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环境：
linux上的tomcat中部署了一个web服务，
时好时坏，经常上午启动，下午就无法访问。
总是莫名其妙的宕机。
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解决步骤：
目录是在你的tomcat的目录下的logs目录下
tail -n 200 -f catalina.out
收集到的日志大致如下：
[GC [PSYoungGen: 1610144K->54342K(1998336K)] 2233750K->678204K(6777344K), 0.0687220 secs] [Times: user=0.22 sys=0.00, real=0.07 secs] [GC [PSYoungGen: 1661510K->91007K(2016768K)] 2285372K->764127K(6795776K), 0.1119750 secs] [Times: user=0.29 sys=0.01, real=0.11 secs] [GC [PSYoungGen: 1721727K->3808K(2003456K)] 2394847K->760833K(6782464K), 0.0980690 secs] [Times: user=0.27 sys=0.03, real=0.10 secs] java.net.ConnectException: Connection timed out at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:579) at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:117) at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:177) at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:131) at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:611) at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:446) at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:882) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82) at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107) at util.httpclient.HttpXmlClient.sendRequest(HttpXmlClient.java:234) at util.httpclient.HttpXmlClient.invoke(HttpXmlClient.java:201) at util.httpclient.HttpXmlClient.post(HttpXmlClient.java:43) at quartz.InvoiceApplyOrderStatusJob.getSalOrderStatus(InvoiceApplyOrderStatusJob.java:87) at quartz.InvoiceApplyOrderStatusJob.findOrderStatus(InvoiceApplyOrderStatusJob.java:45) at quartz.InvoiceApplyOrderStatusJob.excute(InvoiceApplyOrderStatusJob.java:37) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:64) at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:53) at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask.run(FutureTask.java:262) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) [ERROR][quartz.InvoiceApplyOrderStatusJob] [ ] [ERROR][org.springframework.scheduling.support.TaskUtils$LoggingErrorHandler] [ Unexpected error occurred in scheduled task. ] java.lang.NullPointerException at quartz.InvoiceApplyOrderStatusJob.findOrderStatus(InvoiceApplyOrderStatusJob.java:48) at quartz.InvoiceApplyOrderStatusJob.excute(InvoiceApplyOrderStatusJob.java:37) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:64) at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:53) at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask.run(FutureTask.java:262) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) [GC [PSYoungGen: 1634528K->3520K(2018304K)] 2391553K->761134K(6797312K), 0.0790130 secs] [Times: user=0.21 sys=0.00, real=0.08 secs] [GC [PSYoungGen: 1647552K->71575K(2015232K)] 2405166K->829734K(6794240K), 0.1101140 secs] [Times: user=0.34 sys=0.01, real=0.11 secs] [GC [PSYoungGen: 1715607K->75061K(2053120K)] 2473766K->898535K(6832128K), 0.1175420 secs] [Times: user=0.37 sys=0.00, real=0.12 secs] Java HotSpot(TM) 64-Bit Server VM warning: Attempt to protect stack guard pages failed. Java HotSpot(TM) 64-Bit Server VM warning: Attempt to deallocate stack guard pages failed. Java HotSpot(TM) 64-Bit Server VM warning: Attempt to deallocate stack guard pages failed. Java HotSpot(TM) 64-Bit Server VM warning: Attempt to deallocate stack guard pages failed. Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f906fa7b000, 12288, 0) failed; error='Cannot allocate memory' (errno=12) # # There is insufficient memory for the Java Runtime Environment to continue. # Native memory allocation (malloc) failed to allocate 12288 bytes for committing reserved memory. # An error report file with more information is saved as: # /backup/tomcat7/bin/hs_err_pid916618.log Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f8f11051000, 12288, 0) failed; error='Cannot allocate memory' (errno=12)