfunction(func):
          for out in func(*args, **kwargs):
            self._output_append(out)
        else:
          out = func(*args, **kwargs)
          self._output_append(out)
      except Exception as e:
        logging.warning('Caught exception: %s', e)
        exc_info = sys.exc_info()
        logging.info(''.join(traceback.format_tb(exc_info[2])))
        self._outputs_exceptions_cond.acquire()
        try:
          self._exceptions.append(exc_info)
          self._outputs_exceptions_cond.notifyAll()
        finally:
          self._outputs_exceptions_cond.release()
      finally:
        try:
          self.tasks.task_done()
        except Exception as e:
          # We need to catch and log this error here because this is the root
          # function for the thread, nothing higher will catch the error.
          logging.exception('Caught exception while marking task as done: %s',
                            e)

  def _output_append(self, out):
    if out is not None:
      self._outputs_exceptions_cond.acquire()
      try:
        self._outputs.append(out)
        self._outputs_exceptions_cond.notifyAll()
      finally:
        self._outputs_exceptions_cond.release()

  def join(self):
    """Extracts all the results from each threads unordered.

    Call repeatedly to extract all the exceptions if desired.

    Note: will wait for all work items to be done before returning an exception.
    To get an exception early, use get_one_result().
    """
    # TODO(maruel): Stop waiting as soon as an exception is caught.
    self.tasks.join()
    self._outputs_exceptions_cond.acquire()
    try:
      if self._exceptions:
        e = self._exceptions.pop(0)
        raise e[0], e[1], e[2]
      out = self._outputs
      self._outputs = []
    finally:
      self._outputs_exceptions_cond.release()
    return out

  def get_one_result(self):
    """Returns the next item that was generated or raises an exception if one
    occured.

    Warning: this function will hang if there is no work item left. Use join
    instead.
    """
    self._outputs_exceptions_cond.acquire()
    try:
      while True:
        if self._exceptions:
          e = self._exceptions.pop(0)
          raise e[0], e[1], e[2]
        if self._outputs:
          return self._outputs.pop(0)
        self._outputs_exceptions_cond.wait()
    finally:
      self._outputs_exceptions_cond.release()

  def close(self):
    """Closes all the threads."""
    for _ in range(len(self._workers)):
      # Enqueueing None causes the worker to stop.
      self.tasks.put(None)
    for t in self._workers:
      t.join()

  def __enter__(self):
    """Enables 'with' statement."""
    return self

  def __exit__(self, _exc_type, _exc_value, _traceback):
    """Enables 'with' statement."""
    self.close()


def valid_file(filepath, size):
  """Determines if the given files appears valid (currently it just checks
  the file's size)."""
  if size == UNKNOWN_FILE_SIZE:
    return True
  actual_size = os.stat(filepath).st_size
  if size != actual_size:
    logging.warning(
        'Found invalid item %s; %d != %d',
        os.path.basename(filepath), actual_size, size)
    return False
  return True


class Profiler(object):
  def __init__(self, name):
    self.name = name
    self.start_time = None

  def __enter__(self):
    self.start_time = time.time()
    return self

  def __exit__(self, _exc_type, _exec_value, _traceback):
    time_taken = time.time() - self.start_time
    logging.info('Profiling: Section %s took %3.3f seconds',
                 self.name, time_taken)


class Remote(object):
  """Priority based worker queue to fetch or upload files from a
  content-address server. Any function may be given as the fetcher/upload,
  as long as it takes two inputs (the item contents, and their relative
  destination).

  Supports local file system, CIFS or http remotes.

