Some fixes related to commit f838b2d799 and
Rows_log_event::do_apply_event() and Update_rows_log_event::do_exec_row()
for system-versioned tables were provided by Nikita Malyavin.
This was required by test versioning.rpl,trx_id,row.
When using semi-sync replication with
rpl_semi_sync_master_wait_point=AFTER_COMMIT, the performance of the
primary can significantly reduce compared to AFTER_SYNC's
performance for workloads with many concurrent users executing
transactions. This is because all connections on the primary share
the same cond_wait variable/mutex pair, so any time an ACK is
received from a replica, all waiting connections are awoken to check
if the ACK was for itself, which is done in mutual exclusion.
This patch changes this such that the waiting THD will use its own
local condition variable, and the ACK receiver thread only signals
connections which have been ACKed for wakeup. That is, the
THD::LOCK_wakeup_ready condition variable is re-used for this
purpose, and the Active_tranx queue nodes are extended to hold the
waiting thread, so it can be signalled once ACKed.
Additionally:
1) Removed part of MDEV-11853 additions, which allowed suspended
connection threads awaiting their semi-sync ACKs to live until their
ACKs had been received. This part, however, wasn't needed. That is,
all that was needed was for the Ack_thread to survive. So now the
connection threads are killed during phase 1. Thereby
THD::is_awaiting_semisync_ack, and all its related code was removed.
2) COND_binlog_send is repurposed to signal on the condition when
Active_tranx is emptied during clear_active_tranx_nodes.
3) At master shutdown (when waiting for slaves), instead of the
main loop individually waiting for each ACK, await_slave_reply()
(renamed await_all_slave_replies()) just waits once for the
repurposed COND_binlog_send to signal it is empty.
4) Test rpl_semi_sync_shutdown_await_ack is updates as following:
4.1) Added test case (adapted from Kristian Nielsen) to ensure
that if a thread awaiting its ACK is killed while SHUTDOWN WAIT FOR
ALL SLAVES is issued, the primary will still wait for the ACK from
the killed thread.
4.2) As connections which by-passed phase 1 of thread killing no
longer are delayed for kill until phase 2, we can no longer query
yes/no tx after receiving an ACK/timeout. The check for these
variables is removed.
4.3) Comment descriptions are updated which mention that the
connection is alive; and adjusted to be the Ack_thread.
Reviewed By:
============
Kristian Nielsen <knielsen@knielsen-hq.org>
signal_hand(): Remove the cmake -DWITH_DBUG_TRACE=ON instrumentation.
It can cause a crash on shutdown when the only other thread is
waiting in wait_for_signal_thread_to_end().
This removes the error:
"Failed to load slave replication state from table mysql.gtid_slave_pos:
1017: Can't find file: './mysql/' (errno: 2 "No such file or directory")
my_malloc_size_cb_func() can be called from contexts where it is not safe to
wait for LOCK_thd_kill, for example while holding LOCK_plugin. This could
lead to (probably very unlikely) deadlock of the server.
Fix by skipping the enforcement of --max-session-mem-used in the rare cases
when LOCK_thd_kill cannot be obtained. The limit will instead be enforced on
the following memory allocation. This does not significantly degrade the
behaviour of --max-session-mem-used; that limit is in any case only enforced
"softly", not taking effect until the next point at which the thread does a
check_killed().
Reviewed-by: Monty <monty@mariadb.org>
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
binlog_space_limit is a variable in Percona server used to limit the total
size of all binary logs.
This implementation is based on code from Percona server 5.7.
In MariaDB we decided to call the variable max-binlog-total-size to be
similar to max-binlog-size. This makes it easier to find in the output
from 'mariadbd --help --verbose'). MariaDB will also support
binlog_space_limit for compatibility with Percona.
Some internal notes to explain implementation notes:
- When running MariaDB does not delete binary logs that are either
used by slaves or have active xid that are not yet committed.
Some implementation notes:
- max-binlog-total-size is by default 0 (no limit).
- max-binlog-total-size can be changed without server restart.
- Binlog file sizes are checked on startup, or if
max-binlog-total-size is set to a value > 0, not for every log write.
The total size of all binary logs is cached and dynamically updated
when updating the binary log on binary log rotation.
- max-binlog-total-size is checked against existing log files during
serverstart, binlog rotation, FLUSH LOGS, when writing to binary log
or when max-binlog-total-size changes value.
