Mercurial > hg
view tests/test-remotefilelog-http.t @ 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
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | a495435d980e |
children | 1d075b857c90 |
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#require no-windows $ . "$TESTDIR/remotefilelog-library.sh" $ hg init master $ cd master $ cat >> .hg/hgrc <<EOF > [remotefilelog] > server=True > EOF $ echo x > x $ echo y > y $ hg commit -qAm x $ hg serve -p $HGPORT -d --pid-file=../hg1.pid -E ../error.log -A ../access.log Build a query string for later use: $ GET=`hg debugdata -m 0 | $PYTHON -c \ > 'import sys ; print([("?cmd=x_rfl_getfile&file=%s&node=%s" % tuple(s.split("\0"))) for s in sys.stdin.read().splitlines()][0])'` $ cd .. $ cat hg1.pid >> $DAEMON_PIDS $ hgcloneshallow http://localhost:$HGPORT/ shallow -q 2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob) $ grep getfile access.log * "GET /?cmd=batch HTTP/1.1" 200 - x-hgarg-1:cmds=x_rfl_getfile+*node%3D1406e74118627694268417491f018a4a883152f0* (glob) Clear filenode cache so we can test fetching with a modified batch size $ rm -r $TESTTMP/hgcache Now do a fetch with a large batch size so we're sure it works $ hgcloneshallow http://localhost:$HGPORT/ shallow-large-batch \ > --config remotefilelog.batchsize=1000 -q 2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob) The 'remotefilelog' capability should *not* be exported over http(s), as the getfile method it offers doesn't work with http. $ get-with-headers.py localhost:$HGPORT '?cmd=capabilities' | grep lookup | identifyrflcaps x_rfl_getfile x_rfl_getflogheads $ get-with-headers.py localhost:$HGPORT '?cmd=hello' | grep lookup | identifyrflcaps x_rfl_getfile x_rfl_getflogheads $ get-with-headers.py localhost:$HGPORT '?cmd=this-command-does-not-exist' | head -n 1 400 no such method: this-command-does-not-exist $ get-with-headers.py localhost:$HGPORT '?cmd=x_rfl_getfiles' | head -n 1 400 no such method: x_rfl_getfiles Verify serving from a shallow clone doesn't allow for remotefile fetches. This also serves to test the error handling for our batchable getfile RPC. $ cd shallow $ hg serve -p $HGPORT1 -d --pid-file=../hg2.pid -E ../error2.log $ cd .. $ cat hg2.pid >> $DAEMON_PIDS This GET should work, because this server is serving master, which is a full clone. $ get-with-headers.py localhost:$HGPORT "$GET" 200 Script output follows 0\x00x\x9c3b\xa8\xe0\x12a{\xee(\x91T6E\xadE\xdcS\x9e\xb1\xcb\xab\xc30\xe8\x03\x03\x91 \xe4\xc6\xfb\x99J,\x17\x0c\x9f-\xcb\xfcR7c\xf3c\x97r\xbb\x10\x06\x00\x96m\x121 (no-eol) (esc) This GET should fail using the in-band signalling mechanism, because it's not a full clone. Note that it's also plausible for servers to refuse to serve file contents for other reasons, like the file contents not being visible to the current user. $ get-with-headers.py localhost:$HGPORT1 "$GET" 200 Script output follows 1\x00cannot fetch remote files from shallow repo (no-eol) (esc) Clones should work with httppostargs turned on $ cd master $ hg --config experimental.httppostargs=1 serve -p $HGPORT2 -d --pid-file=../hg3.pid -E ../error3.log $ cd .. $ cat hg3.pid >> $DAEMON_PIDS Clear filenode cache so we can test fetching with a modified batch size $ rm -r $TESTTMP/hgcache $ hgcloneshallow http://localhost:$HGPORT2/ shallow-postargs -q 2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob) All error logs should be empty: $ cat error.log $ cat error2.log $ cat error3.log