This patch changes how old rows in mysql.gtid_slave_pos* tables are deleted.
Instead of doing it as part of every replicated transaction in
record_gtid(), it is done periodically (every @@gtid_cleanup_batch_size
transaction) in the slave background thread.
This removes the deletion step from the replication process in SQL or worker
threads, which could speed up replication with many small transactions. It
also decreases contention on the global mutex LOCK_slave_state. And it
simplifies the logic, eg. when a replicated transaction fails after having
deleted old rows.
With this patch, the deletion of old GTID rows happens asynchroneously and
slightly non-deterministic. Thus the number of old rows in
mysql.gtid_slave_pos can temporarily exceed @@gtid_cleanup_batch_size. But
all old rows will be deleted eventually after sufficiently many new GTIDs
have been replicated.
There was a failure in rpl_delayed_slave after recent MDEV-14528 commit.
The parallel applier should not set its
Relay_log::last_master_timestamp from Format-descriptor log event.
The latter may reflect a deep past so Seconds-behind-master will be
computed through it and displayed all time while the first possibly
"slow" group of events is executed.
The main MDEV-14528 is refined, rpl_delayed_slave now passes also
in the parallel mode.
When replicated events are from Master unaware of MariaDB GTID their handling by
the Parallel slave misses Seconds_Behind_Master updating.
In the bug condition the Show-Slave-Status' field remains unchanged.
Because in such case event execution is sequential the bug
is fixed with deploying the same logics as in the explicit single-threaded mode
with is to set
Relay_log_event::last_master_timestamp
member early at the end of event reading from the relay log.
Replicated transaction extra gtid statement on slave failed to specify
an engine gtid_slave_pos name correctly. In case lower-case-table-names > 0
the InnoDB table name was generated to reproduce the lower-case-table-names=0 version
which is of mixed cases.
In rpl.rpl_mdev12179 test run this triggered a failure to DROP table which
was due to the innodb table handle was not closed:
InnoDB: Waited XYZ seconds for ref-count on table: `mysql`.`gtid_slave_pos_innodb`
on windows.
The closing issue was caused by having the table registered twice in the table cache,
for its lower- and mixed- case name versions. The DROP-table handler closed only
only one of the cache item to leave the 2nd one active.
(On Linux a failure occurs earlier at attempt to open an expected lower-cased table:
Last_Error: Error during XID COMMIT: failed to update GTID state in mysql.gtid_slave_pos: 1146: Table 'mysql.gtid_slave_pos_InnoDB' doesn't exist
but the table's name as the message shows is not in the right case).
Fixed with consulting lower-case-table-names when the engine gtid-slave-pos table
is created.
Note the lower-case-table-names=a-value created table will not recognized when next
the lower case option changes to a different value.
In 10.4 a follow-up patch is going to lowercase gtid-slave-pos autocreated table
at once at their origination, and a warning is issued in the 10.3 current patch.
Introduced new alter algorithm type called NOCOPY & INSTANT for
inplace alter operation.
NOCOPY - Algorithm refuses any alter operation that would
rebuild the clustered index. It is a subset of INPLACE algorithm.
INSTANT - Algorithm allow any alter operation that would
modify only meta data. It is a subset of NOCOPY algorithm.
Introduce new variable called alter_algorithm. The values are
DEFAULT(0), COPY(1), INPLACE(2), NOCOPY(3), INSTANT(4)
Message to deprecate old_alter_table variable and make it alias
for alter_algorithm variable.
alter_algorithm variable for slave is always set to default.
These test can sporadically show mutex deadlock warnings between LOCK_wsrep_thd
and LOCK_thd_data mutexes. This means that these mutexes can be locked in opposite
order by different threads, and thus result in deadlock situation.
To fix such issue, the locking policy of these mutexes should be revised and
enforced to be uniform. However, a quick code review shows that the number of
lock/unlock operations for these mutexes combined is between 100-200, and all these
mutex invocations should be checked/fixed.
