The SyslogAppender currently can only send messages using the machine hostname as the sender identifier. The appender can only use SyslogStartConverter.getLocalHostname(). This has come up in a few situations:

• the caller can't set a different value that better describes the machine or the sender. This has come up when: the OS hostname is set from an IP or MAC address (and isn't the most useful identifier); many machines are treated as a single sender; multiple apps run on one system, and even aside from the tag, the sender identifier should be more specific.
• variables which are usable in a pattern layout can't be used in the syslog sender identifier
• the appender has to work around situations where the machine name isn't usable (example: http://jira.qos.ch/browse/LOGBACK-749)

I'm opening this to get comments on (a) whether a patch would be accepted, and if so, (b) what it should do. I see two possibilities:

• let the caller configure the hostname, like destination host and port, and pass it to the converter
• let the caller provide the entire pattern layout, overriding everything after the syslog priority