Source code for apache_beam.internal.util

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"""Utility functions used throughout the package.

For internal use only. No backwards compatibility guarantees.
"""

import logging
from multiprocessing.pool import ThreadPool
import threading
import weakref


[docs]class ArgumentPlaceholder(object): """For internal use only; no backwards-compatibility guarantees. A place holder object replacing PValues in argument lists. A Fn object can take any number of "side inputs", which are PValues that will be evaluated during pipeline execution and will be provided to the function at the moment of its execution as positional or keyword arguments. This is used only internally and should never be used by user code. A custom Fn object by the time it executes will have such values replaced with real computed values. """ def __eq__(self, other): """Tests for equality of two placeholder objects. Args: other: Another placeholder object to compare to. This method is used only for test code. All placeholder objects are equal to each other. """ return isinstance(other, ArgumentPlaceholder)
[docs]def remove_objects_from_args(args, kwargs, pvalue_classes): """For internal use only; no backwards-compatibility guarantees. Replaces all objects of a given type in args/kwargs with a placeholder. Args: args: A list of positional arguments. kwargs: A dictionary of keyword arguments. pvalue_classes: A tuple of class objects representing the types of the arguments that must be replaced with a placeholder value (instance of ArgumentPlaceholder) Returns: A 3-tuple containing a modified list of positional arguments, a modified dictionary of keyword arguments, and a list of all objects replaced with a placeholder value. """ pvals = [] def swapper(value): pvals.append(value) return ArgumentPlaceholder() new_args = [swapper(v) if isinstance(v, pvalue_classes) else v for v in args] # Make sure the order in which we process the dictionary keys is predictable # by sorting the entries first. This will be important when putting back # PValues. new_kwargs = dict((k, swapper(v)) if isinstance(v, pvalue_classes) else (k, v) for k, v in sorted(kwargs.iteritems())) return (new_args, new_kwargs, pvals)
[docs]def insert_values_in_args(args, kwargs, values): """For internal use only; no backwards-compatibility guarantees. Replaces all placeholders in args/kwargs with actual values. Args: args: A list of positional arguments. kwargs: A dictionary of keyword arguments. values: A list of values that will be used to replace placeholder values. Returns: A 2-tuple containing a modified list of positional arguments, and a modified dictionary of keyword arguments. """ # Use a local iterator so that we don't modify values. v_iter = iter(values) new_args = [ v_iter.next() if isinstance(arg, ArgumentPlaceholder) else arg for arg in args] new_kwargs = dict( (k, v_iter.next()) if isinstance(v, ArgumentPlaceholder) else (k, v) for k, v in sorted(kwargs.iteritems())) return (new_args, new_kwargs)
[docs]def run_using_threadpool(fn_to_execute, inputs, pool_size): """For internal use only; no backwards-compatibility guarantees. Runs the given function on given inputs using a thread pool. Args: fn_to_execute: Function to execute inputs: Inputs on which given function will be executed in parallel. pool_size: Size of thread pool. Returns: Results retrieved after executing the given function on given inputs. """ # ThreadPool crashes in old versions of Python (< 2.7.5) if created # from a child thread. (http://bugs.python.org/issue10015) if not hasattr(threading.current_thread(), '_children'): threading.current_thread()._children = weakref.WeakKeyDictionary() pool = ThreadPool(min(pool_size, len(inputs))) try: # We record and reset logging level here since 'apitools' library Beam # depends on updates the logging level when used with a threadpool - # https://github.com/google/apitools/issues/141 # TODO: Remove this once above issue in 'apitools' is fixed. old_level = logging.getLogger().level return pool.map(fn_to_execute, inputs) finally: pool.terminate() logging.getLogger().setLevel(old_level)