On the other hand, it turns out that LOCK_wsrep_thd is used for protecting access to
wsrep variables of THD (wsrep_conflict_state, wsrep_query_state), whereas LOCK_thd_data
protects query, db and mysys_var variables in THD. Extending LOCK_thd_data to protect
also wsrep variables looks like a viable solution, as there should not be a use case
where separate threads need simultaneous access to wsrep variables and THD data variables.
In this commit LOCK_wsrep_thd mutex is refactored to be replaced by LOCK_thd_data.
By bluntly replacing LOCK_wsrep_thd by LOCK_thd_data, will result in double locking
of LOCK_thd_data, and some adjustements have been performed to fix such situations.
Modern compilers (such as GCC 8) emit warnings that the
'register' keyword is deprecated and not valid C++17.
Let us remove most use of the 'register' keyword.
Code in 'extra/' is not touched.
In this commit we are adding three more status variable to SHOW SLAVE
STATUS. Slave_DDL_Events and Slave_Non_Transactional_Events.
Slave_DDL_Groups:- This status variable counts the occurrence of DDL
statements
Slave_Non_Transactional_Groups:- This variable count the occurrence
of non-transnational event group.
Slave_Transactional_Groups:- This variable count the occurrence
of transnational event group.
Patch Credit:- Kristian Nielsen
Handle string length as size_t, consistently (almost always:))
Change function prototypes to accept size_t, where in the past
ulong or uint were used. change local/member variables to size_t
when appropriate.
This fix excludes rocksdb, spider,spider, sphinx and connect for now.
This was done in, among other things:
- thd->db and thd->db_length
- TABLE_LIST tablename, db, alias and schema_name
- Audit plugin database name
- lex->db
- All db and table names in Alter_table_ctx
- st_select_lex db
Other things:
- Changed a lot of functions to take const LEX_CSTRING* as argument
for db, table_name and alias. See init_one_table() as an example.
- Changed some function arguments from LEX_CSTRING to const LEX_CSTRING
- Changed some lists from LEX_STRING to LEX_CSTRING
- threads_mysql.result changed because process list_db wasn't always
correctly updated
- New append_identifier() function that takes LEX_CSTRING* as arguments
- Added new element tmp_buff to Alter_table_ctx to separate temp name
handling from temporary space
- Ensure we store the length after my_casedn_str() of table/db names
- Removed not used version of rename_table_in_stat_tables()
- Changed Natural_join_column::table_name and db_name() to never return
NULL (used for print)
- thd->get_db() now returns db as a printable string (thd->db.str or "")
commit 3dc3ab1a30 introduced
Rows_event_tracker, using a mismatch of size_t (the native
register width) and my_off_t (the file offset width, usually
64 bits). Use my_off_t both in member fields and member functions.
Problems --------
The slave io thread did not conduct integrity check
for a group of row-based events. Specifically it tolerates missed
terminal block event that must be flagged with STMT_END. Failure to
react on its loss can confuse the applier thread in various ways.
Another potential issue was that there were no check of impossible
second in row Gtid-log-event while the slave io thread is receiving
to be skipped events after reconnect.
Fixes
-----
The slave io thread is made by this patch to track the rows event
STMT_END status.
Whenever at next event reading the IO thread finds out that a preceding
Rows event did not actually had the flag, an
explicit error is issued.
Replication can be resumed after the source of failure is eliminated,
see a provided test.
Note that currently the row-based group integrity check excludes
the compressed version 2 Rows events (which are not generated by MariaDB
master).
Its uncompressed counterpart is manually tested.
The 2nd issue is covered to produce an error in case the io thread
receives a successive Gtid_log_event while it is post-reconnect
skipping.
Other things, mainly to get
create_mysqld_error_find_printf_error tool to work:
- Added protection to not include mysqld_error.h twice
- Include "unireg.h" instead of "mysqld_error.h" in server
- Added protection if ER_XX messages are already defined
- Removed wrong calls to my_error(ER_OUTOFMEMORY) as
my_malloc() and my_alloc will do this automatically
- Added missing %s to ER_DUP_QUERY_NAME
- Removed old and wrong calls to my_strerror() when using
MY_ERROR_ON_RENAME (wrong merge)
- Fixed deadlock error message from Galera. Before the extra
information given to ER_LOCK_DEADLOCK was missing because
ER_LOCK_DEADLOCK doesn't provide any extra information.