- Option --slave-connections-needed-for-purge with 1 as default added.
This allows one to ensure that we do not delete binary logs if there
is less than 'slave-connections-needed-for-purge' connected.
Without this option max-binlog-total-size would potentially delete
binlogs needed by slaves on server startup or when a slave disconnects
as there are then no connected slaves to protect active binlogs.
- PURGE BINARY LOGS TO ... will be executed as if
slave-connectitons-needed-for-purge would be zero. In other words
it will do the purge even if there is no slaves connected. If there
are connected slaves working on the logs, these will be protected.
- If binary log is on and max-binlog-total_size <> 0 then the status
variable 'Binlog_disk_use' shows the current size of all old binary
logs + the state of the current one.
- Removed test of strcmp(log_file_name, log_info.log_file_name) in
purge_logs_before_date() as this is tested in can_purge_logs()
- To avoid expensive calls of log_in_use() we cache the result for the
last log that is in use by a slave. Future calls to can_purge_logs()
for this binary log will be quickly detected and false will be returned
until a slave starts working on a new log.
- Note that after a binary log rotation caused by max_binlog_size,
the last log will not be purged directly as it is still in use
internally. The next binary log write will purge binlogs if needed.
Reviewer:Kristian Nielsen <knielsen@knielsen-hq.org>
This test was prone to failures for a few reasons, summarized below:
1) MDEV-32168 introduced “only_running_threads=1” to
slave_stop.inc, which allowed the stop logic to bypass an
attempting-to-reconnect IO thread. That is, the IO thread could
realize the master shutdown in `read_event()`, and thereby call into
`try_to_reconnect()`. This would leave the IO thread up when the
test expected it to be stopped. Fixed by explicitly stopping the
IO thread and allowing an error state, as the above case would
lead to errno 2003.
2) On slow systems (or those running profiling tools, e.g. MSAN),
the waiting-for-ack transaction can complete before the system
processes the `SHUTDOWN WAIT FOR ALL SLAVES`. There was shutdown
preparation logic in-between the transaction and shutdown itself,
which contributes to this problem. This patch also moves this
preparation logic before the transaction, so there is less to do
in-between the calls.
3) Changed work-around for MDEV-28141 to use debug_sync instead
of sleep delay, as it was still possible to hit the bug on very
slow systems.
4) Masked MTR variable reset with disable/enable query log
Reviewed By:
============
Kristian Nielsen <knielsen@knielsen-hq.org>
if the client enabled --ssl-verify-server-cert, then
the server certificate is verified as follows:
* if --ssl-ca or --ssl-capath were specified, the cert must have
a proper signature by the specified CA (or CA in the path)
and the cert's hostname must match the server's hostname.
If the cert isn't signed or a hostname is wrong - the
connection is aborted.
* if MARIADB_OPT_TLS_PEER_FP was used and the fingerprint matches,
the connection is allowed, if it doesn't match - aborted.
* If the connection uses unix socket or named pipes - it's allowed.
(consistent with server's --require-secure-transport behavior)
otherwise the cert is still in doubt, we don't know if we can trust
it or there's an active MitM in progress.
* If the user has provided no password or the server requested an
authentication plugin that sends the password in cleartext -
the connection is aborted.
* Perform the authentication. If the server accepts the password,
it'll send SHA2(scramble || password hash || cert fingerprint)
with the OK packet.
* Verify the SHA2 digest, if it matches - the connection is allowed,
otherwise it's aborted.
This commit addresses multiple server shutdown problems observed on macOS,
Solaris, and FreeBSD:
1. Corrected a non-portable assumption where socket shutdown was expected
to wake up poll() with listening sockets in the main thread.
Use more robust self-pipe to wake up poll() by writing to the pipe's write
end.
2. Fixed a random crash on macOS from pthread_kill(signal_handler)
when the signal_handler was detached and the thread had already exited.
Use more robust `kill(getpid(), SIGTERM)` to wake up the signal handler
thread.
3. Made sure, that signal handler thread always exits once `abort_loop` is
set, and also calls `my_thread_end()` and clears `signal_thread_in_use`
when exiting.
This fixes warning "1 thread did not exit" by `my_global_thread_end()`
seen on FreeBSD/macOS when the process is terminated via signal.
