lazy_seq_persistence.clj

(ns buffers-test
  (:require  [manifold.deferred :as d]))


(defn buffers-for [n size]
  (for [n (range n)]
    (java.nio.ByteBuffer/allocate size)))


(defn buffers [size]
  (lazy-seq
    (cons (java.nio.ByteBuffer/allocate size)
          (buffers size))))



(defn loop-buffers [bs]
  (loop [bs bs]
    (when-not (empty? bs)
      (println (.capacity (first bs)))
      (recur (rest bs)))))

(defn d-loop-buffers [bs]
  @(d/loop [bs bs]
    (when-not (empty? bs)
      (println (.capacity (first bs)))
      (d/recur (rest bs)))))

(defn d-loop-buffers-fut [bs]
  (d/future
    @(d/loop [bs bs]
      (when-not (empty? bs)
        (println (.capacity (first bs)))
        (d/recur (rest bs))))))



; Run this with -Xmx1G
; or otherwise set SIZE to a value so that
; 10 * SIZE bytes is enough to OOM
(def SIZE (* 250 1024 1024))

; These work fine
(loop-buffers (take 10 (buffers SIZE)))

(d-loop-buffers (take 10 (buffers SIZE)))
@(d/future (d-loop-buffers (take 10 (buffers SIZE))))

; These result in OOM
(loop-buffers (buffers-for 10 SIZE))

(d-loop-buffers (buffers-for 10 SIZE))
@(d-loop-buffers-fut (take 10 (buffers SIZE)))
@(d-loop-buffers-fut (buffers-for 10 SIZE))