From: Han Xin <hanxin.hx@bytedance.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: chiyutianyi@gmail.com, derrickstolee@github.com,
git@vger.kernel.org, haiyangtand@gmail.com,
Taylor Blau <me@ttaylorr.com>, Patrick Steinhardt <ps@pks.im>
Subject: Re: Re: [PATCH v1] commit-graph.c: no lazy fetch in lookup_commit_in_graph()
Date: Wed, 22 Jun 2022 11:17:23 +0800 [thread overview]
Message-ID: <CAKgqsWUdRpm8Aa6+oLqHGGXMzXB76f7mM9vf89mG8XVSsQ-1aw@mail.gmail.com> (raw)
In-Reply-To: <20220621182322.3444926-1-jonathantanmy@google.com>
On Wed, Jun 22, 2022 at 2:23 AM Jonathan Tan <jonathantanmy@google.com> wrote:
>
> Han Xin <hanxin.hx@bytedance.com> writes:
> > If a commit is in the commit graph, we would expect the commit to also
> > be present. So we should use has_object() instead of
> > repo_has_object_file(), which will help us avoid getting into an endless
> > loop of lazy fetch.
> >
> > We can see the endless loop issue via this[1].
> >
> > 1. https://lore.kernel.org/git/20220612161707.21807-1-chiyutianyi@gmail.com/
>
> As described in SubmittingPatches:
>
> Try to make sure your explanation can be understood
> without external resources. Instead of giving a URL to a mailing list
> archive, summarize the relevant points of the discussion.
>
Nod.
> > +test_expect_success 'setup' '
> > + git init --bare dest.git &&
> > + test_commit one &&
> > + git checkout -b tmp &&
> > + test_commit two &&
> > + git push dest.git --all
> > +'
>
> You can commit directly to the repo by using "test_commit -C dest.git".
> Also, can the repositories be better named? I see a "dest.git" (which
> seems to contain all the objects), "alternates" (which seems to contain
> everything except refs/heads/tmp), "source" (which only contains the
> commit graph), and the current directory. It would probably be better to
> name them e.g. "with-commit", "without-commit", "only-commit-graph", and
> omit using the current directory altogether.
Yes, it makes sense to me.
>
> > +test_expect_success 'prepare a alternates repository without commit two' '
> > + git clone --bare dest.git alternates &&
> > + oid=$(git -C alternates rev-parse refs/heads/tmp) &&
> > + git -C alternates update-ref -d refs/heads/tmp &&
> > + git -C alternates gc --prune=now &&
> > + pack=$(echo alternates/objects/pack/*.pack) &&
> > + git verify-pack -v "$pack" >have &&
> > + ! grep "$oid" have
> > +'
>
> OK, except refs/heads/tmp could probably have a better name.
I'll rethink the naming here.
>
> > +test_expect_success 'prepare a repository with a commit-graph contains commit two' '
> > + git init source &&
> > + echo "$(pwd)/dest.git/objects" >source/.git/objects/info/alternates &&
> > + git -C source remote add origin "$(pwd)/dest.git" &&
> > + git -C source config remote.origin.promisor true &&
> > + git -C source config remote.origin.partialclonefilter blob:none &&
> > + # the source repository has the whole refs contains refs/heads/tmp
> > + git -C source fetch origin &&
> > + (
> > + cd source &&
> > + test_commit three &&
> > + git -c gc.writeCommitGraph=true gc
> > + )
> > +'
>
> Is the purpose of the fetch only to add a ref? If yes, it's clearer just
> to create that branch instead of fetching.
Nod.
>
> > +test_expect_success 'change the alternates of source to that without commit two' '
> > + # now we have a commit-graph in the source repository but without the commit two
> > + echo "$(pwd)/alternates/objects" >source/.git/objects/info/alternates
> > +'
>
> OK.
>
> > +test_expect_success 'fetch the missing commit' '
> > + git -C source fetch origin $oid 2>fetch.out &&
> > + grep "$oid" fetch.out
> > +'
>
> Is the bug triggered by fetching the missing commit or by fetching any
> commit (which triggers the usage of the commit graph)? If any commit,
> then it's clearer to create an arbitrary commit and then fetch it.
>
Yes, using the missing object in the commit-graph seems to be a little
misleading.
> Also, I thought that the issue was an infinite loop, and the thing being
> tested here looks different from that. If you want to ensure that
> nothing is being fetched, you can use GIT_TRACE="$(pwd)/trace" to
> observe a fetch-pack command being invoked or
> GIT_TRACE_PACKET="$(pwd)/trace" to observe the packet being sent. If
> you're worried about an infinite loop, you can set origin to a directory
> that does not exist (so that the fetch immediately fails).