Additionally, the shutdown code underwent light refactoring
for better readability and maintainability:
- Modified `break_connect_loop()` to no longer wait for the main thread,
aligning behavior with Windows (since 10.4).
- Removed dead code related to the unused `USE_ONE_SIGNAL_HAND`
preprocessor constant.
- Eliminated support for `#ifndef HAVE_POLL` in `handle_connection_sockets`
This code is also dead, since 10.4
Improve the performance of slave connect using B+-Tree indexes on each binlog
file. The index allows fast lookup of a GTID position to the corresponding
offset in the binlog file, as well as lookup of a position to find the
corresponding GTID position.
This eliminates a costly sequential scan of the starting binlog file
to find the GTID starting position when a slave connects. This is
especially costly if the binlog file is not cached in memory (IO
cost), or if it is encrypted or a lot of slaves connect simultaneously
(CPU cost).
The size of the index files is generally less than 1% of the binlog data, so
not expected to be an issue.
Most of the work writing the index is done as a background task, in
the binlog background thread. This minimises the performance impact on
transaction commit. A simple global mutex is used to protect index
reads and (background) index writes; this is fine as slave connect is
a relatively infrequent operation.
Here are the user-visible options and status variables. The feature is on by
default and is expected to need no tuning or configuration for most users.
binlog_gtid_index
On by default. Can be used to disable the indexes for testing purposes.
binlog_gtid_index_page_size (default 4096)
Page size to use for the binlog GTID index. This is the size of the nodes
in the B+-tree used internally in the index. A very small page-size (64 is
the minimum) will be less efficient, but can be used to stress the
BTree-code during testing.
binlog_gtid_index_span_min (default 65536)
Control sparseness of the binlog GTID index. If set to N, at most one
index record will be added for every N bytes of binlog file written.
This can be used to reduce the number of records in the index, at
the cost only of having to scan a few more events in the binlog file
before finding the target position
Two status variables are available to monitor the use of the GTID indexes:
Binlog_gtid_index_hit
Binlog_gtid_index_miss
The "hit" status increments for each successful lookup in a GTID index.
The "miss" increments when a lookup is not possible. This indicates that the
index file is missing (eg. binlog written by old server version
without GTID index support), or corrupt.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
The reason for disabling transparent huge pages (THP) is that they
do not work well with MariaDB (or other databases, see links in
MDEV-33279). The effect of using THP are that MariaDB will use much more
(10x) more memory and will no be able to release memory back to the system.
Disabling THP is done after all storage engines are started, to allow
buffer pools and keybuffers (big allocations) to be allocated as huge
pages.
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.
Since 0930eb86cb, system table creation
needed for spider init is delayed to the signal_ddl_recovery_done
callback. Since it is part of the init, failure should result in
spider deinit.
We also remove the call to spider_init_system_tables() from
spider_db_init(), as it was removed in the commit mentioned above and
accidentally restored in a merge.
In commit b4ff64568c the
signature of mysql_show_var_func was changed, but not all functions
of that type were adjusted.
When the server is configured with `cmake -DWITH_ASAN=ON` and
compiled with clang, runtime errors would be flagged for invoking
functions through an incompatible function pointer.
Reviewed by: Michael 'Monty' Widenius
Systemd socket activation cannot handle a shutdown on the file
descriptor[1].
Enumerate past the socket activation descriptors.
If there was no shutdown to trigger the breaking of the event loop,
then write to the termination_event_fd that was setup during
the socket activation code for this purpose.
As abort_loop= true is already set at the top of break_connect_loop,
and this is checked in loop before sockets are processed, no
additional checking to read from the termination_event_fd is needed.
Without socket activation defined, or used, termination_event_fd keeps
its -1 default value.
Close the eventfd outside the while loop so retries can happen if
the write fails for some reason.
ref[1]: https://www.freedesktop.org/software/systemd/man/latest/sd_listen_fds.html
Reviewed by: Vladislav Vaintroub
This allows to simplify net_real_read() and net_real_write() a bit.
Removed some superfluous #ifdef/ifndef MYSQL_SERVER from net_serv.cc
The code always runs in server, either normal or embedded.
Dead code for switching socket between blocking and non-blocking modes,
is also removed.
Removed pthread_kill() with alarm signal that woke up main thread on
server shutdown. Used shutdown(2) on polling sockets instead, to the same
effect.
Removed yet another superstitious pthread_kill(), that ran on non-Windows
in terminate_slave_thread().
