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reftable/stack: gracefully handle failed auto-compaction due to locks

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Whenever we commit a new table to the reftable stack we will end up
invoking auto-compaction of the stack to keep the total number of tables
at bay. This auto-compaction may fail though in case at least one of the
tables which we are about to compact is locked. This is indicated by the
compaction function returning `REFTABLE_LOCK_ERROR`. We do not handle
this case though, and thus bubble that return value up the calling
chain, which will ultimately cause a failure.

Fix this bug by ignoring `REFTABLE_LOCK_ERROR`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Patrick Steinhardt 2024-03-25 11:02:50 +01:00 committed by Junio C Hamano
parent 33358350eb
commit a2f711ade0
3 changed files with 76 additions and 1 deletions
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13
reftable/stack.c
View File

@ -680,8 +680,19 @@ int reftable_addition_commit(struct reftable_addition *add)
if (err)
goto done;
if (!add->stack->disable_auto_compact)
if (!add->stack->disable_auto_compact) {
/*
* Auto-compact the stack to keep the number of tables in
* control. It is possible that a concurrent writer is already
* trying to compact parts of the stack, which would lead to a
* `REFTABLE_LOCK_ERROR` because parts of the stack are locked
* already. This is a benign error though, so we ignore it.
*/
err = reftable_stack_auto_compact(add->stack);
if (err < 0 && err != REFTABLE_LOCK_ERROR)
goto done;
err = 0;
}
done:
reftable_addition_close(add);

44
reftable/stack_test.c
View File

@ -343,6 +343,49 @@ static void test_reftable_stack_transaction_api_performs_auto_compaction(void)
clear_dir(dir);
}
static void test_reftable_stack_auto_compaction_fails_gracefully(void)
{
struct reftable_ref_record ref = {
.refname = "refs/heads/master",
.update_index = 1,
.value_type = REFTABLE_REF_VAL1,
.value.val1 = {0x01},
};
struct reftable_write_options cfg = {0};
struct reftable_stack *st;
struct strbuf table_path = STRBUF_INIT;
char *dir = get_tmp_dir(__LINE__);
int err;
err = reftable_new_stack(&st, dir, cfg);
EXPECT_ERR(err);
err = reftable_stack_add(st, write_test_ref, &ref);
EXPECT_ERR(err);
EXPECT(st->merged->stack_len == 1);
EXPECT(st->stats.attempts == 0);
EXPECT(st->stats.failures == 0);
/*
* Lock the newly written table such that it cannot be compacted.
* Adding a new table to the stack should not be impacted by this, even
* though auto-compaction will now fail.
*/
strbuf_addf(&table_path, "%s/%s.lock", dir, st->readers[0]->name);
write_file_buf(table_path.buf, "", 0);
ref.update_index = 2;
err = reftable_stack_add(st, write_test_ref, &ref);
EXPECT_ERR(err);
EXPECT(st->merged->stack_len == 2);
EXPECT(st->stats.attempts == 1);
EXPECT(st->stats.failures == 1);
reftable_stack_destroy(st);
strbuf_release(&table_path);
clear_dir(dir);
}
static void test_reftable_stack_validate_refname(void)
{
struct reftable_write_options cfg = { 0 };
@ -1089,6 +1132,7 @@ int stack_test_main(int argc, const char *argv[])
RUN_TEST(test_reftable_stack_tombstone);
RUN_TEST(test_reftable_stack_transaction_api);
RUN_TEST(test_reftable_stack_transaction_api_performs_auto_compaction);
RUN_TEST(test_reftable_stack_auto_compaction_fails_gracefully);
RUN_TEST(test_reftable_stack_update_index_check);
RUN_TEST(test_reftable_stack_uptodate);
RUN_TEST(test_reftable_stack_validate_refname);

20
t/t0610-reftable-basics.sh
View File

@ -340,6 +340,26 @@ test_expect_success 'ref transaction: empty transaction in empty repo' '
EOF
'
test_expect_success 'ref transaction: fails gracefully when auto compaction fails' '
test_when_finished "rm -rf repo" &&
git init repo &&
(
cd repo &&
test_commit A &&
for i in $(test_seq 10)
do
git branch branch-$i &&
for table in .git/reftable/*.ref
do
touch "$table.lock" || exit 1
done ||
exit 1
done &&
test_line_count = 13 .git/reftable/tables.list
)
'
test_expect_success 'pack-refs: compacts tables' '
test_when_finished "rm -rf repo" &&
git init repo &&