Clojurians Log v2

bb seems more aggressive than clojure when shutting down. compare bb -e '(future @(promise))' and clojure -e '(future @(promise))'.

clojure will wait a bit before shutting down, you need to call shutdown-agents manually but bb does this for you clojure -X or -T (forgot which) has altered this behavior for clojure as well since it just makes more sense for scripts/tools

This is the behavior clojure -X/etc has: https://github.com/clojure/brew-install/blob/3d4829c16deab48d1b3278102f70909f8eae8891/src/main/clojure/clojure/run/exec.clj#L170-L183

but bb simply just calls shutdown-agents at the end of the script

Perhaps I could try to do the daemon thread approach in bb, but so far this worked out ok

I double checked an httpkit server example invoked with -X and it doesn't seem to quit right away:

(ns script)

(require '[org.httpkit.server :refer [run-server]])

(defn handler [_req]
  {:status 200
   :headers {"Content-Type" "text/plain"}
   :body "Hello from http-kit in Babashka!"})

(defn doit [_]
  (run-server handler {:port 8080})
  (println "Server running at "))

;; @(promise) ; Keeps the server running

$ clj -X script/doit
Server running at 

Ah, it's probably because there is one ServerThread which is not a daemon thread: https://github.com/http-kit/http-kit/blob/eefe7c13c0ed36283d26bf8b2d936e1ae69465a5/src/java/org/httpkit/server/HttpServer.java#L450

Yeah, this is the difference:

(ns script)

(defn doit [_]
  (-> (doto (new java.lang.Thread (fn []
                                    (Thread/sleep 1000000)) )
        (.setDaemon true)
        (.start)))
  (println "Server running at "))

Oh no, wait, it's not about shutdown-agents, it's about bb doing a System/exit :)

(defn doit [_]
  (-> (doto (new java.lang.Thread (fn []
                                    (Thread/sleep 1000000)) )
        #_(.setDaemon true)
        (.start)))
  (println "Server running at ")
  (System/exit 0))

I guess if I would change babashka.main to:

(let [exit-code (run args)]
      (when-not (zero? exit-code)
        (System/exit exit-code)))

Let's see if CI likes this commit or not... https://github.com/babashka/babashka/commit/f4f1d9e94509a08f2b0ae35d9cda0060ba76e7f7

lol:

lein test babashka.agent-test
=== agent-binding-conveyance-test


Too long with no output (exceeded 10m0s): context deadline exceeded

locally this test does just terminate though:

$ ./bb -e '(def ^:dynamic *foo* 1) (def a (agent nil)) (binding [*foo* 2] (send-off a (fn [_] *foo*))) (await a) @a'
2

With the change in place, this does still work but hangs:

(import '(java.util.concurrent Executors ExecutorService))
(let [fut (.submit ^ExecutorService (Executors/newCachedThreadPool) ^Callable (fn [] 3))]
  (prn (.get fut)))

I would revisit this if people were adamant about changing this behavior.

The workaround doesn't seem too tricky, although I wouldn't have figured it out for awhile if I didn't see it in another sample code - maybe just a note would suffice, or somehow tie to httpkit's start call in stderr