/// <summary>
/// In this example
/// - consumer group functionality (i.e. .Subscribe + offset commits) is not used.
/// - the consumer is manually assigned to a partition and always starts consumption
/// from a specific offset (0).
/// </summary>
public static void Run_ManualAssign(string brokerList, List <string> topics, CancellationToken cancellationToken)
{
var config = new ConsumerConfig
{
// the group.id property must be specified when creating a consumer, even
// if you do not intend to use any consumer group functionality.
GroupId = new Guid().ToString(),
BootstrapServers = brokerList,
// partition offsets can be committed to a group even by consumers not
// subscribed to the group. in this example, auto commit is disabled
// to prevent this from occuring.
EnableAutoCommit = true
};
using (var consumer = new Consumer <Ignore, string>(config))
{
consumer.Assign(topics.Select(topic => new TopicPartitionOffset(topic, 0, Offset.Beginning)).ToList());
consumer.OnError += (_, e)
=> Console.WriteLine($"Error: {e.Reason}");
consumer.OnPartitionEOF += (_, topicPartitionOffset)
=> Console.WriteLine($"End of partition: {topicPartitionOffset}");
while (!cancellationToken.IsCancellationRequested)
{
try
{
var consumeResult = consumer.Consume(cancellationToken);
Console.WriteLine($"Received message at {consumeResult.TopicPartitionOffset}: ${consumeResult.Message}");
}
catch (ConsumeException e)
{
Console.WriteLine($"Consume error: {e.Error}");
}
}
consumer.Close();
}
}
/// <summary>
/// In this example
/// - offsets are manually committed.
/// - no extra thread is created for the Poll (Consume) loop.
/// </summary>
public static void Run_Consume(string brokerList, List <string> topics, CancellationToken cancellationToken)
{
var config = new ConsumerConfig
{
BootstrapServers = brokerList,
GroupId = "csharp-consumer",
EnableAutoCommit = false,
StatisticsIntervalMs = 5000,
SessionTimeoutMs = 6000,
AutoOffsetReset = AutoOffsetResetType.Earliest
};
const int commitPeriod = 5;
using (var serdeProvider = new AvroSerdeProvider(new AvroSerdeProviderConfig {
SchemaRegistryUrl = "192.168.100.153:8081"
}))
using (var consumer = new Consumer <Ignore, com.landoop.social.reddit.post.reddit_post>(config, null, serdeProvider.GetDeserializerGenerator <com.landoop.social.reddit.post.reddit_post>()))
// using (var consumer = new Consumer<Ingore, string>(config))
{
// Note: All event handlers are called on the main .Consume thread.
// Raised when the consumer has been notified of a new assignment set.
// You can use this event to perform actions such as retrieving offsets
// from an external source / manually setting start offsets using
// the Assign method. You can even call Assign with a different set of
// partitions than those in the assignment. If you do not call Assign
// in a handler of this event, the consumer will be automatically
// assigned to the partitions of the assignment set and consumption
// will start from last committed offsets or in accordance with
// the auto.offset.reset configuration parameter for partitions where
// there is no committed offset.
consumer.OnPartitionsAssigned += (_, partitions)
=> Console.WriteLine($"Assigned partitions: [{string.Join(", ", partitions)}], member id: {consumer.MemberId}");
// Raised when the consumer's current assignment set has been revoked.
consumer.OnPartitionsRevoked += (_, partitions)
=> Console.WriteLine($"Revoked partitions: [{string.Join(", ", partitions)}]");
consumer.OnPartitionEOF += (_, tpo)
=> Console.WriteLine($"Reached end of topic {tpo.Topic} partition {tpo.Partition}, next message will be at offset {tpo.Offset}");
consumer.OnError += (_, e)
=> Console.WriteLine($"Error: {e.Reason}");
//consumer.OnStatistics += (_, json)
// => Console.WriteLine($"Statistics: {json}");
consumer.Subscribe(topics);
while (!cancellationToken.IsCancellationRequested)
{
try
{
var consumeResult = consumer.Consume(cancellationToken);
Console.WriteLine($"Topic: {consumeResult.Topic}");
Console.WriteLine($"Partition: {consumeResult.Partition} Offset: {consumeResult.Offset}");
Console.WriteLine($"Subreddit Topic: { consumeResult.Value.subreddit }");
Console.WriteLine($"{ consumeResult.Value.body }");
Console.WriteLine("---");
Thread.Sleep(1000);
if (consumeResult.Offset % commitPeriod == 0)
{
// The Commit method sends a "commit offsets" request to the Kafka
// cluster and synchronously waits for the response. This is very
// slow compared to the rate at which the consumer is capable of
// consuming messages. A high performance application will typically
// commit offsets relatively infrequently and be designed handle
// duplicate messages in the event of failure.
var committedOffsets = consumer.Commit(consumeResult);
Console.WriteLine($"Committed offset: {committedOffsets}");
}
}
catch (ConsumeException e)
{
Console.WriteLine($"Consume error: {e.Error}");
}
}
consumer.Close();
}
}
