[zeromq-dev] Zyre Wi-Fi Rejoin Issue

[Pieter Hintjens]

OK, I've pushed a patch that fixes it, using your workaround more or less.

I want to test this at the libzmq level, it's weird that old messages
are getting through and the new ones aren't.

-Pieter

On Fri, Jun 6, 2014 at 6:36 PM, Pieter Hintjens <ph at imatix.com> wrote:
> OK, I've reproduced the problem quite easily. Something strange with
> messages being delivered even though the socket they're sent on is
> torn down entirely. I'm investigating...
>
> On Fri, Jun 6, 2014 at 5:57 PM, Pieter Hintjens <ph at imatix.com> wrote:
>> OK, I'll simulate this in the code. The peers should automatically
>> resend HELLO if they lost contact.
>>
>> No thanks needed, we enjoy making this software and use it in
>> everything we make. :-)
>>
>> On Fri, Jun 6, 2014 at 4:12 PM, Steve Rasmussen
>> <Steve.Rasmussen at rassimtech.com> wrote:
>>>> In principle if the connection is re-established there should be no new
>>> HELLO message sent.
>>>
>>> This problem occurs after the Wi-Fi connection has been down long enough for
>>> the peers to remove each other. When the connection come back up, as I
>>> understand it, the HELLO message is necessary to kick-off handshaking.
>>>
>>>> Can you find a way to reproduce the problem easily?
>>> The easiest method that I've found is using a modified version of the
>>> zpinger tool on two laptops. The modified zpinger tool is set up to send a
>>> whisper, after a time delay, anytime it receives a whisper from a peer. I
>>> either turn the Wi-Fi adapter off/on or move the laptop out of range to
>>> perform the test.
>>>
>>> It seems like this may have something to do with the sockets maintaining the
>>> TCP/IP connection during the break and then being in a bad state when the
>>> Wi-Fi connection comes back up. Is this possible? If so is there some way to
>>> reset the TCP/IP connection?
>>>
>>>> Thanks for taking the time to analyse the problem.
>>>
>>> I need this capability for the system I'm developing. Thank you and your
>>> colleagues for ZeroMQ, CZMQ, Zyre, ...
>>>
>>> Regards,
>>>
>>> Steve
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: zeromq-dev-bounces at lists.zeromq.org
>>> [mailto:zeromq-dev-bounces at lists.zeromq.org] On Behalf Of Pieter Hintjens
>>> Sent: Thursday, June 5, 2014 5:22 PM
>>> To: ZeroMQ development list
>>> Subject: Re: [zeromq-dev] Zyre Wi-Fi Rejoin Issue
>>>
>>> On Thu, Jun 5, 2014 at 5:32 PM, Steve Rasmussen
>>> <Steve.Rasmussen at rassimtech.com> wrote:
>>>
>>>> The problem seems to be with the TCP/IP connection not the beacon. After a
>>> network break, the beacon reestablishes the connection, but no data is
>>> getting through the tcp/ip connection.
>>>> It looks as if there are messages that are being buffered before the break
>>> and then delivered after. This prevents the "HELLO" message from getting
>>> through. I've tried various things, but the closest the I've come, so far,
>>> is to keep removing the peer until it is reported as being ready. I'm doing
>>> this in the "zyre_node_require_peer" function. If a peer exists I check to
>>> see if it is ready, "zyre_peer_ready" and if not, I remove the peer,
>>> "zyre_node_remove_peer". This seems to fix the problem that I'm having, but
>>> it seems a little kludgie.
>>>
>>> Thanks for taking the time to analyse the problem.
>>>
>>> In principle if the connection is re-established there should be no new
>>> HELLO message sent. Can you find a way to reproduce the problem easily?
>>>
>>> Feel free to make a pull request with your change anyhow. I'm reworking a
>>> lot of this code atm so will try to include your change if I can reproduce
>>> the error.
>>>
>>> -Pieter
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