I'm logging from the plugin to an rsyslog server. I'm getting duplicate timestamps in my syslog messages.

Example from Jenkins UI system log:

May 30, 2017 9:53:16 PM INFO hudson.slaves.RetentionStrategy$Demand check
Launching computer nettools1-centralus as it has been in demand for 8 hr 13 min
 

Example in /var/log/syslog on the rsyslog server:

May 30 22:12:14 aznetsysjenkins INFO jenkins May 30, 2017 10:12:14 PM hudson.slaves.RetentionStrategy$Demand check#012INFO: Launching computer nettools1-centralus as it has been in demand for 8 hr 32 min

File format template:

$template ACSFileFormat,"%TIMESTAMP% %HOSTNAME% %syslogseverity-text:::uppercase% %syslogtag%%msg:::sp-if-no-1st-sp%%msg:::drop-last-lf%\n"

It looks to me like the java logger format being used inserts the timestamp into the Message field for some reason. This seems a duplicate. Can someone look at the code?