[zeromq-dev] ROUTER not routing?

[Justin Karneges]

Here's some small sample code to reproduce the issue:
https://gist.github.com/jkarneges/ab2b1abea1ee4cfc1332

A (ztest1.py) creates REQ and ROUTER sockets. B (ztest2.py) creates REP 
and ROUTER sockets. B binds and provides a random identity to its ROUTER 
socket. A connects its sockets to B. A queries for B's id using the REQ 
socket, and then attempts to send a message via the ROUTER socket right 
after that. This is repeated every 2 seconds.

A and B can be started in any order. A can be restarted and things will 
still work. If B is restarted, then A's ROUTER socket will never work 
again until A is restarted also.

A uses ZMQ_ROUTER_MANDATORY to show that the failures are on A's side.

On 02/07/2014 02:16 PM, Justin Karneges wrote:
> It is my understanding that being able to route requires the socket to
> have an identity mapping in its routing table for the peer.
>
> For peers that do not explicitly specify their own identity, then I
> believe you are correct that routing is not possible until at least one
> message has been received from the peer. It is at this point that the
> ROUTER socket will make up an identity for this peer and store it in its
> routing table.
>
> However, for peers that *do* explicitly specify their own identity (as I
> am doing), then this identity information is delivered immediately after
> the connection is established, allowing routing to the peer even if the
> peer has not sent a message yet.
>
> I should have been more clear in my original message. The B program is
> explicitly specifying a random UUID as the identity of its socket before
> binding.
>
> On 02/07/2014 02:06 PM, Panu Wetterstrand wrote:
>> I did not quite get the problem but could this be because (I think)
>> router is not able to route messages to socket from which it has not
>> reveived data first...
>>
>> 7.2.2014 22.51 kirjoitti "Justin Karneges" <justin at affinix.com
>> <mailto:justin at affinix.com>>:
>>
>>      Hi,
>>
>>      1) ROUTER in program A is set to connect to a bind socket in program B.
>>      2) Both programs are started, and the connection is established.
>>      3) A determines B's socket identity out-of-band, and is able to send
>>      messages to B.
>>      3) B is terminated and the connection is lost.
>>      4) B is started again, and the connection is re-established.
>>      5) A determines B's socket identity out-of-band, and is no longer able
>>      to send messages to B.
>>
>>      It seems this problem does not happen if B retains the same socket
>>      identity across reconnects. However, if it uses a random identity (to be
>>      discovered out-of-band by A), then routing will never work again after
>>      the first restart of B. The A program must be restarted in order to make
>>      things right again.
>>
>>      My guess is that each connect queue on a ROUTER socket is somehow bound
>>      for life against the first identity it sees. Is this intentional
>>      behavior?
>>
>>      Thanks,
>>      Justin
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>>
>>
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