rpl_semi_sync_slave_enabled_consistent.test and the first part of
the commit message comes from Brandon Nesterenko.
A test to show how to induce the "Read semi-sync reply magic number
error" message on a primary. In short, if semi-sync is turned on
during the hand-shake process between a primary and replica, but
later a user negates the rpl_semi_sync_slave_enabled variable while
the replica's IO thread is running; if the io thread exits, the
replica can skip a necessary call to kill_connection() in
repl_semisync_slave.slave_stop() due to its reliance on a global
variable. Then, the replica will send a COM_QUIT packet to the
primary on an active semi-sync connection, causing the magic number
error.
The test in this patch exits the IO thread by forcing an error;
though note a call to STOP SLAVE could also do this, but it ends up
needing more synchronization. That is, the STOP SLAVE command also
tries to kill the VIO of the replica, which makes a race with the IO
thread to try and send the COM_QUIT before this happens (which would
need more debug_sync to get around). See THD::awake_no_mutex for
details as to the killing of the replica’s vio.
Notes:
- The MariaDB documentation does not make it clear that when one
enables semi-sync replication it does not matter if one enables
it first in the master or slave. Any order works.
Changes done:
- The rpl_semi_sync_slave_enabled variable is now a default value for
when semisync is started. The variable does not anymore affect
semisync if it is already running. This fixes the original reported
bug. Internally we now use repl_semisync_slave.get_slave_enabled()
instead of rpl_semi_sync_slave_enabled. To check if semisync is
active on should check the @@rpl_semi_sync_slave_status variable (as
before).
- The semisync protocol conflicts in the way that the original
MySQL/MariaDB client-server protocol was designed (client-server
send and reply packets are strictly ordered and includes a packet
number to allow one to check if a packet is lost). When using
semi-sync the master and slave can send packets at 'any time', so
packet numbering does not work. The 'solution' has been that each
communication starts with packet number 1, but in some cases there
is still a chance that the packet number check can fail. Fixed by
adding a flag (pkt_nr_can_be_reset) in the NET struct that one can
use to signal that packet number checking should not be done. This
is flag is set when semi-sync is used.
- Added Master_info::semi_sync_reply_enabled to allow one to configure
some slaves with semisync and other other slaves without semisync.
Removed global variable semi_sync_need_reply that would not work
with multi-master.
- Repl_semi_sync_master::report_reply_packet() can now recognize
the COM_QUIT packet from semisync slave and not give a
"Read semi-sync reply magic number error" error for this case.
The slave will be removed from the Ack listener.
- On Windows, don't stop semisync Ack listener just because one
slave connection is using socket_id > FD_SETSIZE.
- Removed busy loop in Ack_receiver::run() by using
"Self-pipe trick" to signal new slave and stop Ack_receiver.
- Changed some Repl_semi_sync_slave functions that always returns 0
from int to void.
- Added Repl_semi_sync_slave::slave_reconnect().
- Removed dummy_function Repl_semi_sync_slave::reset_slave().
- Removed some duplicate semisync notes from the error log.
- Add test of "if (get_slave_enabled() && semi_sync_need_reply)"
before calling Repl_semi_sync_slave::slave_reply().
(Speeds up the code as we can skip all initializations).
- If epl_semisync_slave.slave_reply() fails, we disable semisync
for that connection.
- We do not call semisync.switch_off() if there are no active slaves.
Instead we check in Repl_semi_sync_master::commit_trx() if there are
no active threads. This simplices the code.
- Changed assert() to DBUG_ASSERT() to ensure that the DBUG log is
flushed in case of asserts.
- Removed the internal rpl_semi_sync_slave_status as it is not needed
anymore. The @@rpl_semi_sync_slave_status status variable is now
mapped to rpl_semi_sync_enabled.
- Removed rpl_semi_sync_slave_enabled as it is not needed anymore.
Repl_semi_sync_slave::get_slave_enabled() contains the active status.
- Added checking that we do not add a slave twice with
Ack_receiver::add_slave(). This could happen with old code.
- Removed Repl_semi_sync_master::check_and_switch() as it is not
needed anymore.
