Communication link failure:

less than 1 minute read

The major outstanding bug in is a database connection pooling problem that causes the following message to be displayed:

javax.servlet.ServletException: Communication link failure:, underlying cause: Unexpected end of input stream

MESSAGE: Unexpected end of input stream

STACKTRACE: Unexpected end of input stream
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(
at com.mysql.jdbc.MysqlIO.checkErrorPacket(
at com.mysql.jdbc.MysqlIO.sendCommand(
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(
at com.mysql.jdbc.MysqlIO.sqlQuery( 

The problem isn’t usually serious. Repeating whatever you were doing a couple more times will usually get through the problem. I have been trying to fix this for ages, but it is an absolute bastard to track. Occasionally, this problem will cause the site to run out of database connections and the site will hang :(. If you suspect this has happened, email matt at madeye dot com.



Just as a postscript to this report, this problem is related to database connections going stale. If enough people use the site, the connections will not go stale, and this problems will just go away :D