差異處
這裏顯示兩個版本的差異處。
java:java:java8:concurrent:blockingoperationwithcompletablefuture:avoid_transition_task [2019/01/13 15:11] tony [Problem] |
java:java:java8:concurrent:blockingoperationwithcompletablefuture:avoid_transition_task [2023/06/25 09:48] |
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- | ====== CompletableFuture - Avoid transition task from one thread to another. It costs. ====== | ||
- | ===== Problem ===== | ||
- | 這問題通常發生在同時支援sync與async版本的API,或者是沒善用CompletableFuture功能的情況。以下是我的範例程式,基本上就是在透過CompletableFuture送出工作後,再等待執行結果以進行處理: | ||
- | <code java> | ||
- | public Response doSmth(){ | ||
- | return doSmthAsync().join(); | ||
- | } | ||
- | |||
- | public CompletableFuture<Response> doSmthAsync(){ | ||
- | return CompletableFuture.supplyAsync(()->{ | ||
- | return new Response(); | ||
- | }); | ||
- | } | ||
- | |||
- | @Test | ||
- | public void transitionTask(){ | ||
- | Response response = doSmth(); | ||
- | System.out.println(response); | ||
- | } | ||
- | </code> | ||
- | 這程式的執行過程如下圖所示:\\ | ||
- | {{:java:java:java8:concurrent:blockingoperationwithcompletablefuture:java8_completablefuture_perf_block_client.png?450|}}\\ | ||
- | 以單一工作來說,假如你的需求是屬於sync的情況,代表你必須等這個結果才能進行處理,那為何需要另外開一個thread pool來執行這個工作呢? 假如你的需求是要做成async的情況,那為何需要去等待結果去進行處理呢? 這兩者造成了client thread與使用的ExecutorServicec的浪費。\\ | ||
- | (本篇圖片都來自於[[https://qconsf.com/sf2017/system/files/presentation-slides/cf.pdf|link]]) | ||
- | ===== How to resolve? ===== | ||
- | 針對sync的情況,其實你根本不需要額外透過ExecutorService去執行,client thread就可以幫你完成這個任務。如果是針對async的情況,這時候應該要好好善用CompletableFuture的callback功能才對。 | ||
- | ===== Reference ===== | ||
- | * [[https://qconsf.com/sf2017/system/files/presentation-slides/cf.pdf|Asynchronous API with | ||
- | CompletableFuture - Performance Tips and Tricks]] | ||
- | ====== ====== | ||
- | ---- | ||
- | \\ | ||
- | ~~DISQUS~~ |