1. Twisted Logic
PyCon 2013
- Ashwini Oruganti
@_ashfall_

2. Twisted
asynchronous event-driven
networking framework

3. Twisted
asynchronous event-driven
networking framework
aka... HARD

4. Google Summer of Code
spend the summer working on
an open source project with a
mentoring organization

5. Endpoint
an interface with a single method that
takes an argument
*
returns :
a listening port / a connected protocol

6. Server
endpoint = TCP4ServerEndpoint(reactor, 8007)
endpoint.listen(Factory())
Client
endpoint = TCP4ClientEndpoint(reactor,
"localhost", 8007)
endpoint.connect(Factory())

7. class TCP4ServerEndpoint(object):
"""
Implements TCP server endpoint with an IPv4
configuration
"""
...
def __init__(self, reactor, port,
backlog=50, interface=''):
...
def listen(self, protocolFactory):
return defer.execute(
self._reactor.listenTCP,
...)

8. class TCP6ServerEndpoint(object):
"""
Implements TCP server endpoint with an IPv6
configuration
"""
...
def __init__(self, reactor, port,
backlog=50, interface='::'):
...
def listen(self, protocolFactory):
return defer.execute(
self._reactor.listenTCP,
...)

10. It’s just code.

11. class StandardIOEndpoint(object):
"""
A Standard Input/Output endpoint
"""
implements(interfaces.IStreamServerEndpoint)
def __init__(self, reactor):
...
def listen(self, stdioProtocolFactory):
return defer.execute(stdio.StandardIO,
stdioProtocolFactory.buildProtocol(
PipeAddress()))

12. Moral of the story:
Do not get flustered.
Do not overthink..
Forget it's Twisted

13. Moral of the story:
Read the code.
Solve the problem
(write code)

14. There’s nothing more
boring
than the
comfort zone

15. TCP Client Endpoint
IPv6 addresses
Hostname Resolution

16. class TCP6ClientEndpoint(object):
def __init__(self, reactor, host, port,
timeout=30, bindAddress=None):
...
def connect(self, protocolFactory):
"""
Connect via TCP, once the hostname
resolution is done.
"""
...

17. def _nameResolution(self, host):
"""
Resolve the hostname string into a tuple
containing the host IPv6 address.
"""
...
def _resolvedHostConnect(self, resolvedHost,
protocolFactory):
"""
Connect to the server using the resolved
hostname.
"""
...

18. Deferred
Callbacks and Errbacks
Flow is not obvious
Debugging is tricky

19. class SomeState(object):
def __init__(self):
self.values = []
def getValue(self):
return self.values.pop(0)
def addValue(self, value):
self.values.append(value)

20. def foo():
return SomeState()
def bar():
state = foo()
print state.getValue()

21. Firing the Deferred
def foo():
s = SomeState()
s.addValue(2)
return s

22. It’s just code.

23. It’s 'X', when it isn't
really 'X'

24. It’s full of highly
complex concepts!

25. “It was created by a couple of
dudes who dropped out of
school, and a 16-year-old.
HOW HARD COULD IT BE?”

27. It’s foreign!

28. camelCase
PEP8: July 5, 2001
Twisted’s coding
standard: May 2, 2001

29. It’s huge!

30. “Core can fit into a floppy
disk.”

31. Know what you're
doing.

33. <conclusion />