xml-parsing – Clojure Leining REPL OutOfMemoryError Java堆空间

我试图解析一个相当小(<100MB)的xml文件：

(require '[clojure.data.xml :as xml]
         '[clojure.java.io :as io])

(xml/parse (io/reader "data/small-sample.xml"))

我收到一个错误：

OutOfMemoryError Java heap space
    clojure.lang.Numbers.byte_array (Numbers.java:1216)
    clojure.tools.nrepl.bencode/read-bytes (bencode.clj:101)
    clojure.tools.nrepl.bencode/read-netstring* (bencode.clj:153)
    clojure.tools.nrepl.bencode/read-token (bencode.clj:244)
    clojure.tools.nrepl.bencode/read-bencode (bencode.clj:254)
    clojure.tools.nrepl.bencode/token-seq/fn--3178 (bencode.clj:295)
    clojure.core/repeatedly/fn--4705 (core.clj:4642)
    clojure.lang.LazySeq.sval (LazySeq.java:42)
    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.RT.seq (RT.java:484)
    clojure.core/seq (core.clj:133)
    clojure.core/take-while/fn--4236 (core.clj:2564)

这是我的project.clj：

(defproject dats "0.1.0-SNAPSHOT"
  ...
  :dependencies [[org.clojure/clojure "1.5.1"]
                [org.clojure/data.xml "0.0.7"]
                [criterium "0.4.1"]]
  :jvm-opts ["-Xmx1g"])

我尝试在.bash_profile中设置LEIN_JVM_OPTS和JVM_OPTS但没有成功.

当我尝试以下project.clj时：

(defproject barber "0.1.0-SNAPSHOT"
  ...
  :dependencies [[org.clojure/clojure "1.5.1"]
                [org.clojure/data.xml "0.0.7"]
                [criterium "0.4.1"]]
  :jvm-opts ["-xms128m"])

我收到以下错误：

Error occurred during initialization of VM
Incompatible minimum and maximum heap sizes specified
Exception in thread "Thread-5" clojure.lang.ExceptionInfo: Subprocess Failed {:exit-code 1}

知道如何增加leiningen repl的堆大小吗？

谢谢.

解决方法

由于Read-Eval-Print-Loop的打印步骤,在repl的顶层评估的任何形式都是完全实现的.它也存储在堆中,以便您以后可以通过* 1访问它.

如果存储返回值,如下所示：

(def解析(xml / parse(io / reader“data / small-sample.xml”)))

这会立即返回,即使对于数百兆字节的文件(我已在本地验证).然后,您可以遍历结果,该结果通过迭代返回的c​​lojure.data.xml.Element树完全实现,因为它是从输入流中解析的.

如果你没有坚持元素(通过绑定它们以便它们仍然可访问),你可以迭代整个结构而不使用更多的ram而不是保存xml树的单个节点.

user> (time (def n (xml/parse (clojure.java.io/reader "/home/justin/clojure/ok/data.xml"))))
"Elapsed time: 0.739795 msecs"
#'user/n
user> (time (keys n))
"Elapsed time: 0.025683 msecs"
(:tag :attrs :content)
user> (time (-> n :tag))
"Elapsed time: 0.031224 msecs"
:catalog
user> (time (-> n :attrs))
"Elapsed time: 0.136522 msecs"
{}
user> (time (-> n :content first))
"Elapsed time: 0.095145 msecs"
#clojure.data.xml.Element{:tag :book,:attrs {:id "bk101"},:content (#clojure.data.xml.Element{:tag :author,:attrs {},:content ("Gambardella,Matthew")} #clojure.data.xml.Element{:tag :title,:content ("XML Developer's Guide")} #clojure.data.xml.Element{:tag :genre,:content ("Computer")} #clojure.data.xml.Element{:tag :price,:content ("44.95")} #clojure.data.xml.Element{:tag :publish_date,:content ("2000-10-01")} #clojure.data.xml.Element{:tag :description,:content ("An in-depth look at creating applications \n      with XML.")})}
user> (time (-> n :content count))
"Elapsed time: 48178.512106 msecs"
459000
user> (time (-> n :content count))
"Elapsed time: 86.931114 msecs"
459000
;; redefining n so that we can test the performance without the pre-parsing done when we counted
user> (time (def n (xml/parse (clojure.java.io/reader "/home/justin/clojure/ok/data.xml"))))
"Elapsed time: 0.702885 msecs"
#'user/n
user> (time (doseq [el (take 100 (drop 100 (-> n :content)))] (println (:tag el))))
:book
:book
.... ;; output truncated
"Elapsed time: 26.019374 msecs"
nil
user>

请注意,只有当我第一次询问n的内容计数(从而强制解析整个文件)时才会发生巨大的时间延迟.如果我对结构的各个部分进行了测量,则会很快发生这种情况.