- Ensure that when we call Ack_receiver::remove_slave() that the slave
is removed from the listener before function returns.
- Call listener.listen_on_sockets() outside of mutex for better
performance and less contested mutex.
- Ensure that listening is ignoring newly added slaves when checking for
responses.
- Fixed the master ack_receiver listener is not killed if there are no
connected slaves (and thus stop semisync handling of future
connections). This could happen if all slaves sockets where would be
marked as unreliable.
- Added unlink() to base_ilist_iterator and remove() to
I_List_iterator. This enables us to remove 'dead' slaves in
Ack_recever::run().
- kill_zombie_dump_threads() now does killing of dump threads properly.
- It can now kill several threads (should be impossible but could
happen if IO slaves reconnects very fast).
- We now wait until the dump thread is done before starting the
dump.
- Added an error if kill_zombie_dump_threads() fails.
- Set thd->variables.server_id before calling
kill_zombie_dump_threads(). This simplies the code.
- Added a lot of comments both in code and tests.
- Removed DBUG_EVALUATE_IF "failed_slave_start" as it is not used.
Test changes:
- rpl.rpl_session_var2 added which runs rpl.rpl_session_var test with
semisync enabled.
- Some timings changed slight with startup of slave which caused
rpl_binlog_dump_slave_gtid_state_info.text to fail as it checked the
error log file before the slave had started properly. Fixed by
adding wait_for_pattern_in_file.inc that allows waiting for the
pattern to appear in the log file.
- Tests have been updated so that we first set
rpl_semi_sync_master_enabled on the master and then set
rpl_semi_sync_slave_enabled on the slaves (this is according to how
the MariaDB documentation document how to setup semi-sync).
- Error text "Master server does not have semi-sync enabled" has been
replaced with "Master server does not support semi-sync" for the
case when the master supports semi-sync but semi-sync is not
enabled.
Other things:
- Some trivial cleanups in Repl_semi_sync_master::update_sync_header().
- We should in 11.3 changed the default value for
rpl-semi-sync-master-wait-no-slave from TRUE to FALSE as the TRUE
does not make much sense as default. The main difference with using
FALSE is that we do not wait for semisync Ack if there are no slave
threads. In the case of TRUE we wait once, which did not bring any
notable benefits except slower startup of master configured for
using semisync.
Co-author: Brandon Nesterenko <brandon.nesterenko@mariadb.com>
This solves the problem reported in MDEV-32960 where a new
slave may not be registered in time and the master disables
semi sync because of that.
The following tests are disabled when running --valgrding without --big:
- rpl.rpl_ssl
- rpl.rpl_semi_sync_event
- All encryption test (which includes have_file_key_management.inc)
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
Did the following renames to match other similar variables
key_ss_mutex_LOCK_binlog_ > key_LOCK_bing
key_ss_cond_COND_binlog_send_ -> key_COND_binlog_send
COND_binlog_send_ -> COND_binlog_send
LOCK_binlog_ -> LOCK_binlog
debian/mariadb-server-10.2.install does not install semisync libs.
mysql-test/suite/innodb/t/group_commit_crash.test:
remove autoincrement to avoid rbr being used for insert ... select
mysql-test/suite/innodb/t/group_commit_crash_no_optimize_thread.test:
remove autoincrement to avoid rbr being used for insert ... select
mysys/my_addr_resolve.c:
a pointer to a buffer is returned to the caller -> the buffer cannot be on the stack
mysys/stacktrace.c:
my_vsnprintf() is ok here, in 5.5
Problem: Statements that write to tables with auto_increment columns
based on the selection from another table, may lead to master
and slave going out of sync, as the order in which the rows
are retrieved from the table may differ on master and slave.
Solution: We mark writing to a table with auto_increment table
based on the rows selected from another table as unsafe. This
will cause the execution of such statements to throw a warning
and forces the statement to be logged in ROW if the logging
format is mixed.
Changes:
1. All the statements that writes to a table with auto_increment
column(s) based on the rows fetched from another table, will now
be unsafe.
