从一个OutOfMemoryError 学会了分析Java内存泄漏问题

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以前都是好好的，最近出现了 oom。

问题

开始是： java.lang.OutOfMemoryError: Java heap space

-- ::41.678 ERROR --- [nio--exec-] c.e.p.s.c.c.core.ELDictionaryController : 系统异常org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.OutOfMemoryError: Java heap space
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:) ~[spring-webmvc-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:) ~[spring-webmvc-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:) [spring-webmvc-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:) [spring-webmvc-5.1..RELEASE.jar!/:5.1..RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:) [spring-webmvc-5.1..RELEASE.jar!/:5.1..RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:) [tomcat-embed-websocket-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:) [spring-web-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:) [spring-web-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.filters.RemoteIpFilter.doFilter(RemoteIpFilter.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.filters.RemoteIpFilter.doFilter(RemoteIpFilter.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:) [druid-1.1..jar!/:1.1.]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at com.lkk.platform.system.controller.filter.CORSFilter.doFilter(CORSFilter.java:) [erdp_system_controller-2.0.-GA.jar!/:2.0.-GA]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:) [spring-web-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:) [spring-web-5.1..RELEASE.jar!/:5.1..RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:) [na:1.8.0_212]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:) [na:1.8.0_212]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:) [tomcat-embed-core-9.0..jar!/:9.0.]
at java.lang.Thread.run(Thread.java:) [na:1.8.0_212]
Caused by: java.lang.OutOfMemoryError: Java heap space
at java.util.jar.Manifest.read(Manifest.java:) ~[na:1.8.0_212]
at sun.security.util.SignatureFileVerifier.processImpl(SignatureFileVerifier.java:) ~[na:1.8.0_212]
at sun.security.util.SignatureFileVerifier.process(SignatureFileVerifier.java:) ~[na:1.8.0_212]
at java.util.jar.JarVerifier.processEntry(JarVerifier.java:) ~[na:1.8.0_212]
at java.util.jar.JarVerifier.update(JarVerifier.java:) ~[na:1.8.0_212]
at java.util.jar.JarInputStream.read(JarInputStream.java:) ~[na:1.8.0_212]
at java.util.zip.ZipInputStream.closeEntry(ZipInputStream.java:) ~[na:1.8.0_212]
at java.util.zip.ZipInputStream.getNextEntry(ZipInputStream.java:) ~[na:1.8.0_212]
at java.util.jar.JarInputStream.getNextEntry(JarInputStream.java:) ~[na:1.8.0_212]
at java.util.jar.JarInputStream.getNextJarEntry(JarInputStream.java:) ~[na:1.8.0_212]
at org.apache.catalina.webresources.JarWarResourceSet.getArchiveEntries(JarWarResourceSet.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.webresources.AbstractArchiveResourceSet.getResource(AbstractArchiveResourceSet.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.webresources.StandardRoot.getResourceInternal(StandardRoot.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.webresources.Cache.getResource(Cache.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.webresources.StandardRoot.getResource(StandardRoot.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.webresources.StandardRoot.getClassLoaderResource(StandardRoot.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.findClassIgnoringNotFound(TomcatEmbeddedWebappClassLoader.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.doLoadClass(TomcatEmbeddedWebappClassLoader.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.loadClass(TomcatEmbeddedWebappClassLoader.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:) ~[tomcat-embed-core-9.0..jar!/:9.0.]
at ch.qos.logback.classic.spi.PackagingDataCalculator.loadClass(PackagingDataCalculator.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.PackagingDataCalculator.bestEffortLoadClass(PackagingDataCalculator.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.PackagingDataCalculator.computeBySTEP(PackagingDataCalculator.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.PackagingDataCalculator.populateFrames(PackagingDataCalculator.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.PackagingDataCalculator.calculate(PackagingDataCalculator.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.ThrowableProxy.calculatePackagingData(ThrowableProxy.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.spi.LoggingEvent.<init>(LoggingEvent.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:) ~[logback-classic-1.2..jar!/:na]
at ch.qos.logback.classic.Logger.error(Logger.java:) ~[logback-classic-1.2..jar!/:na]

512M 不够吗？很有可能啊...

增加内存到1G 后仍然出现问题：Failed to mark a promise as failure because it has failed already: [DefaultChannelPromise@33a99639(failure: io.netty.handler.codec.EncoderException: java.lang.OutOfMemoryError: GC overhead limit exceeded), io.netty.handler.codec.EncoderException: java.lang.OutOfMemoryError: GC overhead limit exceeded

java.lang.OutOfMemoryError: GC overhead limit exceeded-- ::42.648 WARN --- [erverWorker--] o.a.d.r.exchange.codec.ExchangeCodec : [DUBBO] Fail to encode response: Response [id=, version=2.0., status=, event=false, error=null, result=RpcResult [result=null, exception=org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is java.lang.OutOfMemoryError: GC overhead limit exceeded]], send bad_response info instead, cause: GC overhead limit exceeded, dubbo version: 2.7., current host: 192.168.11.183java.lang.OutOfMemoryError: GC overhead limit exceeded-- ::43.907 ERROR --- [-thread-] o.a.dubbo.rpc.filter.ExceptionFilter : [DUBBO] Got unchecked and undeclared exception which called by 192.168.11.183. service: com.elead.platform.system.domain.service.ELCommonCodeRegulationService, method: GetCode, exception: java.lang.OutOfMemoryError: GC overhead limit exceeded, dubbo version: 2.7., current host: 192.168.11.183