  When the priority of items is equals, works in strict FIFO mode.
  """
  # Initial and maximum number of worker threads.
  INITIAL_WORKERS = 2
  MAX_WORKERS = 16
  # Priorities.
  LOW, MED, HIGH = (1<<8, 2<<8, 3<<8)
  INTERNAL_PRIORITY_BITS = (1<<8) - 1
  RETRIES = 5

  def __init__(self, destination_root):
    # Function to fetch a remote object or upload to a remote location..
    self._do_item = self.get_file_handler(destination_root)
    # Contains tuple(priority, obj).
    self._done = Queue.PriorityQueue()
    self._pool = ThreadPool(self.INITIAL_WORKERS, self.MAX_WORKERS, 0)

  def join(self):
    """Blocks until the queue is empty."""
    return self._pool.join()

  def add_item(self, priority, obj, dest, size):
    """Retrieves an object from the remote data store.

    The smaller |priority| gets fetched first.

    Thread-safe.
    """
    assert (priority & self.INTERNAL_PRIORITY_BITS) == 0
    return self._add_item(priority, obj, dest, size)

  def _add_item(self, priority, obj, dest, size):
    assert isinstance(obj, basestring), obj
    assert isinstance(dest, basestring), dest
    assert size is None or isinstance(size, int), size
    return self._pool.add_task(
        priority, self._task_executer, priority, obj, dest, size)

  def get_one_result(self):
    return self._pool.get_one_result()

  def _task_executer(self, priority, obj, dest, size):
    """Wraps self._do_item to trap and retry on IOError exceptions."""
    try:
      self._do_item(obj, dest)
      if size and not valid_file(dest, size):
        download_size = os.stat(dest).st_size
        os.remove(dest)
        raise IOError('File incorrect size after download of %s. Got %s and '
                      'expected %s' % (obj, download_size, size))
      # TODO(maruel): Technically, we'd want to have an output queue to be a
      # PriorityQueue.
      return obj
    except IOError as e:
      logging.debug('Caught IOError: %s', e)
      # Retry a few times, lowering the priority.
      if (priority & self.INTERNAL_PRIORITY_BITS) < self.RETRIES:
        self._add_item(priority + 1, obj, dest, size)
        return
      raise

  def get_file_handler(self, file_or_url):  # pylint: disable=R0201
    """Returns a object to retrieve objects from a remote."""
    if re.match(r'^https?://.+$', file_or_url):
      def download_file(item, dest):
        # TODO(maruel): Reuse HTTP connections. The stdlib doesn't make this
        # easy.
        try:
          zipped_source = file_or_url + item
          logging.debug('download_file(%s)', zipped_source)

          # Because the app engine DB is only eventually consistent, retry
          # 404 errors because the file might just not be visible yet (even
          # though it has been uploaded).
          connection = url_open(zipped_source, retry_404=True)
          if not connection:
            raise IOError('Unable to open connection to %s' % zipped_source)
          decompressor = zlib.decompressobj()
          size = 0
          with open(dest, 'wb') as f:
            while True:
              chunk = connection.read(ZIPPED_FILE_CHUNK)
              if not chunk:
                break
              size += len(chunk)
              f.write(decompressor.decompress(chunk))
          # Ensure that all the data was properly decompressed.
          uncompressed_data = decompressor.flush()
          assert not uncompressed_data
        except IOError:
          logging.error('Encountered an exception with (%s, %s)' % (item, dest))
          raise
        except httplib.HTTPException as e:
          raise IOError('Encountered an HTTPException.\n%s' % e)
        except zlib.error as e:
          # Log the first bytes to see if it's uncompressed data.
          logging.warning('%r', e[:512])
          raise IOError(
              'Problem unzipping data for item %s. Got %d bytes.\n%s' %
              (item, size, e))

      return download_file

    def copy_file(item, dest):
      source = os.path.join(file_or_url, item)
      if source == dest:
        logging.info('Source and destination are the same, no action required')
        return
      logging.debug('copy_file(%s, %s)', source, dest)
      shutil.copy(source, dest)
    return copy_file