2. CREATE TABLE with SELECT will now be unsafe.
sql/share/errmsg-utf8.txt:
Added new warning messages.
sql/sql_base.cc:
-Created function to check statements that write to
tables with auto_increment column and has select.
-Marked all the statements that write to a table
with auto_increment column based on rows fetched
from other table(s) as unsafe.
sql/sql_table.cc:
mark CREATE TABLE[with auto_increment column] as unsafe.
Problem: Statements that write to tables with auto_increment columns
based on the selection from another table, may lead to master
and slave going out of sync, as the order in which the rows
are retrived from the table may differ on master and slave.
Solution: We mark writing to a table with auto_increment table
as unsafe. This will cause the execution of such statements to
throw a warning and forces the statement to be logged in ROW if
the logging format is mixed.
Changes:
1. All the statements that writes to a table with auto_increment
column(s) based on the rows fetched from another table, will now
be unsafe.
2. CREATE TABLE with SELECT will now be unsafe.
sql/share/errmsg-utf8.txt:
Added new Warning messages
sql/sql_base.cc:
created a new function that checks for select + write on a autoinc table
made all such statements to be unsafe.
sql/sql_parse.cc:
made create autoincremnet tabble + select unsafe
Conflicts:
Text conflict in .bzr-mysql/default.conf
Text conflict in mysql-test/extra/rpl_tests/rpl_loaddata.test
Text conflict in mysql-test/r/mysqlbinlog2.result
Text conflict in mysql-test/suite/binlog/r/binlog_stm_mix_innodb_myisam.result
Text conflict in mysql-test/suite/binlog/r/binlog_unsafe.result
Text conflict in mysql-test/suite/rpl/r/rpl_insert_id.result
Text conflict in mysql-test/suite/rpl/r/rpl_loaddata.result
Text conflict in mysql-test/suite/rpl/r/rpl_stm_auto_increment_bug33029.result
Text conflict in mysql-test/suite/rpl/r/rpl_udf.result
Text conflict in mysql-test/suite/rpl/t/rpl_slow_query_log.test
Text conflict in sql/field.h
Text conflict in sql/log.cc
Text conflict in sql/log_event.cc
Text conflict in sql/log_event_old.cc
Text conflict in sql/mysql_priv.h
Text conflict in sql/share/errmsg.txt
Text conflict in sql/sp.cc
Text conflict in sql/sql_acl.cc
Text conflict in sql/sql_base.cc
Text conflict in sql/sql_class.h
Text conflict in sql/sql_db.cc
Text conflict in sql/sql_delete.cc
Text conflict in sql/sql_insert.cc
Text conflict in sql/sql_lex.cc
Text conflict in sql/sql_lex.h
Text conflict in sql/sql_load.cc
Text conflict in sql/sql_table.cc
Text conflict in sql/sql_update.cc
Text conflict in sql/sql_view.cc
Conflict adding files to storage/innobase. Created directory.
Conflict because storage/innobase is not versioned, but has versioned children. Versioned directory.
Conflict adding file storage/innobase. Moved existing file to storage/innobase.moved.
Conflict adding files to storage/innobase/handler. Created directory.
Conflict because storage/innobase/handler is not versioned, but has versioned children. Versioned directory.
Contents conflict in storage/innobase/handler/ha_innodb.cc
Before this patch, semisync assumed transactions running in parallel
can not be larger than max_connections, but this is not true when
the event scheduler is executing events, and cause semisync run out
of preallocated transaction nodes.
Fix the problem by allocating transaction nodes dynamically.
This patch also fixed a possible deadlock when running UNINSTALL
PLUGIN rpl_semi_sync_master and updating in parallel. Fixed by
releasing the internal Delegate lock before unlock the plugins.
mysql-test/suite/rpl/t/rpl_semi_sync_event.test:
Add test case for bug#49020
plugin/semisync/semisync_master.cc:
Allocating TranxNode dynamically
plugin/semisync/semisync_master.h:
Allocating TranxNode dynamically
sql/rpl_handler.cc:
Unlock plugins after we have released the Delegate lock to avoid possible deadlock when uninstalling semisync master plugin and doing update in parallel.
