MDEV-5217: Incorrect event pos update leading to corruption of reading of events from relay log
The rli->event_relay_log_pos was sometimes undated incorrectly when using
parallel replication, especially around relay log rotates. This could cause
the SQL thread to seek into an invalid position in the relay log, resulting in
errors about invalid events or even random corruption in some cases.
CAN RETURN WRONG RESULT SET
PROBLEM
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In ha_partition::cmp_ref() we were only calling the
underlying cmp_ref() of storage engine if the records
are in the same partiton,else we sort by partition and
returns the result.But the index merge intersect
algorithm expects first to sort by row-id first and
then by partition id.
FIX
---
Compare the refernces first using storage engine cmp_ref
and then if references are equal(only happens if
non clustered index is used) then sort it by partition id.
[Approved by Mattiasj #rb3755]
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MDEV-5217: Last_sql_error lost in parallel replication.
For some reason, the query execution code in log_event.cc call
rli->clear_error for each event (part of clear_all_errors()).
This causes a problem in parallel replication, where the
execution in one worker thread could clear the error set by
another thread, causing the SQL thread to stop but leaving no
error visible in SHOW SLAVE STATUS.
There seems to be no reason to clear the global error code
in Relay_log_info for each event execution, from code review
and from running the test suite. So remove this clearing of
the error code to make things work also in the parallel case.
MDEV-5217: SQL thread hangs during stop if error occurs in the middle of an event group
Normally, when we stop the slave SQL thread in parallel replication, we want
the worker threads to continue processing events until the end of the current
event group. But if we stop due to an error that prevents further events from
being queued, such as an error reading the relay log, no more events can be
queued for the workers, so they have to abort even if they are in the middle
of an event group. There was a bug that we would deadlock, the workers
waiting for more events to be queued for the event group, the SQL thread
stopped and waiting for the workers to complete their current event group
before exiting.
Fixed by now signalling from the SQL thread to all workers when it is about
to exit, and cleaning up in all workers when so signalled.
This patch fixes one of multiple problems reported in MDEV-5217.
- thread_pool_size command line option upper limit increased to 100 000
(same as for max_connections)
- thread_pool_size system variable upper limit is maximum of 128 or
the value given at command line
- thread groups are now allocated dynamically
Different limit for command line option and system variable was done to
avoid additional mutex for all_groups and threadpool_max_size.
extend table names discovery (ha_discover_table_names() and Discovered_table_list) to return
or optionally filter out temporary tables ("#sql..."). SHOW commands and I_S tables
typically want temp table filtered out, while DROP DATABASE wants to see them too.
additonally, remove the supression for the warning "Invalid (old?) table or database name"
from mtr, and add it to .test files as needed (we need to test that this warning
does *not* happen in drop.test)
Updated --help text to declare --slave-parallel-threads as an alpha feature
mysql-test/r/mysqld--help.result:
Updated --help text
sql/slave.cc:
Added missing trans_retries++ that caused rpl_deadlock_innodb.test to fail.
This is safe as this part is never run in parallel.
sql/sql_base.cc:
Fixed temporary table handling (part of merge)
sql/sys_vars.cc:
Updated --help text to declare --slave-parallel-threads as an alpha feature
The merge is still missing a few hunks related to temporary tables and
InnoDB log file size. The associated code did not seem to exist in
10.0, so the merge of that needs more work. Until this is fixed, there
are a number of test failures as a result.
In parallel replication, there are two kinds of events which are
executed in different ways.
Normal events that are part of event groups/transactions are executed
asynchroneously by being queued for a worker thread.
Other events like format description and rotate and such are executed
directly in the driver SQL thread.
If the direct execution of the other events were to update the old-style
position, then the position gets updated too far ahead, before the normal
events that have been queued for a worker thread have been executed. So
this patch adds some special cases to prevent such position updates ahead
of time, and instead queues dummy events for the worker threads, so that
they will at an appropriate time do the position updates instead.
(Also fix a race in a test case that happened to trigger while running
tests for this patch).
Fix a couple of issues in MDEV-4506, Parallel replication:
- Missing mysql_cond_signal(), which could cause hangs.
- Fix incorrect update of old-style replication position.
- Change assertion to error handling (can trigger on manipulated/
corrupt binlog).
There was 2 problems:
1) coping/moving of the same type (usually casting) as sizeof() (solved in different ways depends on the cause);
2) using 'const' in SSL_CTX::getVerifyCallback() which return object (not reference) and so copy of the object will be created and 'const' has no sens.
In parallel replication, when the IO thread switches relay log,
the SQL thread re-opens the current relaylog and seeks to the
current position. There was a race that would cause it to
sometimes seek to the wrong position, causing corruption and
crash.
Analysis:
st_select_lex_unit::prepare() computes can_skip_order_by as TRUE.
As a result join->prepare() gets called with order == NULL, and
doesn't do name resolution for the inner ORDER clause. Due to this
the prepare phase doesn't detect that the query references non-exiting
function and field.
Later join->optimize() calls update_used_tables() for a non-resolved
Item_field, which understandably has no Field object. This call results
in a crash.
Solution:
Resolve unnecessary ORDER BY clauses to detect if they reference non-exising
objects. Then remove such clauses from the JOIN object.
MDEV-5189: Error handling in parallel replication.
Fix error handling in parallel worker threads when a query fails:
- Report the error to the error log.
- Return the error back, and set rli->abort_slave.
- Stop executing more events after the error.
GRANT ... IDENTIFIED BY [ PASSWORD ] ...
GRANT ... IDENTIFIED VIA ... [ USING ... ]
GRANT ... REQUIRE ...
GRANT ... MAX_xxx ...
SET PASSWORD FOR ... = ...
Two problems were fixed:
1. When not in GTID mode (master_use_gtid=no), then we must not apply events
in different domains in parallel (in non-GTID mode we are not capable of
restarting at different points in different domains).
2. When transactions B and C group commit together, but after and separate
from A, we can apply B and C in parallel, but both B and C must not start
until A has committed. Fix sub_id to be globally increasing (not just
per-domain increasing) so that this wait (which is based on sub_id) can be
done correctly.
Do not update relay-log.info and master.info on disk after every event
when using GTID mode:
- relay-log.info and master.info are not crash-safe, and are not used
when slave restarts in GTID mode (slave connects with GTID position
instead and immediately rewrites the file with the new, correct
information found).
- When using GTID and parallel replication, the position in
relay-log.info is misleading at best and simply wrong at worst.
- When using parallel replication, the fact that every single
transaction needs to do a write() syscall to the same file is
likely to become a serious bottleneck.
The files are still written at normal slave stop.
In non-GTID mode, the files are written as normal (this is needed to
be able to restart after slave crash, even if such restart is then not
crash-safe, no change).
- Backport MySQL's fix: do set ha_partition::m_pkey_is_clustered for ha_partition
objects created with handler->clone() call.
- Also, include a testcase.
Fix some more parts of old-style position updates.
Now we save in rgi some coordinates for master log and relay log, so
that in do_update_pos() we can use the right set of coordinates with
the right events.
The Rotate_log_event::do_update_pos() is fixed in the parallel case
to not directly update relay-log.info (as Rotate event runs directly
in the driver SQL thread, ahead of actual event execution). Instead,
group_master_log_file is updated as part of do_update_pos() in each
event execution.
In the parallel case, position updates happen in parallel without
any ordering, but taking care that position is not updated backwards.
Since position update happens only after event execution this leads
to the right result.
Also fix an access-after-free introduced in an earlier commit.
