From: Xing Xin <xingxin.xx@xxxxxxxxxxxxx>
When using the bundle-uri mechanism with a bundle list containing
multiple interrelated bundles, we encountered a bug where tips from
downloaded bundles were not discovered, thus resulting in rather slow
clones. This was particularly problematic when employing the
"creationTokens" heuristic.
To reproduce this issue, consider a repository with a single branch
"main" pointing to commit "A". Firstly, create a base bundle with:
git bundle create base.bundle main
Then, add a new commit "B" on top of "A", and create an incremental
bundle for "main":
git bundle create incr.bundle A..main
Now, generate a bundle list with the following content:
[bundle]
version = 1
mode = all
heuristic = creationToken
[bundle "base"]
uri = base.bundle
creationToken = 1
[bundle "incr"]
uri = incr.bundle
creationToken = 2
A fresh clone with the bundle list above should result in a reference
"refs/bundles/main" pointing to "B" in the new repository. However, git
would still download everything from the server, as if it had fetched
nothing locally.
So why the "refs/bundles/main" is not discovered? After some digging I
found that:
1. Bundles in bundle list are downloaded to local files via
`bundle-uri.c:download_bundle_list` or via
`bundle-uri.c:fetch_bundles_by_token` for the "creationToken"
heuristic.
2. Each bundle is unbundled via `bundle-uri.c:unbundle_from_file`, which
is called by `bundle-uri.c:unbundle_all_bundles` or called within
`bundle-uri.c:fetch_bundles_by_token` for the "creationToken"
heuristic.
3. To get all prerequisites of the bundle, the bundle header is read
inside `bundle-uri.c:unbundle_from_file` to by calling
`bundle.c:read_bundle_header`.
4. Then it calls `bundle.c:unbundle`, which calls
`bundle.c:verify_bundle` to ensure the repository contains all the
prerequisites.
5. `bundle.c:verify_bundle` calls `parse_object`, which eventually
invokes `packfile.c:prepare_packed_git` or
`packfile.c:reprepare_packed_git`, filling
`raw_object_store->packed_git` and setting `packed_git_initialized`.
6. If `bundle.c:unbundle` succeeds, it writes refs via
`refs.c:refs_update_ref` with `REF_SKIP_OID_VERIFICATION` set. Here
bundle refs which can target arbitrary objects are written to the
repository.
7. Finally, in `fetch-pack.c:do_fetch_pack_v2`, the functions
`fetch-pack.c:mark_complete_and_common_ref` and
`fetch-pack.c:mark_tips` are called with `OBJECT_INFO_QUICK` set to
find local tips for negotiation. The `OBJECT_INFO_QUICK` flag
prevents `packfile.c:reprepare_packed_git` from being called,
resulting in failures to parse OIDs that reside only in the latest
bundle.
In the example above, when unbunding "incr.bundle", "base.pack" is added
to `packed_git` due to prerequisites verification. However, "B" cannot
be found for negotiation because it exists in "incr.pack", which is not
included in `packed_git`.
This commit fixes the bug by removing `REF_SKIP_OID_VERIFICATION` flag
when writing bundle refs. When `refs.c:refs_update_ref` is called to to
write the corresponding bundle refs, it triggers
`refs.c:ref_transaction_commit`. This, in turn, invokes
`refs.c:ref_transaction_prepare`, which calls `transaction_prepare` of
the refs storage backend. For files backend, this function is
`files-backend.c:files_transaction_prepare`, and for reftable backend,
it is `reftable-backend.c:reftable_be_transaction_prepare`. Both
functions eventually call `object.c:parse_object`, which can invoke
`packfile.c:reprepare_packed_git` to refresh `packed_git`. This ensures
that bundle refs point to valid objects and that all tips from bundle
refs are correctly parsed during subsequent negotiations.
A test has been added to demonstrate that bundles with incorrect
headers, where refs point to non-existent objects, do not result in any
bundle refs being created in the repository. Additionally, a set of
negotiation-related tests for fetching with bundle-uri has been
included.
