由于OOM导致锁没有释放的定位问题是怎么就觉得，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
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最近发现业务上返回慢，并且feign的fallback被触发了。查看日志，发现触发了重试，是什么触发的重试呢，通过异常堆栈发现：
Caused by: feign.RetryableException: connect timed out executing GET http://test-service/test-api at feign.FeignException.errorExecuting(FeignException.java:65) ~[feign-core-9.7.0.jar!/:?] at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:105) ~[feign-core-9.7.0.jar!/:?] at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:77) ~[feign-core-9.7.0.jar!/:?] at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:107) ~[feign-hystrix-9.7.0.jar!/:?] at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:302) ~[hystrix-core-1.5.18.jar!/:1.5.18] at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:298) ~[hystrix-core-1.5.18.jar!/:1.5.18] at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:46) ~[rxjava-1.3.8.jar!/:1.3.8] ... 27 more Caused by: java.net.SocketTimeoutException: connect timed out at java.net.PlainSocketImpl.socketConnect(Native Method) ~[?:?] at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:399) ~[?:?] at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:242) ~[?:?] at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:224) ~[?:?] at java.net.Socket.connect(Socket.java:591) ~[?:?] at sun.net.NetworkClient.doConnect(NetworkClient.java:177) ~[?:?] at sun.net.www.http.HttpClient.openServer(HttpClient.java:474) ~[?:?] at sun.net.www.http.HttpClient.openServer(HttpClient.java:569) ~[?:?] at sun.net.www.http.HttpClient.(HttpClient.java:242) ~[?:?] at sun.net.www.http.HttpClient.New(HttpClient.java:341) ~[?:?] at sun.net.www.http.HttpClient.New(HttpClient.java:362) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1248) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1187) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1081) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1015) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1587) ~[?:?] at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1515) ~[?:?] at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:527) ~[?:?] at feign.Client$Default.convertResponse(Client.java:150) ~[feign-core-9.7.0.jar!/:?] at feign.Client$Default.execute(Client.java:72) ~[feign-core-9.7.0.jar!/:?] at org.springframework.cloud.sleuth.instrument.web.client.feign.TracingFeignClient.execute(TracingFeignClient.java:91) ~[spring-cloud-sleuth-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at org.springframework.cloud.sleuth.instrument.web.client.feign.LazyTracingFeignClient.execute(LazyTracingFeignClient.java:55) ~[spring-cloud-sleuth-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at org.springframework.cloud.openfeign.ribbon.RetryableFeignLoadBalancer$1.doWithRetry(RetryableFeignLoadBalancer.java:103) ~[spring-cloud-openfeign-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at org.springframework.cloud.openfeign.ribbon.RetryableFeignLoadBalancer$1.doWithRetry(RetryableFeignLoadBalancer.java:88) ~[spring-cloud-openfeign-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:287) ~[spring-retry-1.2.4.RELEASE.jar!/:?] at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:180) ~[spring-retry-1.2.4.RELEASE.jar!/:?] at org.springframework.cloud.openfeign.ribbon.RetryableFeignLoadBalancer.execute(RetryableFeignLoadBalancer.java:88) ~[spring-cloud-openfeign-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at org.springframework.cloud.openfeign.ribbon.RetryableFeignLoadBalancer.execute(RetryableFeignLoadBalancer.java:54) ~[spring-cloud-openfeign-core-2.0.3.RELEASE.jar!/:2.0.3.RELEASE] at com.netflix.client.AbstractLoadBalancerAwareClient$1.call(AbstractLoadBalancerAwareClient.java:104) ~[ribbon-loadbalancer-2.2.5.jar!/:2.2.5] at com.netflix.loadbalancer.reactive.LoadBalancerCommand$3$1.call(LoadBalancerCommand.java:303) ~[ribbon-loadbalancer-2.2.5.jar!/:2.2.5] at com.netflix.loadbalancer.reactive.LoadBalancerCommand$3$1.call(LoadBalancerCommand.java:287) ~[ribbon-loadbalancer-2.2.5.jar!/:2.2.5] at rx.internal.util.ScalarSynchronousObservable$3.call(ScalarSynchronousObservable.java:231) ~[rxjava-1.3.8.jar!/:1.3.8] at rx.internal.util.ScalarSynchronousObservable$3.call(ScalarSynchronousObservable.java:228) ~[rxjava-1.3.8.jar!/:1.3.8] at rx.Observable.unsafeSubscribe(Observable.java:10327) ~[rxjava-1.3.8.jar!/:1.3.8]
发现调用微服务test-service连接超时，注意是连接超时，而不是读取超时。接下来，首先查看ribbon连接超时配置，看是否配置的连接超时过短，发现是：
