Do not repeat yourself.
Instead of having the same DBUG_EXECUTE_IF code in threadpool and
thread-per-connection, add this code to setup_connection_thread_globals()
which is executed in all scheduling modes.
Prior to this patch, it is possible to access freed memory
(THD::event_scheduler) from tp_post_kill_notification().
With this patch, memory is freed only when THD is no more accessible
from other threads, i.e after it is removed from the thread_list.
Amend check for unread client data in threadpool.
THD::NET will have unread data, in case client uses compression, and
wraps multiple commands into a single compression packet
MariaDB C/C sends COM_STMT_RESET+COM_STMT_EXECUTE, and wraps it into
a single compressed packet, when compression is on, thus trying to use
compression and prepared statements against a threadpool-enabled server
will result into a hang, before this patch.
Due to restricted size of the threadpool, execution of client queries can
be delayed (queued) for a while. This delay was interpreted as client
inactivity, and connection is closed, if client idle time + queue time
exceeds wait_timeout.
But users did not expect queue time to be included into wait_timeout.
This patch changes the behavior. We don't close connection anymore,
if there is some unread data present on connection,
even if wait_timeout is exceeded. Unread data means that client
was not idle, it sent a query, which we did not have time to process yet.
All changes (except one) is of type
thd->transaction. -> thd->transaction->
thd->transaction points by default to 'thd->default_transaction'
This allows us to 'easily' have multiple active transactions for a
THD object, like when reading data from the mysql.proc table
read TLS with my_thread_var
write TLS with set_mysys_var()
my_thread_var is no longer __attribute__ ((const)): this attribute
is simply incorrect here. Read gcc manual for more information.
sql/threadpool_generic.cc fails with that attribute.
MariaDB 10.4 was crashing when thread-handling was set to
pool-of-threads and wsrep was enabled.
There were two apparent reasons for the crash:
- Connection handling in threadpool_common.cc was missing calls to
control wsrep client state.
- Thread specific storage which contains thread variables (THR_KEY_mysys)
was not handled appropriately by wsrep patch when pool-of-threads
was configured.
This patch addresses the above issues in the following way:
- Wsrep client state open/close was moved in thd_prepare_connection() and
end_connection() to have common handling for one-thread-per-connection
and pool-of-threads.
- Thread local storage handling in wsrep patch was reworked by introducing
set of wsrep_xxx_threadvars() calls which replace calls to
THD store_globals()/reset_globals() and deal with thread handling
specifics internally.
Wsrep-lib was updated to version which relaxes internal concurrency
related sanity checks.
Rollback code from wsrep_rollback_process() was extracted to separate calls
for better readability.
Post rollback thread was removed as it was completely unused.
Plugin fixed to not lock the LOCK_operations when not active.
Server fixed to lock the LOCK_plugin less - do it once per
thread and then only if a plugin was installed/uninstalled.
stalls etc better.
- thread_pool_exact_stats - uses high precision timestamp for
the time when connection was added to the queue. This timestamp helps
calculating queuing time shown in I_S.THREADPOOL_QUEUES entries.
- If thread_pool_dedicated_listener is on, then each group will have its
own dedicated listener, that does not convert to worker.
With this variable on, the queueing time in I_S.THREADPOOL_QUEUES , and
actual queue size in I_S.THREADPOOOL_GROUPS will be more exact, since
IO request are immediately dequeued from poll, without delay.
Part of MDEV-19313.
Removed LOCK_connection_count.
Removed duplicate denied_connections and connection_errors_max_connection
increment from create_new_thread(). Another increment done by
CONNECT::close_with_error().
Simplified away CONNECT::thread_count_incremented. Now close_with_error()
is always called with connection_count incremented.
Part of MDEV-19515 - Improve connect speed
Code properly integrated into callers instead.
do_handle_one_connection(): no need to reset thd and thd->thread_stack
as they're not updated by cache_thread().
Part of MDEV-19515 - Improve connect speed
It was meaningful only for one-thread-per-connection scheduler anyway,
so call init_new_connection_handler_thread() directly from
handle_one_connection().
It was somewhat harmful for no-threads scheduler, because it'd attempt to
detach main thread on AIX_3_2 and Siemens unix (and DEC OSF/1 3.2 too).
Also it does duplicate my_thread_init() call, which may produce a warning
under EXTRA_DEBUG_THREADS.
start_wsrep_THD() shouldn't have called it at all: it already detached
and called my_thread_init().
Part of MDEV-19515 - Improve connect speed
This commit is based on the work of Michal Schorm, rebased on the
earliest MariaDB version.
Th command line used to generate this diff was:
find ./ -type f \
-exec sed -i -e 's/Foundation, Inc., 59 Temple Place, Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
-exec sed -i -e 's/Foundation, Inc. 59 Temple Place.* Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
-exec sed -i -e 's/MA.*.....-1307.*USA/MA 02110-1335 USA/g' {} \; \
-exec sed -i -e 's/Foundation, Inc., 59 Temple/Foundation, Inc., 51 Franklin/g' {} \; \
-exec sed -i -e 's/Place, Suite 330, Boston, MA.*02111-1307.*USA/Street, Fifth Floor, Boston, MA 02110-1335 USA/g' {} \; \
-exec sed -i -e 's/MA.*.....-1307/MA 02110-1335/g' {} \;
Implemented and integrated THD_list as a replacement for the global
thread list. It uses own mutex instead of LOCK_thread_count for THD
list protection.
Removed unused first_global_thread() and next_global_thread().
delayed_insert_threads is now protected by LOCK_delayed_insert. Although
this patch doesn't fix very wrong synchronization of this variable.
After this patch there are only 2 legitimate uses of LOCK_thread_count
left, both in mysqld.cc: thread_count and ready_to_exit.
Aim is to reduce usage of LOCK_thread_count and COND_thread_count.
Part of MDEV-15135.
LOCK_thd_data was used to protect both THD data and
ensure that the THD is not deleted while it was in use
This patch moves the THD delete protection to LOCK_thd_kill,
which already protects the THD for kill.
The benefits are:
- More well defined what LOCK_thd_data protects
- LOCK_thd_data usage is now much simpler and easier to verify
- Less chance of deadlocks in SHOW PROCESS LIST as there is less
chance of interactions between mutexes
- Remove not needed LOCK_thread_count from
thd_get_error_context_description()
- Fewer mutex taken for thd->awake()
Other things:
- Don't take mysys->var mutex in show processlist to check if thread
is kill marked
- thd->awake() now automatically takes the LOCK_thd_kill mutex
(Simplifies code)
- Apc uses LOCK_thd_kill instead of LOCK_thd_data
