Mercurial > hg
view tests/test-exchange-obsmarkers-case-A6.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 | 34a46d48d24e |
children |
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============================================ Testing obsolescence markers push: Cases A.6 ============================================ Mercurial pushes obsolescences markers relevant to the "pushed-set", the set of all changesets that requested to be "in sync" after the push (even if they are already on both side). This test belongs to a series of tests checking such set is properly computed and applied. This does not tests "obsmarkers" discovery capabilities. Category A: simple cases TestCase 6: new markers between changesets already known on both side Variants: # a: explicit push # b: bare push A.6 new markers between changesets already known on both side ============================================================== .. {{{ .. A ◕⇠● B .. |/ .. ● O .. }}} .. .. Marker exist from: .. .. * `A◕⇠● B` .. .. Command runs: .. .. * hg push -r B .. * hg push .. .. Expected exchange: .. .. * `A◕⇠● B` Setup ----- $ . $TESTDIR/testlib/exchange-obsmarker-util.sh initial $ setuprepos A.6 creating test repo for test case A.6 - pulldest - main - pushdest cd into `main` and proceed with env setup $ cd main $ mkcommit A0 $ hg update -q 0 $ mkcommit A1 created new head make both changeset known in remote $ hg push -qf ../pushdest $ hg push -qf ../pulldest create a marker after this $ hg debugobsolete `getid 'desc(A0)'` `getid 'desc(A1)'` 1 new obsolescence markers obsoleted 1 changesets $ hg log -G --hidden @ e5ea8f9c7314 (draft): A1 | | x 28b51eb45704 (draft): A0 |/ o a9bdc8b26820 (public): O $ inspect_obsmarkers obsstore content ================ 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} $ cd .. $ cd .. $ cp -R A.6 A.6.a $ cp -R A.6 A.6.b Actual Test (explicit push version) ----------------------------------- $ dotest A.6.a A1 ## Running testcase A.6.a # testing echange of "A1" (e5ea8f9c7314) ## initial state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest # obstore: pulldest ## pushing "A1" from main to pushdest pushing to pushdest searching for changes no changes found remote: 1 new obsolescence markers remote: obsoleted 1 changesets ## post push state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest ## pulling "e5ea8f9c7314" from main into pulldest pulling from main no changes found 1 new obsolescence markers obsoleted 1 changesets ## post pull state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} Actual Test (bare push version) ------------------------------- $ dotest A.6.b ## Running testcase A.6.b ## initial state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest # obstore: pulldest ## pushing from main to pushdest pushing to pushdest searching for changes no changes found remote: 1 new obsolescence markers remote: obsoleted 1 changesets ## post push state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest ## pulling from main into pulldest pulling from main searching for changes no changes found 1 new obsolescence markers obsoleted 1 changesets ## post pull state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}