I have made a web Server/Application using Tomcat Server 8.5.xx.
I use servlet as the Server Technology. XML-RPC to communicate with the user. and MySQL as a database.
When I run the application (the server), sometimes I become the following error:
06-Sep-2017 12:39:06.260 WARNUNG [commons-pool-EvictionTimer] org.apache.tomcat.dbcp.dbcp2.SwallowedExceptionLogger.onSwallowException An internal object pool swallowed an Exception.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 4.740.870 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:989)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3746)
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1873)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1226)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2194)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2225)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2024)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:779)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
at org.apache.tomcat.dbcp.dbcp2.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at org.apache.tomcat.dbcp.dbcp2.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:257)
at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.create(GenericObjectPool.java:888)
at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.ensureIdle(GenericObjectPool.java:952)
at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.ensureMinIdle(GenericObjectPool.java:931)
at org.apache.tomcat.dbcp.pool2.impl.BaseGenericObjectPool$Evictor.run(BaseGenericObjectPool.java:1047)
at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)
Caused by: java.net.SocketException: Software caused connection abort: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(Unknown Source)
at java.net.SocketOutputStream.write(Unknown Source)
at java.io.BufferedOutputStream.flushBuffer(Unknown Source)
at java.io.BufferedOutputStream.flush(Unknown Source)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3728)
... 22 more
I can provide any data that is needed to solve the problem.
It works and communicates with the DB, but some times it hangs and then give this problem and then it functions another time.
I guess that the problem comes from the idle unused connections that MySQL closes but JDBC does nothing about that and it tries to use them.
