无法连接kafka集群时无异常

Question

I am unable get an exception when the program fails to connect to the kafka cluster. The code outputs the exception in the console logs but I need it throw an exception. I am using this c# library: https://github.com/confluentinc/confluent-kafka-do.net

ProducerConfig _configKafka = new ProducerConfig { BootstrapServers ="localhost:9092/" };

ProducerBuilder<string, string> _kafkaProducer = new ProducerBuilder<string, string>(_configKafka);
using (var kafkaProducer = _kafkaProducer.Build())
{

    try
    {
        var dr = kafkaProducer.ProduceAsync("Kafka_Messages", new Message<string, string> { Key = null, Value = $"message {i++}" });
        dr.Wait(TimeSpan.FromSeconds(10));

        if(dr.Exception!=null)
        {
            Console.WriteLine($"Delivery failed:");
        }

        var status = dr.Status;

        //Console.WriteLine($"Delivered '{dr.Value}' to '{dr.TopicPartitionOffset}'");
    }

    catch (ProduceException<Null, string> e)
    {
        Console.WriteLine($"Delivery failed: {e.Error.Reason}");
    }
}

Below is the error printed by confluent-kafka in console:

%3|1565248275.024|FAIL|rdkafka#producer-1| [thrd:localhst:9092/bootstrap]: localhst:9092/bootstrap: Failed to resolve 'localhst:9092': No such host is known.  (after 2269ms in state CONNECT)
%3|1565248275.024|ERROR|rdkafka#producer-1| [thrd:localhst:9092/bootstrap]: localhst:9092/bootstrap: Failed to resolve 'localhst:9092': No such host is known.  (after 2269ms in state CONNECT)
%3|1565248275.025|ERROR|rdkafka#producer-1| [thrd:localhst:9092/bootstrap]: 1/1 brokers are down

Answer 1

To get the actual exception within your application you need to add .SetErrorHandler() :

    ProducerBuilder<string, string> _kafkaProducer = new ProducerBuilder<string, string>(_configKafka);

    using (var kafkaProducer = _kafkaProducer.SetErrorHandler((producer, error) =>
                        {
                           //You can handle error right here

                        }).Build())

error.Reason contains the error message

Answer 2

You can use both .SetLogHandler and .SetErrorHandler in your consumer and producer code. Otherwise it kind of silently fails without providing much details. You can forward the messages to your logger there.