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Great. I'm just doing some experiments to evaluate REQ/REP pattern.

It seems that your implementation is completed.

Looking forward to reviewing your updates.

On Mon, Mar 30, 2015 at 4:02 PM, ozamiatin <ozamiatin at mirantis.com> wrote:
> Hi,
>
> Sorry for not replying on [1] comments too long.
> I'm almost ready to return to the spec with updates.
>
> The main lack of current zmq-driver implementation is that
> it manually implements REQ/REP on top of PUSH/PULL.
>
> It results in:
>
> 1. PUSH/PULL is one way directed socket (reply needs another connection)
>     We need to support backwards socket pipeline (two pipelines). In REQ/REP
>     we have it all in one socket pipeline.
>
> 2. Supporting delivery of reply over second pipeline (REQ/REP state
> machine).
>
> I would like to propose such socket pipeline:
> rpc_client(REQ(tcp)) <=> proxy_frontend(ROUTER(tcp)) <=>
> proxy_backend(DEALER(ipc)) <=> rpc_server(REP(ipc))
>
> ROUTER and DEALER are asynchronous substitution for REQ/REP for building 1-N
> and N-N
> topologies, and they don't break the pattern.
>
> Recommended pipeline nicely matches for CALL.
> However CAST can also be implemented over REQ/REP, using
> reply as message delivery acknowledgement, but not returning it to caller.
> Listening to reply for CAST in background thread keeps it async as well.
>
> Regards,
> Oleksii Zamiatin
>
>
> On 30.03.15 06:39, Li Ma wrote:
>>
>> Hi all,
>>
>> I'd like to propose a simple but straightforward method to improve the
>> stability of the current implementation.
>>
>> Here's the current implementation:
>>
>> receiver(PULL(tcp)) <-- service(PUSH(tcp))
>> receiver(PUB(ipc)) --> service(SUB(ipc))
>> receiver(PUSH(ipc)) --> service(PULL(ipc))
>>
>> Actually, as far as I know, the local IPC method is much more stable
>> than network. I'd like to switch PULL/PUSH to REP/REQ for TCP
>> communication.
>>
>> The change is very simple but effective for stable network
>> communication. I cannot apply the patch for our production systems. I
>> tried it in my lab, and it works well.
>>
>> I know there's another blueprint for REP/REQ pattern [1], but it's not
>> the same, I think.
>>
>> I'd like to discuss it about how to take advantage of REP/REQ of zeromq.
>>
>> [1]
>> https://review.openstack.org/#/c/154094/2/specs/kilo/zmq-req-rep-call.rst
>>
>> Best regards,
>
>



-- 

Li Ma (Nick)
Email: skywalker.nick at gmail.com