zeromq/general

General community discussion

Kevin Sapper

@sappo

@Alex-CodeLab the poller will notify the caller if there's a new message present on the socket

Alex ⚡

@Alex-CodeLab

thanks. that makes sense. I tried to read the manual about it, but it was a bit too technical.

Kevin Sapper

@sappo

The poll.poll(<request_timeout>) call will return either if there's a new message available on one of the registered sockets or it will return after the request timeout.

The poll.register(client, zmq.POLLIN) registers the client socket with the poller and the zmq.POLLIN parameter will tell the poller to return on the poll call if there's a new incoming message on the socket. Another option could be zmq.POLLOUT but you will usually not require to use it.

Alex ⚡

@Alex-CodeLab

thanks a lot.

Joséphine Barthel

@JoBarthel_gitlab

Hello again, I am still doing some research regarding ZeroMQ possible applications in video game development. Let's say I want to have a permanent record of data regarding my players ; and I want each player to have access to it. For instance, a leaderboard, or an inventory system. Would it make sense to have a pub/sub architecture for it ? Or should I use a classic request-reply pattern ?
After reading The Guide, I understand there is 4 main patterns that are implemented by defaut in ZMQ (pub/sub, pipeline, request-reply and exclusive pairs) but I struggle to understand for which real-life case each one is appropriate.

Joséphine Barthel

@JoBarthel_gitlab

@sappo Thank you for your answer. Would Peer-to-Peer pub/sub be able to handle reconnect in case a player gets dropped during a game ? Let's say I'm only sending input - wouldn't those messages be lost ?

Kevin Sapper

@sappo

If you use plain pub/sub then a subscriber will not get messages redelivered that have been sent while it has been offline.

But using Dafka a consumer can read messages that have been sent while it was offline with the help of the consumer offset

Regarding permanent records Dafka has the concept of stores which will save events that can be reread even if the producer is already dead

Kevin Sapper

@sappo

Regarding the pattern, some common use cases would be (but not exclusive):

Exclusive pair -> interprocess communication
Pipeline -> processing workflow with multiple steps
Request/Reply -> Clients request something from a server

Alex ⚡

@Alex-CodeLab

@JoBarthel_gitlab you could store a copy of each message on the server, and on reconnect the client just tells what his latest received message-id was. Then it is up to you if you want to send the latest state, or all missed messages.

Joséphine Barthel

@JoBarthel_gitlab

Thank you for your help !

Иван Сердюк

@oceanfish81_twitter

https://github.com/p-org/PSharp/issues/441#issuecomment-564701307

Adriano Ribeiro

@drr00t

Hi guys, is it possible to use dafka with netmq? 😁

Adriano Ribeiro

@drr00t

@sappo if not. Is it to hard implement consumers? I would like to build my services using Kafka streams style architecture. But I'm working with dotnet and netmq

Kevin Sapper

@sappo

@somdoron started to port dafka to netmq. Not sure what the current state of his effort is though

Kevin Sapper

@sappo

@drr00t it is rather easy to to implement the consumers. The implementation part of the consumer is extensively documented in the README

If you need any help feel free to contact me

Doron Somech

@somdoron

I will look into port to .net in couple of weeks.

Will use in production soon

Adriano Ribeiro

@drr00t

Nice @somdoron i wondering to use in production too. Good to know that, thank you @sappo and @somdoron I will back to metter

Tushar Mathur

@tusharmath

I am trying to distribute my worker over a set of workers. I have 1 Request socket on Client and N Reply Sockets on N Workers. Is this the right combination?

Right now the execution is such that only one message is being sent by the Request and until a response is recieved no new message can be sent.

Is there a better way?

Kevin Sapper

@sappo

Yes, use the pipeline pattern with PUSH and PULL sockets: https://zeromq.org/socket-api/#pipeline-pattern

Tushar Mathur

@tusharmath

I am using this — https://github.com/imatix/zguide/raw/master/images/fig20.png

But its not being parallel really. @sappo

Kevin Sapper

@sappo

This is an example using the pipeline pattern: https://zeromq.org/socket-api/#pipeline-pattern

To make your current code work asynchronous read this: http://zguide.zeromq.org/page:all#The-Asynchronous-Client-Server-Pattern

Tushar Mathur

@tusharmath

@sappo What is wrong with my pattern?