#ribbon默认连接超时 ribbon.ConnectTimeout=500
500ms建立tcp连接已经不短了，所以配置没有问题。从当前实例手动调用微服务实例的接口，看是否是通的：
curl http://test-service的ip:test-service的端口
发现访问成功，没有阻塞。证明网络连接没有问题，我们来看下netstat网络连接状态：
Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 test-5c665cc496-6jkx5:54644 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54666 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54680 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54088 ip-10-238-8-68.eu-central-1.compute.internal:8211 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54674 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54682 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54652 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 32 0 test-5c665cc496-6jkx5:47092 244-213-201-91.test.com:https CLOSE_WAIT tcp 0 0 test-5c665cc496-6jkx5:54662 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54624 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 32 0 test-5c665cc496-6jkx5:47098 244-213-201-91.test.com:https CLOSE_WAIT tcp 0 0 test-5c665cc496-6jkx5:54672 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54630 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:58758 ip-10-238-9-71.eu-central-1.compute.internal:MySQL ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:8251 10-238-8-117.api-gateway.test1.svc.cluster.local:43132 FIN_WAIT2 tcp 0 0 test-5c665cc496-6jkx5:54648 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:58778 ip-10-238-9-71.eu-central-1.compute.internal:mysql ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54646 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54628 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54650 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54632 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:54638 ip-10-238-8-119.eu-central-1.compute.internal:6379 ESTABLISHED tcp 0 0 test-5c665cc496-6jkx5:59434 ip-10-238-9-71.eu-central-1.compute.internal:mysql ESTABLISHED tcp 32 0 test-5c665cc496-6jkx5:47104 244-213-201-91.test.com:https CLOSE_WAIT tcp 1 0 test-5c665cc496-6jkx5:54146 ip-10-238-8-68.eu-central-1.compute.internal:8211 CLOSE_WAIT tcp 32 0 test-5c665cc496-6jkx5:47100 244-213-201-91.test.com:https CLOSE_WAIT tcp 32 0 test-5c665cc496-6jkx5:47106 244-213-201-91.test.com:https CLOSE_WAIT
发现：
并没有建立与现在service-test这个微服务任何实例ip的链接
并没有很多网络连接，也并没有很多Timed_waiting还有close_wait
猜想，可能是调用的service-test的ip地址不是最新的。
现在该Athas登场了，启动Arthas，我们查看下feign调用的真实ip： 由于我们使用了sleuth，所以这里用sleuth监控的feigh client去看调用ip：
watch org.springframework.cloud.sleuth.instrument.web.client.feign.TracingFeignClient execute params[0].url()
对应的代码是：
package org.springframework.cloud.sleuth.instrument.web.client.feign;
final class TracingFeignClient implements Client {
@Override public Response execute(Request request, Request.Options options)
throws IOException {
//.....
}
}通过观察，我们发现，确实是以前的ip。 那么为什么没有更新呢，我们来查看下EurekaClient相关的代码，参考我另一篇文章：Spring Cloud Eureka 全解 （4） - 核心流程-服务与实例列表获取详解. 我们来看下PollingServerListUpdater这个类，负责更新的线程池是：
int coreSize = poolSizeProp.get();
ThreadFactory factory = (new ThreadFactoryBuilder())
.setNameFormat("PollingServerListUpdater-%d")
.setDaemon(true)
.build();
_serverListRefreshExecutor = new ScheduledThreadPoolExecutor(coreSize, factory);谢天谢地，这个线程是有名字的。我们通过Arthas看下线程列表：
[arthas@24]$ thread thread Threads Total: 736, NEW: 0, RUNNABLE: 81, BLOCKED: 0, WAITING: 634, TIMED_WAITIN G: 21, TERMINATED: 0 ID NAME GROUP PRIORI STATE %CPU TIME INTER DAEMON 11 Log4j2-TF-2-AsyncLo main 5 TIMED 39 138:46 false true 17 Log4j2-TF-5-AsyncLo main 5 TIMED 37 137:27 false true 1045 as-command-execute- system 10 RUNNA 19 0:0 false true 1027 AsyncAppender-Worke system 9 WAITI 0 0:0 false true 68 AsyncResolver-boots main 5 TIMED 0 0:0 false true 264 AsyncResolver-boots main 5 WAITI 0 0:0 false true 1025 Attach Listener system 9 RUNNA 0 0:0 false true 9 Common-Cleaner InnocuousThr 8 TIMED 0 0:0 false true 151 DataPublisher main 5 TIMED 0 0:2 false true 107 DestroyJavaVM main 5 RUNNA 0 0:37 false false 69 DiscoveryClient-0 main 5 TIMED 0 0:1 false true 70 DiscoveryClient-1 main 5 WAITI 0 0:1 false true 748 DiscoveryClient-Cac main 5 WAITI 0 0:9 false true 751 DiscoveryClient-Hea main 5 WAITI 0 0:7 false true 71 DiscoveryClient-Ins main 5 TIMED 0 0:0 false true 24 Druid-ConnectionPoo main 5 WAITI 0 0:0 false true 21 Druid-ConnectionPoo main 5 WAITI 0 0:0 false true 25 Druid-ConnectionPoo main 5 TIMED 0 0:0 false true 22 Druid-ConnectionPoo main 5 TIMED 0 0:0 false true 20 Druid-ConnectionPoo