CentOS Linux release 7.2.1511 (Core)
MySQL 5.6.27

Did you use the correct command to create MySQL database as documented here?

mysql> create database zabbix character set utf8 collate utf8_bin;

Or maybe you have correct character set for database, but the default character set for connections is not utf8. Frontend does SET NAMES utf8; explicitly, but sever does not. So, if MySQL assumes Zabbix server connects in latin1 it will send back '?' instead of non-ASCII characters in results. Server simply takes these '???' from template and copies to discovered hosts.

I failed to reproduce your issue by messing around with /etc/mysql/my.cnf. Could you provide more details?

Managed to reproduce. I believe the decisive moment was when I added this line to /etc/mysql/my.cnf:

[mysqld]
...
init-connect='SET character_set_results = latin1'

Hm, server does set names utf8 too...

ZBX-10665 could be the same

ADD INFO.

After restart the zabbix-server (systemctl restart zabbix-server) , LLD created normal entrys.
About 1 days later(maybe) from restart, LLD created normal entrys.
About 2 days later from restart, LLD created illegal("?????") entrys.

I think MySQL setting is normal.
But I tryed.

1st settings
character-set-server = utf8
skip-character-set-client-handshake

2nd settings
character-set-server = utf8
skip-character-set-client-handshake
collation-server=utf8_bin

Still relapsing....

Now it's clear to me. ZBX-6163 enabled auto-reconnection to MySQL, but result of set names utf8; is lost on reconnection. That's why this bug is so random. Whenever Zabbix process loses connection to database MySQL automatically reconnects and falls back to default encoding.

Simple test with mysql client:

mysql> select * from test_utf8;    <--- default settings
+------+------+
| id   | data |
+------+------+
|    1 | ???? |
|    2 | ???? |
+------+------+
2 rows in set (0.00 sec)

mysql> set names utf8;    <--- correct settings
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test_utf8;
+------+----------+
| id   | data     |
+------+----------+
|    1 | фыва |
|    2 | олдж |
+------+----------+
2 rows in set (0.00 sec)

mysql> select * from test_utf8;
ERROR 2006 (HY000): MySQL server has gone away    <--- restarted MySQL server in the meantime
No connection. Trying to reconnect...
Connection id:    37
Current database: test_utf8

+------+------+
| id   | data |    <--- default settings again
+------+------+
|    1 | ???? |
|    2 | ???? |
+------+------+
2 rows in set (0.00 sec)

As a temporary workaround try to set character_set_connection, character_set_result and character_set_client to utf8 in MySQL server settings ("[client]" section).

When the workaround has not applied,

1.
Connect mysql

2.
mysql> select * from triggers;
<<<RETURN IS OK>>>

3.
<<<reboot mysql server>>>

4.
mysql> set names latin1;
mysql> select * from triggers;
<<<RETURN IS NG "??????">>>

5.
mysql> set names utf8;
mysql> select * from triggers;
<<<RETURN IS OK>>>

I think "skip-character-set-client-handshake" is working.

But now the workaround has applied.
And Let's wait and see.

I think the workaround does not working

1. Set the workaround ( set the my.cnf on the Zabbix Server = mysql client )
2. Exec "systemctl restart zabbix-server"
3. Reboot mysql server <----- maybe disconnect mysql connection?
4. LLD created illegal("?????") entrys.

Fix for version 3.0 is available in development branch svn://svn.zabbix.com/branches/dev/ZBX-10540 revision 59441.

Patch attached. Fix is really simple. To test I had to restart MySQL server in order to cause automatic reconnects. takahisa, BcTpe4HbIu, your help in testing on more or less loaded system where reconnects are normal will be highly appreciated.

Gleb, with this patch everything seems to be normal. No more question marks spotted.

Igor, very nice to hear that. Thank you for testing!

Successfully tested.

Fixed in pre-3.0.3rc1 r59665, pre-3.1.0 (trunk) r59666.

(1) Documented in known issues.

sandis.neilands CLOSED with minor changes.