The issue is caused by 59a0236da4 commit.
The initial intention of the commit was to speed up
"mariabackup --prepare".
The call stack of binlog position reading is the following:
▾ trx_rseg_mem_restore
▾ trx_rseg_array_init
▾ trx_lists_init_at_db_start
▸ srv_start
Both trx_lists_init_at_db_start() and trx_rseg_mem_restore() contain
special cases for srv_operation == SRV_OPERATION_RESTORE condition, and
on this condition only rseg headers are read to parse binlog position.
Performance impact is not so big.
The solution is to revert 59a0236da4.
mariabackup does not load dictionary during backup, but it loads
tablespaces, that is why fil_system.max_assigned_id is not set with
dict_check_tablespaces_and_store_max_id(). There is no sense to issue the
warning during backup.
- Store the deferred tablespace name while loading the tablespace
for backup process.
- Mariabackup stores the list of space ids which has page0 INIT_PAGE
records. backup_first_page_op() and first_page_init() was introduced
to track the page0 INIT_PAGE records.
- backup_file_op() and log_file_op() was changed to handle
FILE_MODIFY redo log records. It is used to identify the
deferred tablespace space id.
- Whenever file operation redo log was processed by backup,
backup_file_op() should check whether the space name exist
in deferred tablespace. If it is then it needs to store the
space id, name when FILE_MODIFY, FILE_RENAME redo log processed
and it should delete the tablespace name from defer list in other
cases.
- backup_fix_ddl() should check whether deferred tablespace has
any page0 init records. If it is then consider the tablespace
as newly created tablespace. If not then backup should try
to reload the tablespace with SRV_BACKUP_NO_DEFER mode to
avoid the deferring of tablespace.
The InnoDB DATA DIRECTORY attribute is not implemented via
symbolic links but something similar, *.isl files that contain
the names of data files.
InnoDB failed to ignore the DATA DIRECTORY attribute even though
the server was started with --skip-symbolic-links.
Native ALTER TABLE in InnoDB will retain the DATA DIRECTORY attribute
of the table, no matter if the table will be rebuilt or not.
Generic ALTER TABLE (with ALGORITHM=COPY) as well as TRUNCATE TABLE
will discard the DATA DIRECTORY attribute.
All tests have been run with and without the ./mtr option
--mysqld=--skip-symbolic-links
and some tests that use the InnoDB DATA DIRECTORY attribute
have been adjusted for this.
MDEV-26193 exposed a race condition in the test
mariabackup.log_page_corruption by no longer waking up purge tasks
on every transaction commit. (Note that there never was a guarantee
that the purge tasks would actually run as quickly as the test expected
it to happen; that would depend on the CPU load.)
If an ALTER TABLE that affected a table with FULLTEXT INDEX was
in progress while a backup was made, InnoDB would crash or hang
during the first startup after restoring the backup,
while trying to drop the #sql-alter- table for the DDL operation.
drop_garbage_tables_after_restore(): Invoke dict_sys.unlock()
before invoking the FTS functions. Also, invoke purge_sys.stop_FTS()
in debug builds to silence debug assertions. (Purge is not yet
running at this point.)
The issue was that we sent two different signals to different threads
after each other. The DEBUG_SYNC functionality cannot handle this (as
the signal is stored in a global variable) and the first one can get
lost.
Fixed by using the same signal for both threads.
In commit 1c5ae99194 (MDEV-25666)
we had changed Mariabackup so that it would no longer skip files
whose names start with #sql. This turned out to be wrong.
Because operations on such named files are not protected by any
locks in the server, it is not safe to copy them.
Not copying the files may make the InnoDB data dictionary
inconsistent with the file system. So, we must do something
in InnoDB to adjust for that.
