I'm stupid. When completable future is used with openfegin, it even reports an error

cause

In an iterative requirement , You need to record user behavior , Thinking about recording user behavior, this part of business logic can be modified to execute asynchronously , I used CompletableFuture Of runAsync() Method to implement asynchronous , Originally, the local environment did not report an error , But when it was sent to the development environment server, it reported an error .

Error reporting pseudo code

 CompletableFuture.runAsync(()->{
            // Drop out user The service saves user behavior 
            userClient.saveUserBehavior();
 });
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Error messages and the environment in which they are used

Environmental Science ：jdk It uses openjdk11,SpringCloud The version is 2020.0.3

java.lang.ClassNotFoundException: org.springframework.boot.autoconfigure.condition.OnPropertyCondition
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Problem solving process

Because there is no error in the local environment , But the development environment is wrong , So I didn't merge when I first checked the code , Whether the code is not submitted to the development environment . But after rechecking , It is found that the code has been merged and submitted to the development branch . Then start to analyze the cause of the error , When you see this mistake , I believe you, like me, will think that the first reaction is Jar Package conflict , But carefully check the dependent Spring Version of , Find out Spring Version of the does not conflict . Thinking about whether it is the code I changed that has changed something wrong ？ I'm in a panic , I just changed the code to asynchronous , So I changed the code back to synchronization , As expected, there is no problem .

Try to find the cause of the problem

Although the problem has been solved , But I'm a curious programmer , Why is it CompletableFuture Drop out Fegin The interface will report an error , What is the cause ？ With this question , I started in GitHub I went shopping . I thought I was not the only one who used it like this , So many students should also encounter such problems . Sure enough github It didn't disappoint me , There is really something I want on it .（ So programmers should be more Github Go fishing ）

In this issues in , I found the answer ,issues The submitter of is the same as the problem I encountered , Even the error information is so similar , I immediately felt happy . In general Fegin Interfaces are lazy , Only when we first use this Fegin Interface will be right Fegin Interface to initialize , But if ForkJoinWorkerThread Use in Fegin Interface , Will appear ClassNotFoundException. Use other common JVM There will be no problem with thread pool .

Let's take a look Spring Cloud The team's answer to this question

Spring Cloud The answer given by the team is ：

Roughly speaking, in parallel flow （ Multithreading ） Call in FeignBlockingLoadBalancerClient When it comes to ClassNotFoundException.

But after local testing , Only in use ForkJoinPool Call in the thread pool Fegin The interface will report an error , If we were ThreadPoolExecutor Customize the thread pool or use jdk Thread pool provided （ for example FixedThreadPool） Call in Fegin The interface will not report errors , By coincidence CompletableFuture The default thread pool in is also through ForkJoinPool Thread pool . Is there really such a coincidence ？ These two developers confirmed that in ForkJoinPool Use in Fegin This error will appear in the interface , But the others JVM Thread pool can work normally .

Then why is there no problem testing in the local environment , But publish to dev The environment is having problems ？

With this question, I checked the differences between the development environment and the local environment , Discover the JDk The version is 11, however dev Used in the environment JDK yes Openjdk11. Then I replace it locally jdk The version is openJdk, Conduct further tests locally .

Sure enough, the code reported an error again .

 java.lang.ClassNotFoundException: org.springframework.boot.autoconfigure.condition.OnPropertyCondition
      at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source) ~[na:na]
      at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source) ~[na:na]
      at java.base/java.lang.ClassLoader.loadClass(Unknown Source) ~[na:na]
      at java.base/java.lang.Class.forName0(Native Method) ~[na:na]
      at java.base/java.lang.Class.forName(Unknown Source) ~[na:na]
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So this question Spring Cloud Has the team solved it ？

unfortunately , There is no solution .Spring Cloud The team believes that the priority of this problem is not high , And not recommended in CompletableFuture Call in Fegin Interface , It also said that if someone in the community is willing to submit code for this problem ,Spring Cloud The team will also carefully review the code , If passed, the code will also be merged .

ok , It seems that I can only use custom TreadPool To achieve asynchrony （ You can also use it mq）.

summary

Only in openJDK11 This problem only occurs in version （ I also tried it when I got home JDK8, There's no exception ）, And if it's in ForkJoinPool Call in Fegin Interface , Then there will be ClassNotFoundException. because Spring Cloud The team believes that the priority of this problem is not high , It doesn't solve the problem . although CompletableFuture It really works , But if you need to be in CompletableFuture Call in Fegin Interface , Then it is suggested to define a custom thread pool , Don't use the default ForkJoinPool.

Use the following api,CompletableFuture We will use our incoming thread pool to execute tasks .

public static CompletableFuture<Void> runAsync(Runnable runnable,
                                                   Executor executor) {
        return asyncRunStage(screenExecutor(executor), runnable);
    }
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So if you need to call asynchronously Fegin Interface , You need to pay more attention , Avoid trampling .

If there are any questions , Feel free to leave a comment in the comments section below . Last , Originality is not easy. , If this article helps you , Then give a compliment before you go .