##// END OF EJS Templates
revlog: add a mechanism to verify expected file position before appending...
revlog: add a mechanism to verify expected file position before appending If someone uses `hg debuglocks`, or some non-hg process writes to the .hg directory without respecting the locks, or if the repo's on a networked filesystem, it's possible for the revlog code to write out corrupted data. The form of this corruption can vary depending on what data was written and how that happened. We are in the "networked filesystem" case (though I've had users also do this to themselves with the "`hg debuglocks`" scenario), and most often see this with the changelog. What ends up happening is we produce two items (let's call them rev1 and rev2) in the .i file that have the same linkrev, baserev, and offset into the .d file, while the data in the .d file is appended properly. rev2's compressed_size is accurate for rev2, but when we go to decompress the data in the .d file, we use the offset that's recorded in the index file, which is the same as rev1, and attempt to decompress rev2.compressed_size bytes of rev1's data. This usually does not succeed. :) When using inline data, this also fails, though I haven't investigated why too closely. This shows up as a "patch decode" error. I believe what's happening there is that we're basically ignoring the offset field, getting the data properly, but since baserev != rev, it thinks this is a delta based on rev (instead of a full text) and can't actually apply it as such. For now, I'm going to make this an optional component and default it to entirely off. I may increase the default severity of this in the future, once I've enabled it for my users and we gain more experience with it. Luckily, most of my users have a versioned filesystem and can roll back to before the corruption has been written, it's just a hassle to do so and not everyone knows how (so it's a support burden). Users on other filesystems will not have that luxury, and this can cause them to have a corrupted repository that they are unlikely to know how to resolve, and they'll see this as a data-loss event. Refusing to create the corruption is a much better user experience. This mechanism is not perfect. There may be false-negatives (racy writes that are not detected). There should not be any false-positives (non-racy writes that are detected as such). This is not a mechanism that makes putting a repo on a networked filesystem "safe" or "supported", just *less* likely to cause corruption. Differential Revision: https://phab.mercurial-scm.org/D9952

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document.py
122 lines | 3.9 KiB | text/x-python | PythonLexer
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
""" Pretty-Print an Interface object as structured text (Yum)
This module provides a function, asStructuredText, for rendering an
interface as structured text.
"""
from __future__ import absolute_import
from . import Interface
def asStructuredText(I, munge=0, rst=False):
""" Output structured text format. Note, this will whack any existing
'structured' format of the text.
If `rst=True`, then the output will quote all code as inline literals in
accordance with 'reStructuredText' markup principles.
"""
if rst:
inline_literal = lambda s: "``%s``" % (s,)
else:
inline_literal = lambda s: s
r = [inline_literal(I.getName())]
outp = r.append
level = 1
if I.getDoc():
outp(_justify_and_indent(_trim_doc_string(I.getDoc()), level))
bases = [base
for base in I.__bases__
if base is not Interface
]
if bases:
outp(_justify_and_indent("This interface extends:", level, munge))
level += 1
for b in bases:
item = "o %s" % inline_literal(b.getName())
outp(_justify_and_indent(_trim_doc_string(item), level, munge))
level -= 1
namesAndDescriptions = sorted(I.namesAndDescriptions())
outp(_justify_and_indent("Attributes:", level, munge))
level += 1
for name, desc in namesAndDescriptions:
if not hasattr(desc, 'getSignatureString'): # ugh...
item = "%s -- %s" % (inline_literal(desc.getName()),
desc.getDoc() or 'no documentation')
outp(_justify_and_indent(_trim_doc_string(item), level, munge))
level -= 1
outp(_justify_and_indent("Methods:", level, munge))
level += 1
for name, desc in namesAndDescriptions:
if hasattr(desc, 'getSignatureString'): # ugh...
_call = "%s%s" % (desc.getName(), desc.getSignatureString())
item = "%s -- %s" % (inline_literal(_call),
desc.getDoc() or 'no documentation')
outp(_justify_and_indent(_trim_doc_string(item), level, munge))
return "\n\n".join(r) + "\n\n"
def asReStructuredText(I, munge=0):
""" Output reStructuredText format. Note, this will whack any existing
'structured' format of the text."""
return asStructuredText(I, munge=munge, rst=True)
def _trim_doc_string(text):
""" Trims a doc string to make it format
correctly with structured text. """
lines = text.replace('\r\n', '\n').split('\n')
nlines = [lines.pop(0)]
if lines:
min_indent = min([len(line) - len(line.lstrip())
for line in lines])
for line in lines:
nlines.append(line[min_indent:])
return '\n'.join(nlines)
def _justify_and_indent(text, level, munge=0, width=72):
""" indent and justify text, rejustify (munge) if specified """
indent = " " * level
if munge:
lines = []
line = indent
text = text.split()
for word in text:
line = ' '.join([line, word])
if len(line) > width:
lines.append(line)
line = indent
else:
lines.append(line)
return '\n'.join(lines)
else:
return indent + \
text.strip().replace("\r\n", "\n") .replace("\n", "\n" + indent)