Exemple #1
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  def write_zipped_internal_cache(cls, pex, pex_info):
    prefix_length = len(pex_info.internal_cache) + 1
    existing_cached_distributions = []
    newly_cached_distributions = []
    zip_safe_distributions = []
    with open_zip(pex) as zf:
      # Distribution names are the first element after ".deps/" and before the next "/"
      distribution_names = set(filter(None, (filename[prefix_length:].split('/')[0]
          for filename in zf.namelist() if filename.startswith(pex_info.internal_cache))))
      # Create Distribution objects from these, and possibly write to disk if necessary.
      for distribution_name in distribution_names:
        internal_dist_path = '/'.join([pex_info.internal_cache, distribution_name])
        # First check if this is already cached
        dist_digest = pex_info.distributions.get(distribution_name) or CacheHelper.zip_hash(
            zf, internal_dist_path)
        cached_location = os.path.join(pex_info.install_cache, '%s.%s' % (
          distribution_name, dist_digest))
        if os.path.exists(cached_location):
          dist = DistributionHelper.distribution_from_path(cached_location)
          if dist is not None:
            existing_cached_distributions.append(dist)
            continue
        else:
          dist = DistributionHelper.distribution_from_path(os.path.join(pex, internal_dist_path))
          if dist is not None:
            if DistributionHelper.zipsafe(dist) and not pex_info.always_write_cache:
              zip_safe_distributions.append(dist)
              continue

        with TRACER.timed('Caching %s' % dist):
          newly_cached_distributions.append(
            CacheHelper.cache_distribution(zf, internal_dist_path, cached_location))

    return existing_cached_distributions, newly_cached_distributions, zip_safe_distributions
Exemple #2
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  def _add_dist_zip(self, path, dist_name):
    # We need to distinguish between wheels and other zips. Most of the time,
    # when we have a zip, it contains its contents in an importable form.
    # But wheels don't have to be importable, so we need to force them
    # into an importable shape. We can do that by installing it into its own
    # wheel dir.
    if dist_name.endswith("whl"):
      from pex.third_party.wheel.install import WheelFile
      tmp = safe_mkdtemp()
      whltmp = os.path.join(tmp, dist_name)
      os.mkdir(whltmp)
      wf = WheelFile(path)
      wf.install(overrides=self._get_installer_paths(whltmp), force=True)
      for root, _, files in os.walk(whltmp):
        pruned_dir = os.path.relpath(root, tmp)
        for f in files:
          fullpath = os.path.join(root, f)
          target = os.path.join(self._pex_info.internal_cache, pruned_dir, f)
          self._copy_or_link(fullpath, target)
      return CacheHelper.dir_hash(whltmp)

    with open_zip(path) as zf:
      for name in zf.namelist():
        if name.endswith('/'):
          continue
        target = os.path.join(self._pex_info.internal_cache, dist_name, name)
        self._chroot.write(zf.read(name), target)
      return CacheHelper.zip_hash(zf)
Exemple #3
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def test_hash_consistency():
  for reverse in (False, True):
    with temporary_content(CONTENT) as td:
      dir_hash = CacheHelper.dir_hash(td)
      with named_temporary_file() as tf:
        write_zipfile(td, tf.name, reverse=reverse)
        with contextlib.closing(zipfile.ZipFile(tf.name, 'r')) as zf:
          zip_hash = CacheHelper.zip_hash(zf)
          assert zip_hash == dir_hash
          assert zip_hash != sha1().hexdigest()  # make sure it's not an empty hash
Exemple #4
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 def _add_dist_dir(self, path, dist_name):
   for root, _, files in os.walk(path):
     for f in files:
       filename = os.path.join(root, f)
       relpath = os.path.relpath(filename, path)
       target = os.path.join(self._pex_info.internal_cache, dist_name, relpath)
       self._copy_or_link(filename, target)
   return CacheHelper.dir_hash(path)
Exemple #5
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def test_hash():
    empty_hash = sha1().hexdigest()

    with temporary_file() as fp:
        fp.flush()
        assert empty_hash == CacheHelper.hash(fp.name)

