15 Upgrade notes for 7.2.5

Asynchronous DNS resolution

The agent poller and SNMP poller can now be configured to use the c-ares library (version 1.16.0 or newer) instead of the libevent DNS resolver, providing potentially faster and more flexible DNS resolution.

If you want to use c-ares library, configure Zabbix with the --with-ares option:

  --with-ares[=ARG]       use c-ares library [default=no],
         --with-ares-include=DIR use c-ares include headers from given path.
         --with-ares-lib=DIR     use c-ares libraries from given path.

Note that starting from c-ares 1.31.0, DNS caching is enabled by default.

Escaping of backslashes in history function parameters

Proper escaping of backslashes has been added in history function string parameters since Zabbix 7.0.0.

As additional backslashes are added during the upgrade from pre-7.0 Zabbix versions, this leads to longer parameters which may result in broken trigger functions if the parameter length exceeds the maximum data size of 255 characters.

To avoid this problem it is suggested to manually move long parameters into user macros before the upgrade.

Note that since Zabbix 7.2.5 additional checks for the resulting parameter length have been added for upgrades from pre-7.0 Zabbix versions. If the resulting length exceeds the maximum size, such parameters are not upgraded while printing a warning in the logs asking users to fix the listed parameters manually.

See also escaping-related upgrade issues.