轉自： http://xmdxzyf.iteye.com/blog/1698819
?
這幾天在解決一個用mina開發的高并發通信過程中產生的一個bug。
?? 模擬場景為：
?? 通過定時觸發啟動線程模擬高并發短連接測試，測試的服務端有2個，一個是服務有起，一個沒起，客戶端和服務端均在同一服務器上。執行一段時間后linux主機上通過lsof命令查看，發現有遞增的文件句柄，pipe和eventpoll。
?? 拋出的異常如下：
??
Java代碼
?
?
- 2012 - 10 - 13 ? 10 : 09 : 48 ?-org.apache.mina.core.service.SimpleIoProcessorPool.<init>(SimpleIoProcessorPool.java: 197 )??
- ?Failed?to?create?a? new ?instance?of?org.apache.mina.transport.socket.nio.NioProcessor: null ??
- java.lang.reflect.InvocationTargetException??
- ????????at?sun.reflect.GeneratedConstructorAccessor110.newInstance(Unknown?Source)??
- ????????at?sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java: 27 )??
- ????????at?java.lang.reflect.Constructor.newInstance(Constructor.java: 513 )??
- ????????at?org.apache.mina.core.service.SimpleIoProcessorPool.<init>(SimpleIoProcessorPool.java: 180 )??
- ????????at?org.apache.mina.core.service.SimpleIoProcessorPool.<init>(SimpleIoProcessorPool.java: 112 )??
- ????????at?org.apache.mina.core.polling.AbstractPollingIoConnector.<init>(AbstractPollingIoConnector.java: 93 )??
- ????????at?org.apache.mina.transport.socket.nio.NioSocketConnector.<init>(NioSocketConnector.java: 56 )??
- ????????at?com.develop.webplatform.funnel.client.JobClient.sendMessage(JobClient.java: 39 )??
- ????????at?com.develop.webplatform.funnel.client.JobClient.sendJob(JobClient.java: 126 )??
- ????????at?com.develop.webplatform.funnel.extend.JobExecRemotelyBySocket.execJobByTask(JobExecRemotelyBySocket.java: 66 )??
- ????????at?com.develop.webplatform.funnel.JobManager.execJobByTask(JobManager.java: 27 )??
- ????????at?com.develop.webplatform.quartz.job.TaskJob.executeInternal(TaskJob.java: 38 )??
- ????????at?org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java: 86 )??
- ????????at?org.quartz.core.JobRunShell.run(JobRunShell.java: 223 )??
- ????????at?org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java: 549 )??
- Caused?by:?org.apache.mina.core.RuntimeIoException:?Failed?to?open?a?selector.??
- ????????at?org.apache.mina.transport.socket.nio.NioProcessor.<init>(NioProcessor.java: 61 )??
- ????????...? 15 ?more??
- Caused?by:?java.io.IOException:?Too?many?open?files??
- ????????at?sun.nio.ch.IOUtil.initPipe(Native?Method)??
- ????????at?sun.nio.ch.EPollSelectorImpl.<init>(EPollSelectorImpl.java: 49 )??
- ????????at?sun.nio.ch.EPollSelectorProvider.openSelector(EPollSelectorProvider.java: 18 )??
- ????????at?java.nio.channels.Selector.open(Selector.java: 209 )??
- ????????at?org.apache.mina.transport.socket.nio.NioProcessor.<init>(NioProcessor.java: 59 )??
- ????????...? 15 ?more??
????
??? 原代碼中，關于客戶端連接的代碼如下：
???
Java代碼
?
?
- final ?NioSocketConnector?connector?=? new ?NioSocketConnector();??
- ???????? final ?String[]?result?=? new ?String[ 1 ];??
- ????????connector.getFilterChain().addLast( "codec" ,??
- ???????????????? new ?ProtocolCodecFilter( new ?ObjectSerializationCodecFactory()));??
- ????????connector.setHandler(handler);??
- ??
- ???????? //設置超時 ??
- ????????connector.setConnectTimeoutMillis(defaultConnectTimeOut);??
- ????????ConnectFuture?connectFuture?=?connector.connect(address);??
- ????????connectFuture.awaitUninterruptibly();??? //同步，等待，直到連接完成 ??
- ???????? if ?(connectFuture.isDone())?{??
- ???????????? if ?(!connectFuture.isConnected())?{? //若在指定時間內沒連接成功，則拋出異常 ??
- ????????????????logger.info( "fail?to?connect?" ?+?logInfo);??
- ??
- ???????????????? throw ? new ?Exception();??
- ????????????}??
- ????????}??
???????
???????? 經過分析，導致主機文件句柄泄露的原因為，客戶端發起服務端連接時，會請求系統分配相關的文件句柄，在原代碼中，僅僅判斷是否連接成功，而未對連接失敗進行資源釋放，從而造成文件句柄泄露。當總的文件句柄數超過系統設置值（ulimit -n 查看同一個進程允許的最大文件句柄數），則拋出異常“java.io.IOException: Too many open files",導致無法創建新的連接，服務器掛掉。
????? 更改后的代碼如下：
??
Java代碼
?
?
- final ?NioSocketConnector?connector?=? new ?NioSocketConnector();??
- ???????? final ?String[]?result?=? new ?String[ 1 ];??
- ????????connector.getFilterChain().addLast( "codec" ,??
- ???????????????? new ?ProtocolCodecFilter( new ?ObjectSerializationCodecFactory()));??
- ????????connector.setHandler(handler);??
- ??
- ???????? //設置超時 ??
- ????????connector.setConnectTimeoutMillis(defaultConnectTimeOut);??
- ????????ConnectFuture?connectFuture?=?connector.connect(address);??
- ????????connectFuture.awaitUninterruptibly();??? //同步，等待，直到連接完成 ??
- ???????? if ?(connectFuture.isDone())?{??
- ???????????? if ?(!connectFuture.isConnected())?{? //若在指定時間內沒連接成功，則拋出異常 ??
- ????????????????logger.info( "fail?to?connect?" ?+?logInfo);??
- ????????????????connector.dispose();???? //不關閉的話會運行一段時間后拋出，too?many?open?files異常，導致無法連接 ??
- ??
- ???????????????? throw ? new ?Exception();??
- ????????????}??
- ????????}??
?
更多文章、技術交流、商務合作、聯系博主
微信掃碼或搜索：z360901061
微信掃一掃加我為好友
QQ號聯系： 360901061
您的支持是博主寫作最大的動力，如果您喜歡我的文章，感覺我的文章對您有幫助，請用微信掃描下面二維碼支持博主2元、5元、10元、20元等您想捐的金額吧，狠狠點擊下面給點支持吧，站長非常感激您！手機微信長按不能支付解決辦法：請將微信支付二維碼保存到相冊，切換到微信，然后點擊微信右上角掃一掃功能，選擇支付二維碼完成支付。
【本文對您有幫助就好】元
