[zeromq-dev] What exact networking problems ZMQ does solve?

artemv zmq artemv.zmq at gmail.com
Wed Dec 11 11:57:11 CET 2013


Cool!  I saw Bruno response.  Justin, thanks for patience and for keep
replying,  I much appreciate that.


BR
-artemv



2013/12/11 Justin Cook <jhcook at gmail.com>

> Artem,
>
> There is no way to know that a node on the network went down without the
> lack of receiving acknowledgements that the message was received — either
> with TCP ACKs or a messaging pattern in 0MQ such as REQ/REP.
>
> If the the server is not up yet, and you have not established a session,
> then Bruno has given you the option to workaround that. If the server goes
> down, and their is an established session, there is no way to know that
> without further communication, or no response where response is expected.
>
> If there is, I would love to know about it.
>
> --
> Justin Cook
>
>
> On Wednesday, 11 December 2013 at 10:42, artemv zmq wrote:
>
> > hi Justin. Thanks for heads up.
> >
> > Ok. Clear. Especially about steady stream.
> >
> > But, again, let me make it very clear.
> > I imagine following situations and desired outcomes:
> > - Server is not up yet, and client tries to send a message. Desired
> outcome: big red alarm -- "fail" w/o waiting for reply.
> > - Server is up, client sends a message, gets reply, everything is
> smooth. Then the network between client and server is getting down (e.g.
> "ifdown eth0" on server). The client tries to send a message... Desired
> outcome: big red alarm -- "fail" w/o waiting for reply.
> >
> > I don't care server is up or down, or in what status an infrastructure
> is. I want to know one thing -- did all frames (of my message) been sent or
> not ?
> >
> > Is it posible with ZMQ?
> >
> >
> > BR
> > -artemv
> >
> >
> >
> > 2013/12/11 Justin Cook <jhcook at gmail.com (mailto:jhcook at gmail.com)>
> > > Artem,
> > >
> > > This is a problem that every network developer faces. Did my message
> make it to its destination? If I send a message, is it likely to make it to
> the recipient?
> > >
> > > Fortunately, there are patterns to use to increase reliability, but
> even then there is no way to be 100% sure that when a message is sent, it
> will flow across the infrastructure and be delivered with 100% certainty
> without an acknowledgement.
> > >
> > > You cannot _instantly_ get an indication a server failed — or the
> associated infrastructure — unless you have a steady stream of bytes going
> across the wire, and they suddenly stop. If you want to know a node went
> down, you will need heartbeat messages. There are a few ways to do this.
> > >
> > > Please look at the paranoid pirate example and this:
> > >
> > > http://zguide.zeromq.org/page:all#Heartbeating
> > >
> > > --
> > > Justin Cook
> > >
> > >
> > > On Wednesday, 11 December 2013 at 09:59, artemv zmq wrote:
> > >
> > > > Okay. Thanks for your thoughts. Again, I read the guide, and I know
> on practice what's pub/sub/push/pull/ .. and so on.
> > > >
> > > > But let me ask one more time very concrete and simple question. I
> want to develop a client/server appl. Okay. I pick dealer/router pattern.
> Fine. Now my requirement is following:
> > > > if server is unaccessible (wrong ip address, server is not online,
> server was online and then went offline, etc.) -- in this case I want to
> get (_instantly_) some indication that client can't send a message because
> server is unaccessible. It's clear? Again, I don't want to await for reply,
> I want to know right now that I can't send a message.
> > > >
> > > > Realistically, this is very classic networking issue :) So, how can
> ZMQ help me? Or is it possible/eligible et al to implement transactional
> (not batching!) applications on ZMQ?
> > > >
> > > >
> > > > BR
> > > > -artemv
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > 2013/12/11 Bruno D. Rodrigues <bruno.rodrigues at litux.org (mailto:
> bruno.rodrigues at litux.org) (mailto:bruno.rodrigues at litux.org)>
> > > > > zeromq.org (http://zeromq.org) (http://zeromq.org) - learn the
> basics - http://zeromq.org/intro:read-the-manual - the guide -
> http://zguide.zeromq.org/page:all
> > > > >
> > > > > I just gave you a short description of how Ømq is solving the
> network problems for me.
> > > > >
> > > > > On Dec 11, 2013, at 6:59, asif saeed <asif.lse2 at gmail.com (mailto:
> asif.lse2 at gmail.com) (mailto:asif.lse2 at gmail.com)> wrote:
> > > > > > Hi Bruno,
> > > > > >
> > > > > > On Wed, Dec 11, 2013 at 12:38 AM, Bruno D. Rodrigues <
> bruno.rodrigues at litux.org (mailto:bruno.rodrigues at litux.org) (mailto:
> bruno.rodrigues at litux.org)> wrote:
> > > > > > > Xsub xpub for distribution load balancing
> > > > > >
> > > > > >
> > > > > >
> > > > > > What is Xsub xpub? Could you please explain these terms or give
> me a link to an online resource where these terms are explained in detail?
> > > > > >
> > > > > > Thanks in advance,
> > > > > > -Asif
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
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