通讯链接故障问题

Question

I hosted my first Java EE web site but my mySQL connections are timing out after few minutes and I am getting this error message:

HTTP Status 500 - com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

type Exception report

message com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

description The server encountered an internal error that prevented it from fulfilling this request.

exception

dao.DAOException: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.
dao.OffreDaoImpl.lister(OffreDaoImpl.java:95)
filters.PrechargementFilter.doFilter(PrechargementFilter.java:96)
org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)

root cause

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.
sun.reflect.GeneratedConstructorAccessor28.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:525)
com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2985)
com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2871)
com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3414)
com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)
com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)
com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1885)
com.jolbox.bonecp.PreparedStatementHandle.executeQuery(PreparedStatementHandle.java:172)
dao.OffreDaoImpl.lister(OffreDaoImpl.java:90)
filters.PrechargementFilter.doFilter(PrechargementFilter.java:96)
org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)

root cause

java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2431)
com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2882)
com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2871)
com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3414)
com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)
com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)
        com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1885)
com.jolbox.bonecp.PreparedStatementHandle.executeQuery(PreparedStatementHandle.java:172)
dao.OffreDaoImpl.lister(OffreDaoImpl.java:90)
filters.PrechargementFilter.doFilter(PrechargementFilter.java:96)
org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108) 

I asked my hoster to increase the timeout value and here is his response:

Please accept our sincerest apologizes for misunderstanding. Unfortunately due to shared hosting environment your request could not be >accomplished - it will affect other customers, that share server resources >for you. (10 min is max value for this parameter). Since you strongly need some features - we can only suggest you considering >to move to VPS or dedicated server where you will have full admin >privileges and can do whatever you want without affecting of another >customers.

As a solution, we would like to suggest you to add in your jdbc connection >string following command: &autoReconnect=true&failOverReadOnly=false&maxReconnects=10

In this case, after timeout, you will be reconnected again.

So I edited my config.properties file:

url = jdbc:mysql://localhost:3306/myDatabase&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
driver = com.mysql.jdbc.Driver
username = xxxxxx
password = xxxxxx

But I am still facing the same issue.

Answer 1

Yes I am using localhost even when I host the website. But I tried to replace localhost string by the server address IP in the URL connection and I got this error message:

Caused by: java.sql.SQLException: Unable to open a test connection to the given database. JDBC url = jdbc:mysql://xxx.xxx.xxx.xx:3306/database_db?autoReconnect=true&failOverReadOnly=false&maxReconnects=10, username = user_name. Terminating connection pool. Original Exception: ------ com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 10 times. Giving up.

So I noted the issue to my hoster and here is his reply:

Dear Customer,

Kindly use localhost instead IP address, as for your string, we actually asking you to not maintain connections as long as you wish. The thing is we have hard limit on opened connections overall = 300 and 50 per user.

And as this is shared server these connections are being allocated on demand to each user, and if your account consumes 50 connections it is 1/6 of all connections available.