class CachePolicies(object):
  def __init__(self, max_cache_size, min_free_space, max_items):
    """
    Arguments:
    - max_cache_size: Trim if the cache gets larger than this value. If 0, the
                      cache is effectively a leak.
    - min_free_space: Trim if disk free space becomes lower than this value. If
                      0, it unconditionally fill the disk.
    - max_items: Maximum number of items to keep in the cache. If 0, do not
                 enforce a limit.
    """
    self.max_cache_size = max_cache_size
    self.min_free_space = min_free_space
    self.max_items = max_items


class NoCache(object):
  """This class is intended to be usable everywhere the Cache class is.
  Instead of downloading to a cache, all files are downloaded to the target
  directory and then moved to where they are needed.
  """

  def __init__(self, target_directory, remote):
    self.target_directory = target_directory
    self.remote = remote

  def retrieve(self, priority, item, size):
    """Get the request file."""
    self.remote.add_item(priority, item, self.path(item), size)
    self.remote.get_one_result()

  def wait_for(self, items):
    """Download the first item of the given list if it is missing."""
    item = items.iterkeys().next()

    if not os.path.exists(self.path(item)):
      self.remote.add_item(Remote.MED, item, self.path(item), UNKNOWN_FILE_SIZE)
      downloaded = self.remote.get_one_result()
      assert downloaded == item

    return item

  def path(self, item):
    return os.path.join(self.target_directory, item)


class Cache(object):
  """Stateful LRU cache.

  Saves its state as json file.
  """
  STATE_FILE = 'state.json'

  def __init__(self, cache_dir, remote, policies):
    """
    Arguments:
    - cache_dir: Directory where to place the cache.
    - remote: Remote where to fetch items from.
    - policies: cache retention policies.
    """
    self.cache_dir = cache_dir
    self.remote = remote
    self.policies = policies
    self.state_file = os.path.join(cache_dir, self.STATE_FILE)
    # The tuple(file, size) are kept as an array in a LRU style. E.g.
    # self.state[0] is the oldest item.
    self.state = []
    self._state_need_to_be_saved = False
    # A lookup map to speed up searching.
    self._lookup = {}
    self._lookup_is_stale = True

    # Items currently being fetched. Keep it local to reduce lock contention.
    self._pending_queue = set()

    # Profiling values.
    self._added = []
    self._removed = []
    self._free_disk = 0

    with Profiler('Setup'):
      if not os.path.isdir(self.cache_dir):
        os.makedirs(self.cache_dir)
      if os.path.isfile(self.state_file):
        try:
          self.state = json.load(open(self.state_file, 'r'))
        except (IOError, ValueError), e:
          # Too bad. The file will be overwritten and the cache cleared.
          logging.error(
              'Broken state file %s, ignoring.\n%s' % (self.STATE_FILE, e))
          self._state_need_to_be_saved = True
        if (not isinstance(self.state, list) or
            not all(
              isinstance(i, (list, tuple)) and len(i) == 2
              for i in self.state)):
          # Discard.
          self._state_need_to_be_saved = True
          self.state = []

      # Ensure that all files listed in the state still exist and add new ones.
      previous = set(filename for filename, _ in self.state)
      if len(previous) != len(self.state):
        logging.warn('Cache state is corrupted, found duplicate files')
        self._state_need_to_be_saved = True
        self.state = []

      added = 0
      for filename in os.listdir(self.cache_dir):
        if filename == self.STATE_FILE:
          continue
        if filename in previous:
          previous.remove(filename)
          continue
        # An untracked file.
        if not RE_IS_SHA1.match(filename):
          logging.warn('Removing unknown file %s from cache', filename)
          os.remove(self.path(filename))
          continue
        # Insert as the oldest file. It will be deleted eventually if not
        # accessed.
        self._add(filename, False)
        logging.warn('Add unknown file %s to cache', filename)
        added += 1

      if added:
        logging.warn('Added back %d unknown files', added)
      if previous:
        logging.warn('Removed %d lost files', len(previous))
        # Set explicitly in case self._add() wasn't called.
        self._state_need_to_be_saved = True
        # Filter out entries that were not found while keeping the previous
        # order.
        self.state = [
          (filename, size) for filename, size in self.state
          if filename not in previous
        ]
      self.trim()