这就奇怪了！注意到出现次数比较多是 com.lkk.platform.system.domain.service.ELCommonCodeRegulationService, method: GetCode，

@Transactional(readOnly = false)
public String GetCode(String name){
RLock rlock = redissonManager.getRedisson().getLock(name);
boolean getLock = false;
try{
getLock = rlock.tryLock(, , TimeUnit.SECONDS);
if (getLock){
ELCodeDef elCodeDef = findCommonCode(name);
super.updateById(elCodeDef);
return elCodeDef.getCode();
}
}catch (Exception ex){
ex.printStackTrace();
}finally {
if (getLock) {
rlock.unlock();
}
}
return "";
}

而
@Autowired
RedissonManager redissonManager;

分析

由此怀疑这个地方有些问题。虽然出现了oom，但是进程没有死，似乎依然可以响应某些请求，于是把线程dump 下来，观察一番，发现 redisson-netty 竟然有上千个

就是这个

"redisson-netty-25-32" # prio= os_prio= tid=0x00007f7ec0187800 nid=0x3625 runnable [0x00007f7e77d6c000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:)
at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:)
- locked <0x00000000e90b27a0> (a io.netty.channel.nio.SelectedSelectionKeySet)
- locked <0x00000000e90b27f8> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000e90b2708> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:)
at io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:)
at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:)
at io.netty.util.concurrent.SingleThreadEventExecutor$.run(SingleThreadEventExecutor.java:)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:)
at java.lang.Thread.run(Thread.java:)

太不正常了！但是这里的redisson-netty- 仍然是 RUNNABLE 状态，看起来也不是问题啊！仔细检查了下，也没发现死锁啊！！

那就不是线程问题吗？

redisson 的bug 吗？ redisson 的官网的issue 搜索一番，无果。郁闷了！而且我的 redisson 版本是 3.1.1，已经很新的了吧！！

堆栈分析吧！！把java 的heap 拔下来，

jps -l, 然后 jmap -dump:format=b,file=dumpFileName pid

看到有些异常：

肯定不是 spring 的classloader 吧。

看到 netty 的PoolThreadCache 比较可疑啊，还有 mybatis。

Biggest Top-Level Dominator Packages 跟之前一样的提示，一个是netty的 PollThreadCache，一个是netty 的epoll，还有是redision，还有是sun 的EPollArrayWrapper，还有mybatis，其他也看不出什么来啊！

分析只能到此为止了吗？ io.netty.buffer.PoolThreadCache 是什么东东？我不熟悉啊！看过netty 源码，已经全忘了！

是内存泄漏吗？好像也看不出来。不太确定。网上搜索看看吧！！

还是从redision 入手吧。咦， redision 的用法好像不太对哦！！！改一下吧：

@Autowired
RedissonClient redissonClient;
==>
@Autowired
RedissonManager redissonManager; RLock rlock = redissonClient.getLock(name); ==> RLock lock = redissonManager.getRedisson().getLock(name);

而RedissonManager如下：

import org.apache.commons.lang3.StringUtils;
import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.redisson.config.ReadMode;
import org.redisson.config.SentinelServersConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;@Component
public class RedissonManager { @Autowired
RedisTemplate<String, Object> redisTemplate; @Value("${spring.redis.password}")
private String redisPassword; @Value("${spring.redis.port}")
private String redisPort; @Value("${spring.redis.host}")
private String redisHost; @Value("${spring.redis.timeout}")
private String redisTimeout; @Value("${spring.redis.sentinel.node}")
private String redisSentinelNode; @Value("${spring.redis.sentinel.master}")
private String redisSentinelMaster; @Bean
public RedissonClient getRedisson() {
Config config = new Config();
if (StringUtils.isNotEmpty(redisPort)) {
config.useSingleServer().setAddress("redis://" + redisHost + ":" + redisPort).setPassword(redisPassword);
} else if (StringUtils.isNotEmpty(redisSentinelNode)) {
String[] nodes = redisSentinelNode.split(",");
List<String> newNodes = new ArrayList(nodes.length);
Arrays.stream(nodes).forEach((index) -> newNodes.add(index.startsWith("redis://") ? index : "redis://" + index));
SentinelServersConfig serverConfig = config.useSentinelServers()
.addSentinelAddress(newNodes.toArray(new String[]))
.setMasterName(redisSentinelMaster)
.setReadMode(ReadMode.SLAVE)
.setTimeout(Integer.valueOf(redisTimeout));
if(StringUtils.isNotEmpty(redisPassword)){
serverConfig.setPassword(redisPassword);
}
}
return Redisson.create(config);
}
}

改了就好了！！突然自己明白了，原来就是这个redision 用法错误导致的！！

不信？重新拔下来heap dump 分析一下：

最大的 com.mysql.cj.jdbc.AbandonedConnectionCleanupThread 才占用2m，不是什么问题。可见已经没有了什么

PoolThreadCache 已经下滑到了第七位，总占用7M ,38个对象，看起来正常了许多！！：

总结

花了2天时间终于搞定！！

其实上面的 thread dump 和 heap dump 已经给出了比较明显的答案了！！就是 PoolThreadCache 占用了过多的内存，其原因就是 PoolThreadCache 错误的创建了太多！———— 本来应该是单例的对象，被搞成了 prototype，你说是不是引起了大错！！！一个 PoolThreadCache占用内存差不多196,000byte， 921个就是 180516000 byte 也就是差不多下图的180M，一类对象就 180M，总共才1G，当然会不够用！！