/// <summary>
/// Constructor.
/// </summary>
/// <param name="producer">the producer in charge of redirecting erroneous objects.</param>
/// <param name="listener">the listener to decorate.</param>
/// <param name="errorTopic">the error topic used.</param>
/// <exception cref="ArgumentNullException">if any of the method parameters is <code>null</code>.</exception>
public GojulMQFailedMessageListener(IGojulMQMessageProducer <T> producer,
GojulMQMessageListener <T> listener, string errorTopic)
{
Condition.Requires(producer).IsNotNull();
Condition.Requires(listener).IsNotNull();
Condition.Requires(errorTopic).IsNotNullOrWhiteSpace();
this._producer = producer;
this._listener = listener;
this._errorTopic = errorTopic;
}
/// <see cref="IGojulMQMessageConsumer{T}.ConsumeMessages(string, OnMessage{T}, CancellationToken)"/>
public void ConsumeMessages(string topic, GojulMQMessageListener <T> messageListener,
CancellationToken cancellationToken)
{
Condition.Requires(topic, "topic").IsNotNull().IsNotEmpty();
Condition.Requires(messageListener, "messageListener").IsNotNull();
// CancellationToken cannot be null as it is a struct.
_consumer.Subscribe(topic);
try
{
while (!cancellationToken.IsCancellationRequested)
{
int count = 0;
var msg = _consumer.Consume(cancellationToken);
while (!cancellationToken.IsCancellationRequested)
{
// We try to commit on every 100 messages, or when
// the cancellation token has been triggered.
if (msg != null)
{
messageListener(msg.Value);
count++;
if (count % 100 == 0)
{
_consumer.Commit();
count = 0;
}
}
msg = _consumer.Consume(cancellationToken);
}
if (count > 0)
{
_consumer.Commit();
}
}
}
catch (KafkaException e)
{
_log.Fatal(e, string.Format("A fatal error occured : {0} - aborting the consumer", e.Message));
throw new GojulMQException("Kafka error encountered", e);
}
cancellationToken.ThrowIfCancellationRequested();
}
