Why does my clojure boot script stop running

Question

I want to start a server with clojure boot that must keep on running. So I made a -main function so that I can run ./build.boot and that will execute the main function. In the main function I start a non-daemon thread with the idea that the JVM keeps on running as long as there is a non-daemon thread. However the boot script stops and my server stops as well. What am I doing wrong?

#!/usr/bin/env boot

(defn -main [& args]
  (let [t (Thread. #(loop []
                      (println (java.util.Date.))
                      (Thread/sleep 500)
                      (recur)))]
    (.setDaemon t false)
    (.start t)
    (Thread/sleep 3000)
    (println "I have started a non-daemon thread, but still I exit???")))

Output

#inst "2016-06-23T08:39:23.453-00:00"
#inst "2016-06-23T08:39:24.005-00:00"
#inst "2016-06-23T08:39:24.507-00:00"
#inst "2016-06-23T08:39:25.009-00:00"
#inst "2016-06-23T08:39:25.511-00:00"
#inst "2016-06-23T08:39:26.013-00:00"
I have started a non-daemon thread, but still I exit???

After which the script ends.

Answer 1

I guess boot calls System/exit once the tasks are done (their function call ends).

You need to modify your task to join to your spawned thread so the -main function doesn't complete until your spawned thread hasn't finished:

(.join t)