    with temporary_file() as fp:
        string = b'asdf' * 1024 * sha1().block_size + b'extra padding'
        fp.write(string)
        fp.flush()
        assert sha1(string).hexdigest() == CacheHelper.hash(fp.name)

    with temporary_file() as fp:
        empty_hash = sha1()
        fp.write(b'asdf')
        fp.flush()
        hash_output = CacheHelper.hash(fp.name, digest=empty_hash)
        assert hash_output == empty_hash.hexdigest()
Exemple #6
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def test_hash():
  empty_hash = sha1().hexdigest()

  with named_temporary_file() as fp:
    fp.flush()
    assert empty_hash == CacheHelper.hash(fp.name)

  with named_temporary_file() as fp:
    string = b'asdf' * 1024 * sha1().block_size + b'extra padding'
    fp.write(string)
    fp.flush()
    assert sha1(string).hexdigest() == CacheHelper.hash(fp.name)

  with named_temporary_file() as fp:
    empty_hash = sha1()
    fp.write(b'asdf')
    fp.flush()
    hash_output = CacheHelper.hash(fp.name, digest=empty_hash)
    assert hash_output == empty_hash.hexdigest()
Exemple #7
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def test_hash():
    # type: () -> None
    empty_hash_digest = sha1().hexdigest()

    with named_temporary_file() as fp:
        fp.flush()
        assert empty_hash_digest == CacheHelper.hash(fp.name)

    with named_temporary_file() as fp:
        string = b"asdf" * 1024 * sha1().block_size + b"extra padding"
        fp.write(string)
        fp.flush()
        assert sha1(string).hexdigest() == CacheHelper.hash(fp.name)

    with named_temporary_file() as fp:
        empty_hash = sha1()
        fp.write(b"asdf")
        fp.flush()
        hash_output = CacheHelper.hash(fp.name, digest=empty_hash)
        assert hash_output == empty_hash.hexdigest()
Exemple #8
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 def _write_zipped_internal_cache(cls, zf, pex_info):
     cached_distributions = []
     for distribution_name, dist_digest in pex_info.distributions.items():
         internal_dist_path = '/'.join(
             [pex_info.internal_cache, distribution_name])
         cached_location = os.path.join(pex_info.install_cache, dist_digest,
                                        distribution_name)
         dist = CacheHelper.cache_distribution(zf, internal_dist_path,
                                               cached_location)
         cached_distributions.append(dist)
     return cached_distributions
Exemple #9
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 def _add_dist_dir(self, path, dist_name):
     target_dir = os.path.join(self._pex_info.internal_cache, dist_name)
     if self._copy_mode == CopyMode.SYMLINK:
         self._copy_or_link(path, target_dir)
     else:
         for root, _, files in os.walk(path):
             for f in files:
                 filename = os.path.join(root, f)
                 relpath = os.path.relpath(filename, path)
                 target = os.path.join(target_dir, relpath)
                 self._copy_or_link(filename, target)
     return CacheHelper.dir_hash(path)
Exemple #10
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def isolated():
    """Returns a chroot for third_party isolated from the ``sys.path``.

  PEX will typically be installed in site-packages flat alongside many other distributions; as such,
  adding the location of the pex distribution to the ``sys.path`` will typically expose many other
  distributions. An isolated chroot can be used as a ``sys.path`` entry to effect only the exposure
  of pex.

  :return: An isolation result.
  :rtype: :class:`IsolationResult`
  """
    global _ISOLATED
    if _ISOLATED is None:
        from pex import vendor
        from pex.common import atomic_directory
        from pex.util import CacheHelper
        from pex.variables import ENV
        from pex.third_party.pkg_resources import resource_isdir, resource_listdir, resource_stream

        module = 'pex'

        def recursive_copy(srcdir, dstdir):
            os.mkdir(dstdir)
            for entry_name in resource_listdir(module, srcdir):
                # NB: Resource path components are always separated by /, on all systems.
                src_entry = '{}/{}'.format(
                    srcdir, entry_name) if srcdir else entry_name
                dst_entry = os.path.join(dstdir, entry_name)
                if resource_isdir(module, src_entry):
                    recursive_copy(src_entry, dst_entry)
                elif not entry_name.endswith('.pyc'):
                    with open(dst_entry, 'wb') as fp:
                        shutil.copyfileobj(resource_stream(module, src_entry),
                                           fp)