Maybe we can use "ulimit" ?
Then the test case can be:
test_expect_success 'fetch the missing commit once' '
ulimit -u 512 &&
GIT_TRACE="$(pwd)/trace" git -C source fetch origin $oid 2>err &&
! grep "error: cannot fork" err &&
test $(grep "fetch origin" trace | wc -l) -eq 1
'
Without this fix, "git fetch" would finally succeed because we didn't
check the return value of promise_remote_get_direct(). We can find
the err output like this:
error: cannot fork() for -c: Resource temporarily unavailable
fatal: promisor-remote: unable to fork off fetch subprocess
And we can see a lot of trace logs as follows:
trace: run_command: git -c fetch.negotiationAlgorithm=noop fetch
origin --no-tags --no-write-fetch-head --recurse-submodules=no
--filter=blob:none --stdin
trace: built-in: git fetch origin --no-tags --no-write-fetch-head
--recurse-submodules=no --filter=blob:none --stdin
Thanks.
-Han Xin
next prev parent reply other threads:[~2022-06-22 3:17 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 7:25 An endless loop fetching issue with partial clone, alternates and commit graph Haiyng Tan
2022-06-15 2:18 ` Taylor Blau
2022-06-16 3:38 ` [RFC PATCH 0/2] " Han Xin
2022-06-16 3:38 ` [RFC PATCH 1/2] commit-graph.c: add "flags" to lookup_commit_in_graph() Han Xin
2022-06-16 3:38 ` [RFC PATCH 2/2] fetch-pack.c: pass "oi_flags" " Han Xin
2022-06-17 21:47 ` [RFC PATCH 0/2] Re: An endless loop fetching issue with partial clone, alternates and commit graph Jonathan Tan
2022-06-18 3:01 ` [PATCH v1] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-20 7:07 ` Patrick Steinhardt
2022-06-20 8:53 ` [External] " 欣韩
2022-06-20 9:05 ` Patrick Steinhardt
2022-06-21 18:23 ` Jonathan Tan
2022-06-22 3:17 ` Han Xin [this message]
2022-06-24 5:27 ` [PATCH v2 0/2] " Han Xin
2022-06-24 5:27 ` [PATCH v2 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-24 16:03 ` Junio C Hamano
2022-06-25 1:35 ` Han Xin
2022-06-27 12:22 ` Junio C Hamano
2022-06-24 5:27 ` [PATCH v2 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-24 16:56 ` Junio C Hamano
2022-06-25 2:25 ` Han Xin
2022-06-25 2:31 ` Han Xin
2022-06-28 2:02 ` [PATCH v3 0/2] " Han Xin
2022-06-28 2:02 ` [PATCH v3 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-28 2:02 ` [PATCH v3 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-28 7:49 ` Ævar Arnfjörð Bjarmason
2022-06-28 17:36 ` Junio C Hamano
2022-06-30 12:21 ` Johannes Schindelin
2022-06-30 13:43 ` Ævar Arnfjörð Bjarmason
2022-06-30 15:40 ` Junio C Hamano
2022-06-30 18:47 ` Ævar Arnfjörð Bjarmason
2022-07-01 19:31 ` Johannes Schindelin
2022-07-01 20:47 ` Junio C Hamano
2022-06-29 2:08 ` Han Xin
2022-06-30 17:37 ` test name conflict + js/ci-github-workflow-markup regression (was: [PATCH v3 0/2] no lazy fetch in lookup_commit_in_graph()) Ævar Arnfjörð Bjarmason
2022-07-01 1:34 ` [PATCH v4 0/1] no lazy fetch in lookup_commit_in_graph() Han Xin
2022-07-01 1:34 ` [PATCH v4 1/1] commit-graph.c: " Han Xin
2022-07-09 12:23 ` Michael J Gruber
2022-07-11 15:09 ` Jeff King
2022-07-11 20:17 ` Junio C Hamano
2022-07-12 1:52 ` [External] " Han Xin
2022-07-12 5:23 ` Junio C Hamano
2022-07-12 5:32 ` Han Xin
2022-07-12 6:37 ` [External] " Jeff King
2022-07-12 14:19 ` Junio C Hamano
2022-07-12 6:50 ` [PATCH v5 0/1] " Han Xin
2022-07-12 6:50 ` [PATCH v5 1/1] commit-graph.c: " Han Xin
2022-07-12 9:50 ` Ævar Arnfjörð Bjarmason
2022-07-13 1:26 ` Han Xin
2022-07-12 6:58 ` [PATCH v5 0/1] " Jeff King
2022-07-12 8:01 ` [PATCH v1] t5330: remove run_with_limited_processses() Han Xin
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