If the work isn't distributed, what is the purpose of having multiple REP?

:point_up: December 31, 2019 7:59 PM Thanks i will take a look at this.

Kevin Sapper

@sappo

It only makes sense if you also have multiple REQ sockets @tusharmath

Tushar Mathur

@tusharmath

Oooh .... it doesn't say so in the doc though.

I mean the diagram is from the doc.

Apparently the middle proxy layer is supposed to make this system async.

Kevin Sapper

@sappo

The second link I send does exactly this ;)

iqbaldzone

@iqbaldzone

Hey Guy, I am using jeromq 0.5.1 version and i got this warning Warning:(31, 26) java: createSocket(int) in org.zeromq.ZContext has been deprecated. any have idea what i need to use.

iqbaldzone

@iqbaldzone

and getting this error too while shutdowning program

org.zeromq.ZMQException: Errno 4
    at org.zeromq.ZMQ$Socket.mayRaise(ZMQ.java:3533) ~[jeromq-0.5.1.jar:?]

 zmq.ZError$IOException: java.nio.channels.ClosedByInterruptException
    at zmq.Signaler.send(Signaler.java:101) ~[jeromq-0.5.1.jar:?]
    at zmq.Mailbox.send(Mailbox.java:71) ~[jeromq-0.5.1.jar:?]
    at zmq.Ctx.sendCommand(Ctx.java:540) ~[jeromq-0.5.1.jar:?]
    at zmq.ZObject.sendCommand(ZObject.java:382) ~[jeromq-0.5.1.jar:?]
    at zmq.ZObject.sendPipeTerm(ZObject.java:246) ~[jeromq-0.5.1.jar:?]
    at zmq.pipe.Pipe.terminate(Pipe.java:458) ~[jeromq-0.5.1.jar:?]
    at zmq.SocketBase.termEndpoint(SocketBase.java:639) ~[jeromq-0.5.1.jar:?]
    at org.zeromq.ZMQ$Socket.disconnect(ZMQ.java:3082) ~[jeromq-0.5.1.jar:?]

Doron Somech

@somdoron

You probably need to create the socket directly with a constructor. Context has been deprecated in some bindings and ports

iqbaldzone

@iqbaldzone

could you please give a example how can i create ?

@somdoron Because currently i create socket in constructor.

Kevin Sapper

@sappo

@iqbaldzone check the examples from the guide. Those should use non-deprecated API: https://github.com/zeromq/jeromq/tree/master/src/test/java/guide

iqbaldzone

@iqbaldzone

Okay thank @sappo ,
any suggestion to close socket multi threading socket

zmq.ZError$IOException: java.nio.channels.ClosedByInterruptException
    at zmq.Signaler.send(Signaler.java:101) ~[jeromq-0.5.1.jar:?]
    at zmq.Mailbox.send(Mailbox.java:71) ~[jeromq-0.5.1.jar:?]
    at zmq.Ctx.sendCommand(Ctx.java:540) ~[jeromq-0.5.1.jar:?]
    at zmq.ZObject.sendCommand(ZObject.java:382) ~[jeromq-0.5.1.jar:?]
    at zmq.ZObject.sendPipeTerm(ZObject.java:246) ~[jeromq-0.5.1.jar:?]
    at zmq.pipe.Pipe.terminate(Pipe.java:458) ~[jeromq-0.5.1.jar:?]
    at zmq.SocketBase.termEndpoint(SocketBase.java:639) ~[jeromq-0.5.1.jar:?]
    at org.zeromq.ZMQ$

Kevin Sapper

@sappo

@iqbaldzone to terminate you could do something like this https://github.com/zeromq/jdafka/blob/master/src/main/java/org/zeromq/dafka/DafkaConsumer.java#L129

Also be aware that you shouldn't use one socket from multiple threads

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