  def __enter__(self):
    return self

  def __exit__(self, _exc_type, _exec_value, _traceback):
    with Profiler('CleanupTrimming'):
      self.trim()

    logging.info(
        '%5d (%8dkb) added', len(self._added), sum(self._added) / 1024)
    logging.info(
        '%5d (%8dkb) current',
        len(self.state),
        sum(i[1] for i in self.state) / 1024)
    logging.info(
        '%5d (%8dkb) removed', len(self._removed), sum(self._removed) / 1024)
    logging.info('       %8dkb free', self._free_disk / 1024)

  def remove_file_at_index(self, index):
    """Removes the file at the given index."""
    try:
      self._state_need_to_be_saved = True
      filename, size = self.state.pop(index)
      # If the lookup was already stale, its possible the filename was not
      # present yet.
      self._lookup_is_stale = True
      self._lookup.pop(filename, None)
      self._removed.append(size)
      os.remove(self.path(filename))
    except OSError as e:
      logging.error('Error attempting to delete a file\n%s' % e)

  def remove_lru_file(self):
    """Removes the last recently used file."""
    self.remove_file_at_index(0)

  def trim(self):
    """Trims anything we don't know, make sure enough free space exists."""
    # Ensure maximum cache size.
    if self.policies.max_cache_size and self.state:
      while sum(i[1] for i in self.state) > self.policies.max_cache_size:
        self.remove_lru_file()

    # Ensure maximum number of items in the cache.
    if self.policies.max_items and self.state:
      while len(self.state) > self.policies.max_items:
        self.remove_lru_file()

    # Ensure enough free space.
    self._free_disk = get_free_space(self.cache_dir)
    while (
        self.policies.min_free_space and
        self.state and
        self._free_disk < self.policies.min_free_space):
      self.remove_lru_file()
      self._free_disk = get_free_space(self.cache_dir)

    self.save()

  def retrieve(self, priority, item, size):
    """Retrieves a file from the remote, if not already cached, and adds it to
    the cache.

    If the file is in the cache, verifiy that the file is valid (i.e. it is
    the correct size), retrieving it again if it isn't.
    """
    assert not '/' in item
    path = self.path(item)
    self._update_lookup()
    index = self._lookup.get(item)

    if index is not None:
      if not valid_file(self.path(item), size):
        self.remove_file_at_index(index)
        index = None
      else:
        assert index < len(self.state)
        # Was already in cache. Update it's LRU value by putting it at the end.
        self._state_need_to_be_saved = True
        self._lookup_is_stale = True
        self.state.append(self.state.pop(index))

    if index is None:
      if item in self._pending_queue:
        # Already pending. The same object could be referenced multiple times.
        return
      self.remote.add_item(priority, item, path, size)
      self._pending_queue.add(item)

  def add(self, filepath, obj):
    """Forcibly adds a file to the cache."""
    self._update_lookup()
    if not obj in self._lookup:
      link_file(self.path(obj), filepath, HARDLINK)
      self._add(obj, True)

  def path(self, item):
    """Returns the path to one item."""
    return os.path.join(self.cache_dir, item)

  def save(self):
    """Saves the LRU ordering."""
    if self._state_need_to_be_saved:
      json.dump(self.state, open(self.state_file, 'wb'), separators=(',',':'))
      self._state_need_to_be_saved = False

  def wait_for(self, items):
    """Starts a loop that waits for at least one of |items| to be retrieved.

    Returns the first item retrieved.
    """
    # Flush items already present.
    self._update_lookup()
    for item in items:
      if item in self._lookup:
        return item

    assert all(i in self._pending_queue for i in items), (
        items, self._pending_queue)
    # Note that:
    #   len(self._pending_queue) ==
    #   ( len(self.remote._workers) - self.remote._ready +
    #     len(self._remote._queue) + len(self._remote.done))
    # There is no lock-free way to verify that.
    while self._pending_queue:
      item = self.remote.get_one_result()
      self._pending_queue.remove(item)
      self._add(item, True)
      if item in items:
        return item

  def _add(self, item, at_end):
    """Adds an item in the internal state.

