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.
Problem was that wsrep thread argument was deleted on wrong
place. Furthermore, scan method incorrectly used unsafe c_ptr().
Finally, fixed wsrep thread initialization to correctly set
up thread_id and pass correct argument to functions and
fix signess problem causing compiler errors.
Refactored wsrep patch to not use LOCK_thread_count and COND_thread_count anymore.
This has partially been replaced by using old LOCK_wsrep_slave_threads mutex.
For slave thread count change waiting, new COND_wsrep_slave_threads signal has been added
Added LOCK_wsrep_cluster_config mutex to control that cluster address change cannot happen in parallel
Protected wsrep_slave_threads variable changes with LOCK_cluster_config mutex
This is for avoiding concurrent slave thread count and cluster joining operations to happen
Fixes according to Teemu's review
* Removed all references related to wsrep_thd_pool (which was removed)
* Removed unused declarations in wsrep_schema.h
* The following would result invalid reads in
Wsrep_schema::replay_transaction():
```
frag_table->field[4]->val_str(&buf);
Wsrep_schema_impl::end_index_scan(frag_table);
Wsrep_schema_impl::finish_stmt(thd);
ret= wsrep_apply_events(thd, rli, buf.c_ptr_safe(), buf.length());
```
because `buf` was accessed after closing the table. The fix is to
perform storage reads using a different THD.
* In Wsrep_schema::recover_sr_transactions(), cluster_table was opened
for write, however it is only read here. And frag_table was opened
for read, wereas write is potentially needed.
Also, avoid copy caused by String::c_ptr() to zero terminate the c
string, use c_ptr_quick instead.
