[英]Stack overflow exception in compojure web project
I've been playing around with clojure and have been using it to build a simple little audio player. 我一直在玩clojure,并一直使用它来构建一个简单的小音频播放器。 The strange thing is that sometimes, maybe one out of twenty, when contacting the server I will get the following error:
奇怪的是,有时联系服务器时,可能会十分之一,出现以下错误:
2010-04-20 15:33:20.963::WARN: Error for /control
java.lang.StackOverflowError
at clojure.lang.RT.seq(RT.java:440)
at clojure.core$seq__4245.invoke(core.clj:105)
at clojure.core$filter__5084$fn__5086.invoke(core.clj:1794)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:440)
at clojure.core$seq__4245.invoke(core.clj:105)
at clojure.core$filter__5084$fn__5086.invoke(core.clj:1794)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:440)
at clojure.core$seq__4245.invoke(core.clj:105)
at clojure.core$filter__5084$fn__5086.invoke(core.clj:1794)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:440)
at clojure.core$seq__4245.invoke(core.clj:105)
at clojure.core$filter__5084$fn__5086.invoke(core.clj:1794)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:440)
...
If I do it right after again it always works. 如果我一次又一次这样做,它将始终有效。 So it appears to be related to timing or something.
因此,它似乎与时机或某些东西有关。 The code in question is:
有问题的代码是:
(defn add-track [t]
(common/ref-add tracks t))
(defn add-collection [coll]
(doseq [track coll] (add-track track)))
and 和
(defn ref-add [ref value]
(dosync (ref-set ref (conj @ref value))))
where coll is extracted from this function: 从此函数中提取coll的位置:
(defn tracks-by-album [album]
(sort sort-tracks (filter #(= (:album %) album) @tracks)))
which uses: 使用:
(defn get-album-from-track [track]
(seq/find-first #(= (:album track) (:name %)) @albums))
(defn sort-tracks [track1 track2]
(cond (= (:album track1) (:album track2))
(cond (and (:album-track track1) (:album-track track2))
(< (:album-track track1) (:album-track track2))
:else 0)
:else
(> (:year (get-album-from-track track1)) (:year (get-album-from-track track2)))))
it gets called more or less directly from the request I get in: 它或多或少直接从我收到的请求中被调用:
(when-handle-command cmd params (audio/tracks-by-album decoded-name))
(defn when-handle-command [cmd params data]
(println (str "handling command:" cmd))
....)
I never get the handling command in my log, so it must die when it does the tracks-by-album. 我从来没有在日志中得到处理命令,因此当它按专辑进行录制时,它必须死掉。
so it does appear to be the tracks-by-album function from the stack trace. 因此它看起来确实是堆栈跟踪中的逐专辑功能。 I just don't see why it sometimes works and sometimes doesn't.
我只是不明白为什么它有时起作用而有时却不起作用。 I say that it's tracks-by-album because it's the only function (including it's children) that does filter, as can be seen in the trace.
我说这是按专辑跟踪的,因为它是唯一可以过滤的功能(包括它的子功能),可以在跟踪中看到。
All the source code is available at: http://code.google.com/p/mucomp/ . 所有源代码都可以通过以下网址获得: http : //code.google.com/p/mucomp/ 。 It's my little hobby project to learn clojure and so far it's quite buggy (this is just one bug :)) so I havn't really liked to tell too many people about it yet :)
这是我学习clojure的一个小爱好项目,到目前为止,它是相当多的错误(这只是一个错误:)),所以我还不太喜欢告诉太多的人:)
I asked the question on the clojure mailing list. 我在clojure邮件列表上问了这个问题。 And it appears that the answer is that filter returns a lazy seq, and when you chain those, you'll end in a stack overflow at some point.
看来答案是过滤器返回了一个惰性序列,当您链接这些序列时,有时会在堆栈溢出中结束。 One can force the generation of the sequence using doall.
可以使用doall强制生成序列。
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