view tests/test-parseindex2.py @ 46607:e9901d01d135

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

"""This unit test primarily tests parsers.parse_index2().

It also checks certain aspects of the parsers module as a whole.
"""

from __future__ import absolute_import, print_function

import os
import struct
import subprocess
import sys
import unittest

from mercurial.node import (
    bin,
    hex,
    nullid,
    nullrev,
)
from mercurial import (
    policy,
    pycompat,
)

parsers = policy.importmod('parsers')

# original python implementation
def gettype(q):
    return int(q & 0xFFFF)


def offset_type(offset, type):
    return int(int(offset) << 16 | type)


indexformatng = ">Qiiiiii20s12x"


def py_parseindex(data, inline):
    s = 64
    cache = None
    index = []
    nodemap = {nullid: nullrev}
    n = off = 0

    l = len(data) - s
    append = index.append
    if inline:
        cache = (0, data)
        while off <= l:
            e = struct.unpack(indexformatng, data[off : off + s])
            nodemap[e[7]] = n
            append(e)
            n += 1
            if e[1] < 0:
                break
            off += e[1] + s
    else:
        while off <= l:
            e = struct.unpack(indexformatng, data[off : off + s])
            nodemap[e[7]] = n
            append(e)
            n += 1
            off += s

    e = list(index[0])
    type = gettype(e[0])
    e[0] = offset_type(0, type)
    index[0] = tuple(e)

    return index, cache


data_inlined = (
    b'\x00\x01\x00\x01\x00\x00\x00\x00\x00\x00\x01\x8c'
    b'\x00\x00\x04\x07\x00\x00\x00\x00\x00\x00\x15\x15\xff\xff\xff'
    b'\xff\xff\xff\xff\xff\xebG\x97\xb7\x1fB\x04\xcf\x13V\x81\tw\x1b'
    b'w\xdduR\xda\xc6\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
    b'x\x9c\x9d\x93?O\xc30\x10\xc5\xf7|\x8a\xdb\x9a\xa8m\x06\xd8*\x95'
    b'\x81B\xa1\xa2\xa2R\xcb\x86Pd\x9a\x0b5$vd_\x04\xfd\xf6\x9c\xff@'
    b'\x11!\x0b\xd9\xec\xf7\xbbw\xe7gG6\xad6\x04\xdaN\xc0\x92\xa0$)'
    b'\xb1\x82\xa2\xd1%\x16\xa4\x8b7\xa9\xca\xd4-\xb2Y\x02\xfc\xc9'
    b'\xcaS\xf9\xaeX\xed\xb6\xd77Q\x02\x83\xd4\x19\xf5--Y\xea\xe1W'
    b'\xab\xed\x10\xceR\x0f_\xdf\xdf\r\xe1,\xf5\xf0\xcb\xf5 \xceR\x0f'
    b'_\xdc\x0e\x0e\xc3R\x0f_\xae\x96\x9b!\x9e\xa5\x1e\xbf\xdb,\x06'
    b'\xc7q\x9a/\x88\x82\xc3B\xea\xb5\xb4TJ\x93\xb6\x82\x0e\xe16\xe6'
    b'KQ\xdb\xaf\xecG\xa3\xd1 \x01\xd3\x0b_^\xe8\xaa\xa0\xae\xad\xd1'
    b'&\xbef\x1bz\x08\xb0|\xc9Xz\x06\xf6Z\x91\x90J\xaa\x17\x90\xaa'
    b'\xd2\xa6\x11$5C\xcf\xba#\xa0\x03\x02*2\x92-\xfc\xb1\x94\xdf\xe2'
    b'\xae\xb8\'m\x8ey0^\x85\xd3\x82\xb4\xf0`:\x9c\x00\x8a\xfd\x01'
    b'\xb0\xc6\x86\x8b\xdd\xae\x80\xf3\xa9\x9fd\x16\n\x00R%\x1a\x06'
    b'\xe9\xd8b\x98\x1d\xf4\xf3+\x9bf\x01\xd8p\x1b\xf3.\xed\x9f^g\xc3'
    b'^\xd9W81T\xdb\xd5\x04sx|\xf2\xeb\xd6`%?x\xed"\x831\xbf\xf3\xdc'
    b'b\xeb%gaY\xe1\xad\x9f\xb9f\'1w\xa9\xa5a\x83s\x82J\xb98\xbc4\x8b'
    b'\x83\x00\x9f$z\xb8#\xa5\xb1\xdf\x98\xd9\xec\x1b\x89O\xe3Ts\x9a4'
    b'\x17m\x8b\xfc\x8f\xa5\x95\x9a\xfc\xfa\xed,\xe5|\xa1\xfe\x15\xb9'
    b'\xbc\xb2\x93\x1f\xf2\x95\xff\xdf,\x1a\xc5\xe7\x17*\x93Oz:>\x0e'
)