Reviewed-by: Karthik Nayak <karthik.188@xxxxxxxxx>
Reviewed-by: Patrick Steinhardt <ps@xxxxxx>
Signed-off-by: Xing Xin <xingxin.xx@xxxxxxxxxxxxx>
---
bundle-uri.c | 3 +-
t/t5558-clone-bundle-uri.sh | 153 +++++++++++++++++++++++++++++++++++-
2 files changed, 150 insertions(+), 6 deletions(-)
diff --git a/bundle-uri.c b/bundle-uri.c
index 91b3319a5c1..65666a11d9c 100644
--- a/bundle-uri.c
+++ b/bundle-uri.c
@@ -400,8 +400,7 @@ static int unbundle_from_file(struct repository *r, const char *file)
refs_update_ref(get_main_ref_store(the_repository),
"fetched bundle", bundle_ref.buf, oid,
has_old ? &old_oid : NULL,
- REF_SKIP_OID_VERIFICATION,
- UPDATE_REFS_MSG_ON_ERR);
+ 0, UPDATE_REFS_MSG_ON_ERR);
}
bundle_header_release(&header);
diff --git a/t/t5558-clone-bundle-uri.sh b/t/t5558-clone-bundle-uri.sh
index 1ca5f745e73..8f4f802e4f1 100755
--- a/t/t5558-clone-bundle-uri.sh
+++ b/t/t5558-clone-bundle-uri.sh
@@ -19,10 +19,19 @@ test_expect_success 'fail to clone from non-bundle file' '
test_expect_success 'create bundle' '
git init clone-from &&
- git -C clone-from checkout -b topic &&
- test_commit -C clone-from A &&
- test_commit -C clone-from B &&
- git -C clone-from bundle create B.bundle topic
+ (
+ cd clone-from &&
+ git checkout -b topic &&
+
+ test_commit A &&
+ git bundle create A.bundle topic &&
+
+ test_commit B &&
+ git bundle create B.bundle topic &&
+
+ # Create a bundle with reference pointing to non-existent object.
+ sed "s/$(git rev-parse A)/$(git rev-parse B)/" <A.bundle >bad-header.bundle
+ )
'
test_expect_success 'clone with path bundle' '
@@ -33,6 +42,16 @@ test_expect_success 'clone with path bundle' '
test_cmp expect actual
'
+test_expect_success 'clone with bundle that has bad header' '
+ git clone --bundle-uri="clone-from/bad-header.bundle" \
+ clone-from clone-bad-header 2>err &&
+ # Write bundle ref fails, but clone can still proceed.
+ commit_b=$(git -C clone-from rev-parse B) &&
+ test_grep "trying to write ref '\''refs/bundles/topic'\'' with nonexistent object $commit_b" err &&
+ git -C clone-bad-header for-each-ref --format="%(refname)" >refs &&
+ ! grep "refs/bundles/" refs
+'
+
test_expect_success 'clone with path bundle and non-default hash' '
test_when_finished "rm -rf clone-path-non-default-hash" &&
GIT_DEFAULT_HASH=sha256 git clone --bundle-uri="clone-from/B.bundle" \
@@ -259,6 +278,132 @@ test_expect_success 'clone bundle list (file, any mode, all failures)' '
! grep "refs/bundles/" refs
'
+#########################################################################
+# Clone negotiation related tests begin here
+
+test_expect_success 'negotiation: bundle with part of wanted commits' '
+ test_when_finished rm -rf trace*.txt &&
+ GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+ git clone --no-local --bundle-uri="clone-from/A.bundle" \
+ clone-from nego-bundle-part &&
+ git -C nego-bundle-part for-each-ref --format="%(refname)" >refs &&
+ grep "refs/bundles/" refs >actual &&
+ cat >expect <<-\EOF &&
+ refs/bundles/topic
+ EOF
+ test_cmp expect actual &&
+ # Ensure that refs/bundles/topic are sent as "have".
