It's Master <-> Slave replication.
Some times the server crash.

2018-12-28 16:15:27 23 [Note] Slave I/O thread killed during or after a reconnect done to recover from failed read
2018-12-28 16:15:27 23 [Note] Slave I/O thread exiting, read up to log 'mysql-bin.000003', position 8185; GTID position 0-3232245844-12
181228 16:15:27 [ERROR] mysqld got signal 11 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.

To report this bug, see https://mariadb.com/kb/en/reporting-bugs

We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

Server version: 10.3.8-MariaDB-log
key_buffer_size=16777216
read_buffer_size=1048576
max_used_connections=7
max_threads=2534
thread_count=5
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 7857705 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x7fe1000009a8
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0x7fe1640dab20 thread_stack 0x40000
/u01/mariadb/bin/mysqld(my_print_stacktrace+0x2e)[0x7fe1717b363e]
/u01/mariadb/bin/mysqld(handle_fatal_signal+0x357)[0x7fe1712412e7]
sigaction.c:0(__restore_rt)[0x7fe17068e100]
/u01/mariadb/bin/mysqld(mysql_real_connect+0x259)[0x7fe17121b6a9]
/u01/mariadb/bin/mysqld(_ZN20Repl_semi_sync_slave15kill_connectionEP8st_mysql+0xa1)[0x7fe171192171]
/u01/mariadb/bin/mysqld(_ZN20Repl_semi_sync_slave10slave_stopEP11Master_info+0x30)[0x7fe171192210]
/u01/mariadb/bin/mysqld(handle_slave_io+0x496)[0x7fe170fd8616]
pthread_create.c:0(start_thread)[0x7fe170686dc5]
/lib64/libc.so.6(clone+0x6d)[0x7fe16ead5ced]