[Twisted-Python] client connecting to 2 servers (non simultaneously)

[Kevin Horn]

Using a deque for this is a fantastic idea, though I would have used
rotate(-1), as your example looks like it rotate's "backwards" to me.

Matter of taste I suppose.  It doesn't make much actual difference.

Kevin Horn

On Tue, Jan 11, 2011 at 7:11 AM, Jason Rennie <jrennie at gmail.com> wrote:

> You could probably generalize and simplify by using a collections.deque of
> hosts/ports and using the rotate() method before each reactor.connectTCP.
>  Also, no need for multiple reactor imports---one at the top of the code is
> fine.  Note that if the connection is "lost" in a non-clean fashion, you may
> also want to reconnect.  IIUC, "fail" only handles the case that no
> connection is made (protocol is never created).
>
> import collections
> from twisted.internet import reactor
>
> class MyClientFactory(object):
>     protocol = MyClientProtocol
>     def __init__(self, hosts):
>         self.hosts = collections.deque(hosts)
>         reactor.callWhenRunning(reactor.connectTCP, self.hosts[0][0],
> self.hosts[0][1], self)
>         self.hosts.rotate(1)
>     def clientConnectionFailed(self, connector, reason):
>         reactor.callLater(2.0, connectTCP, self.hosts[0][0],
> self.hosts[0][1], self)
>         self.hosts.rotate(1)
>
> factory = MyClientFactory([('host1', port1), ('host2', port2), ...])
> reactor.run()
>
> Cheers,
>
> Jason
>
> On Tue, Jan 11, 2011 at 5:17 AM, <benjamin.bertrand at lfv.se> wrote:
>
>> Hi,
>>
>> I'm new to twisted and I have started to write a new protocol with a TCP
>> client and server.
>> In my protocol, a client should be able to connect to 2 servers
>> (master/slave node - only the master accepts connection).
>> The client should try to connect to server1. If it fails, try to connect
>> to server2 (after a specific timeout). If that fails, try server1...
>> I came up with a solution (see below).
>> As I'm new to twisted and I haven't seen anything like that in the
>> examples, I'd like to check if that's a proper way to do it.
>> Any comments is welcome.
>>
>> Thanks
>>
>> Benjamin
>>
>> ***********************************************
>> class MyClientFactory(ClientFactory):
>>
>>    protocol = MyClientProtocol
>>
>>    def __init__(self, host2=None):
>>        self.host1 = None
>>        self.host2 = host2
>>
>>    def clientConnectionFailed(self, connector, reason):
>>        from twisted.internet import reactor
>>        if self.host2 is None:
>>            # host2 is not defined, reconnect to host1
>>            reactor.callLater(2.0, connector.connect)
>>        else:
>>            destination = connector.getDestination()
>>            if self.host1 is None:
>>                # First connection failed, initialize host1, and try
>> host2
>>                self.host1 = destination.host
>>                host = self.host2
>>            elif destination.host == self.host1:
>>                # Connection to host1 failed, try host2
>>                host = self.host2
>>            else:
>>                # Connection to host2 failed, try host1
>>                host = self.host1
>>            reactor.callLater(2.0, reactor.connectTCP, host,
>> destination.port, self)
>>
>>
>> factory = MyClientFactory(server2)
>> from twisted.internet import reactor
>> reactor.connectTCP(server1, 8010, factory)
>> reactor.run()
>> ***********************************************
>>
>>
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>>
>
>
>
> --
> Jason Rennie
> Research Scientist, ITA Software
> 617-714-2645
> http://www.itasoftware.com/
>
>
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>
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