If InnoDB is being started up without the redo log (ib_logfile0)
or with a zero-length log file, we will assume that the server
was restored from a backup, and adjust things as follows:
dict_check_sys_tables(), fil_ibd_open(): Do not complain about
missing #sql files if they would be dropped a little later.
dict_stats_update_if_needed(): Never add #sql tables to
the recomputing queue. This avoids a potential race condition when
dropping the garbage tables.
drop_garbage_tables_after_restore(): Try to drop any garbage tables.
innodb_ddl_recovery_done(): Invoke drop_garbage_tables_after_restore()
if srv_start_after_restore (a new flag) was set and we are not in
read-only mode (innodb_read_only=ON or innodb_force_recovery>3).
The tests and dbug_mariabackup_event() instrumentation
were developed by Vladislav Vaintroub, who also reviewed this.
Problem:
=======
When the semisync master is crashed and restarted as slave it could
recover transactions that former slaves may never have seen.
A known method existed to clear out all prepared transactions
with --tc-heuristic-recover=rollback does not care to adjust
binlog accordingly.
Fix:
===
The binlog-based recovery is made to concern of the slave semisync role of
post-crash restarted server.
No changes in behavior is done to the "normal" binloggging server
and the semisync master.
When the restarted server is configured with
--rpl-semi-sync-slave-enabled=1
the refined recovery attempts to roll back prepared transactions
and truncate binlog accordingly.
In case of a partially committed (that is committed at least
in one of the engine participants) such transaction gets committed.
It's guaranteed no (partially as well) committed transactions
exist beyond the truncate position.
In case there exists a non-transactional replication event
(being in a way a committed transaction) past the
computed truncate position the recovery ends with an error.
As after master crash and failover to slave, the demoted-to-slave
ex-master must be ready to face and accept its own (generated by)
events, without generally necessary --replicate-same-server-id.
So the acceptance conditions are relaxed for the semisync slave
to accept own events without that option.
While gtid_strict_mode ON ensures no duplicate transaction can be
(re-)executed the master_use_gtid=none slave has to be
configured with --replicate-same-server-id.
*NOTE* for reviewers.
This patch does not handle the user XA which is done
in next git commit.
Many InnoDB data dictionary cache operations require that the
table name be copied so that it will be NUL terminated.
(For example, SYS_TABLES.NAME is not guaranteed to be NUL-terminated.)
dict_table_t::is_garbage_name(): Check if a name belongs to
the background drop table queue.
dict_check_if_system_table_exists(): Remove.
dict_sys_t::load_sys_tables(): Load the non-hard-coded system tables
SYS_FOREIGN, SYS_FOREIGN_COLS, SYS_VIRTUAL on startup.
dict_sys_t::create_or_check_sys_tables(): Replaces
dict_create_or_check_foreign_constraint_tables() and
dict_create_or_check_sys_virtual().
dict_sys_t::load_table(): Replaces dict_table_get_low()
and dict_load_table().
dict_sys_t::find_table(): Renamed from get_table().
dict_sys_t::sys_tables_exist(): Check whether all the non-hard-coded
tables SYS_FOREIGN, SYS_FOREIGN_COLS, SYS_VIRTUAL exist.
trx_t::has_stats_table_lock(): Moved to dict0stats.cc.
Some error messages will now report table names in the internal
databasename/tablename format, instead of `databasename`.`tablename`.
The problem was that tdc_remove_referenced_share() did not take into
account that someone could push things into share->free_tables() even
if there is a MDL_EXCLUSIVE lock on the table.
This can happen if flush_tables() uses the table cache to flush a
a non transactional table to disk.
During data file creation, InnoDB holds dict_sys mutex, tries to
write page 0 of the file and flushes the file. This not only causing
unnecessary contention but also a deviation from the write-ahead
logging protocol.
The clean sequence of operations is that we first start a dictionary
transaction and write SYS_TABLES and SYS_INDEXES records that identify
the tablespace. Then, we durably write a FILE_CREATE record to the
write-ahead log and create the file.
Recovery should not unnecessarily insist that the first page of each
data file that is referred to by the redo log is valid. It must be
enough that page 0 of the tablespace can be initialized based on the
redo log contents.
