Clojure 可以监视STM';竞争级别是多少?
是否有任何方法可以轮询Clojure的STM事务是否正在重试,以及以何种速率重试?您可以观察ref的Clojure 可以监视STM';竞争级别是多少?,clojure,stm,Clojure,Stm,是否有任何方法可以轮询Clojure的STM事务是否正在重试,以及以何种速率重试?您可以观察ref的历史计数,这将表明存在争用: user=> (def my-ref (ref 0 :min-history 1)) #'user/my-ref user=> (ref-history-count my-ref) 0 user=> (dosync (alter my-ref inc)) 1 user=> (ref-history-count my-ref) 1 历史记录计数
历史计数,这将表明存在争用:
user=> (def my-ref (ref 0 :min-history 1))
#'user/my-ref
user=> (ref-history-count my-ref)
0
user=> (dosync (alter my-ref inc))
1
user=> (ref-history-count my-ref)
1
历史记录计数并不直接表示争用。相反,它表示为服务并发读取而维护的过去值的数量
历史记录的大小受min
和max
值的限制。默认情况下,它们分别是0
和10
,但您可以在创建ref
时更改它们(参见上文)。由于默认情况下min history
为0
,因此通常不会看到ref history count
返回非零值,除非ref上存在争用
有关历史记录计数的更多讨论,请参见此处:
我认为目前没有任何方法可以通过clojure.core
观察STM事务的速率。当然,您可以做一些类似于@Chouser在其
i、 e.在交易中增加一个计数器。每次尝试事务时都会发生增量。如果try count
大于1
,则会重试事务。通过引入命名的dosync块和提交计数(命名的dosync成功的次数),可以很容易地跟踪线程重试给定事务的次数
(def ^{:doc "ThreadLocal<Map<TxName, Map<CommitNumber, TriesCount>>>"}
local-tries (let [l (ThreadLocal.)]
(.set l {})
l))
(def ^{:doc "Map<TxName, Int>"}
commit-number (ref {}))
(def history ^{:doc "Map<ThreadId, Map<TxName, Map<CommitNumber, TriesCount>>>"}
(atom {}))
(defn report [_ thread-id tries]
(swap! history assoc thread-id tries))
(def reporter (agent nil))
(defmacro dosync [tx-name & body]
`(clojure.core/dosync
(let [cno# (@commit-number ~tx-name 0)
tries# (update-in (.get local-tries) [~tx-name] update-in [cno#] (fnil inc 0))]
(.set local-tries tries#)
(send reporter report (.getId (Thread/currentThread)) tries#))
~@body
(alter commit-number update-in [~tx-name] (fnil inc 0))))
…@history
的计算结果为:
;; {thread-id {tx-name {commit-number tries-count}}}
{40 {:x {3 1, 2 4, 1 3, 0 1}}, 39 {:x {2 1, 1 3, 0 1}}, ...}
这种附加实现实质上更简单
;; {thread-id retries-of-latest-tx}
(def tries (atom {}))
;; The max amount of tries any thread has performed
(def max-tries (atom 0))
(def ninc (fnil inc 0))
(def reporter (agent nil))
(defn report [_ tid]
(swap! max-tries #(max % (get @tries tid 0)))
(swap! tries update-in [tid] (constantly 0)))
(defmacro dosync [& body]
`(clojure.core/dosync
(swap! tries update-in [(.getId (Thread/currentThread))] ninc)
(commute commit-id inc)
(send reporter report (.getId (Thread/currentThread)))
~@body))
从未想过使用历史计数或txs中的原子。谢谢你的建议!另见:
;; {thread-id {tx-name {commit-number tries-count}}}
{40 {:x {3 1, 2 4, 1 3, 0 1}}, 39 {:x {2 1, 1 3, 0 1}}, ...}
;; {thread-id retries-of-latest-tx}
(def tries (atom {}))
;; The max amount of tries any thread has performed
(def max-tries (atom 0))
(def ninc (fnil inc 0))
(def reporter (agent nil))
(defn report [_ tid]
(swap! max-tries #(max % (get @tries tid 0)))
(swap! tries update-in [tid] (constantly 0)))
(defmacro dosync [& body]
`(clojure.core/dosync
(swap! tries update-in [(.getId (Thread/currentThread))] ninc)
(commute commit-id inc)
(send reporter report (.getId (Thread/currentThread)))
~@body))