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  Thank you for your helpful comments.

  I'd like to update my proposal as follows:

   1. Set an integer cookie value to taas flows.
      Maybe all "1" for short term tentative value.
   2. Modify the cleanup logic in ovs-agent not to delete flows
      which have a reserved integer cookie value.


> Sorry, that I don't see this earlier. Yes, cookies have integer values, so
> we won't be able to set string there. May be we can have a reserved integer
> cookie value for a project like all "1".
>
> I won't support idea of modifying cleanup logic not to drop 0x0 cookies.
> During implementation of graceful restart it was not dropped at first, but
> I get rid of it  as having a lot of flows not related to anything was not
> desirable, so we should try to avoid it here, too.
>
> On Wed, Dec 16, 2015 at 7:46 AM, Soichi Shigeta <
> shigeta.soichi at jp.fujitsu.com> wrote:
>
>>
>>     o) An idea to fix:
>>>
>>>        1. Set "taas" stamp(*) to taas flows.
>>>        2. Modify the cleanup logic in ovs-agent not to delete entries
>>>           stamped as "taas".
>>>
>>>        * Maybe a static string.
>>>          If we need to use a string which generated dynamically
>>>          (e.g. uuid), API to interact with ovs-agent is required.
>>>
>>>
>>    Last week I proposed to set a static string (e.g. "taas") as cookie
>>    of flows created by taas agent.
>>
>>    But I found that the value of a cookie should not be a string,
>>    but an integer.
>>
>>    At line 187 in
>> "neutron/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_neutron_agent.py":
>>    self.agent_uuid_stamp = uuid.uuid4().int & UINT64_BITMASK
>>
>>    In case of we set an integer value to cookie, coordination
>>    (reservation of range) is required to avoid conflict of cookies with
>>    other neutron sub-projects.
>>
>>    As an alternative (*** short term ***) solution, my idea is:
>>    Modify the clean up logic in ovs agent not to delete flows whose
>>    "cookie = 0x0".
>>    Because old flows created by ovs agent have an old stamp, "cookie =
>>    0x0" means it was created by other than ovs agent.
>>
>>    # But, this idea has a disadvantage:
>>      If there are flows which have been created by older version of ovs
>>      agent, they can not be cleaned.
>>