We introduce a new data structure deferred_spaces that keeps track
of corrupted-looking files during recovery. The data structure holds
the last LSN of a FILE_ record referring to the data file, the
tablespace identifier, and the last known file name.
There are two scenarios can happen during recovery:
i) Sufficient memory: InnoDB can reconstruct the
tablespace after parsing all redo log records.
ii) Insufficient memory(multiple apply phase): InnoDB should
store the deferred tablespace redo logs even though
tablespace is not present. InnoDB should start constructing
the tablespace when it first encounters deferred tablespace
id.
Mariabackup copies the zero filled ibd file in backup_fix_ddl() as
the extension of .new file. Mariabackup test case does page flushing
when it deals with DDL operation during backup operation.
fil_ibd_create(): Remove the write of page0 and flushing of file
fil_ibd_load(): Return FIL_LOAD_DEFER if the tablespace has
zero filled page0
Datafile: Clean up the error handling, and do not report errors
if we are in the middle of recovery. The caller will check
Datafile::m_defer.
fil_node_t::deferred: Indicates whether the tablespace loading was
deferred during recovery
FIL_LOAD_DEFER: Returned by fil_ibd_load() to indicate that tablespace
file was cannot be loaded.
recv_sys_t::recover_deferred(): Invoke deferred_spaces.create() to
initialize fil_space_t based on buffered metadata and records to
initialize page 0. Ignore the flags in fil_name_t, because they are
intentionally invalid.
fil_name_process(): Update deferred_spaces.
recv_sys_t::parse(): Store the redo log if the tablespace id
is present in deferred spaces
recv_sys_t::recover_low(): Should recover the first page of
the tablespace even though the tablespace instance is not
present
recv_sys_t::apply(): Initialize the deferred tablespace
before applying the deferred tablespace records
recv_validate_tablespace(): Skip the validation for deferred_spaces.
recv_rename_files(): Moved and revised from recv_sys_t::apply().
For deferred-recovery tablespaces, do not attempt to rename the
file if a deferred-recovery tablespace is associated with the name.
recv_recovery_from_checkpoint_start(): Invoke recv_rename_files()
and initialize all deferred tablespaces before applying redo log.
fil_node_t::read_page0(): Skip page0 validation if the tablespace
is deferred
buf_page_create_deferred(): A variant of buf_page_create() when
the fil_space_t is not available yet
This is joint work with Thirunarayanan Balathandayuthapani,
who implemented an initial prototype.
During the prepare phase of restoring backups, "mariabackup" does
not seem to allow (or recognize) the option "innodb_force_recovery"
for the embedded InnoDB server instance that it starts.
If page corruption observed during page recovery, the prepare step
fails. While this is indeed the correct behavior ideally, allowing
this option to be set in case of emergencies might be useful when
the current backup is the only copy available. Some error messages
during "--prepare" suggest to set "innodb_force_recovery" to 1:
[ERROR] InnoDB: Set innodb_force_recovery=1 to ignore corruption.
For backwards compatibility, "mariabackup --innobackupex --apply-log"
should also have this option.
Signed-off-by: Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>
btr_cur_upd_rec_in_place(): Prefer WRITE to MEMSET for a single-byte
operation.
log_phys_t::apply(): Relax the assertion to allow a single-byte MEMSET,
even though it is 1 byte longer than a WRITE record.
We implement an idea that was suggested by Michael 'Monty' Widenius
in October 2017: When InnoDB is inserting into an empty table or partition,
we can write a single undo log record TRX_UNDO_EMPTY, which will cause
ROLLBACK to clear the table.
For this to work, the insert into an empty table or partition must be
covered by an exclusive table lock that will be held until the transaction
has been committed or rolled back, or the INSERT operation has been
rolled back (and the table is empty again), in lock_table_x_unlock().
