Source code for luigi.target

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# Copyright 2012-2015 Spotify AB
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"""
The abstract :py:class:`Target` class.
It is a central concept of Luigi and represents the state of the workflow.
"""

import abc
import io
import os
import random
import tempfile
import logging
import warnings
from luigi import six

logger = logging.getLogger('luigi-interface')


[docs]@six.add_metaclass(abc.ABCMeta) class Target(object): """ A Target is a resource generated by a :py:class:`~luigi.task.Task`. For example, a Target might correspond to a file in HDFS or data in a database. The Target interface defines one method that must be overridden: :py:meth:`exists`, which signifies if the Target has been created or not. Typically, a :py:class:`~luigi.task.Task` will define one or more Targets as output, and the Task is considered complete if and only if each of its output Targets exist. """
[docs] @abc.abstractmethod def exists(self): """ Returns ``True`` if the :py:class:`Target` exists and ``False`` otherwise. """ pass
[docs]class FileSystemException(Exception): """ Base class for generic file system exceptions. """ pass
[docs]class FileAlreadyExists(FileSystemException): """ Raised when a file system operation can't be performed because a directory exists but is required to not exist. """ pass
[docs]class MissingParentDirectory(FileSystemException): """ Raised when a parent directory doesn't exist. (Imagine mkdir without -p) """ pass
[docs]class NotADirectory(FileSystemException): """ Raised when a file system operation can't be performed because an expected directory is actually a file. """ pass
[docs]@six.add_metaclass(abc.ABCMeta) class FileSystem(object): """ FileSystem abstraction used in conjunction with :py:class:`FileSystemTarget`. Typically, a FileSystem is associated with instances of a :py:class:`FileSystemTarget`. The instances of the py:class:`FileSystemTarget` will delegate methods such as :py:meth:`FileSystemTarget.exists` and :py:meth:`FileSystemTarget.remove` to the FileSystem. Methods of FileSystem raise :py:class:`FileSystemException` if there is a problem completing the operation. """
[docs] @abc.abstractmethod def exists(self, path): """ Return ``True`` if file or directory at ``path`` exist, ``False`` otherwise :param str path: a path within the FileSystem to check for existence. """ pass
[docs] @abc.abstractmethod def remove(self, path, recursive=True, skip_trash=True): """ Remove file or directory at location ``path`` :param str path: a path within the FileSystem to remove. :param bool recursive: if the path is a directory, recursively remove the directory and all of its descendants. Defaults to ``True``. """ pass
[docs] def mkdir(self, path, parents=True, raise_if_exists=False): """ Create directory at location ``path`` Creates the directory at ``path`` and implicitly create parent directories if they do not already exist. :param str path: a path within the FileSystem to create as a directory. :param bool parents: Create parent directories when necessary. When parents=False and the parent directory doesn't exist, raise luigi.target.MissingParentDirectory :param bool raise_if_exists: raise luigi.target.FileAlreadyExists if the folder already exists. """ raise NotImplementedError("mkdir() not implemented on {0}".format(self.__class__.__name__))
[docs] def isdir(self, path): """ Return ``True`` if the location at ``path`` is a directory. If not, return ``False``. :param str path: a path within the FileSystem to check as a directory. *Note*: This method is optional, not all FileSystem subclasses implements it. """ raise NotImplementedError("isdir() not implemented on {0}".format(self.__class__.__name__))
[docs] def listdir(self, path): """Return a list of files rooted in path. This returns an iterable of the files rooted at ``path``. This is intended to be a recursive listing. :param str path: a path within the FileSystem to list. *Note*: This method is optional, not all FileSystem subclasses implements it. """ raise NotImplementedError("listdir() not implemented on {0}".format(self.__class__.__name__))
[docs] def move(self, path, dest): """ Move a file, as one would expect. """ raise NotImplementedError("move() not implemented on {0}".format(self.__class__.__name__))
[docs] def rename_dont_move(self, path, dest): """ Potentially rename ``path`` to ``dest``, but don't move it into the ``dest`` folder (if it is a folder). This relates to :ref:`AtomicWrites`. This method has a reasonable but not bullet proof default implementation. It will just do ``move()`` if the file doesn't ``exists()`` already. """ warnings.warn("File system {} client doesn't support atomic mv.".format(self.__class__.__name__)) if self.exists(dest): raise FileAlreadyExists() self.move(path, dest)
[docs] def rename(self, *args, **kwargs): """ Alias for ``move()`` """ self.move(*args, **kwargs)
