Ah ok. Yes, I'm running it as a service via systemctl start logstash.service
I added LS_HOME_JAVA="/usr/bin/java" to /etc/defaults/logstash that gets logstash to use LS_JAVA_HOME but it still doesn't start.
Jun 17 21:10:11 elk systemd[1]: Started logstash.
Jun 17 21:10:11 elk logstash[14699]: Using LS_JAVA_HOME defined java: /usr/bin/java.
Jun 17 21:10:11 elk logstash[14699]: Invalid LS_JAVA_HOME, doesn't contain bin/java executable.
Jun 17 21:10:11 elk logstash[14699]: Could not find java; set LS_JAVA_HOME or ensure java is in PATH.
Jun 17 21:10:11 elk systemd[1]: logstash.service: Main process exited, code=exited, status=1/FAILURE
Jun 17 21:10:11 elk systemd[1]: logstash.service: Failed with result 'exit-code'.
Jun 17 21:10:11 elk systemd[1]: logstash.service: Scheduled restart job, restart counter is at 2.
Jun 17 21:10:11 elk systemd[1]: Stopped logstash.