    If |at_end| is False, self._lookup becomes inconsistent and
    self._update_lookup() must be called.
    """
    size = os.stat(self.path(item)).st_size
    self._added.append(size)
    self._state_need_to_be_saved = True
    if at_end:
      self.state.append((item, size))
      self._lookup[item] = len(self.state) - 1
    else:
      self._lookup_is_stale = True
      self.state.insert(0, (item, size))

  def _update_lookup(self):
    if self._lookup_is_stale:
      self._lookup = dict(
          (filename, index) for index, (filename, _) in enumerate(self.state))
      self._lookup_is_stale = False


class IsolatedFile(object):
  """Represents a single parsed .isolated file."""
  def __init__(self, obj_hash):
    """|obj_hash| is really the sha-1 of the file."""
    logging.debug('IsolatedFile(%s)' % obj_hash)
    self.obj_hash = obj_hash
    # Set once all the left-side of the tree is parsed. 'Tree' here means the
    # .isolate and all the .isolated files recursively included by it with
    # 'includes' key. The order of each sha-1 in 'includes', each representing a
    # .isolated file in the hash table, is important, as the later ones are not
    # processed until the firsts are retrieved and read.
    self.can_fetch = False

    # Raw data.
    self.data = {}
    # A IsolatedFile instance, one per object in self.includes.
    self.children = []

    # Set once the .isolated file is loaded.
    self._is_parsed = False
    # Set once the files are fetched.
    self.files_fetched = False

  def load(self, content):
    """Verifies the .isolated file is valid and loads this object with the json
    data.
    """
    logging.debug('IsolatedFile.load(%s)' % self.obj_hash)
    assert not self._is_parsed
    self.data = load_isolated(content)
    self.children = [IsolatedFile(i) for i in self.data.get('includes', [])]
    self._is_parsed = True

  def fetch_files(self, cache, files):
    """Adds files in this .isolated file not present in |files| dictionary.

    Preemptively request files.

    Note that |files| is modified by this function.
    """
    assert self.can_fetch
    if not self._is_parsed or self.files_fetched:
      return
    logging.debug('fetch_files(%s)' % self.obj_hash)
    for filepath, properties in self.data.get('files', {}).iteritems():
      # Root isolated has priority on the files being mapped. In particular,
      # overriden files must not be fetched.
      if filepath not in files:
        files[filepath] = properties
        if 'h' in properties:
          # Preemptively request files.
          logging.debug('fetching %s' % filepath)
          cache.retrieve(Remote.MED, properties['h'], properties['s'])
    self.files_fetched = True


class Settings(object):
  """Results of a completely parsed .isolated file."""
  def __init__(self):
    self.command = []
    self.files = {}
    self.read_only = None
    self.relative_cwd = None
    # The main .isolated file, a IsolatedFile instance.
    self.root = None

  def load(self, cache, root_isolated_hash):
    """Loads the .isolated and all the included .isolated asynchronously.

    It enables support for "included" .isolated files. They are processed in
    strict order but fetched asynchronously from the cache. This is important so
    that a file in an included .isolated file that is overridden by an embedding
    .isolated file is not fetched neededlessly. The includes are fetched in one
    pass and the files are fetched as soon as all the ones on the left-side
    of the tree were fetched.

