2013/10/21 FUJITA Tomonori <[email protected]>
> On Sat, 12 Oct 2013 20:04:35 +0900
> Satoshi Kobayashi <[email protected]> wrote:
>
> > I noticed that an event between modules may get confused in multithread.
> It
> > is the following scenarios.
> >
> > 1. The module A sends an event to the module B
> > 2. The module B requires time to process the event...
> > 3. The module A sends an event to the module C
> > 4. The module C returns an answer soon
> > 5. The module A is misunderstanding that It is the response from the
> module
> > B (in fact the module C)
> >
> > I wrote PoC reproducing this issue as follows.
>
> Yeah, you need a trick like using request ids to do such. We have been
> thinking about the better way for component communication (such as
> JSON RPC, Message Pack RPC, etc). Also it could be used for
> communication with non Ryu software.
>
> Any proposals?
>
I wrote PoC to avoid confusion on a application. However, this is
troublesome and dirty hack. I grope for the way to avoid on Ryu.
----------
import time
import uuid
from ryu.base import app_manager
from ryu.controller.event import EventRequestBase, EventReplyBase
from ryu.lib import hub
class HasAutogenXid(object):
def __init__(self):
self.xid = uuid.uuid4()
class A2BRequest(EventRequestBase,
HasAutogenXid):
def __init__(self):
super(A2BRequest, self).__init__()
self.dst = 'AppB'
class A2BReply(EventReplyBase):
def __init__(self, dst, xid):
super(A2BReply, self).__init__(dst)
self.xid = xid
class A2CRequest(EventRequestBase,
HasAutogenXid):
def __init__(self):
super(A2CRequest, self).__init__()
self.dst = 'AppC'
class A2CReply(EventReplyBase):
def __init__(self, dst, xid):
super(A2CReply, self).__init__(dst)
self.xid = xid
class AppA(app_manager.RyuApp):
def __init__(self, *args, **kwargs):
super(AppA, self).__init__(*args, **kwargs)
# Request in parallel
hub.spawn(self._request_to_b)
hub.spawn(self._request_to_c)
def _request_to_b(self):
request = A2BRequest()
reply = self._send_request_with_retry(request)
assert isinstance(reply, A2BReply), 'Reply is %s' % reply.__class__
print('The request to B was completed normally')
def _request_to_c(self):
request = A2CRequest()
reply = self._send_request_with_retry(request)
assert isinstance(reply, A2CReply), 'Reply is %s' % reply.__class__
print('The request to C was completed normally')
def _send_request_with_retry(self, request):
reply = self.send_request(request)
while True:
if reply.xid == request.xid:
# This is expected
return reply
# Mistake
self.replies.put(reply)
# Switch other thread
time.sleep(0)
# Retry
reply = self.replies.get()
----------
import time
from ryu.base import app_manager
from ryu.controller.handler import set_ev_cls
from app_a import A2BRequest, A2BReply
class AppB(app_manager.RyuApp):
@set_ev_cls(A2BRequest)
def requst_handler(self, request):
time.sleep(5) # Take time
reply = A2BReply(request.src, request.xid)
self.reply_to_request(request, reply)
----------
from ryu.base import app_manager
from ryu.controller.handler import set_ev_cls
from app_a import A2CRequest, A2CReply
class AppC(app_manager.RyuApp):
@set_ev_cls(A2CRequest)
def requst_handler(self, request):
reply = A2CReply(request.src, request.xid)
self.reply_to_request(request, reply)
----------
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