mirror of https://github.com/scrapy/scrapy.git
72 lines
2.0 KiB
Python
72 lines
2.0 KiB
Python
"""This module provides some functions and classes to record and report
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references to live object instances.
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If you want live objects for a particular class to be tracked, you only have to
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subclass from object_ref (instead of object).
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About performance: This library has a minimal performance impact when enabled,
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and no performance penalty at all when disabled (as object_ref becomes just an
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alias to object in that case).
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"""
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from __future__ import print_function
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import weakref
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from time import time
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from operator import itemgetter
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from collections import defaultdict
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import six
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NoneType = type(None)
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live_refs = defaultdict(weakref.WeakKeyDictionary)
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class object_ref(object):
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"""Inherit from this class (instead of object) to a keep a record of live
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instances"""
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__slots__ = ()
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def __new__(cls, *args, **kwargs):
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obj = object.__new__(cls)
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live_refs[cls][obj] = time()
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return obj
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def format_live_refs(ignore=NoneType):
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"""Return a tabular representation of tracked objects"""
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s = "Live References\n\n"
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now = time()
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for cls, wdict in sorted(six.iteritems(live_refs),
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key=lambda x: x[0].__name__):
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if not wdict:
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continue
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if issubclass(cls, ignore):
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continue
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oldest = min(six.itervalues(wdict))
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s += "%-30s %6d oldest: %ds ago\n" % (
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cls.__name__, len(wdict), now - oldest
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)
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return s
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def print_live_refs(*a, **kw):
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"""Print tracked objects"""
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print(format_live_refs(*a, **kw))
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def get_oldest(class_name):
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"""Get the oldest object for a specific class name"""
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for cls, wdict in six.iteritems(live_refs):
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if cls.__name__ == class_name:
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if not wdict:
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break
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return min(six.iteritems(wdict), key=itemgetter(1))[0]
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def iter_all(class_name):
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"""Iterate over all objects of the same class by its class name"""
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for cls, wdict in six.iteritems(live_refs):
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if cls.__name__ == class_name:
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return six.iterkeys(wdict)
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