Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
I'd advise against trying to use identities to make this failover work. Okay. You're going to be fighting 0MQ's autoreconnect. Instead, provide authentication in the protocol itself and design the router app to do the failover itself. I don't understand what you mean when you say design the router app to do the failover itself. Some more info about my topology: I know in advance who all the primary services are. And if a failover scenerio happens, a leader election occurs and I will know about the new primary's hostname and ports. I can essentially do this: zmq_connect(s, Service 234) zmq_send (s, data, sizeof (data), 0); The pattern I'm trying to implement is a reliable pipeline. I want to be able to guarantee that what I send from the front endpoint won't be lost on it's way to the back endpoint. I use a pipeline to distribute the work/values and was toying with the DEALER/ROUTER setup that was described earlier for acknowledgements. This is my first attempt at the pattern: https://gist.github.com/trevorbernard/5029260/raw/9ab008dd931f3dfc6ec435beb7f3039a02a0c9a0/gistfile1.txt Looking forward to your feedback, Trev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
On Mon, Feb 25, 2013 at 1:24 PM, Trevor Bernard trevor.bern...@gmail.com wrote: The pattern I'm trying to implement is a reliable pipeline. I want to be able to guarantee that what I send from the front endpoint won't be lost on it's way to the back endpoint. OK, the simplest design is to assume that failure is possible in workers due to them running application code, whereas ventilator and sink are robust. Then, you detect failure by having a loss in the sink, and you recover from failure by resubmitting the whole batch. If it fails more than once, you flag it as toxic and stop retrying. If you want to handle failed sinks or ventilators, you can use redundancy and simply choose a sink/ventilator at start up, since these are stateless. You can do all this with PUSH/PULL I think. Clearly you're trying something more sophisticated so my guess is either we don't mean the same thing with reliable pipeline, or you're building a too-complex solution. My advice on reliability is to identify real failures and solve those in order of probability. -Pieter ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
On Mon, Feb 25, 2013 at 4:23 PM, Trevor Bernard trevor.bern...@gmail.com wrote: All I want to do is send work upstream reliably and have the ventilator be notified by the sink through an acknowledgement if the batch was successful or not so I can take appropriate action. How would you suggest I go about this? The ventilator can tell the sink directly how many jobs to expect. If there's any missing after a timeout, that means a worker died. The sink would then tell the client Failed and the client could decide to retry, or cancel. This handles the probably most common failure, which is crashed workers. If you want to handle workers that get into endless loops but appear to be alive, you would have to add heartbeating and it all gets more complex. I'd not go there in a first design. Trick is to make the simplest possible design you can, break it with simulated failures, and solve those. The common trap is to over-design your first architecture. A reliable pipeline was one of the patterns I'd meant to build but didn't get around to. Sorry about that. -Pieter ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
On Mon, Feb 25, 2013 at 4:50 PM, Trevor Bernard trevor.bern...@gmail.com wrote: A reliable pipeline was one of the patterns I'd meant to build but didn't get around to. Sorry about that. I can help you flesh this out. I'd start by taking the existing pipeline example and adding random failures to the workers. Then, add the control message that lets the sink detect a failure. -Pieter ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
Hi, Please try using ROUTER_MANDATORY at router socket. If you get EHOSTUNREACH at send, you should retry send. Thanks Min 2013년 2월 25일 월요일에 Trevor Bernard님이 작성: Hi, I have a use case where I'd like to re-cycle DEALER identities when a failover situation occurs. I have one service SV1 that creates a DEALER connection to a ROUTER socket on SVn. SV1 has a hot standby and uses the same identity in a failover situation. The first connect goes as you would expect, but in the situation of a failover, the second SV1 never receives any messages from SVn. Can someone point me in the right direction on how to route back the response? -Trev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org javascript:; http://lists.zeromq.org/mailman/listinfo/zeromq-dev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
Hi Min, Thanks for the suggestion. I added ROUTER_MANDATORY to my ROUTER but this didn't resolve my original problem however. The problem is after I reconnect on a different DEALER socket with the same identity, it no longer correctly routes the response. I'm curious if there is a way to reuse identities upon disconnects. I'd rather not send a unique GUID with my payload since I already have my service information readily available. -Trev On Sun, Feb 24, 2013 at 9:27 PM, Min mini...@gmail.com wrote: Hi, Please try using ROUTER_MANDATORY at router socket. If you get EHOSTUNREACH at send, you should retry send. Thanks Min 2013년 2월 25일 월요일에 Trevor Bernard님이 작성: Hi, I have a use case where I'd like to re-cycle DEALER identities when a failover situation occurs. I have one service SV1 that creates a DEALER connection to a ROUTER socket on SVn. SV1 has a hot standby and uses the same identity in a failover situation. The first connect goes as you would expect, but in the situation of a failover, the second SV1 never receives any messages from SVn. Can someone point me in the right direction on how to route back the response? -Trev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] DEALER to ROUTER and reusing identity.
On Mon, Feb 25, 2013 at 1:53 AM, Trevor Bernard trevor.bern...@gmail.com wrote: I have a use case where I'd like to re-cycle DEALER identities when a failover situation occurs. I have one service SV1 that creates a DEALER connection to a ROUTER socket on SVn. SV1 has a hot standby and uses the same identity in a failover situation. The first connect goes as you would expect, but in the situation of a failover, the second SV1 never receives any messages from SVn. I'd advise against trying to use identities to make this failover work. You're going to be fighting 0MQ's autoreconnect. Instead, provide authentication in the protocol itself and design the router app to do the failover itself. -Pieter ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
