ASSERTION THD->TRANSACTION.XID_STATE.XID.IS_NULL()
FAILED
The triggered assert checks that the previous XA transaction has
done proper cleanup before a new XA transaction is started.
The bug that caused it to be triggered was that XA COMMIT did not
clean up error state if XA COMMIT discovered that the current XA
transaction had to be rolled back.
This patch fixes the problem by resetting the XA error state
before XA COMMIT calls ha_rollback_trans(). This allows following
XA transactions to be started without triggering the assert.
Test case added to xa.test.
TRX->CONC_STATE == 0 || TRX->CONC_STATE == 1
This bug was a different manifestation of Bug#11766752,
which was previously only fixed on mysql-trunk.
This patch backports the fix for Bug#11766752 to mysql-5.5,
which fixes the problem. The patch also adds some extra test
coverage.
Assert in Diagnostics_area::set_ok_status() for XA COMMIT
This assert was triggered if XA COMMIT was issued when an XA transaction
already had encountered an error (e.g. a deadlock) which required
the XA transaction to be rolled back.
In general, the assert is triggered if a statement tries to send OK to
the client when an error has already been reported. It was triggered
in this case because the trans_xa_commit() function first reported an
error, then rolled back the transaction and finally returned FALSE,
indicating success. Since trans_xa_commit() reported success,
mysql_execute_command() tried to report OK, triggering the assert.
This patch fixes the problem by fixing trans_xa_commit() to return TRUE
if it encounters an error that requires rollback, even if the rollback
itself is successful.
Test case added to xa.test.
The problem was that issuing XA END when the XA transaction was
already ended, caused an assertion. This assertion tests that
the server does not try to send OK to the client if there has
already been an error reported. The bug was only noticeable on
debug versions of the server.
The reason for the problem was that the trans_xa_end() function
reported success if the transaction was at XA_IDLE state at the
end regardless of any errors occured during processing of
trans_xa_end(). So if the transaction state was XA_IDLE already,
reported errors would be ignored.
This patch fixes the problem by having trans_xa_end() take into
consideration any reported errors. The patch also fixes a similar
bug with XA PREPARE.
Test case added to xa.test.
SET autocommit=1 while XA transaction is active may
cause various side effects, including memory corruption
and server crash.
The problem is that SET autocommit=1 and further queries
attempt to commit local transaction, whereas XA transaction
is still active.
As local and XA transactions are mutually exclusive, this
patch forbids enabling autocommit mode while XA transaction
is active.
XA START may cause assertion failure/server crash when it is called
after unilateral roll back issued by the Resource Manager (both
in regular transaction and after XA transaction).
The problem was that rm_error variable wasn't set/reset properly.
The problem is that the one phase commit function failed to
properly end a empty transaction. The solution is to ensure
that the transaction cleanup procedure is invoked even for
empty transactions.
The problem is that when a optimization of read-only transactions
(bypass 2-phase commit) was implemented, it removed the code that
reseted the XID once a transaction wasn't active anymore:
sql/sql_parse.cc:
- bzero(&thd->transaction.stmt, sizeof(thd->transaction.stmt));
- if (!thd->active_transaction())
- thd->transaction.xid_state.xid.null();
+ thd->transaction.stmt.reset();
This mostly worked fine as the transaction commit and rollback
functions (in handler.cc) reset the XID once the transaction is
ended. But those functions wouldn't reset the XID in case of
a empty transaction, leading to a assertion when a new starting
a new XA transaction.
The solution is to ensure that the XID state is reset when empty
transactions are ended (by either commit or rollback). This is
achieved by reorganizing the code so that the transaction cleanup
routine is invoked whenever a transaction is ended.
The problem was that the server did not robustly handle a
unilateral roll back issued by the Resource Manager (RM)
due to a resource deadlock within the transaction branch.
By not acknowledging the roll back, the server (TM) would
eventually corrupt the XA transaction state and crash.
The solution is to mark the transaction as rollback-only
if the RM indicates that it rolled back its branch of the
transaction.
