NetStreams

A light weight .NET streaming api for Kafka.

Running the project locally

NPM & Docker will need to be installed.

Clone the repository and execute the npm script docker-up. This script will start kafka locally and enable different authentication methods.

npm run docker-up

Create a stream and handle messages

  var stream = new NetStreamBuilder<Null, MyMessage>(
        cfg =>
        {
            cfg.BootstrapServers = "localhost:9092";
            cfg.ConsumerGroup = "MyConsumer";
        })
        .Stream(sourceTopic)
        .Handle(context => Console.WriteLine($"Handling message value={context.Message.Value}"))
        .Build()
        .StartAsync(new CancellationToken());

Filter Messages to be handled

  var stream = new NetStreamBuilder<Null, MyMessage>(
        cfg =>
        {
            cfg.BootstrapServers = "localhost:9092";
            cfg.ConsumerGroup = "MyConsumer";
        })
        .Stream(sourceTopic)
        .Filter(context => context.Message.Value % 3 == 0)
        .Handle(context => Console.WriteLine($"Handling message value={context.Message.Value}"))
        .Build()
        .StartAsync(new CancellationToken());

Use the transform method and write output to kafka topic

This example leverages mediator to dispatch a command and then writes the output to the destination topic

var stream = new NetStreamBuilder<string, OrderCommand>(
    cfg =>
    {
        cfg.BootstrapServers = "localhost:9092";
        cfg.ConsumerGroup = "Orders.Consumer";
    })
    .Stream(sourceTopic)
    .TransformAsync(async context => await mediator.Send(context.Message))
    .ToTopic<string, OrderEvent>("Order.Events", message => message.Key)
    .Build()
    .StartAsync(CancellationToken.None);

Configure topics for auto creation

This example leverages mediator to dispatch a command and then writes the output to the destination topic

  var builder = new NetStreamBuilder(
        cfg =>
        {
            cfg.BootstrapServers = "localhost:9092";
            cfg.ConsumerGroup = "Orders.Consumer";
            cfg.AddTopicConfiguration(cfg =>
            {
                cfg.Name = "Order.Commands";
                cfg.Partitions = 2;
            });
            cfg.AddTopicConfiguration(cfg =>
            {
                cfg.Name = "Order.Events";
                cfg.Partitions = 2;
            });
        });

Delivery Mode

A delivery mode can be configured to control committing the offset.

For more information regarding delivery modes, check out this article

Options:

• At Most Once (Default Behavior if left blank)
• At Least Once
• Custom Delivery Mode

var builder = new NetStreamBuilder(
        cfg =>
        {
            cfg.BootstrapServers = "localhost:9092";
            cfg.ConsumerGroup = "MyConsumer";
            cfg.DeliveryMode = DeliveryMode.At_Least_Once
            //cfg.DeliveryMode = DeliveryMode.At_Most_Once
            //cfg.DeliveryMode = new DeliveryMode(true, 10000);
        });

Custom Pipeline Steps

The pipeline for handling messages is extensible by adding custom pipeline steps.

  // extended
  public class CustomPipelineStep<TKey, TMessage> : PipelineStep<TKey,TMessage>
    {
        ...
    }

    // Implement Execute. Send your result on 
    public override async Task<NetStreamResult> Execute(IConsumeContext<TKey, TMessage> consumeContext, CancellationToken token, NetStreamResult result = null)
    {
        // do logic pre next step
        
        var response = await Next.Execute(consumeContext, token, result);

        // do logic post next step 
    }
     ...

This example logs application insights telemetry.

var stream = new NetStreamBuilder<Null, MyMessage>(
                cfg =>
                {
                    cfg.BootstrapServers = "localhost:9092";
                    cfg.ConsumerGroup = "AppInsightsExample.Consumer";
                    cfg.PipelineSteps
                        .Add(new ApplicationInsightsPipelineStep<TKey, TMessage>(GetTelemetryClient()));
                })
                .Stream(sourceTopic)
                .Filter(context => context.Message.Value % 3 == 0)
                .Handle(context => Console.WriteLine($"Handling message value={context.Message.Value}"))
                .Build()
                .StartAsync(new CancellationToken());

Skipping Malformed Messages

By default, NetStreams will skip a malformed message and log the offset and partition that was skipped. To turn this feature off, set the skip malformed messages property to false

new NetStreamBuilder<Null, MyMessage>(
    cfg =>
    {
        cfg.BootstrapServers = "localhost:9092";
        cfg.ConsumerGroup = "my-consumer";
        cfg.ShouldSkipMalformedMessages = false;
    })

Controlling Netstreams on Error

By default Netstreams is set to set to continue on error. This means that if an exception is encountered when processing a message, Netstreams will log the exception and move on to the next offset. NetStreams does not commit until a successful message is processed.

NetStreams can be configured to not continue on error but instead continue to process the the same offset until it is processed succesfully or manually skipped.

new NetStreamBuilder<Null, MyMessage>(
    cfg =>
    {
        cfg.BootstrapServers = "localhost:9092";
        cfg.ConsumerGroup = "my-consumer";
        cfg.ContinueOnError = false;
    })

Cluster Authentication

NetStreams supports the following cluster authentication methods:

• PlainText
• SSL
• SaslScram256
• SaslScram512

var builder = new NetStreamBuilder<Null, MyMessage>(
    cfg =>
    {
        cfg.UseAuthentication(new PlainTextAuthentication());
        //cfg.UseAuthentication(new SslAuthentication("sslCaCertPath", "sslClientCertPath", "sslClientKeyPath", "sslClientKeyPwd"));
        //cfg.UseAuthentication(new SaslScram256Authentication("username", "password", "sslCaCertPath"));
        //cfg.UseAuthentication(new SaslScram512Authentication("username", "password", "sslCaCertPath"));
        cfg.BootstrapServers = "localhost:9092";
    })

Generating New Certs for Docker Cluster and Testing

In the /secrets folder you'll find a handful of bash scripts. These can be used to generate a new round of certs if you need them.

(The certs, keys, credentials, etc. that have been checked-in with this repo aren't in use anywhere. They are included simply to make git clone . && npm run build possible.)

To generate a new batch of secrets:

1. Open a bash prompt. I use cygwin on Windows, but the scripts also work in Windows Subsystem for Linux.
2. Copy the following files into the /src/NetStream.Specs/ssl folder:
   • snakeoil-ca-1.crt
   • client.key
   • client.pem

Enable Message Correlation

Message correlation between a consumed message and one produced can be enabled using the CorrelationPipelineBehavior. This value is stored in the Kafka headers as X-NETSTREAM-CORRELATION

To enable this functionality, reference the NetStreams.Correlation library and enable the behavior using the configuration extension.

var builder = new NetStreamBuilder<Null, MyMessage>(
    cfg =>
    {
        cfg.BootstrapServers = "localhost:9092";
        cfg.EnableMessageCorrelation();
    })