[Twisted-Python] help using deferred
luigiandcosolutions at gmail.com
Fri May 15 10:58:11 EDT 2009
2009/5/11 Jean-Paul Calderone <exarkun at divmod.com>
> On Mon, 11 May 2009 19:49:19 +0200, Luigi Conte <
> luigiandcosolutions at gmail.com> wrote:
> > [snip]
> >in my script I have to use connect method and then I have to do some
> >operations first of calling the start method
> >1) start connection
> > def startConnection(self):
> > d = my_api.connect(self.ctrl_ip, self.ctrl_port, self.user,
> > d.addCallback(self.postConnection)
> Since you omitted the definition of postConnection, I have no way to know
> what this does.
> > d.addErrback(twisted.python.log.err)
> Regardless, this is the wrong place to insert this errback. You should
> the Deferred documentation to learn what consequence it will have on your
> program's flow.
> http://twistedmatrix.com/projects/core/documentation/howto/defer.html is
> probably a good place to start.
> > print "Connection added"
> > return d
> >2) operation before starting a virtual machine:
> >def newVMCfg(self, new_vms_cfg):
> > #...
> > #some operations
> > #if condition valid I try to start the virtual machine
> > # is this the correct way to pass args to the
> > d = self.d.addCallback(self.startVM,(new_vm,
> > print "started vm %s"%new_vm
> > return d
> >in the main process I call them as:
> >d = startConnection()
> >d.addCallback(newVMCfg, arg)
> >Is it correct? Because the process stops at the first method called: I see
> >only "connection added".
> That should indicate to you that something is going wrong after that print
> statement is reached. So examine what your program tries to do after that
> point. You may want to use a debugger. You may want to try writing some
> unit tests.
> Twisted-Python mailing list
> Twisted-Python at twistedmatrix.com
I looked at the documentation and I understood something about defferd and
callbacks. I edited my code but it does nothing...
I'm going to explain the scenario and what I want to do:
- there is an api that provides some methods (connect, start, disconnect).
- all those methods return a deferred object
- I have an object that first tries to connect, then reads a file and calls
the start method many times in a loop cicle of his method.
I want to use the connect and wait until I'm really connected. How can I do
this using the deferred object that the api returns to me?
I want to do the same thing each time I call the start method from the api:
I want to wait the completing of start operation before doing another start
so I do:
in the main process:
d = gest.connettiCLI_to_CTRL()
in gest class I have:
d = api.connect(self.ctrl_ip, self.ctrl_port, self.user, self.pwd)
def cbConnected(self, connectResult):
# I do something but I don't call api's methods here
# then I go to the next step returning the next method
def interpretaNewVMCfg(self, new_vms_cfg):
for i in candidati:
#start operation in loop
#here I want to control each start operation
d = api.startVM(new_vm, self.lnms[i])
thank you so much
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