        pex_path = os.path.join(vendor.VendorSpec.ROOT, 'pex')
        with _tracer().timed('Hashing pex'):
            dir_hash = CacheHelper.dir_hash(pex_path)
        isolated_dir = os.path.join(ENV.PEX_ROOT, 'isolated', dir_hash)

        with _tracer().timed('Isolating pex'):
            with atomic_directory(isolated_dir) as chroot:
                if chroot:
                    with _tracer().timed(
                            'Extracting pex to {}'.format(isolated_dir)):
                        recursive_copy('', os.path.join(chroot, 'pex'))

        _ISOLATED = IsolationResult(pex_hash=dir_hash,
                                    chroot_path=isolated_dir)
    return _ISOLATED
Exemple #11
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def isolated():
    """Returns a chroot for third_party isolated from the ``sys.path``.

  PEX will typically be installed in site-packages flat alongside many other distributions; as such,
  adding the location of the pex distribution to the ``sys.path`` will typically expose many other
  distributions. An isolated chroot can be used as a ``sys.path`` entry to effect only the exposure
  of pex.

  :return: The path of the chroot.
  :rtype: str
  """
    global _ISOLATED
    if _ISOLATED is None:
        from pex import vendor
        from pex.common import atomic_directory, safe_copy
        from pex.util import CacheHelper
        from pex.variables import ENV

        pex_path = os.path.join(vendor.VendorSpec.ROOT, 'pex')
        with _tracer().timed('Isolating pex'):
            isolated_dir = os.path.join(ENV.PEX_ROOT, 'isolated',
                                        CacheHelper.dir_hash(pex_path))
            with atomic_directory(isolated_dir) as chroot:
                if chroot:
                    with _tracer().timed(
                            'Extracting pex to {}'.format(isolated_dir)):
                        pex_path = os.path.join(vendor.VendorSpec.ROOT, 'pex')
                        for root, dirs, files in os.walk(pex_path):
                            relroot = os.path.relpath(root, pex_path)
                            for d in dirs:
                                os.makedirs(
                                    os.path.join(chroot, 'pex', relroot, d))
                            for f in files:
                                if not f.endswith('.pyc'):
                                    safe_copy(
                                        os.path.join(root, f),
                                        os.path.join(chroot, 'pex', relroot,
                                                     f))

        _ISOLATED = isolated_dir
    return _ISOLATED
Exemple #12
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    def _prepare_code(self):
        self._pex_info.code_hash = CacheHelper.pex_code_hash(
            self._chroot.path())
        self._pex_info.pex_hash = hashlib.sha1(
            self._pex_info.dump().encode("utf-8")).hexdigest()
        self._chroot.write(self._pex_info.dump().encode("utf-8"),
                           PexInfo.PATH,
                           label="manifest")

        bootstrap = BOOTSTRAP_ENVIRONMENT.format(
            bootstrap_dir=BOOTSTRAP_DIR,
            pex_root=self._pex_info.raw_pex_root,
            pex_hash=self._pex_info.pex_hash,
            interpreter_constraints=self._pex_info.interpreter_constraints,
            pex_path=self._pex_info.pex_path,
            is_unzip=self._pex_info.unzip,
            is_venv=self._pex_info.venv,
        )
        self._chroot.write(to_bytes(self._preamble + "\n" + bootstrap),
                           "__main__.py",
                           label="main")
Exemple #13
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 def _prepare_code_hash(self):
   self._pex_info.code_hash = CacheHelper.pex_hash(self._chroot.path())
Exemple #14
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def isolated():
    """Returns a chroot for third_party isolated from the ``sys.path``.

    PEX will typically be installed in site-packages flat alongside many other distributions; as such,
    adding the location of the pex distribution to the ``sys.path`` will typically expose many other
    distributions. An isolated chroot can be used as a ``sys.path`` entry to effect only the exposure
    of pex.