main 5 TIMED 0 0:0 false true 67 Eureka-JerseyClient main 5 WAITI 0 0:0 false true 3 Finalizer system 8 WAITI 0 0:0 false true 119 ForkJoinPool.common main 5 WAITI 0 0:9 false true 30 I/O dispatcher 1 main 5 RUNNA 0 0:2 false false 155 NFLoadBalancer-Ping main 5 TIMED 0 0:0 false true 150 PollingServerListUp main 5 WAITI 0 0:0 false true 157 PollingServerListUp main 5 WAITI 0 0:0 false true 2 Reference Handler system 10 RUNNA 0 0:0 false true 146 RibbonApacheHttpCli main 5 TIMED 0 0:0 false true 135 RxComputationSchedu main 5 TIMED 0 1:44 false true 132 RxIoScheduler-1 (Ev main 5 TIMED 0 0:0 false true 4 Signal Dispatcher system 9 RUNNA 0 0:0 false true 114 SimplePauseDetector main 5 TIMED 0 2:10 false true 115 SimplePauseDetector main 5 TIMED 0 2:10 false true 116 SimplePauseDetector main 5 TIMED 0 2:12 false true
发现关键字PollingServerListUp有两个线程，150和157，分别看看他们在干什么：
[arthas@24]$ thread 150 thread 150 "PollingServerListUpdater-0" Id=150 WAITING on java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject@778af81b at java.base@11.0.4/jdk.internal.misc.Unsafe.park(Native Method) - waiting on java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject@778af81b at java.base@11.0.4/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194) at java.base@11.0.4/java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2081) at java.base@11.0.4/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1170) at java.base@11.0.4/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:899) at java.base@11.0.4/java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1054) at java.base@11.0.4/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1114) at java.base@11.0.4/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base@11.0.4/java.lang.Thread.run(Thread.java:834) Affect(row-cnt:0) cost in 322 ms. [arthas@24]$ thread 157 thread 157 "PollingServerListUpdater-1" Id=157 WAITING on java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync@3adcda2 at java.base@11.0.4/jdk.internal.misc.Unsafe.park(Native Method) - waiting on java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync@3adcda2 at java.base@11.0.4/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194) at java.base@11.0.4/java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:885) at java.base@11.0.4/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:917) at java.base@11.0.4/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1240) at java.base@11.0.4/java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:959) at com.netflix.loadbalancer.BaseLoadBalancer.setServersList(BaseLoadBalancer.java:475) at com.netflix.loadbalancer.DynamicServerListLoadBalancer.setServersList(DynamicServerListLoadBalancer.java:156) at com.netflix.loadbalancer.DynamicServerListLoadBalancer.updateAllServerList(DynamicServerListLoadBalancer.java:267) at com.netflix.loadbalancer.DynamicServerListLoadBalancer.updateListOfServers(DynamicServerListLoadBalancer.java:250) at com.netflix.loadbalancer.DynamicServerListLoadBalancer$1.doUpdate(DynamicServerListLoadBalancer.java:62) at com.netflix.loadbalancer.PollingServerListUpdater$1.run(PollingServerListUpdater.java:116) at java.base@11.0.4/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) at java.base@11.0.4/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) at java.base@11.0.4/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) at java.base@11.0.4/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base@11.0.4/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base@11.0.4/java.lang.Thread.run(Thread.java:834) Number of locked synchronizers = 1 - java.util.concurrent.ThreadPoolExecutor$Worker@6ab1c5f9
发现PollingServerListUpdater-1一直等待获取锁，看来问题就在这里了，查看对应的Ribbon代码，发现：
PollingServerListUpdater-1需要获取allServerLock的写锁
allServerLock的读锁，只有runPinger（对于每个实例ping，需要读取实例列表）获取。
那么是不是Ping出了问题，我们看下对应的获取锁的代码BaseLoadBalancer：
public void runPinger() throws Exception {
//省略无用代码
allLock = allServerLock.readLock();
allLock.lock();
allServers = allServerList.toArray(new Server[allServerList.size()]);
allLock.unlock();我们看到，这里的代码，并没有用try{lock} finally {unlock}的套路，如果中间代码异常，则会锁不能释放。 并且这里是重入锁，lock多少次就要unlock多少次，少一次，其他线程都获取不到。
allServers = allServerList.toArray(new Server[allServerList.size()]);并没有涉及任何IO，只是数据变换，也没有空指针异常。猜想是发生了OOM异常，导致内存没有分配。检查日志，果然发现了OOM。
这件事告诉我们，对于锁，一定要try{lock} finally {unlock}。就算代码不会抛出任何异常，发生OOM时，也有可能导致锁不能释放
关于由于OOM导致锁没有释放的定位问题是怎么就觉得问题的解答就分享到这里了，希望以上内容可以对大家有一定的帮助，如果你还有很多疑惑没有解开，可以关注创新互联行业资讯频道了解更多相关知识。
