Experimental Physics and
Industrial Control System

David Brodrick <[email protected]> · Mon, 23 May 2011 15:17:00 +1000

Hi,

We've been doing some scalability tests on our Java software that uses

JCA/CAJ.

I came across a CAJ problem which resulted in all monitor events from an

instance of our test IOC ceasing to arrive. Then another instance would

stop sending events, etc.. Eventually CAJ wasn't giving me any monitor

events at all.

I have tracked this down to the processRead method in

com.cosylab.epics.caj.impl.CATransport. Basically if flow control gets

enabled, and then there is a zero-byte read, then flow control never

gets turned off and we never hear from the IOC again. I have addressed

the bug by checking the flow control logic before checking for the

zero-byte read, something like this:

 // read
 int bytesRead = channel.read(socketBuffer);
 if (bytesRead < 0)
 {
   // error (disconnect, end-of-stream) detected
   close (true);
   return;
 }

 // flow control check

 if (socketBuffer.hasRemaining())
 {
   // buffer not full, disable flow control
   bufferFullCount = 0;
   if (flowControlActive)
     disableFlowControl();

 }

 if (bytesRead == 0) {

   break;
 }

Perhaps the CAJ maintainers would like to incorporate this fix or

something similar into the upstream source?

Regards,
 David

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System