data_non_inlined = (
    b'\x00\x00\x00\x01\x00\x00\x00\x00\x00\x01D\x19'
    b'\x00\x07e\x12\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff'
    b'\xff\xff\xff\xff\xd1\xf4\xbb\xb0\xbe\xfc\x13\xbd\x8c\xd3\x9d'
    b'\x0f\xcd\xd9;\x8c\x07\x8cJ/\x00\x00\x00\x00\x00\x00\x00\x00\x00'
    b'\x00\x00\x00\x00\x00\x00\x01D\x19\x00\x00\x00\x00\x00\xdf\x00'
    b'\x00\x01q\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x00\xff'
    b'\xff\xff\xff\xc1\x12\xb9\x04\x96\xa4Z1t\x91\xdfsJ\x90\xf0\x9bh'
    b'\x07l&\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
    b'\x00\x01D\xf8\x00\x00\x00\x00\x01\x1b\x00\x00\x01\xb8\x00\x00'
    b'\x00\x01\x00\x00\x00\x02\x00\x00\x00\x01\xff\xff\xff\xff\x02\n'
    b'\x0e\xc6&\xa1\x92\xae6\x0b\x02i\xfe-\xe5\xbao\x05\xd1\xe7\x00'
    b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01F'
    b'\x13\x00\x00\x00\x00\x01\xec\x00\x00\x03\x06\x00\x00\x00\x01'
    b'\x00\x00\x00\x03\x00\x00\x00\x02\xff\xff\xff\xff\x12\xcb\xeby1'
    b'\xb6\r\x98B\xcb\x07\xbd`\x8f\x92\xd9\xc4\x84\xbdK\x00\x00\x00'
    b'\x00\x00\x00\x00\x00\x00\x00\x00\x00'
)


def parse_index2(data, inline):
    index, chunkcache = parsers.parse_index2(data, inline)
    return list(index), chunkcache


def importparsers(hexversion):
    """Import mercurial.parsers with the given sys.hexversion."""
    # The file parsers.c inspects sys.hexversion to determine the version
    # of the currently-running Python interpreter, so we monkey-patch
    # sys.hexversion to simulate using different versions.
    code = (
        "import sys; sys.hexversion=%s; "
        "import mercurial.cext.parsers" % hexversion
    )
    cmd = "\"%s\" -c \"%s\"" % (os.environ['PYTHON'], code)
    # We need to do these tests inside a subprocess because parser.c's
    # version-checking code happens inside the module init function, and
    # when using reload() to reimport an extension module, "The init function
    # of extension modules is not called a second time"
    # (from http://docs.python.org/2/library/functions.html?#reload).
    p = subprocess.Popen(
        cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT
    )
    return p.communicate()  # returns stdout, stderr


def hexfailmsg(testnumber, hexversion, stdout, expected):
    try:
        hexstring = hex(hexversion)
    except TypeError:
        hexstring = None
    return (
        "FAILED: version test #%s with Python %s and patched "
        "sys.hexversion %r (%r):\n Expected %s but got:\n-->'%s'\n"
        % (
            testnumber,
            sys.version_info,
            hexversion,
            hexstring,
            expected,
            stdout,
        )
    )


