Bug #1404
It's impossible to add a 'void' method to a local RPC server in Python
| Status: | Resolved | Start date: | 02/07/2013 | |
|---|---|---|---|---|
| Priority: | Normal | Due date: | ||
| Assignee: | J. Wienke | % Done: | 100% | |
| Category: | Python | |||
| Target version: | rsb-0.9 |
Description
It is impossible to register a method that does not return a value for RPC servers created in Python, because there does not seem to be a counterpart of the VoidType used for this purpose in other languages.
The addMethod call on a (local) server object in Python has a default value of 'object' for the replyType parameter. This creates a problem because by default, there is no converter available for type 'object'.
This leads to the problem that when you try to register a method like in the following example, the server throws a (not very helpful non-descriptive "KeyError") exception when the registered method is called by a client:
[...]
def say(sentence):
print("Saying: '%s'" % sentence)
if __name__ == '__main__':
server = rsb.createServer("/foo/bar")
server.addMethod("say", say, str)
[...]
In the end, there should be way to register a method that does not return a value. why not use pythons NoneType for this? And IMHO this type should then be the default for the replyType parameter of server.addMethod, or it should not have a default parameter value at all (since the unusable default of 'object' is quite misleading).
Associated revisions
Backport: Make converter selection really dynamic in case of Server methods.
- The reply event was attached with the declared data type for the method instead of the one of the data type.
- Added a unit test for this case
refs #1404
Make converter selection really dynamic in case of Server methods.
- The reply event was attached with the declared data type for the method instead of the one of the data type.
- Added a unit test for this case
refs #1404
History
#1 Updated by D. Klotz about 11 years ago
- Description updated (diff)
#2 Updated by J. Moringen about 11 years ago
- Status changed from New to Feedback
Well, there are None and type(None):
[...]
def say(sentence):
print("Saying: '%s'" % sentence)
if __name__ == '__main__':
server = rsb.createServer("/foo/bar")
server.addMethod("say", say, str, type(None))
[...]
Does this solve your Problem?
#3 Updated by J. Moringen about 11 years ago
Btw: could you add the target version to this issue?
#4 Updated by D. Klotz about 11 years ago
- Target version set to rsb-0.7
server.addMethod("say", say, str, type(None)) works, server.addMethod("say", say, str, None) does not (although support for the latter syntax would IMHO be nice). Thanks for the heads up!
But if there is already support for this, why is the default value for the replyType object (i.e. not usable in the default configuration)? I still think that either there should be no default value (so you would be required to specify a type) or the default value should be something usable.
#5 Updated by D. Klotz about 11 years ago
- Target version changed from rsb-0.7 to rsb-0.9
This problem is also present in the master, the default still seems to be object.
#6 Updated by D. Klotz about 11 years ago
This is what happens on the server side, the client just doesn't get an answer:
dklotz@rhodenit:[~/workspace/MSS]python simple_rpc_server.py
No handlers could be found for logger "rsb.transport.rsbspread.InConnector"
Saying: 'Hello World!'
Exception in thread Thread-1:
Traceback (most recent call last):
File "/usr/lib/python2.7/threading.py", line 551, in __bootstrap_inner
self.run()
File "/usr/lib/python2.7/threading.py", line 504, in run
self.__target(*self.__args, **self.__kwargs)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/util.py", line 326, in __worker
self.__delFunc(receiver.receiver, message)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/eventprocessing.py", line 135, in __deliver
action(event)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/patterns/__init__.py", line 318, in _handleRequest
self.informer.publishEvent(reply)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/__init__.py", line 1260, in publishEvent
self.__configurator.handle(event)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/eventprocessing.py", line 357, in handle
self.__sendingStrategy.handle(event)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/eventprocessing.py", line 201, in handle
connector.handle(event)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/transport/rsbspread/__init__.py", line 393, in handle
converter = self.getConverterForDataType(event.type)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/transport/__init__.py", line 177, in getConverterForDataType
return self.__converterMap.getConverterForDataType(dataType)
File "/homes/dklotz/local/x86_64/lib/python2.7/site-packages/rsb_python-0.9.0-py2.7.egg/rsb/converter.py", line 145, in getConverterForDataType
raise KeyError, dataType
KeyError: <type 'object'>#7 Updated by D. Klotz about 11 years ago
- Assignee changed from J. Moringen to J. Wienke
#8 Updated by J. Wienke about 11 years ago
- Status changed from Feedback to Resolved
- % Done changed from 0 to 100