Handling all possible opcua exceptions using freeopcua

[rajnishnationfirst]

Hi team ,

I want to handle the below exceptions using python opcua exceptions like below .

1) BadSessionIdInvalid 
2) BadSessionNotActivated
3)BadTooManyOperations
4) BadSessionIdInvalid

suppose i get the exceptions as :

a) opcua.ua.uaerrors._auto.BadTooManyOperations: The request could not be processed because it specified too many operations.(BadTooManyOperations)

AND

b) opcua.ua.uaerrors._auto.BadSessionIdInvalid: The session id is not valid.(BadSessionIdInvalid)

try:
    ..... code

except (BadSessionIdInvalid ,BadSessionNotActivated,BadTooManyOperations,BadSessionIdInvalid) as errors:
     ....code 

Need help for the handling the exceptions . Request anyone to help with your replies for below questions.

1. Any base class to handle all exceptions of opcua.

It will be great help of me if any one can assist the same .

Rajnish Vishwakarma

[AndreasHeine]

not an issue!

[oroulet]

also if someone comes here the correct syntax is.

try: 
   mys ua code
except ua.UaError:
    do something

this will catch all errors from protocol

[rajnishnationfirst]

Hi Oroulet ,

Thanks a lot for your kind support for me as i have been very new to OPC UA protocol usage.

If i have to receive all possible exceptions for a client-minimal.py example of free-opcua python , is the below code correct to catch all the possible exceptions occurring mentioned above in my first post to this discussion :

1) BadSessionIdInvalid
2) BadSessionNotActivated
3) BadTooManyOperations
4) BadSessionIdInvalid

Is the below code correct for all exceptions mentioned above ?

class SubHandler():

    try: 
          def datachange_notification(self, node, val, data):
               print(datetime.now(), "- Data Change - ", val)
  
          def event_notification(self, event):
              pass

    except ua.UaError:
          do something like reconnect or resuscribe or etc

Thanks

Rajnish Vishwakarma

[swamper123]

If you are excepting UaError you may get one of those:

https://github.com/FreeOpcUa/python-opcua/blob/858274721766907148b527916e97446dbbf6af6d/opcua/ua/uaerrors/_auto.py

Since stuff can change, you can't guarantee that just those 4 will occur.

[swamper123]

And I guess you are aware of #1475 ?!

[rajnishnationfirst]

Thanks @swamper123 for your reply.

yes agreed . Could you pls let me know whether the below code for handling all possible exceptions is correct for a
client-minimal.py example in the freeo-pcua python example list?

Code is as follows :

**Is the below code correct for handling all exceptions in client-minimal.py example mentioned in the freeo-pcua python example list ** ?

class SubHandler():

    try: 
          def datachange_notification(self, node, val, data):
               print(datetime.now(), "- Data Change - ", val)
  
          def event_notification(self, event):
              pass

    except ua.UaError:
          do something like reconnect or resuscribe or etc

Thanks

Rajnish Vishwakarma

[swamper123]

The code you are posting seems to handle UaErrors.
Follow the link in my first answer to see, what is expected what a server may return.

I can't say if this list is uptodate, since this library is deprecated and not sure if even the nodeset from asyncua is uptodate atm.
It is possible that more errors may be possible.