I kept #ifdef mysqld_error_find_printf_error_used in sql_acl.h
to make it easy to do this kind of check again in the future
and specifically the ack receiving functionality.
Semisync is turned to be static instead of plugin so its functions
are invoked at the same points as RUN_HOOKS.
The RUN_HOOKS and the observer interface remain to be removed by later
patch.
Todo:
React on killed status by repl_semisync_master.wait_after_sync(). Currently
Repl_semi_sync_master::commit_trx does not check the killed status.
There were few bugfixes found that are present in mysql and its unclear
whether/how they are covered. Those include:
Bug#15985893: GTID SKIPPED EVENTS ON MASTER CAUSE SEMI SYNC TIME-OUTS
Bug#17932935 CALLING IS_SEMI_SYNC_SLAVE() IN EACH FUNCTION CALL
HAS BAD PERFORMANCE
Bug#20574628: SEMI-SYNC REPLICATION PERFORMANCE DEGRADES WITH A HIGH NUMBER OF THREADS
Part of MDEV-13073 AliSQL Optimize performance of semisync
The idea it to use a dedicated lock detecting if there is new data in
the master's binary log instead of the overused LOCK_log.
Changes:
- Use dedicated COND variables for the relay and binary log signaling.
This was needed as we where the old 'update_cond' variable was used
with different mutex's, which could cause deadlocks.
- Relay log uses now COND_relay_log_updated and LOCK_log
- Binary log uses now COND_bin_log_updated and LOCK_binlog_end_pos
- Renamed signal_cnt to relay_signal_cnt (as we now have two signals)
- Added some missing error handling in MYSQL_BIN_LOG::new_file_impl()
- Reformatted some comments with old style
- Renamed m_key_LOCK_binlog_end_pos to key_LOCK_binlog_end_pos
- Changed 'signal_update()' to update_binlog_end_pos() which works for
both relay and binary log
LOCK_thd_data was used to protect both THD data and
ensure that the THD is not deleted while it was in use
This patch moves the THD delete protection to LOCK_thd_kill,
which already protects the THD for kill.
The benefits are:
- More well defined what LOCK_thd_data protects
- LOCK_thd_data usage is now much simpler and easier to verify
- Less chance of deadlocks in SHOW PROCESS LIST as there is less
chance of interactions between mutexes
- Remove not needed LOCK_thread_count from
thd_get_error_context_description()
- Fewer mutex taken for thd->awake()
Other things:
- Don't take mysys->var mutex in show processlist to check if thread
is kill marked
- thd->awake() now automatically takes the LOCK_thd_kill mutex
(Simplifies code)
- Apc uses LOCK_thd_kill instead of LOCK_thd_data
- Remove not used thd_rpl_is_parallel()
- Remove not used mysql_notify_thread_having_shared_lock()
- Remove not needed LOCK_thread_count from MYSQL_BIN_LOG::reset_logs()
- LOCK_thread_count is not protecting against rollback, so this
code and comment is not needed
- Remove mutex_locks in slave.cc that are not needed.
Added THD::assert_not_linked() to ensure that it was safe to remove
- Fixed not repeatable test load_data_stmt_view
- Updated binlog_killed to test removal of mutex
(thanks to Andrei Elkin for test)
- More code comments
This is about adding more options to force slave retries
Two new variables has been added:
slave_transaction_retry_errors
- Tells the slave thread to retry transaction for replication when a
query event returns an error from the provided list. Deadlock and
elapsed lock wait timeout errors are automatically added to this list
slave-transaction-retry-interval
- Interval of the slave SQL thread will retry a transaction
in case it failed with a deadlock or elapsed lock wait
timeout or listed in slave_transaction_retry_errors
Other changes:
- Simplifed code for slave_skip_errors (to be aligned with
slave_transaction_retry_errors)
- Renamed print_slave_skip_errors() to make_slave_skip_errors_printable()
- Remove printing error from init_slave_skip_errors as my_bitmap_init()
will do that if needed.
- Generalize has_temporary_error()
