On Wed, Oct 14, 2020 at 8:25 AM Petrenko, Vadim <vadim.petre...@ns.nl> wrote:
> Good day, > > We’re trying to implement our Qpid dispatch router network in such a way > that a sender can connect to it at any moment and start sending messages to > a topic. > There might be no receivers at this moment, so the messages would be just > lost. This is ok. > Then an any moment a receiver(s) can connect and start receiving messages > currently being sent, then drop off. The sender will just continue sending > messages, probably into the void. > > It’s about sending data from sensors. Sensor data is short living and > there is no need to buffer it or persist. If no one consumes this data in > realtime, it can be lost. > Senders and receivers in our situation are quite volatile, they appear and > drop off. > > As per docs of Qpid: > === > Dispatch Router uses a credit-based flow control mechanism to ensure that > producers can only send messages to a router if at least one consumer is > available to receive them. Because Dispatch Router does not store messages, > this credit-based flow control prevents producers from sending messages > when there are no consumers present. > === > > I was wondering, maybe there is still a workaround or a trick to implement > the router network the way I described in the beginning? > If possible without extra brokers and only with Qpid dispatch routers? > > Thanks. > > Can your sending client first check whether or not there is credit on the link and if there is no credit simply drop the message rather than sending it? Getting the value of available credit depends on the client API you are using. For example in Proton-C your sender would call pn_link_credit(sending_link_ptr) to get the credit for the sending link. Also keep in mind that since the application is OK with messages being dropped you'll want the sender to settle the message after it is sent (a.k.a. "pre-settled). > > ________________________________ > > Deze e-mail, inclusief eventuele bijlagen, is uitsluitend bestemd voor > (gebruik door) de geadresseerde. De e-mail kan persoonlijke of > vertrouwelijke informatie bevatten. Openbaarmaking, vermenigvuldiging, > verspreiding en/of verstrekking van (de inhoud van) deze e-mail (en > eventuele bijlagen) aan derden is uitdrukkelijk niet toegestaan. Indien u > niet de bedoelde geadresseerde bent, wordt u vriendelijk verzocht degene > die de e-mail verzond hiervan direct op de hoogte te brengen en de e-mail > (en eventuele bijlagen) te vernietigen. > > Informatie vennootschap<http://www.ns.nl/emaildisclaimer> > -- -K
