Exceptions thrown while writing data are not reported.

• Key: DIRMINA-110
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: Trustin Lee
• Reporter: Trustin Lee
• Affects Version/s: 0.8.0
• Fix Version/s: 0.8.1

Description

Niklas Therning wrote:

Hi,

While working on the traffic control implementation I stumbled across a rather nasty bug. When the remote side of a connection has disconnected ch.write() will throw an IOException in the following piece of code. What I've found is that the that exception won't be propagated to the caller (flushSessions()) which has a catch clause for IOException scheduling the session for removal.

for (;;)
{
 ...
 try
 {
   writtenBytes = ch.write( buf.buf() );
 }
 finally
 {
   ...
   if( buf.hasRemaining() )
   {
     ...
     break;
   }
   ...
 }
}

The reason why the exception isn't propagated is the break statement in the finally block. The break causes the thrown IOException to be discarded and the program counter will be positioned right after the end of the for-loop. Since there are still unwritten bytes OP_WRITE will remain on and the selector will wake up immediately on the next iteration. The process will be repeated indefinitely and the CPU will be on 100%.

This bug has probably never appeared before since OP_READ has always been on. If OP_READ is on when the remote side disconnects SocketIoProcessor.read() will handle the removal of the session.

This could be fixed by removing the try and finally statements around this piece of code leaving:

for (;;)
{
 ...
 writtenBytes = ch.write( buf.buf() );
 ...
 if( buf.hasRemaining() )
 {
   ...
   break;
 }
 ...
}