    The prioritization is very important here for nested .isolated files.
    'includes' have the highest priority and the algorithm is optimized for both
    deep and wide trees. A deep one is a long link of .isolated files referenced
    one at a time by one item in 'includes'. A wide one has a large number of
    'includes' in a single .isolated file. 'left' is defined as an included
    .isolated file earlier in the 'includes' list. So the order of the elements
    in 'includes' is important.
    """
    self.root = IsolatedFile(root_isolated_hash)
    cache.retrieve(Remote.HIGH, root_isolated_hash, UNKNOWN_FILE_SIZE)
    pending = {root_isolated_hash: self.root}
    # Keeps the list of retrieved items to refuse recursive includes.
    retrieved = [root_isolated_hash]

    def update_self(node):
      node.fetch_files(cache, self.files)
      # Grabs properties.
      if not self.command and node.data.get('command'):
        self.command = node.data['command']
      if self.read_only is None and node.data.get('read_only') is not None:
        self.read_only = node.data['read_only']
      if (self.relative_cwd is None and
          node.data.get('relative_cwd') is not None):
        self.relative_cwd = node.data['relative_cwd']

    def traverse_tree(node):
      if node.can_fetch:
        if not node.files_fetched:
          update_self(node)
        will_break = False
        for i in node.children:
          if not i.can_fetch:
            if will_break:
              break
            # Automatically mark the first one as fetcheable.
            i.can_fetch = True
            will_break = True
          traverse_tree(i)

    while pending:
      item_hash = cache.wait_for(pending)
      item = pending.pop(item_hash)
      item.load(open(cache.path(item_hash), 'r').read())
      if item_hash == root_isolated_hash:
        # It's the root item.
        item.can_fetch = True

      for new_child in item.children:
        h = new_child.obj_hash
        if h in retrieved:
          raise ConfigError('IsolatedFile %s is retrieved recursively' % h)
        pending[h] = new_child
        cache.retrieve(Remote.HIGH, h, UNKNOWN_FILE_SIZE)

      # Traverse the whole tree to see if files can now be fetched.
      traverse_tree(self.root)
    def check(n):
      return all(check(x) for x in n.children) and n.files_fetched
    assert check(self.root)
    self.relative_cwd = self.relative_cwd or ''
    self.read_only = self.read_only or False


def create_directories(base_directory, files):
  """Creates the directory structure needed by the given list of files."""
  logging.debug('create_directories(%s, %d)', base_directory, len(files))
  # Creates the tree of directories to create.
  directories = set(os.path.dirname(f) for f in files)
  for item in list(directories):
    while item:
      directories.add(item)
      item = os.path.dirname(item)
  for d in sorted(directories):
    if d:
      os.mkdir(os.path.join(base_directory, d))


def create_links(base_directory, files):
  """Creates any links needed by the given set of files."""
  for filepath, properties in files:
    if 'link' not in properties:
      continue
    outfile = os.path.join(base_directory, filepath)
    # symlink doesn't exist on Windows. So the 'link' property should
    # never be specified for windows .isolated file.
    os.symlink(properties['l'], outfile)  # pylint: disable=E1101
    if 'm' in properties:
      lchmod = getattr(os, 'lchmod', None)
      if lchmod:
        lchmod(outfile, properties['m'])


def setup_commands(base_directory, cwd, cmd):
  """Correctly adjusts and then returns the required working directory
  and command needed to run the test.
  """
  assert not os.path.isabs(cwd), 'The cwd must be a relative path, got %s' % cwd
  cwd = os.path.join(base_directory, cwd)
  if not os.path.isdir(cwd):
    os.makedirs(cwd)

  # Ensure paths are correctly separated on windows.
  cmd[0] = cmd[0].replace('/', os.path.sep)
  cmd = fix_python_path(cmd)

  return cwd, cmd


def generate_remaining_files(files):
  """Generates a dictionary of all the remaining files to be downloaded."""
  remaining = {}
  for filepath, props in files:
    if 'h' in props:
      remaining.setdefault(props['h'], []).append((filepath, props))

  return remaining


def download_test_data(isolated_hash, target_directory, remote):
  """Downloads the dependencies to the given directory."""
  if not os.path.exists(target_directory):
    os.makedirs(target_directory)

  settings = Settings()
  no_cache = NoCache(target_directory, Remote(remote))

