19 Large JSON value support

To ensure reliable handling of large JSON values (1MiB or more), review and apply the following configuration changes as needed:

1. If you're using MySQL or MariaDB, increase the maximum allowed packet size in /etc/mysql/my.cnf (it may default to 1MB on some systems):

[mysqld]
       max_allowed_packet=128M
       
       [mysqldump]
       max_allowed_packet=1G

2. Adjust additional MySQL/MariaDB server system variables and InnoDB system variables as needed. For example:

innodb_io_capacity=1900
       connect_timeout=600
       wait_timeout=57600
       interactive_timeout=57600
       net_read_timeout=7200
       net_write_timeout=7200
       net-buffer-length=32704

3. Increase HistoryCacheSize to 2G in the Zabbix server configuration file.

4. If you're using Zabbix proxy, increase HistoryCacheSize to 2G and ProxyMemoryBufferSize to 2G in the proxy configuration file.

5. If you're using Zabbix agent, increase communication timeouts between Zabbix server/proxy and agent (e.g., item timeouts or the Timeout parameter value in the Zabbix server/proxy and agent configuration files). Otherwise, messages between them may not complete, and you may see errors such as "message length does not match expected length". Also, review other timeouts as needed, such as the script timeout or item test timeout.