我提前为这篇笔记的篇幅道歉。我花了相当多的时间使它更短，这是我能得到的最小的。
我有一个谜，会很感激你的帮助。这个谜团来自observer我在 Clojure 中编写的 rxjava 的行为，它来自于observable从在线示例中抄录的几个简单的 s。
一个可观察对象同步向其观察者的处理程序发送消息onNext，而我所谓的有原则的观察者的行为符合预期。
另一个 observable 通过 Clojure 在另一个线程上异步执行相同的操作future。完全相同的观察者不会捕获发布到其的所有事件onNext；它似乎只是在尾部丢失了随机数量的消息。
promise在donCompleted的等待到期和发送到agent收集器的所有事件的等待到期之间存在以下故意竞争。如果获胜promise，我希望false在. 如果获胜，我希望看到来自's 队列的所有消息。我不期望的一个结果是AND来自. 但是，墨菲不睡觉，而这正是我所看到的。我不知道垃圾收集是否有问题，或者 Clojure 的 STM 内部排队，或者我的愚蠢，或者其他什么。onCompletedagentagenttrueonCompletedagenttrueonCompletedagent
我在这里按照自包含形式的顺序呈现源代码，以便它可以直接通过lein repl. 有三个仪式要避免：首先，leiningen 项目文件，project.clj它声明了0.9.0对 Netflix 的 rxjava 版本的依赖：
(defproject expt2 "0.1.0-SNAPSHOT"
:description "FIXME: write description"
:url "http://example.com/FIXME"
:license {:name "Eclipse Public License"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:dependencies [[org.clojure/clojure "1.5.1"]
[com.netflix.rxjava/rxjava-clojure "0.9.0"]]
:main expt2.core)
现在，命名空间和 Clojure 需求以及 Java 导入：
(ns expt2.core
(:require clojure.pprint)
(:refer-clojure :exclude [distinct])
(:import [rx Observable subscriptions.Subscriptions]))
最后，输出到控制台的宏：
(defmacro pdump [x]
`(let [x# ~x]
(do (println "----------------")
(clojure.pprint/pprint '~x)
(println "~~>")
(clojure.pprint/pprint x#)
(println "----------------")
x#)))
最后，给我的观察者。我使用 anagent来收集任何 observable 发送的消息onNext。我使用 anatom来收集潜在的onError. 我使用 apromise以便onCompleted观察者外部的消费者可以等待它。
(defn- subscribe-collectors [obl]
(let [;; Keep a sequence of all values sent:
onNextCollector (agent [])
;; Only need one value if the observable errors out:
onErrorCollector (atom nil)
;; Use a promise for 'completed' so we can wait for it on
;; another thread:
onCompletedCollector (promise)]
(letfn [;; When observable sends a value, relay it to our agent"
(collect-next [item] (send onNextCollector (fn [state] (conj state item))))
;; If observable errors out, just set our exception;
(collect-error [excp] (reset! onErrorCollector excp))
;; When observable completes, deliver on the promise:
(collect-completed [ ] (deliver onCompletedCollector true))
;; In all cases, report out the back end with this:
(report-collectors [ ]
(pdump
;; Wait for everything that has been sent to the agent
;; to drain (presumably internal message queues):
{:onNext (do (await-for 1000 onNextCollector)
;; Then produce the results:
@onNextCollector)
;; If we ever saw an error, here it is:
:onError @onErrorCollector
;; Wait at most 1 second for the promise to complete;
;; if it does not complete, then produce 'false'.
;; I expect if this times out before the agent
;; times out to see an 'onCompleted' of 'false'.
:onCompleted (deref onCompletedCollector 1000 false)
}))]
;; Recognize that the observable 'obl' may run on another thread:
(-> obl
(.subscribe collect-next collect-error collect-completed))
;; Therefore, produce results that wait, with timeouts, on both
;; the completion event and on the draining of the (presumed)
;; message queue to the agent.
(report-collectors))))
现在，这是一个同步的 observable。它将 25 条消息onNext送入观察者的喉咙，然后调用他们onCompleted的 s。
(defn- customObservableBlocking []
(Observable/create
(fn [observer] ; This is the 'subscribe' method.
;; Send 25 strings to the observer's onNext:
(doseq [x (range 25)]
(-> observer (.onNext (str "SynchedValue_" x))))
; After sending all values, complete the sequence:
(-> observer .onCompleted)
; return a NoOpSubsription since this blocks and thus
; can't be unsubscribed (disposed):
(Subscriptions/empty))))
我们订阅我们的观察者这个 observable：
;;; The value of the following is the list of all 25 events:
(-> (customObservableBlocking)
(subscribe-collectors))
它按预期工作，我们在控制台上看到以下结果
{:onNext (do (await-for 1000 onNextCollector) @onNextCollector),
:onError @onErrorCollector,
:onCompleted (deref onCompletedCollector 1000 false)}
~~>
{:onNext
["SynchedValue_0"
"SynchedValue_1"
"SynchedValue_2"
"SynchedValue_3"
"SynchedValue_4"
"SynchedValue_5"
"SynchedValue_6"
"SynchedValue_7"
"SynchedValue_8"
"SynchedValue_9"
"SynchedValue_10"
"SynchedValue_11"
"SynchedValue_12"
"SynchedValue_13"
"SynchedValue_14"
"SynchedValue_15"
"SynchedValue_16"
"SynchedValue_17"
"SynchedValue_18"
"SynchedValue_19"
"SynchedValue_20"
"SynchedValue_21"
"SynchedValue_22"
"SynchedValue_23"
"SynchedValue_24"],
:onError nil,
:onCompleted true}
----------------
这是一个异步 observable，它做的事情完全相同，只是在 afuture的线程上：
(defn- customObservableNonBlocking []
(Observable/create
(fn [observer] ; This is the 'subscribe' method
(let [f (future
;; On another thread, send 25 strings:
(doseq [x (range 25)]
(-> observer (.onNext (str "AsynchValue_" x))))
; After sending all values, complete the sequence:
(-> observer .onCompleted))]
; Return a disposable (unsubscribe) that cancels the future:
(Subscriptions/create #(future-cancel f))))))
;;; For unknown reasons, the following does not produce all 25 events:
(-> (customObservableNonBlocking)
(subscribe-collectors))
但是，令人惊讶的是，这是我们在控制台上看到的：truefor onCompleted，暗示promiseDID NOT TIME-OUT; 但只有一些异步消息。我们看到的实际消息数量因运行而异，这意味着存在一些并发现象。线索赞赏。
----------------
{:onNext (do (await-for 1000 onNextCollector) @onNextCollector),
:onError @onErrorCollector,
:onCompleted (deref onCompletedCollector 1000 false)}
~~>
{:onNext
["AsynchValue_0"
"AsynchValue_1"
"AsynchValue_2"
"AsynchValue_3"
"AsynchValue_4"
"AsynchValue_5"
"AsynchValue_6"],
:onError nil,
:onCompleted true}
----------------