BUG background

JDK: 11.0.4 Spring Cloud Finchley.SR3

Related configuration:

#Enable hystrix
feign.hystrix.enabled=true
#Close the circuit breaker
hystrix.command.default.circuitBreaker.enabled=false
#Disable hystrix remote call timeout
hystrix.command.default.execution.timeout.enabled=false
hystrix.threadpool.default.coreSize=50

Hystrix isolation strategy: thread isolation

When Feign is called, an error will be reported:

Caused by: java.util.concurrent.ExecutionException: Observable onError
        at rx.internal.operators.BlockingOperatorToFuture$2.getValue(BlockingOperatorToFuture.java:118) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.BlockingOperatorToFuture$2.get(BlockingOperatorToFuture.java:102) ~[rxjava-1.3.8.jar!/:1.3.8]
        at com.netflix.hystrix.HystrixCommand$4.get(HystrixCommand.java:423) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.HystrixCommand.execute(HystrixCommand.java:344) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        ... 30 more
Caused by: java.lang.IllegalArgumentException
        at java.util.concurrent.ThreadPoolExecutor.setCorePoolSize(ThreadPoolExecutor.java:1535) ~[?:?]
        at com.netflix.hystrix.HystrixThreadPool$HystrixThreadPoolDefault.touchConfig(HystrixThreadPool.java:230) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.HystrixThreadPool$HystrixThreadPoolDefault.getScheduler(HystrixThreadPool.java:205) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand.executeCommandWithSpecifiedIsolation(AbstractCommand.java:710) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand.executeCommandAndObserve(AbstractCommand.java:638) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand.applyHystrixSemantics(AbstractCommand.java:546) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand.access$200(AbstractCommand.java:60) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand$4.call(AbstractCommand.java:419) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at com.netflix.hystrix.AbstractCommand$4.call(AbstractCommand.java:413) ~[hystrix-core-1.5.18.jar!/:1.5.18]
        at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:46) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:35) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.Observable.unsafeSubscribe(Observable.java:10327) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:48) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:33) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.Observable.unsafeSubscribe(Observable.java:10327) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:41) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:30) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.Observable.unsafeSubscribe(Observable.java:10327) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:41) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:30) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.Observable.unsafeSubscribe(Observable.java:10327) ~[rxjava-1.3.8.jar!/:1.3.8]
        at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:51) ~[rxjava-1.3.8.jar!/:1.3.8]

Restart sometimes repeats, sometimes does not. It is estimated that it is related to class loading and initialization order.

Problem location

View the source code of the problem, initialize the Hytrix thread pool for each microservice call, and dynamically read the configuration:

private void touchConfig() {
    final int dynamicCoreSize = properties.coreSize().get();
    final int configuredMaximumSize = properties.maximumSize().get();
    int dynamicMaximumSize = properties.actualMaximumSize();
    final boolean allowSizesToDiverge = properties.getAllowMaximumSizeToDivergeFromCoreSize().get();
    boolean maxTooLow = false;

    if (allowSizesToDiverge && configuredMaximumSize < dynamicCoreSize) {
        //if user sets maximum < core (or defaults get us there), we need to maintain invariant of core <= maximum
        dynamicMaximumSize = dynamicCoreSize;
        maxTooLow = true;
    }

    // In JDK 6, setCorePoolSize and setMaximumPoolSize will execute a lock operation. Avoid them if the pool size is not changed.
    if (threadPool.getCorePoolSize() != dynamicCoreSize || (allowSizesToDiverge && threadPool.getMaximumPoolSize() != dynamicMaximumSize)) {
        if (maxTooLow) {
            logger.error("Hystrix ThreadPool configuration for : " + metrics.getThreadPoolKey().name() + " is trying to set coreSize = " +
                    dynamicCoreSize + " and maximumSize = " + configuredMaximumSize + ".  Maximum size will be set to " +
                    dynamicMaximumSize + ", the coreSize value, since it must be equal to or greater than the coreSize value");
        }
        threadPool.setCorePoolSize(dynamicCoreSize);
        threadPool.setMaximumPoolSize(dynamicMaximumSize);
    }

    threadPool.setKeepAliveTime(properties.keepAliveTimeMinutes().get(), TimeUnit.MINUTES);
}

The error is reported in threadpool.setcorepoolsize (dynamiccolesize);, see why:

public void setCorePoolSize(int corePoolSize) {
        if (corePoolSize < 0 || maximumPoolSize < corePoolSize)
            throw new IllegalArgumentException();
    //Ignore other codes
}

It is found that there is also a judgment of MaximumPoolSize < CorePoolSize. Therefore, you need to set MaximumPoolSize first, and then CorePoolSize to avoid this problem

Related ISSUES and Solutions

After looking at the community, there are already issues: https://github.com/Netflix/Hystrix/issues/1874 There is also the corresponding PULL REQUEST: https://github.com/Netflix/Hystrix/pull/1877

But at present, it has not been merged, so we have to change it by ourselves. In the project, we add a replacement class with the same name and the same path, and modify it:

//For jdk9 and above, setting coreSize will verify that coreSize must be smaller than maxSize, so change max before setting core
                threadPool.setMaximumPoolSize(dynamicMaximumSize);
                threadPool.setCorePoolSize(dynamicCoreSize);