+ grep "clone> have $(git -C clone-from rev-parse A)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle with all wanted commits' '
+ test_when_finished rm -rf trace*.txt &&
+ GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+ git clone --no-local --single-branch --branch=topic --no-tags \
+ --bundle-uri="clone-from/B.bundle" \
+ clone-from nego-bundle-all &&
+ git -C nego-bundle-all for-each-ref --format="%(refname)" >refs &&
+ grep "refs/bundles/" refs >actual &&
+ cat >expect <<-\EOF &&
+ refs/bundles/topic
+ EOF
+ test_cmp expect actual &&
+ # We already have all needed commits so no "want" needed.
+ ! grep "clone> want " trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list (no heuristic)' '
+ test_when_finished rm -f trace*.txt &&
+ cat >bundle-list <<-EOF &&
+ [bundle]
+ version = 1
+ mode = all
+
+ [bundle "bundle-1"]
+ uri = file://$(pwd)/clone-from/bundle-1.bundle
+
+ [bundle "bundle-2"]
+ uri = file://$(pwd)/clone-from/bundle-2.bundle
+ EOF
+
+ GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+ git clone --no-local --bundle-uri="file://$(pwd)/bundle-list" \
+ clone-from nego-bundle-list-no-heuristic &&
+
+ git -C nego-bundle-list-no-heuristic for-each-ref --format="%(refname)" >refs &&
+ grep "refs/bundles/" refs >actual &&
+ cat >expect <<-\EOF &&
+ refs/bundles/base
+ refs/bundles/left
+ EOF
+ test_cmp expect actual &&
+ grep "clone> have $(git -C nego-bundle-list-no-heuristic rev-parse refs/bundles/left)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list (creationToken)' '
+ test_when_finished rm -f trace*.txt &&
+ cat >bundle-list <<-EOF &&
+ [bundle]
+ version = 1
+ mode = all
+ heuristic = creationToken
+
+ [bundle "bundle-1"]
+ uri = file://$(pwd)/clone-from/bundle-1.bundle
+ creationToken = 1
+
+ [bundle "bundle-2"]
+ uri = file://$(pwd)/clone-from/bundle-2.bundle
+ creationToken = 2
+ EOF
+
+ GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+ git clone --no-local --bundle-uri="file://$(pwd)/bundle-list" \
+ clone-from nego-bundle-list-heuristic &&
+
+ git -C nego-bundle-list-heuristic for-each-ref --format="%(refname)" >refs &&
+ grep "refs/bundles/" refs >actual &&
+ cat >expect <<-\EOF &&
+ refs/bundles/base
+ refs/bundles/left
+ EOF
+ test_cmp expect actual &&
+ grep "clone> have $(git -C nego-bundle-list-heuristic rev-parse refs/bundles/left)" trace-packet.txt
+'
+
+test_expect_success 'negotiation: bundle list with all wanted commits' '
+ test_when_finished rm -f trace*.txt &&
+ cat >bundle-list <<-EOF &&
+ [bundle]
+ version = 1
+ mode = all
+ heuristic = creationToken
+
+ [bundle "bundle-1"]
+ uri = file://$(pwd)/clone-from/bundle-1.bundle
+ creationToken = 1
+
+ [bundle "bundle-2"]
+ uri = file://$(pwd)/clone-from/bundle-2.bundle
+ creationToken = 2
+ EOF
+
+ GIT_TRACE_PACKET="$(pwd)/trace-packet.txt" \
+ git clone --no-local --single-branch --branch=left --no-tags \
+ --bundle-uri="file://$(pwd)/bundle-list" \
+ clone-from nego-bundle-list-all &&
+
+ git -C nego-bundle-list-all for-each-ref --format="%(refname)" >refs &&
+ grep "refs/bundles/" refs >actual &&
+ cat >expect <<-\EOF &&
+ refs/bundles/base
+ refs/bundles/left
+ EOF
+ test_cmp expect actual &&
+ # We already have all needed commits so no "want" needed.
+ ! grep "clone> want " trace-packet.txt
+'
+
#########################################################################
# HTTP tests begin here
--
gitgitgadget