    :return: An isolation result.
    :rtype: :class:`IsolationResult`
    """
    global _ISOLATED
    if _ISOLATED is None:
        from pex import vendor
        from pex.common import atomic_directory
        from pex.util import CacheHelper
        from pex.variables import ENV
        from pex.third_party.pkg_resources import resource_isdir, resource_listdir, resource_stream

        module = "pex"

        # TODO(John Sirois): Unify with `pex.util.DistributionHelper.access_zipped_assets`.
        def recursive_copy(srcdir, dstdir):
            os.mkdir(dstdir)
            for entry_name in resource_listdir(module, srcdir):
                if not entry_name:
                    # The `resource_listdir` function returns a '' entry name for the directory
                    # entry itself if it is either present on the filesystem or present as an
                    # explicit zip entry. Since we only care about files and subdirectories at this
                    # point, skip these entries.
                    continue
                # NB: Resource path components are always separated by /, on all systems.
                src_entry = "{}/{}".format(srcdir, entry_name) if srcdir else entry_name
                dst_entry = os.path.join(dstdir, entry_name)
                if resource_isdir(module, src_entry):
                    recursive_copy(src_entry, dst_entry)
                elif not entry_name.endswith(".pyc"):
                    with open(dst_entry, "wb") as fp:
                        with closing(resource_stream(module, src_entry)) as resource:
                            shutil.copyfileobj(resource, fp)

        pex_path = os.path.join(vendor.VendorSpec.ROOT, "pex")
        with _tracer().timed("Hashing pex"):
            if os.path.isdir(pex_path):
                dir_hash = CacheHelper.dir_hash(pex_path)
            else:
                pex_zip = os.path.abspath(sys.argv[0])
                assert zipfile.is_zipfile(pex_zip) and pex_zip == os.path.commonprefix(
                    (pex_zip, pex_path)
                ), (
                    "Expected the `pex` module to be available via an installed distribution or "
                    "else via a PEX zipfile present as argv0. Loaded the `pex` module from {} and "
                    "argv0 is {}.".format(pex_path, sys.argv[0])
                )
                dir_hash = CacheHelper.zip_hash(pex_zip, os.path.relpath(pex_path, pex_zip))
        isolated_dir = os.path.join(ENV.PEX_ROOT, "isolated", dir_hash)

        with _tracer().timed("Isolating pex"):
            with atomic_directory(isolated_dir, exclusive=True) as chroot:
                if chroot:
                    with _tracer().timed("Extracting pex to {}".format(isolated_dir)):
                        recursive_copy("", os.path.join(chroot, "pex"))

        _ISOLATED = IsolationResult(pex_hash=dir_hash, chroot_path=isolated_dir)
    return _ISOLATED
Exemple #15
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    def finalize_install(self, install_requests):
        self.atomic_dir.finalize()

