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/* Copyright (c) 2022, 2025, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License, version 2.0, for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#ifndef XA_SQL_CMD_XA_SECOND_PHASE
#define XA_SQL_CMD_XA_SECOND_PHASE
#include "sql/mdl_context_backup.h" // MDL_context_backup_manager
#include "sql/sql_cmd.h" // Sql_cmd
#include "sql/xa.h" // xid_t
/**
@class Sql_cmd_xa_second_phase
This class abstracts some functionality used by XA statements involved in
the second phase of the the XA two-phase commit, specifically, `XA
COMMIT` and `XA ROLLBACK` SQL statements.
Common usage of the available methods target the process of detached XA
transactions, code pattern looks like:
bool Sql_cmd_xa_statement::process_detached_xa_statement(THD *thd) {
DBUG_TRACE;
if (this->find_and_initialize_xa_context(thd)) return true;
if (this->acquire_locks(thd)) return true;
raii::Sentry<> xa_lock_guard{
[this]() -> void { this->release_locks(); }};
this->setup_thd_context(thd);
if (this->enter_commit_order(thd)) return true;
this->assign_xid_to_thd(thd);
// SPECIFIC STATEMENT EXECUTION HERE
this->m_result = exec_statement(thd);
this->exit_commit_order(thd);
this->cleanup_context(thd);
return this->m_result;
}
@see Sql_cmd
*/
class Sql_cmd_xa_second_phase : public Sql_cmd {
public:
/**
Class constructor.
@param xid_arg XID of the XA transacation about to be committed
*/
Sql_cmd_xa_second_phase(xid_t *xid_arg);
virtual ~Sql_cmd_xa_second_phase() override = default;
protected:
/** The XID associated with the underlying XA transaction. */
xid_t *m_xid{nullptr};
/** The MDL savepoint used to rollback the MDL context when transient errors
occur */
MDL_savepoint m_mdl_savepoint;
/** The detached transaction context, retrieved from the transaction cache */
std::shared_ptr<Transaction_ctx> m_detached_trx_context{nullptr};
/** Whether or not the initialization of GTIDs returned an error */
bool m_gtid_error{false};
/** Whether or not the OWNED_GTID related structures need to be cleaned */
bool m_need_clear_owned_gtid{false};
/** The incremental success of the several initialization and deinitialization
steps. Is mainly used to steer some of the deinitialization calls */
bool m_result{false};
/**
Tries to find and initialize the `Transaction_ctx` for the underlying
detached XA transaction.
Execution is as follows:
1. Find transaction in the transaction cache.
2. Ensure that the underlying state regards the detached XA
transaction.
@param thd The THD session object used to process the detached XA
transaction.
@return false if the transaction context was successfully initialized,
true otherwise.
*/
bool find_and_initialize_xa_context(THD *thd);
/**
Tries to acquire the locks necessary to finalize the underlying
detached XA transaction. By function exit, all locks have been acquired
or none.
Execution is as follows:
1. An MDL savepoint is set, in order to allow the rollback to this
point if a timeout/locking error is triggered.
2. XID_STATE::m_xa_lock is acquired to prevent concurrent finalization
of the transaction (triggered from different client connections, for
instance).
3. Ensure that between steps 1. and 2. some other session didn't
finalize the transaction, by confirming that the transaction is in
the transaction cache and still in prepared state.
4. Acquire MDL commit locks.
@param thd The THD session object used to process the detached XA
transaction.
@return false if all necessary locks were acquired, true otherwise.
*/
bool acquire_locks(THD *thd);
/**
Release any locks acquires in `acquire_locks` still needing
to be released.
*/
void release_locks() const;
/**
Initializes the necessary parts of the `thd` parameter, transferring
some of the detached XA transaction context to the active session. This
is necessary to use other parts of the infra-structure that rely on
having the active THD session properly initialized.
Execution is as follows:
1. Determine if GTID infra-structure is consistent and ready to
finalize the transaction.
2. Check the detached transaction status.
3. Transfer to the THD session object the state of the detached XA
transaction w.r.t whether or not the transaction has already been
binlogged.
@param thd The THD session object used to process the detached XA
transaction.
*/
void setup_thd_context(THD *thd);
/**
For replica applier threads, enters the wait on the commit order.
Execution is as follows:
1. Enters the wait on the commit order.
2. If the wait fails (timeout or possible deadlock found), resets the
overall state to a point where a retry is possible:
a. Resets the GTID infra-structure.
b. Rolls back the MDL context to the recorded savepoint.
c. Resets the transaction binlogging state.
@param thd The THD session object used to process the detached XA
transaction.
@return false if the commit order wait was successful, true otherwise.
*/
bool enter_commit_order(THD *thd);
/**
Sets the XID_STATE of the THD session object parameter as in detached
state and copies into it the XID of the detached XA transaction.
@param thd The THD session object used to process the detached XA
transaction.
*/
void assign_xid_to_thd(THD *thd) const;
/**
For replica applier threads, finishes the wait on the commit order and
allows other threads to proceed.
@param thd The THD session object used to process the detached XA
transaction.
*/
void exit_commit_order(THD *thd) const;
/**
Cleans up the THD context in order to prepare it for re-use.
Execution is as follows:
1. The active THD session binlogging state is cleared.
2. Any MDL context backup, associated with the detached transaction, is
deleted.
3. The detached transaction context is deleted from the transaction
cache.
4. GTID state is finalized, either committing or rolling back the GTID
information.
@param thd The THD session object used to process the detached XA
transaction.
*/
void cleanup_context(THD *thd) const;
/**
Disposes of member variables that need it, because destructors for `Sql_cmd`
classes aren't invoked (since they are created in the internal memory pool,
memory is disposed as a all block).
*/
void dispose();
};
#endif // XA_SQL_CMD_XA_SECOND_PHASE
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