  # Download all the isolated files.
  with Profiler('GetIsolateds') as _prof:
    settings.load(no_cache, isolated_hash)

  if not settings.command:
    print >> sys.stderr, 'No command to run'
    return 1

  with Profiler('GetRest') as _prof:
    create_directories(target_directory, settings.files)
    create_links(target_directory, settings.files.iteritems())

    cwd, cmd = setup_commands(target_directory, settings.relative_cwd,
                              settings.command[:])

    remaining = generate_remaining_files(settings.files.iteritems())

    # Now block on the remaining files to be downloaded and mapped.
    logging.info('Retrieving remaining files')
    last_update = time.time()
    while remaining:
      obj = no_cache.wait_for(remaining)
      files = remaining.pop(obj)

      for i, (filepath, properties) in enumerate(files):
        outfile = os.path.join(target_directory, filepath)
        logging.info(no_cache.path(obj))

        if i + 1 == len(files):
          os.rename(no_cache.path(obj), outfile)
        else:
          shutil.copyfile(no_cache.path(obj), outfile)

        if 'm' in properties:
          # It's not set on Windows.
          os.chmod(outfile, properties['m'])

      if time.time() - last_update > DELAY_BETWEEN_UPDATES_IN_SECS:
        logging.info('%d files remaining...' % len(remaining))
        last_update = time.time()

  print('.isolated files successfully downloaded and setup in %s' %
        target_directory)
  print('To run this test please run the command %s from the directory %s' %
        (cmd, cwd))

  return 0


def run_tha_test(isolated_hash, cache_dir, remote, policies):
  """Downloads the dependencies in the cache, hardlinks them into a temporary
  directory and runs the executable.
  """
  settings = Settings()
  with Cache(cache_dir, Remote(remote), policies) as cache:
    outdir = make_temp_dir('run_tha_test', cache_dir)
    try:
      # Initiate all the files download.
      with Profiler('GetIsolateds') as _prof:
        # Optionally support local files.
        if not RE_IS_SHA1.match(isolated_hash):
          # Adds it in the cache. While not strictly necessary, this simplifies
          # the rest.
          h = hashlib.sha1(open(isolated_hash, 'rb').read()).hexdigest()
          cache.add(isolated_hash, h)
          isolated_hash = h
        settings.load(cache, isolated_hash)

      if not settings.command:
        print >> sys.stderr, 'No command to run'
        return 1

      with Profiler('GetRest') as _prof:
        create_directories(outdir, settings.files)
        create_links(outdir, settings.files.iteritems())
        remaining = generate_remaining_files(settings.files.iteritems())

        # Do bookkeeping while files are being downloaded in the background.
        cwd, cmd = setup_commands(outdir, settings.relative_cwd,
                                  settings.command[:])

        # Now block on the remaining files to be downloaded and mapped.
        logging.info('Retrieving remaining files')
        last_update = time.time()
        while remaining:
          obj = cache.wait_for(remaining)
          for filepath, properties in remaining.pop(obj):
            outfile = os.path.join(outdir, filepath)
            link_file(outfile, cache.path(obj), HARDLINK)
            if 'm' in properties:
              # It's not set on Windows.
              os.chmod(outfile, properties['m'])

          if time.time() - last_update > DELAY_BETWEEN_UPDATES_IN_SECS:
            logging.info('%d files remaining...' % len(remaining))
            last_update = time.time()

      if settings.read_only:
        make_writable(outdir, True)
      logging.info('Running %s, cwd=%s' % (cmd, cwd))

