Jenkins dedicates a
java.lang.Thread for each executor. Under normal operation, this thread is alive all the time (although unless a build is going on the thread is sleeping.) The "dead executor" sign (see the picture on the right) happens when this thread dies unexpectedly. When this happens, please check your Jenkins system log (
http://server/jenkins/log) and look for a stack trace, then report that to Jenkins users list or the issue tracker.
Obsolete as of Jenkins 2.13.