def makehex(major, minor, micro):
    return int("%x%02x%02x00" % (major, minor, micro), 16)


class parseindex2tests(unittest.TestCase):
    def assertversionokay(self, testnumber, hexversion):
        stdout, stderr = importparsers(hexversion)
        self.assertFalse(
            stdout, hexfailmsg(testnumber, hexversion, stdout, 'no stdout')
        )

    def assertversionfail(self, testnumber, hexversion):
        stdout, stderr = importparsers(hexversion)
        # We include versionerrortext to distinguish from other ImportErrors.
        errtext = b"ImportError: %s" % pycompat.sysbytes(
            parsers.versionerrortext
        )
        self.assertIn(
            errtext,
            stdout,
            hexfailmsg(
                testnumber,
                hexversion,
                stdout,
                expected="stdout to contain %r" % errtext,
            ),
        )

    def testversiondetection(self):
        """Check the version-detection logic when importing parsers."""
        # Only test the version-detection logic if it is present.
        try:
            parsers.versionerrortext
        except AttributeError:
            return
        info = sys.version_info
        major, minor, micro = info[0], info[1], info[2]
        # Test same major-minor versions.
        self.assertversionokay(1, makehex(major, minor, micro))
        self.assertversionokay(2, makehex(major, minor, micro + 1))
        # Test different major-minor versions.
        self.assertversionfail(3, makehex(major + 1, minor, micro))
        self.assertversionfail(4, makehex(major, minor + 1, micro))
        self.assertversionfail(5, "'foo'")

    def testbadargs(self):
        # Check that parse_index2() raises TypeError on bad arguments.
        with self.assertRaises(TypeError):
            parse_index2(0, True)

    def testparseindexfile(self):
        # Check parsers.parse_index2() on an index file against the
        # original Python implementation of parseindex, both with and
        # without inlined data.

        want = py_parseindex(data_inlined, True)
        got = parse_index2(data_inlined, True)
        self.assertEqual(want, got)  # inline data

        want = py_parseindex(data_non_inlined, False)
        got = parse_index2(data_non_inlined, False)
        self.assertEqual(want, got)  # no inline data

        ix = parsers.parse_index2(data_inlined, True)[0]
        for i, r in enumerate(ix):
            if r[7] == nullid:
                i = -1
            try:
                self.assertEqual(
                    ix[r[7]],
                    i,
                    'Reverse lookup inconsistent for %r' % hex(r[7]),
                )
            except TypeError:
                # pure version doesn't support this
                break

    def testminusone(self):
        want = (0, 0, 0, -1, -1, -1, -1, nullid)
        index, junk = parsers.parse_index2(data_inlined, True)
        got = index[-1]
        self.assertEqual(want, got)  # inline data

        index, junk = parsers.parse_index2(data_non_inlined, False)
        got = index[-1]
        self.assertEqual(want, got)  # no inline data

    def testdelitemwithoutnodetree(self):
        index, _junk = parsers.parse_index2(data_non_inlined, False)

        def hexrev(rev):
            if rev == nullrev:
                return b'\xff\xff\xff\xff'
            else:
                return bin('%08x' % rev)

        def appendrev(p1, p2=nullrev):
            # node won't matter for this test, let's just make sure
            # they don't collide. Other data don't matter either.
            node = hexrev(p1) + hexrev(p2) + b'.' * 12
            index.append((0, 0, 12, 1, 34, p1, p2, node))

        appendrev(4)
        appendrev(5)
        appendrev(6)
        self.assertEqual(len(index), 7)

        del index[1:-1]

        # assertions that failed before correction
        self.assertEqual(len(index), 1)  # was 4
        headrevs = getattr(index, 'headrevs', None)
        if headrevs is not None:  # not implemented in pure
            self.assertEqual(index.headrevs(), [0])  # gave ValueError


if __name__ == '__main__':
    import silenttestrunner

    silenttestrunner.main(__name__)