[docs] def copy(self, path, dest): """ Copy a file or a directory with contents. Currently, LocalFileSystem and MockFileSystem support only single file copying but S3Client copies either a file or a directory as required. """ raise NotImplementedError("copy() not implemented on {0}". format(self.__class__.__name__))
[docs]class FileSystemTarget(Target): """ Base class for FileSystem Targets like :class:`~luigi.file.LocalTarget` and :class:`~luigi.contrib.hdfs.HdfsTarget`. A FileSystemTarget has an associated :py:class:`FileSystem` to which certain operations can be delegated. By default, :py:meth:`exists` and :py:meth:`remove` are delegated to the :py:class:`FileSystem`, which is determined by the :py:attr:`fs` property. Methods of FileSystemTarget raise :py:class:`FileSystemException` if there is a problem completing the operation. """ def __init__(self, path): """ Initializes a FileSystemTarget instance. :param str path: the path associated with this FileSystemTarget. """ self.path = path @abc.abstractproperty def fs(self): """ The :py:class:`FileSystem` associated with this FileSystemTarget. """ raise NotImplementedError()
[docs] @abc.abstractmethod def open(self, mode): """ Open the FileSystem target. This method returns a file-like object which can either be read from or written to depending on the specified mode. :param str mode: the mode `r` opens the FileSystemTarget in read-only mode, whereas `w` will open the FileSystemTarget in write mode. Subclasses can implement additional options. """ pass
[docs] def exists(self): """ Returns ``True`` if the path for this FileSystemTarget exists; ``False`` otherwise. This method is implemented by using :py:attr:`fs`. """ path = self.path if '*' in path or '?' in path or '[' in path or '{' in path: logger.warning("Using wildcards in path %s might lead to processing of an incomplete dataset; " "override exists() to suppress the warning.", path) return self.fs.exists(path)
[docs] def remove(self): """ Remove the resource at the path specified by this FileSystemTarget. This method is implemented by using :py:attr:`fs`. """ self.fs.remove(self.path)
[docs] def temporary_path(self): """ A context manager that enables a reasonably short, general and magic-less way to solve the :ref:`AtomicWrites`. * On *entering*, it will create the parent directories so the temporary_path is writeable right away. This step uses :py:meth:`FileSystem.mkdir`. * On *exiting*, it will move the temporary file if there was no exception thrown. This step uses :py:meth:`FileSystem.rename_dont_move` The file system operations will be carried out by calling them on :py:attr:`fs`. The typical use case looks like this: .. code:: python class MyTask(luigi.Task): def output(self): return MyFileSystemTarget(...) def run(self): with self.output().temporary_path() as self.temp_output_path: run_some_external_command(output_path=self.temp_output_path) """ class _Manager(object): target = self def __init__(self): num = random.randrange(0, 1e10) slashless_path = self.target.path.rstrip('/').rstrip("\\") self._temp_path = '{}-luigi-tmp-{:010}{}'.format( slashless_path, num, self.target._trailing_slash()) # TODO: os.path doesn't make sense here as it's os-dependent tmp_dir = os.path.dirname(slashless_path) if tmp_dir: self.target.fs.mkdir(tmp_dir, parents=True, raise_if_exists=False) def __enter__(self): return self._temp_path def __exit__(self, exc_type, exc_value, traceback): if exc_type is None: # There were no exceptions self.target.fs.rename_dont_move(self._temp_path, self.target.path) return False # False means we don't suppress the exception return _Manager()
def _touchz(self): with self.open('w'): pass def _trailing_slash(self): # I suppose one day schema-like paths, like # file:///path/blah.txt?params=etc can be parsed too return self.path[-1] if self.path[-1] in r'\/' else ''
[docs]class AtomicLocalFile(io.BufferedWriter): """Abstract class to create a Target that creates a temporary file in the local filesystem before moving it to its final destination. This class is just for the writing part of the Target. See :class:`luigi.file.LocalTarget` for example """ def __init__(self, path): self.__tmp_path = self.generate_tmp_path(path) self.path = path super(AtomicLocalFile, self).__init__(io.FileIO(self.__tmp_path, 'w'))
[docs] def close(self): super(AtomicLocalFile, self).close() self.move_to_final_destination()
[docs] def generate_tmp_path(self, path): return os.path.join(tempfile.gettempdir(), 'luigi-s3-tmp-%09d' % random.randrange(0, 1e10))
[docs] def move_to_final_destination(self): raise NotImplementedError()
def __del__(self): if os.path.exists(self.tmp_path): os.remove(self.tmp_path) @property def tmp_path(self): return self.__tmp_path def __exit__(self, exc_type, exc, traceback): " Close/commit the file if there are no exception " if exc_type: return return super(AtomicLocalFile, self).__exit__(exc_type, exc, traceback)