NetMQ

When the default Loopback transport doesn’t cover your use-cases, Cambion has other transports available. One of these uses NetMQ to send data between instances of Cambion.

Note

NetMQ uses two TCP ports. These two ports needs to be open in your firewall.

Installation

The NetMQ transport for Cambion is also available on NuGet so you can install it using the NuGet Package Manager Console:

Install-Package Whitestone.Cambion.Transport.NetMQ

Usage

The NetMQ transport is setup during regular Cambion configuration. TCP ports 9998 and 9999 are arbitrary ports, and you can use whichever ports you fancy (that are available). Remember that the ports must be the same (both numerical, and the same order) for all instances of Cambion that will talk to eachother.

Host

In order for Cambion to send and receive data using NetMQ, one of the Cambion instances needs to work as a MessageHost. The other Cambion instances will then connect to the MessageHost as clients.

The NetMQ transport is set up using an extension method for ICambionBuilder. This extension method takes an Action<NetMqConfig> as the input parameter.

Note

The MessageHost will work as a normal client in addition to being the host without any additional configuration

Initialize the NetMQ backend as normal, but set the optional parameter useMessageHost parameter in the UseNetMQ extension to true:

public void ConfigureServices(IServiceCollection services)
{
    services.AddCambion()
        .UseNetMqTransport(conf =>
        {
            conf.PublishAddress = "tcp://localhost:9999";
            conf.SubscribeAddress = "tcp://localhost:9998";
            conf.UseMessageHost = true;
        });
}

Clients

Clients will use the same configuration as above, but will set UseMessageHost to false (or omit it, as it defaults to false)

External configuration

In addition to configuring through Action<NetMqConfig> you can also pass in an Microsoft.Extensions.Configuration.IConfiguration object that has been populated with settings through appsettings.json, environment variables, user secrets, or similar sources.

public void ConfigureServices(HostBuilderContext ctx, IServiceCollection services)
{
    services.AddCambion()
        .UseNetMqTransport(ctx.Configuration);
}

This expects the configuration to have been set up according to Configuration Reader.

Any settings missing in the configuration will be set to the default values for the object type in NetMqConfig.

Any settings defined in the configuration can also be owerwritten through the Action<NetMqConfig>:

public void ConfigureServices(HostBuilderContext ctx, IServiceCollection services)
{
    services.AddCambion()
        .UseNetMqTransport(
            ctx.Configuration,
            conf => conf.PublishAddress = "tcp://localhost:9999");
}

As with the Configuration Reader you can also override which settings object to read from, so instead of the default Cambion override it by passing a new configuration key:

public void ConfigureServices(HostBuilderContext ctx, IServiceCollection services)
{
    services.AddCambion()
        .UseNetMqTransport(ctx.Configuration, "Example");
}

Note

As with the Configuration Reader you cannot change the “Transport” key.

Example JSON

{
    "Cambion": {
        "Transport": {
            "Whitestone.Cambion.Transport.NetMQ": {
                "PublishAddress": "tcp://localhost:9990",
                "SubscribeAddress": "tcp://localhost:9991",
                "UseMessageHost": true
            }
        }
    }
}