Clustered index records that are covered by the TRX_UNDO_EMPTY record
will carry DB_TRX_ID=0 and DB_ROLL_PTR=1<<55, and thus they cannot
be distinguished from what MDEV-12288 leaves behind after purging the
history of row-logged operations.
Concurrent non-locking reads must be adjusted: If the read view was
created before the INSERT into an empty table, then we must continue
to imagine that the table is empty, and not try to read any records.
If the read view was created after the INSERT was committed, then
all records must be visible normally. To implement this, we introduce
the field dict_table_t::bulk_trx_id.
This special handling only applies to the very first INSERT statement
of a transaction for the empty table or partition. If a subsequent
statement in the transaction is modifying the initially empty table again,
we must enable row-level undo logging, so that we will be able to
roll back to the start of the statement in case of an error (such as
duplicate key).
INSERT IGNORE will continue to use row-level logging and locking, because
implementing it would require the ability to roll back the latest row.
Since the undo log that we write only allows us to roll back the entire
statement, we cannot support INSERT IGNORE. We will introduce a
handler::extra() parameter HA_EXTRA_IGNORE_INSERT to indicate to storage
engines that INSERT IGNORE is being executed.
In many test cases, we add an extra record to the table, so that during
the 'interesting' part of the test, row-level locking and logging will
be used.
Replicas will continue to use row-level logging and locking until
MDEV-24622 has been addressed. Likewise, this optimization will be
disabled in Galera cluster until MDEV-24623 enables it.
dict_table_t::bulk_trx_id: The latest active or committed transaction
that initiated an insert into an empty table or partition.
Protected by exclusive table lock and a clustered index leaf page latch.
ins_node_t::bulk_insert: Whether bulk insert was initiated.
trx_t::mod_tables: Use C++11 style accessors (emplace instead of insert).
Unlike earlier, this collection will cover also temporary tables.
trx_mod_table_time_t: Add start_bulk_insert(), end_bulk_insert(),
is_bulk_insert(), was_bulk_insert().
trx_undo_report_row_operation(): Before accessing any undo log pages,
invoke trx->mod_tables.emplace() in order to determine whether undo
logging was disabled, or whether this is the first INSERT and we are
supposed to write a TRX_UNDO_EMPTY record.
row_ins_clust_index_entry_low(): If we are inserting into an empty
clustered index leaf page, set the ins_node_t::bulk_insert flag for
the subsequent trx_undo_report_row_operation() call.
lock_rec_insert_check_and_lock(), lock_prdt_insert_check_and_lock():
Remove the redundant parameter 'flags' that can be checked in the caller.
btr_cur_ins_lock_and_undo(): Simplify the logic. Correctly write
DB_TRX_ID,DB_ROLL_PTR after invoking trx_undo_report_row_operation().
trx_mark_sql_stat_end(), ha_innobase::extra(HA_EXTRA_IGNORE_INSERT),
ha_innobase::external_lock(): Invoke trx_t::end_bulk_insert() so that
the next statement will not be covered by table-level undo logging.
ReadView::changes_visible(trx_id_t) const: New accessor for the case
where the trx_id_t is not read from a potentially corrupted index page
but directly from the memory. In this case, we can skip a sanity check.
row_sel(), row_sel_try_search_shortcut(), row_search_mvcc():
row_sel_try_search_shortcut_for_mysql(),
row_merge_read_clustered_index(): Check dict_table_t::bulk_trx_id.
row_sel_clust_sees(): Replaces lock_clust_rec_cons_read_sees().
lock_sec_rec_cons_read_sees(): Replaced with lower-level code.
btr_root_page_init(): Refactored from btr_create().
dict_index_t::clear(), dict_table_t::clear(): Empty an index or table,
for the ROLLBACK of an INSERT operation.
ROW_T_EMPTY, ROW_OP_EMPTY: Note a concurrent ROLLBACK of an INSERT
into an empty table.
This is joint work with Thirunarayanan Balathandayuthapani,
who created a working prototype.
Thanks to Matthias Leich for extensive testing.
