Multiple NICs and MassTransit

[Jean Lambert]

Hi, I am currently experiencing some design challenges with a system that uses multiple network interface cards each having they own sub-nets.

Setup is as follows:

Host A, eth0: 192.168.1.1, eth1: 10.150.1.1

Host B, eth0: 192.168.1.2

Host C, eth0: 10.150.1.2

Host A is connected to Host B and Host C throughout different networks.

Host A is running RabbitMQ and a process which uses MassTransit.

Host A uses a request-reponse pattern to communicate with Host B and Host C.

The service bus setup on A is as follows:

var bus = ServiceBusFactory.New(sbc =>

{

  sbc.UseRabbitMq();

  sbc.ReceiveFrom("rabbitmq://192.168.1.1/HostA");

}

When sending a message to B for example, I do something like:

var e = bus.GetEndpoint("rabbitmq://192.168.1.1/HostB");

e.SendRequest(new MyMessage(), bus, x =>

{

  x.Handle<IExpectedResponse>(r => { // do something });

  x.SetTimeout(TimeSpan.FromSeconds(30));

  x.SetRequestExpiration(TimeSpan.FromSeconds(10));

}

Host B has a consumer for MyMessage() and uses context.Respond(new ExpectedResponse());

This works fine.

Now, repeat scenario but with Host C.

var e = bus.GetEndpoint("rabbitmq://192.168.1.1/HostC");

e.SendRequest(new MyMessage(), bus, x =>

{

  x.Handle<IExpectedResponse>(r => { // do something });

  x.SetTimeout(TimeSpan.FromSeconds(30));

  x.SetRequestExpiration(TimeSpan.FromSeconds(10));

}

The message is sent and received by HostC, but here is where it gets interesting doing a  context.Respond(new ExpectedResponse()) does not work.

After some investigation it was discovered that context.ResponseAddress was rabbitmq://192.168.1.1/HostA which Host C cannot see since he is on the 10.150.1.2 net.

What strategy is best in such a situation?

Should I have on Host A as many service bus instances as I have network cards and use the right one based on whom I'm communicating with?

Should I set my own ResponseAddress?

Any suggestions?

Thanks,

Jean

[Travis Smith]

I take it just using hostnames is out of the question?

I feel like the easiest thing to do is create one bus per subnet. Then just have your service send messages between as needed. I don't recall speaking with anyone who has to deal with this to date, so I'm not sure I have any good guidance based upon experience. 

-Travis

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[Chris Patterson]

Host names would help, since each machine would resolve them to the property network.

[Jean Lambert]

Hostname did the trick for the time being.

 

We're still in the process of figuring out the best approach in cases where we have no DNS.

 

Thanks!

[Jean Lambert]

Here's a possible solution to this problem:

 

https://gist.github.com/jeandev/5967204