The reconnectionDelayMillis parameter was renamed to reconnectDelayMillis. After updating to release 2.8 I noticed that I was getting the following error:

ERROR Syslog contains an invalid element or attribute "reconnectionDelayMillis"

It appears that change was part of this commit:

commit ed828be67a23ee3513cafc9d2fd0ff16a26c7013
Author: Gary Gregory <ggregory@apache.org>
Date:   Mon Nov 14 15:11:47 2016 -0800

    [LOG4J2-1709]

    Add a Builder to SyslogAppender and deprecate
    SyslogAppender.createAppender().


The documentation (https://logging.apache.org/log4j/2.x/manual/appenders.html#SyslogAppender) still has the parameter listed as "reconnectionDelayMillis" but the code is now obviously looking for "reconnectDelayMillis". I'm going to change my config to use the new name, but I thought I'd point out the disconnect as it had me confused for a bit. Thanks - Sam