Random UnknownHostExceptions

We are seeing random UnknownHostExceptions and are looking for suggestions
on trying to find out the root cause. We are seeing one error per 100K
connections as my best guesstimation.

We are running on CentOS 5.2, tomcat 6.0.29, jdbc 9.0-801.jdbc4 and using
tomcat-dbcp connection pooling.

An example of the failure senario is as follows.

At 2012-06-28 08:46:43,886 we got the exception at the bottom. According
to the tcpdump, there was not a DNS lookup for the server at this time and
we have active DB connections to the server.

According to the db log, we had successful connections before and after the
failure:
Jun 28 08:46:02 iprobe113 postgres[12386]: [2-1] LOG: connection received:
host=192.168.175.21 port=53592
Jun 28 08:46:02 iprobe113 postgres[12387]: [2-1] LOG: connection received:
host=192.168.175.21 port=53593
Jun 28 08:47:58 iprobe113 postgres[12461]: [2-1] LOG: connection received:
host=192.168.175.21 port=53614
Jun 28 08:47:58 iprobe113 postgres[12462]: [2-1] LOG: connection received:
host=192.168.175.21 port=53615
There are no DNS attempts for any of these connections. According to the
tcpdump, the next DNS attempt is not until 8:50.

Any suggestions would be appreciated.
George Woodring

The following is the exception we are seeing

org.postgresql.util.PSQLException: The connection attempt failed.
at org.postgresql.Driver$ConnectThread.getResult(Driver.java:348)
at org.postgresql.Driver.connect(Driver.java:271)
at
org.apache.tomcat.dbcp.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at
org.apache.tomcat.dbcp.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)
at
org.apache.tomcat.dbcp.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1148)
at
org.apache.tomcat.dbcp.dbcp.AbandonedObjectPool.borrowObject(AbandonedObjectPool.java:79)
at
org.apache.tomcat.dbcp.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
at
org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
at
org.apache.commons.dbutils.QueryRunner.prepareConnection(QueryRunner.java:195)
at net.iglass.db.QueryRunner.prepareConnection(QueryRunner.java:211)
at net.iglass.db.QueryRunner.query(QueryRunner.java:287)
at
net.iglass.jglass.core.dao.StaticGraphDAO.fetchCpeHistHealthDataForDataSources(StaticGraphDAO.java:1172)
at
net.iglass.jglass.core.dao.StaticGraphDAO.fetchCpeHistHealthDataSources(StaticGraphDAO.java:591)
at
net.iglass.jglass.jrobin.builder.CpeHistHealthBuilder.addLines(CpeHistHealthBuilder.java:131)
at
net.iglass.jglass.jrobin.builder.AbstractBuilder.buildMiniGraph(AbstractBuilder.java:266)
at
net.iglass.jglass.jrobin.builder.AbstractBuilder.buildGraph(AbstractBuilder.java:179)
at
net.iglass.jglass.jrobin.action.GraphAction.getGraph(GraphAction.java:145)
at
net.iglass.jglass.jrobin.action.GraphAction.doExecute(GraphAction.java:75)

at
com.cc.framework.adapter.struts.ActionUtil.execute(ActionUtil.java:751)
at
com.cc.framework.adapter.struts.FWAction.execute(FWAction.java:279)
at net.iglass.jglass.BaseAction.execute(BaseAction.java:93)
at
com.cc.framework.adapter.struts.FWAction.execute(FWAction.java:314)
at
com.cc.framework.adapter.struts.RequestProcessorUtil.processAction(RequestProcessorUtil.java:76)
at
com.cc.framework.adapter.struts.FWRequestProcessor.processActionPerform(FWRequestProcessor.java:90)
at
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
at
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
at
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
net.iglass.jglass.servlets.SessionListener.doFilter(SessionListener.java:529)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
net.iglass.jglass.servlets.AccessControlFilter.doFilter(AccessControlFilter.java:303)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at
org.apache.coyote.ajp.AjpAprProcessor.process(AjpAprProcessor.java:427)
at
org.apache.coyote.ajp.AjpAprProtocol$AjpConnectionHandler.process(AjpAprProtocol.java:384)
at
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1584)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.net.UnknownHostException: iprobe113

at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:177)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.<init>(Socket.java:375)
at java.net.Socket.<init>(Socket.java:189)
at org.postgresql.core.PGStream.<init>(PGStream.java:62)
at
org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:76)
at
org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:66)
at
org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:125)
at
org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:30)
at
org.postgresql.jdbc3g.AbstractJdbc3gConnection.<init>(AbstractJdbc3gConnection.java:22)
at
org.postgresql.jdbc4.AbstractJdbc4Connection.<init>(AbstractJdbc4Connection.java:30)
at
org.postgresql.jdbc4.Jdbc4Connection.<init>(Jdbc4Connection.java:24)
at org.postgresql.Driver.makeConnection(Driver.java:393)
at org.postgresql.Driver.access$100(Driver.java:47)
at org.postgresql.Driver$ConnectThread.run(Driver.java:308)
... 1 more

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