Experimental Physics and
Industrial Control System

Xiaoqiang Wang <[email protected]> · Sun, 7 Jul 2013 23:02:53 +0200

I have the same headache when debugging pcas applications. 
The server tool library does not provides an exception handler, like in the CA client library, this error could only be checked from the console. Even though, the error seems ambiguous and can not be directly related to the python code. 

So I normally separate functions into its own module/class/function and test them. 
And then interface to it by subclassing pcaspy Driver.

Best
Xiaoqiang

On Jul 7, 2013, at 9:42 PM, Jameson Graef Rollins <[email protected]> wrote:

> Hi, folks.  I'm wondering if it's possible to catch python exceptions in
> the pcaspy Driver class.  For instance, I have a very simple dummy
> server (attached), in whose write() method there is a call that should
> throw a NameError.  However, when the server is running, a CA write
> (e.g. "caput MTEST:RAND 3") produces the following output:
> 
> filename="../../../../src/cas/generic/st/casStreamOS.cc" line number=479
> Internal failure - unexpected problem with client's input - forcing disconnect
> 
> The server process also continues to run.
> 
> Is there a way to get a proper python exception out of this situation?
> I would prefer the server to terminate with the exception, but I would
> be ok with the server continuing to run if the exception in the Driver
> could at least be reported to stderr or the like.  As is it's a little
> tricky to debug these errors.
> 
> Thanks in advance for any help.
> 
> jamie.
> 
> #!/usr/bin/env python
> 
> From pcaspy import Driver, SimpleServer
> 
> prefix = 'MTEST:'
> pvdb = {
>    'RAND' : {
>        'prec' : 3,
>    },
> }
> 
> class myDriver(Driver):
>    def  __init__(self):
>        super(myDriver, self).__init__()
> 
>    def write(self, channel, value):
>        foo        
> 
> if __name__ == '__main__':
>    server = SimpleServer()
>    server.createPV(prefix, pvdb)
>    driver = myDriver()
>    while True:
>        server.process(0.1)

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System