[nanomsg] Re: Where "Channel ID" are managed in the code ?
- From: Martin Sustrik <sustrik@xxxxxxxxxx>
- To: nanomsg@xxxxxxxxxxxxx
- Date: Mon, 13 Jan 2014 14:56:11 +0100
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On 13/01/14 14:48, Laurent Alebarde wrote:
> Thanks Martin.
>
> I could find: "key = nn_getl (nn_chunkref_data (&msg->hdr));" in
> xrep.c / nn_xrep_send and: "memcpy (nn_chunkref_data (&msg->hdr),
> data, i * sizeof (uint32_t));" in xrep.c / nn_xrep_recv which show
> me how to manipulate the channels IDs.
>
> But not in rep.c
>
> What is the difference please functionaly between REP and XREP ?
> Are some design documents available somewhere ? What makes that
> from the API, XREP will be used instead of REP ? Sorry if my
> questions may be stupid.
REP is just a wrapper on top of XREP. What it does is that it assigns
a reuest ID to each request and discards any replies with non-matching ID.
> For my stateful use case, I will pair clients and workers. So in a
> proxy belonging to the server, I will use a XREP on the client side
> and also a XREP on the worker side. First the workers register. I
> store their channel ID. Then when I receive a message from the
> client, I assign it a worker and puts the pair of channels ID in a
> hash table. I then rewrite the channel ID with "memcpy
> (nn_chunkref_data (&msg_from_client->hdr),
> worker_channel_IS_assigned, isizeof (uint32_t));" and send this
> message to the worker.
The problem with statefull req/rep is how to handle partial failure.
If one worker dies, some clients will be stuck forever. You have to
define a mechanism for recovering from such problems.
Martin
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