Hi,
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.
(AppA: the module A)
------------------------------
from ryu.base import app_manager
from ryu.controller.event import EventRequestBase, EventReplyBase
from ryu.lib import hub
class A2BRequest(EventRequestBase):
def __init__(self):
super(A2BRequest, self).__init__()
self.dst = 'AppB'
class A2BReply(EventReplyBase):
def __init__(self, dst):
super(A2BReply, self).__init__(dst)
class A2CRequest(EventRequestBase):
def __init__(self):
super(A2CRequest, self).__init__()
self.dst = 'AppC'
class A2CReply(EventReplyBase):
def __init__(self, dst):
super(A2CReply, self).__init__(dst)
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(request)
assert isinstance(reply, A2BReply), 'Reply is %s' % reply.__class__
def _request_to_c(self):
request = A2CRequest()
reply = self.send_request(request)
assert isinstance(reply, A2CReply), 'Reply is %s' % reply.__class__
------------------------------
(AppB: the module B)
------------------------------
from ryu.base import app_manager
from ryu.controller.handler import set_ev_cls
from app_a import A2BRequest, A2BReply
import time
class AppB(app_manager.RyuApp):
@set_ev_cls(A2BRequest)
def requst_handler(self, request):
time.sleep(5000) # Take time
reply = A2BReply(request.src)
self.reply_to_request(request, reply)
------------------------------
(AppC: the module C)
------------------------------
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)
self.reply_to_request(request, reply)
------------------------------
The following result:
------------------------------
loading app ./app_a.py
loading app ./app_b.py
loading app ./app_c.py
loading app ryu.controller.ofp_handler
instantiating app ./app_c.py
instantiating app ./app_b.py
instantiating app ryu.controller.ofp_handler
instantiating app ./app_a.py
hub: uncaught exception: Traceback (most recent call last):
File
"/Users/satoshi/.virtualenvs/ryu32/lib/python2.7/site-packages/ryu/lib/hub.py",
line 48, in _launch
func(*args, **kwargs)
File "/Users/satoshi/Documents/workspace/ryusample/app_a.py", line 43, in
_request_to_b
assert isinstance(reply, A2BReply), 'Reply is %s' % reply.__class__
AssertionError: Reply is <class 'app_a.A2CReply'>
------------------------------
It is A2CReply although it must be A2BReply.
I found that a simple queue is used for the input of an event in
app_manager.RyuApp. It returns as a result what was pushed more early.
IMHO, This becomes a problem when using two or more modules since a module
be made into multithreading in many cases.
Thanks,
Satoshi
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