race condition: upmap loses data when an exception is raised

[leahneukirchen]

There seems to be some kind of race conditon in upmap such that an exception isn't caught, but processing is terminated and a partial result is returned.

I can reproduce this on claypoole 1.2.2, clojure 1.12.1, openjdk 21.0.7 on Linux x86_64, with a bit of experimentation:

(def thread-pool (com.climate.claypoole/threadpool 16))

(defn faulty [x]
  (let [n (rand-int 100)]
    (Thread/sleep 0 (rand-int 300000))
    (if (zero? n)
      (throw (ex-info "bad luck!" {}))
      x)))

(->> (range 1 100000)
     (mapv
      (fn [_]
        (try
          (into [] (com.climate.claypoole/upmap thread-pool faulty (range 0 50)))
          (catch Exception e
            nil))))
     (remove nil?)
     (remove #(= 50 (count %))))

At some point, this returns a 32-element vector. It probably helps if the JVM is busy in other ways to trigger this.

(We hit this issue in production with a way smaller workload. Bad luck!)