        # The install_chroot is keyed by the hash of the wheel file (zip) we installed. Here we add a
        # key by the hash of the exploded wheel dir (the install_chroot). This latter key is used by
        # zipped PEXes at runtime to explode their wheel chroots to the filesystem. By adding the key
        # here we short-circuit the explode process for PEXes created and run on the same machine.
        #
        # From a clean cache after building a simple pex this looks like:
        # $ rm -rf ~/.pex
        # $ python -mpex -c pex -o /tmp/pex.pex .
        # $ tree -L 4 ~/.pex/
        # /home/jsirois/.pex/
        # ├── built_wheels
        # │   └── 1003685de2c3604dc6daab9540a66201c1d1f718
        # │       └── cp-38-cp38
        # │           └── pex-2.0.2-py2.py3-none-any.whl
        # └── installed_wheels
        #     ├── 2a594cef34d2e9109bad847358d57ac4615f81f4
        #     │   └── pex-2.0.2-py2.py3-none-any.whl
        #     │       ├── bin
        #     │       ├── pex
        #     │       └── pex-2.0.2.dist-info
        #     └── ae13cba3a8e50262f4d730699a11a5b79536e3e1
        #         └── pex-2.0.2-py2.py3-none-any.whl -> /home/jsirois/.pex/installed_wheels/2a594cef34d2e9109bad847358d57ac4615f81f4/pex-2.0.2-py2.py3-none-any.whl  # noqa
        #
        # 11 directories, 1 file
        #
        # And we see in the created pex, the runtime key that the layout above satisfies:
        # $ unzip -qc /tmp/pex.pex PEX-INFO | jq .distributions
        # {
        #   "pex-2.0.2-py2.py3-none-any.whl": "ae13cba3a8e50262f4d730699a11a5b79536e3e1"
        # }
        #
        # When the pex is run, the runtime key is followed to the build time key, avoiding re-unpacking
        # the wheel:
        # $ PEX_VERBOSE=1 /tmp/pex.pex --version
        # pex: Found site-library: /usr/lib/python3.8/site-packages
        # pex: Tainted path element: /usr/lib/python3.8/site-packages
        # pex: Scrubbing from user site: /home/jsirois/.local/lib/python3.8/site-packages
        # pex: Scrubbing from site-packages: /usr/lib/python3.8/site-packages
        # pex: Activating PEX virtual environment from /tmp/pex.pex: 9.1ms
        # pex: Bootstrap complete, performing final sys.path modifications...
        # pex: PYTHONPATH contains:
        # pex:     /tmp/pex.pex
        # pex:   * /usr/lib/python38.zip
        # pex:     /usr/lib/python3.8
        # pex:     /usr/lib/python3.8/lib-dynload
        # pex:     /home/jsirois/.pex/installed_wheels/2a594cef34d2e9109bad847358d57ac4615f81f4/pex-2.0.2-py2.py3-none-any.whl  # noqa
        # pex:   * /tmp/pex.pex/.bootstrap
        # pex:   * - paths that do not exist or will be imported via zipimport
        # pex.pex 2.0.2
        #
        wheel_dir_hash = CacheHelper.dir_hash(self.install_chroot)
        runtime_key_dir = os.path.join(self.installation_root, wheel_dir_hash)
        with atomic_directory(runtime_key_dir) as work_dir:
            if work_dir:
                os.symlink(self.install_chroot,
                           os.path.join(work_dir, self.request.wheel_file))

        return self._iter_requirements_requests(install_requests)
Exemple #16
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 def _prepare_code_hash(self):
   self._pex_info.code_hash = CacheHelper.pex_hash(self._chroot.path())
Exemple #17
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    def _spawn_from_binary_external(cls, binary):
        def create_interpreter(stdout):
            identity = stdout.decode('utf-8').strip()
            if not identity:
                raise cls.IdentificationError(
                    'Could not establish identity of %s' % binary)
            return cls(PythonIdentity.decode(identity))

        # Part of the PythonInterpreter data are environment markers that depend on the current OS
        # release. That data can change when the OS is upgraded but (some of) the installed interpreters
        # remain the same. As such, include the OS in the hash structure for cached interpreters.
        os_digest = hashlib.sha1()
        for os_identifier in platform.release(), platform.version():
            os_digest.update(os_identifier.encode('utf-8'))
        os_hash = os_digest.hexdigest()

        interpreter_cache_dir = os.path.join(ENV.PEX_ROOT, 'interpreters')
        os_cache_dir = os.path.join(interpreter_cache_dir, os_hash)
        if os.path.isdir(
                interpreter_cache_dir) and not os.path.isdir(os_cache_dir):
            with TRACER.timed('GCing interpreter cache from prior OS version'):
                safe_rmtree(interpreter_cache_dir)

        interpreter_hash = CacheHelper.hash(binary)
        cache_dir = os.path.join(os_cache_dir, interpreter_hash)
        cache_file = os.path.join(cache_dir, cls.INTERP_INFO_FILE)
        if os.path.isfile(cache_file):
            try:
                with open(cache_file, 'rb') as fp:
                    return SpawnedJob.completed(create_interpreter(fp.read()))
            except (IOError, OSError, cls.Error, PythonIdentity.Error):
                safe_rmtree(cache_dir)
                return cls._spawn_from_binary_external(binary)
        else:
            pythonpath = third_party.expose(['pex'])
            cmd, env = cls._create_isolated_cmd(binary,
                                                args=[
                                                    '-c',
                                                    dedent("""\
          import os
          import sys