      # TODO(csharp): This should be specified somewhere else.
      # Add a rotating log file if one doesn't already exist.
      env = os.environ.copy()
      env.setdefault('RUN_TEST_CASES_LOG_FILE', RUN_TEST_CASES_LOG)
      try:
        with Profiler('RunTest') as _prof:
          return subprocess.call(cmd, cwd=cwd, env=env)
      except OSError:
        print >> sys.stderr, 'Failed to run %s; cwd=%s' % (cmd, cwd)
        raise
    finally:
      rmtree(outdir)


def main():
  disable_buffering()
  parser = optparse.OptionParser(
      usage='%prog <options>', description=sys.modules[__name__].__doc__)
  parser.add_option(
      '-v', '--verbose', action='count', default=0, help='Use multiple times')
  parser.add_option('--no-run', action='store_true', help='Skip the run part')

  group = optparse.OptionGroup(parser, 'Download')
  group.add_option(
      '--download', metavar='DEST',
      help='Downloads files to DEST and returns without running, instead of '
           'downloading and then running from a temporary directory.')
  parser.add_option_group(group)

  group = optparse.OptionGroup(parser, 'Data source')
  group.add_option(
      '-s', '--isolated',
      metavar='FILE',
      help='File/url describing what to map or run')
  # TODO(maruel): Remove once not used anymore.
  group.add_option(
      '-m', '--manifest', dest='isolated', help=optparse.SUPPRESS_HELP)
  group.add_option(
      '-H', '--hash',
      help='Hash of the .isolated to grab from the hash table')
  parser.add_option_group(group)

  group.add_option(
      '-r', '--remote', metavar='URL',
      default=
          'https://isolateserver.appspot.com/content/retrieve/default-gzip/',
      help='Remote where to get the items. Defaults to %default')
  group = optparse.OptionGroup(parser, 'Cache management')
  group.add_option(
      '--cache',
      default='cache',
      metavar='DIR',
      help='Cache directory, default=%default')
  group.add_option(
      '--max-cache-size',
      type='int',
      metavar='NNN',
      default=20*1024*1024*1024,
      help='Trim if the cache gets larger than this value, default=%default')
  group.add_option(
      '--min-free-space',
      type='int',
      metavar='NNN',
      default=1*1024*1024*1024,
      help='Trim if disk free space becomes lower than this value, '
           'default=%default')
  group.add_option(
      '--max-items',
      type='int',
      metavar='NNN',
      default=100000,
      help='Trim if more than this number of items are in the cache '
           'default=%default')
  parser.add_option_group(group)

  options, args = parser.parse_args()
  level = [logging.ERROR, logging.INFO, logging.DEBUG][min(2, options.verbose)]

  logging_console = logging.StreamHandler()
  logging_console.setFormatter(logging.Formatter(
      '%(levelname)5s %(module)15s(%(lineno)3d): %(message)s'))
  logging_console.setLevel(level)
  logging.getLogger().addHandler(logging_console)

  logging_rotating_file = logging.handlers.RotatingFileHandler(
      RUN_ISOLATED_LOG_FILE,
      maxBytes=10 * 1024 * 1024, backupCount=5)
  logging_rotating_file.setLevel(logging.DEBUG)
  logging_rotating_file.setFormatter(logging.Formatter(
      '%(asctime)s %(levelname)-8s %(module)15s(%(lineno)3d): %(message)s'))
  logging.getLogger().addHandler(logging_rotating_file)

  logging.getLogger().setLevel(logging.DEBUG)

  if bool(options.isolated) == bool(options.hash):
    logging.debug('One and only one of --isolated or --hash is required.')
    parser.error('One and only one of --isolated or --hash is required.')
  if args:
    logging.debug('Unsupported args %s' % ' '.join(args))
    parser.error('Unsupported args %s' % ' '.join(args))

  options.cache = os.path.abspath(options.cache)
  policies = CachePolicies(
      options.max_cache_size, options.min_free_space, options.max_items)

  if options.download:
    return download_test_data(options.isolated or options.hash,
                              options.download, options.remote)
  else:
    try:
      return run_tha_test(
          options.isolated or options.hash,
          options.cache,
          options.remote,
          policies)
    except Exception, e:
      # Make sure any exception is logged.
      logging.exception(e)
      return 1


if __name__ == '__main__':
  sys.exit(main())