如何判断一个参考是否正在由Clojure中的dosync更新？ [英] How can I tell if a ref is being updated by a dosync in Clojure?

问题描述

我有一些更新，需要做一个参考，但我想选择一个时间来执行更新时，ref不大量使用。

I have some updates which need to be made to a ref, but I want to choose a time to perform the updates when the ref is not in heavy use. Is there a way I can programatically tell when the ref is in a transaction?

推荐答案

你可以 < a href =http://clojure.github.com/clojure/clojure.core-api.html#clojure.core/add-watch =nofollow>添加观看 每次你的ref写入时更新一个访问时间（你提到它是写主要）。这将给你一个忙碌的启发。

you could add-watch that would update an access-time each time your ref is written (you mentions it was write mostly). This would give you a huristic for busy.

(def my-ref (ref {}))
(def my-ref-atime (atom 0))
(add-watch my-ref (fn [key ref old new] (swap! my-ref-atime current-time-fn)))) 

那么只有当atime在过去超过10ms时才进行低优先级工作。

then only do low priority work when atime is more than 10ms in the past.

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