          from pex.common import atomic_directory, safe_open
          from pex.interpreter import PythonIdentity


          encoded_identity = PythonIdentity.get().encode()
          sys.stdout.write(encoded_identity)
          with atomic_directory({cache_dir!r}) as cache_dir:
            if cache_dir:
              with safe_open(os.path.join(cache_dir, {info_file!r}), 'w') as fp:
                fp.write(encoded_identity)
          """.format(cache_dir=cache_dir, info_file=cls.INTERP_INFO_FILE))
                                                ],
                                                pythonpath=pythonpath)
            process = Executor.open_process(cmd,
                                            env=env,
                                            stdout=subprocess.PIPE,
                                            stderr=subprocess.PIPE)
            job = Job(command=cmd, process=process)
            return SpawnedJob.stdout(job, result_func=create_interpreter)
Exemple #18
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    def _spawn_from_binary_external(cls, binary):
        def create_interpreter(stdout):
            identity = stdout.decode("utf-8").strip()
            if not identity:
                raise cls.IdentificationError(
                    "Could not establish identity of %s" % binary)
            return cls(PythonIdentity.decode(identity))

        # Part of the PythonInterpreter data are environment markers that depend on the current OS
        # release. That data can change when the OS is upgraded but (some of) the installed interpreters
        # remain the same. As such, include the OS in the hash structure for cached interpreters.
        os_digest = hashlib.sha1()
        for os_identifier in platform.release(), platform.version():
            os_digest.update(os_identifier.encode("utf-8"))
        os_hash = os_digest.hexdigest()

        interpreter_cache_dir = os.path.join(ENV.PEX_ROOT, "interpreters")
        os_cache_dir = os.path.join(interpreter_cache_dir, os_hash)
        if os.path.isdir(
                interpreter_cache_dir) and not os.path.isdir(os_cache_dir):
            with TRACER.timed("GCing interpreter cache from prior OS version"):
                safe_rmtree(interpreter_cache_dir)

        interpreter_hash = CacheHelper.hash(binary)

        # Some distributions include more than one copy of the same interpreter via a hard link (e.g.:
        # python3.7 is a hardlink to python3.7m). To ensure a deterministic INTERP-INFO file we must
        # emit a separate INTERP-INFO for each link since INTERP-INFO contains the interpreter path and
        # would otherwise be unstable.
        #
        # See cls._REGEXEN for a related affordance.
        path_id = binary.replace(os.sep, ".").lstrip(".")

        cache_dir = os.path.join(os_cache_dir, interpreter_hash, path_id)
        cache_file = os.path.join(cache_dir, cls.INTERP_INFO_FILE)
        if os.path.isfile(cache_file):
            try:
                with open(cache_file, "rb") as fp:
                    return SpawnedJob.completed(create_interpreter(fp.read()))
            except (IOError, OSError, cls.Error, PythonIdentity.Error):
                safe_rmtree(cache_dir)
                return cls._spawn_from_binary_external(binary)
        else:
            pythonpath = third_party.expose(["pex"])
            cmd, env = cls._create_isolated_cmd(
                binary,
                args=[
                    "-c",
                    dedent("""\
                        import os
                        import sys

                        from pex.common import atomic_directory, safe_open
                        from pex.interpreter import PythonIdentity


