Exception handling within futures and load-file

Question

I want my clojure program to have a directory of scripts that it can run - each of these scripts is clojure code that I execute with load-file. This happens within a future so that the script runs in its own thread. The problem is I never see any error messages from the scripts. If the script fails there's no way to know what went wrong. I assume that's because there is no exception handling within the future's thread. I can put exception handling into the script, like below, and it works: ``` ;; script code (try (println (/ 10 0)) (catch Exception e (println "Exception: " (.getMessage e)))) ``` However, I'd rather put the exception handling a level up from that, around the load-file, so that I don't have to have the exception handling in the script itself: ``` (defn handleexes [f] (try (f) (catch Exception e (println "exception: " (.getMessage e))))) (defn start-script-play [name] (println "starting script: " name) (let [f (future (handleexes (load-file (str "./scripts/" name))))] (s…

Accepted Answer

You don't appear to ever be dereferencing (either with `deref` or `@`) the futures you're producing in your example.

If an exception is thrown within a future, attempting to dereference that future will result in a `java.util.concurrent.ExecutionException` being thrown. This exception will wrap whatever was thrown in the future.

```
(try
  (future (/ 10 0))
  "done"
  (catch Exception e
    (str "caught " e)))

;=> "done"

(try
  @(future (/ 10 0))
  "done"
  (catch Exception e
    (str "caught " e)))

;=> "caught java.util.concurrent.ExecutionException: java.lang.ArithmeticException: Divide by zero"
```

Exception handling within futures and load-file

Solution

Problem