差異處
這裏顯示兩個版本的差異處。
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java:java:java8:concurrent:blockingoperationwithcompletablefuture:avoid_transition_task [2019/01/13 22:39] tony |
java:java:java8:concurrent:blockingoperationwithcompletablefuture:avoid_transition_task [2023/06/25 09:48] |
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| - | {{tag>java concurrency}} | ||
| - | ====== 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: | ||
| - | <code java> | ||
| - | @Test | ||
| - | public void fixTransitionTask(){ | ||
| - | doSmthAsync() | ||
| - | .thenAccept(response->{ | ||
| - | System.out.println(response); | ||
| - | }); | ||
| - | } | ||
| - | </code> | ||
| - | ===== Reference ===== | ||
| - | * [[https://qconsf.com/sf2017/system/files/presentation-slides/cf.pdf|Asynchronous API with | ||
| - | CompletableFuture - Performance Tips and Tricks]] | ||
| - | |||
| - | ====== ====== | ||
| - | ---- | ||
| - | \\ | ||
| - | ~~DISQUS~~ | ||
