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.
This would happen especially in optimistic parallel replication, where there
is a good chance that a transaction will be rolled back (due to conflicts)
after it has executed record_gtid(). If the transaction did any deletions of
old rows as part of record_gtid(), those deletions will be undone as well.
And the code did not properly ensure that the deletions would be re-tried.
This patch makes record_gtid() remember the list of deletions done as part
of a transaction. Then in rpl_slave_state::update() when the changes have
been committed, we discard the list. However, in case of error and rollback,
in cleanup_context() we will instead put the list back into
rpl_global_gtid_slave_state so that the deletions will be re-tried later.
Probably fixes part of the cause of MDEV-12147 as well.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
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.
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 "")
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
- Added sql/mariadb.h file that should be included first by files in sql
directory, if sql_plugin.h is not used (sql_plugin.h adds SHOW variables
that must be done before my_global.h is included)
- Removed a lot of include my_global.h from include files
- Removed include's of some files that my_global.h automatically includes
- Removed duplicated include's of my_sys.h
- Replaced include my_config.h with my_global.h
Intermediate commit.
Fix compilation failure with different my_atomic implementation.
The my_atomic_loadptr* takes void ** as first argument, so variables
updated with it needs to be void * (it is not legal C to cast
some_type ** to void **).
Intermediate commit.
Move the discovery of mysql.gtid_slave_pos* tables into the SQL thread.
This avoids doing things like opening tables and scanning the mysql
schema for tables inside of the START SLAVE statement, which might
interact badly with existing transaction or table locks.
(Even though START SLAVE is documented to implicitly commit any active
transactions, this appears not to be the case in current code).
Table discovery fits naturally in the SQL thread init code, next to
the loading of mysql.gtid_slave_pos state.
Intermediate commit.
Implement auto-creation of mysql.gtid_slave_pos* tables with needed engines,
if listed in --gtid-pos-auto-engines.
Uses an asynchronous approach to minimise locking overhead.
The list of available tables is extended with a flag. Extra entries are
added for --gtid-pos-auto-engines tables that do not exist yet, marked as
not existing but ready for auto-creation.
If record_gtid() needs a table marked for auto-creation, it sends a request
to the slave background thread to create the table, and continues to use an
existing table for the current and immediately coming transactions.
As soon as the slave background thread has made the new table available, it
will be used for all subsequent relevant transactions in record_gtid().
This asynchronous approach also avoids a lot of complex issues around trying
to do DDL in the middle of an on-going transaction.
Intermediate commit.
This commit implements that record_gtid() selects a gtid_slave_posXXX table
with a storage engine already in use by current transaction, if any.
The default table mysql.gtid_slave_pos is used if no match can be found on
storage engine, or for GTID position updates with no specific storage
engine.
Table discovery of mysql.gtid_slave_pos* happens on initial GTID state load
as well as on every START SLAVE. Some effort is made to make this possible
without additional locking. New tables are added using lock-free atomics.
Removing tables requires stopping all slaves first. A warning is given in
the error log when a table is removed but a non-stopped slave still has a
reference to it.
If multiple mysql.gtid_slave_posXXX tables with same storage engine exist,
one is chosen arbitrarily to be used, with a warning in the error log. GTID
data from all tables is still read, but only one among redundant tables with
same storage engine will be updated.
Intermediate commit.
For each GTID recorded in mysq.gtid_slave_pos, keep track of which
engine the update was made in.
This will be later used to know which rows can be deleted in the table
of a given engine.
Intermediate commit.
Keep track of which mysql.gtid_slave_posXXX tables are available for each
engine, by searching for all tables in the mysql schema with names that
start with "gtid_slave_pos".
The list is computed at server start when the GTID position is loaded, and
it is re-computed on every START SLAVE command. This way, the DBA can
manually add a table for a new engine, and it will be automatically picked
up on next START SLAVE, so a full server restart is not needed.
The list is not yet actually used in the code.
Intermediate commit.
On server start, look for and read all tables mysql.gtid_slave_pos* to
restore the GTID position.
Simple test case that moves the data to a new
mysql.gtid_slave_pos_innodb table and verifies that the new table is
read at server start.
Protection added to reopen_file() and new_file_impl().
Without this we could get an assert in fn_format() as name == 0,
because the file was closed and name reset, atthe same time
new_file_impl() was called.
Description:
============
If you have a relay log index file that has ended up with
some relay log files that do not exists, then RESET SLAVE
ALL is not enough to get back to a clean state.
Analysis:
=========
In the bug scenario slave server is in stopped state and
some of the relay logs got deleted but the relay log index
file is not updated.
During slave server restart replication initialization fails
as some of the required relay logs are missing. User
executes RESET SLAVE/RESET SLAVE ALL command to start a
clean slave. As per the documentation RESET SLAVE command
clears the master info and relay log info repositories,
deletes all the relay log files, and starts a new relay log
file. But in a scenario where the slave server's
Relay_log_info object is not initialized slave will not
purge the existing relay logs. Hence the index file still
remains in a bad state. Users will not be able to start
the slave unless these files are cleared.
Fix:
===
RESET SLAVE/RESET SLAVE ALL commands should do the cleanup
even in a scenario where Relay_log_info object
initialization failed.
Backported a flag named 'error_on_rli_init_info' which is
required to identify slave's Relay_log_info object
initialization failure. This flag exists in MySQL-5.6
onwards as part of BUG#14021292 fix.
During RESET SLAVE/RESET SLAVE ALL execution this flag
indicates the Relay_log_info initialization failure.
In such a case open the relay log index/relay log files
and do the required clean up.
This has no functional changes, but it helps avoid merge problems from 10.0
to 10.1. In 10.0, code that checks for parallel replication uses
opt_slave_parallel_threads > 0, but this check needs to be
mi->using_parallel() in 10.1. By using the same check in 10.0 (with
unchanged semantics), merge problems to 10.1 are avoided.