                        encoded_identity = PythonIdentity.get().encode()
                        sys.stdout.write(encoded_identity)
                        with atomic_directory({cache_dir!r}) as cache_dir:
                            if cache_dir:
                                with safe_open(os.path.join(cache_dir, {info_file!r}), 'w') as fp:
                                    fp.write(encoded_identity)
                        """.format(cache_dir=cache_dir,
                                   info_file=cls.INTERP_INFO_FILE)),
                ],
                pythonpath=pythonpath,
            )
            process = Executor.open_process(cmd,
                                            env=env,
                                            stdout=subprocess.PIPE,
                                            stderr=subprocess.PIPE)
            job = Job(command=cmd, process=process)
            return SpawnedJob.stdout(job, result_func=create_interpreter)
Exemple #19
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 def create(cls, target, wheel_path):
     fingerprint = CacheHelper.hash(wheel_path)
     return cls(target=target,
                wheel_path=wheel_path,
                fingerprint=fingerprint)
Exemple #20
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    def _spawn_from_binary_external(cls, binary):
        def create_interpreter(stdout, check_binary=False):
            identity = stdout.decode("utf-8").strip()
            if not identity:
                raise cls.IdentificationError(
                    "Could not establish identity of {}.".format(binary))
            interpreter = cls(PythonIdentity.decode(identity))
            # We should not need to check this since binary == interpreter.binary should always be
            # true, but historically this could be untrue as noted in `PythonIdentity.get`.
            if check_binary and not os.path.exists(interpreter.binary):
                raise cls.InterpreterNotFound(
                    "Cached interpreter for {} reports a binary of {}, which could not be found"
                    .format(binary, interpreter.binary))
            return interpreter

        # Part of the PythonInterpreter data are environment markers that depend on the current OS
        # release. That data can change when the OS is upgraded but (some of) the installed interpreters
        # remain the same. As such, include the OS in the hash structure for cached interpreters.
        os_digest = hashlib.sha1()
        for os_identifier in platform.release(), platform.version():
            os_digest.update(os_identifier.encode("utf-8"))
        os_hash = os_digest.hexdigest()

        interpreter_cache_dir = os.path.join(ENV.PEX_ROOT, "interpreters")
        os_cache_dir = os.path.join(interpreter_cache_dir, os_hash)
        if os.path.isdir(
                interpreter_cache_dir) and not os.path.isdir(os_cache_dir):
            with TRACER.timed("GCing interpreter cache from prior OS version"):
                safe_rmtree(interpreter_cache_dir)

        interpreter_hash = CacheHelper.hash(binary)

        # Some distributions include more than one copy of the same interpreter via a hard link (e.g.:
        # python3.7 is a hardlink to python3.7m). To ensure a deterministic INTERP-INFO file we must
        # emit a separate INTERP-INFO for each link since INTERP-INFO contains the interpreter path and
        # would otherwise be unstable.
        #
        # See cls._REGEXEN for a related affordance.
        #
        # N.B.: The path for --venv mode interpreters can be quite long; so we just used a fixed
        # length hash of the interpreter binary path to ensure uniqueness and not run afoul of file
        # name length limits.
        path_id = hashlib.sha1(binary.encode("utf-8")).hexdigest()

        cache_dir = os.path.join(os_cache_dir, interpreter_hash, path_id)
        cache_file = os.path.join(cache_dir, cls.INTERP_INFO_FILE)
        if os.path.isfile(cache_file):
            try:
                with open(cache_file, "rb") as fp:
                    return SpawnedJob.completed(
                        create_interpreter(fp.read(), check_binary=True))
            except (IOError, OSError, cls.Error, PythonIdentity.Error):
                safe_rmtree(cache_dir)
                return cls._spawn_from_binary_external(binary)
        else:
            pythonpath = third_party.expose(["pex"])
            cmd, env = cls._create_isolated_cmd(
                binary,
                args=[
                    "-c",
                    dedent("""\
                        import os
                        import sys

                        from pex.common import atomic_directory, safe_open
                        from pex.interpreter import PythonIdentity


                        encoded_identity = PythonIdentity.get(binary={binary!r}).encode()
                        sys.stdout.write(encoded_identity)
                        with atomic_directory({cache_dir!r}, exclusive=False) as cache_dir:
                            if cache_dir:
                                with safe_open(os.path.join(cache_dir, {info_file!r}), 'w') as fp:
                                    fp.write(encoded_identity)
                        """.format(binary=binary,
                                   cache_dir=cache_dir,
                                   info_file=cls.INTERP_INFO_FILE)),
                ],
                pythonpath=pythonpath,
            )
            process = Executor.open_process(cmd,
                                            env=env,
                                            stdout=subprocess.PIPE,
                                            stderr=subprocess.PIPE)
            job = Job(command=cmd, process=process)
            return SpawnedJob.stdout(job, result_func=create_interpreter)