The hang can happen between a lock connection issuing KILL CONNECTION for a victim,
which is in committing phase.
There happens two resource deadlockwhere killer is holding victim's
LOCK_thd_data and requires trx mutex for the victim.
The victim, otoh, holds his own trx mutex, but requires LOCK_thd_data
in wsrep_commit_ordered(). Hence a classic two thread deadlock happens.
The fix in this commit changes innodb commit so that wsrep_commit_ordered()
is not called while holding trx mutex. With this, wsrep patch commit time mutex
locking does not violate the locking protocol of KILL command
(i.e. LOCK_thd_data -> trx mutex)
Also, a new test case has been added in galera.galera_bf_kill.test for scenario
where a client connection is killed in committting phase.
Problem was that trx->lock.was_chosen_as_wsrep_victim variable was
not set back to false after it was set true.
wsrep_thd_bf_abort
Add assertions for correct mutex status and take necessary
mutexes before calling thd->awake_no_mutex().
innobase_rollback_trx()
Reset trx->lock.was_chosen_as_wsrep_victim
wsrep_abort_slave_trx()
Removed unused function.
wsrep_innobase_kill_one_trx()
Added function comment, removed unnecessary parameters
and added debug assertions to enforce correct usage. Added
more debug output to help out on error analysis.
wsrep_abort_transaction()
Added debug assertions and removed unused variables.
trx0trx.h
Removed assert_trx_is_free macro and replaced it with
assert_freed() member function.
trx_create()
Use above assert_free() and initialize wsrep variables.
trx_free()
Use assert_free()
trx_t::commit_in_memory()
Reset lock.was_chosen_as_wsrep_victim
trx_rollback_for_mysql()
Reset trx->lock.was_chosen_as_wsrep_victim
Add test case galera_bf_kill
This is a backport of the applicable part of
commit 93475aff8d and
commit 2c39f69d34
from 10.4.
Before 10.4 and Galera 4, WSREP_ON is a macro that points to
a global Boolean variable, so it is not that expensive to
evaluate, but we will add an unlikely() hint around it.
WSREP_ON_NEW: Remove. This macro was introduced in
commit c863159c32
when reverting WSREP_ON to its previous definition.
We replace some use of WSREP_ON with WSREP(thd), like it was done
in 93475aff8d. Note: the macro
WSREP() in 10.1 is equivalent to WSREP_NNULL() in 10.4.
Item_func_rand::seed_random(): Avoid invoking current_thd
when WSREP is not enabled.
If a transaction had no effect due to INSERT IGNORE and a new
transaction was started with START TRANSACTION without committing
the previous one, the server crashed on assertion when starting
a new wsrep transaction.
As a fix, refined the condition to do wsrep_commit_empty() at the end
of the ha_commit_trans().
When binlog is disabled, WSREP will not behave correctly when
SAVEPOINT ROLLBACK is executed since we don't register handlers for such case.
Fixed by registering WSREP handlerton for SAVEPOINT related commands.
* Remove dead code
* MDEV-21675 Data inconsistency after multirow insert rollback
This patch fixes data inconsistencies that happen after rollback of
multirow inserts, with binlog disabled.
For example, statements such as `INSERT INTO t1 VALUES (1,'a'),(1,'b')`
that fail with duplicate key error. In such cases the whole statement
is rolled back. However, with wsrep_emulate_binlog in effect, the
IO_CACHE would not be truncated, and the pending rows events would be
replicated to the rest of the cluster. In the above example, it would
result in row (1,'a') being replicated, whereas locally the statement
is rolled back entirely. Making the cluster inconsistent.
The patch changes the code so that prior to statement rollback,
pending rows event are removed and the stmt cache reset.
That patch also introduces MTR tests that excercise multirow insert
statements for regular, and streaming replication.
