Netty Server accept connection and do nothing

Question

I didnt trace-out the reason for this bug "My netty Server didnt proceess any message after the following exception."

  org.jboss.netty.channel.SimpleChannelHandler - EXCEPTION, please implement com.kakapo.unity.handler.RegistrationHandler.exceptionCaught() for proper handling.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 223,384,284 milliseconds ago.  The last packet sent successfully to the server was 223,384,284 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
    at sun.reflect.GeneratedConstructorAccessor13.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
    at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3364)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1983)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2624)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2127)
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2293)
    at snaq.db.CachedPreparedStatement.executeQuery(CachedPreparedStatement.java:81)
    at com.kakapo.unity.handler.CustomIPFilterHandler.accept(CustomIPFilterHandler.java:46)
    at org.jboss.netty.handler.ipfilter.IpFilteringHandlerImpl.handleUpstream(IpFilteringHandlerImpl.java:118)
    at org.jboss.netty.handler.logging.LoggingHandler.handleUpstream(LoggingHandler.java:333)
    at org.jboss.netty.channel.Channels.fireChannelConnected(Channels.java:227)
    at org.jboss.netty.channel.socket.nio.NioWorker$RegisterTask.run(NioWorker.java:187)
    at org.jboss.netty.channel.socket.nio.AbstractNioWorker.processRegisterTaskQueue(AbstractNioWorker.java:430)
    at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:329)
    at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:35)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)
Caused by: java.net.SocketException: Connection timed out
    at java.net.SocketOutputStream.socketWrite0(Native Method)
    at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109)
    at java.net.SocketOutputStream.write(SocketOutputStream.java:153)
    at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
    at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
    at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3345)
    ... 17 more

But i have already put auto reconnect = true to my JDBC. and also am using OrderedMemoryAwareThreadPoolExecutor

ExecutionHandler channelExecutionHandler = new ExecutionHandler(new OrderedMemoryAwareThreadPoolExecutor(Runtime.getRuntime()
                .availableProcessors(), 0, 0)); 

I use awaituninteruptable function to close a channel. like

ctx.getChannel().write(new ErrMessage(e.getChannel().getRemoteAddress().toString()).getEncodedMessage())

Is this causing any type of infinite loop activity. Now the present situation is server accept the coonections and do not process any kind of message.We have worker thread and boss. But the logging handler works fine. Am using snaq.db.connection pool for maintaining DB Connections.

Answer 1

You seem to use MySQL connection quite straight-forward with DriverManager.getConnection() . Therefore you either don't close opened connection at all, or create so many connections, that MySQL server's limit is exceeded.

In highly-concurrent environment (and Netty certainly is implemented for that) I would strongly recommend using database connection pools: c3p0 or commons-dbcp . With proper settings you may avoid MySQL connections issues.