問題描述

　　生產環境下有幾臺tomcat,但突然某個時候發現所有的請求都不能響應了,由于我們的web server使用的是nginx,會將請求反向到tomcat上,所以起初懷疑是nginx就沒有收到請求,但查看日志后發現,nginx中大量出現499的返回,這說明問題還是出在tomcat上.

　　問題排查

　　首先我想到的是不是CPU跑滿了,雖說CPU沒有報警但還是本能的top命令看下系統負載,發現系統只有0.x的負載,cpu,內存消耗都是正常的.

　　由于CPU沒有出現異常,所以應該不是GC出現了問題,但還是檢查了下GC log,果然GC也沒問題

　　此時必須讓jstack上場了,果然在使用jstack后發現很多線程都是WAITING狀態

"http-nio-127.0.0.1-801-exec-498" daemon prio=10 tid=0x00002ada7c14f800 nid=0x16a6 waiting on condition [0x00002ada9c905000]　　java.lang.Thread.State: WAITING (parking)　　at sun.misc.Unsafe.park(Native Method)　　- parking to wait for <0x00000007873e6990> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)　　at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)　　at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)　　at org.apache.http.pool.PoolEntryFuture.await(PoolEntryFuture.java:133)　　at org.apache.http.pool.AbstractConnPool.getPoolEntryBlocking(AbstractConnPool.java:282)　　at org.apache.http.pool.AbstractConnPool.access$000(AbstractConnPool.java:64)　　at org.apache.http.pool.AbstractConnPool$2.getPoolEntry(AbstractConnPool.java:177)　　at org.apache.http.pool.AbstractConnPool$2.getPoolEntry(AbstractConnPool.java:170)　　at org.apache.http.pool.PoolEntryFuture.get(PoolEntryFuture.java:102)　　at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:240)　　at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:227)　　at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:173)　　at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)　　at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:85)　　at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)　　at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:186)　　at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)　　at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:106)　　at com.weimai.utils.HttpClientUtil.doGet(HttpClientUtil.java:105)　　at com.weimai.utils.HttpClientUtil.doGet(HttpClientUtil.java:87)　　at com.weimai.utils.WeiBoUtil.checkUser(WeiBoUtil.java:214)　　at com.weimai.web.UserInfoController.newWeiboLogin(UserInfoController.java:1223)　　at sun.reflect.GeneratedMethodAccessor390.invoke(Unknown Source)　　at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)　　at java.lang.reflect.Method.invoke(Method.java:606)