/// <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)
{
var config = new Dictionary <string, object>
{
// the group.id property must be specified when creating a consumer, even
// if you do not intend to use any consumer group functionality.
{ "group.id", new Guid().ToString() },
{ "bootstrap.servers", 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.
{ "enable.auto.commit", false }
};
using (var consumer = new Consumer <Ignore, string>(config, null, new StringDeserializer(Encoding.UTF8)))
{
consumer.Assign(topics.Select(topic => new TopicPartitionOffset(topic, 0, Offset.Beginning)).ToList());
// Raised on critical errors, e.g. connection failures or all brokers down.
consumer.OnError += (_, error)
=> Console.WriteLine($"Error: {error}");
// Raised on deserialization errors or when a consumed message has an error != NoError.
consumer.OnConsumeError += (_, error)
=> Console.WriteLine($"Consume error: {error}");
while (true)
{
if (consumer.Consume(out Message <Ignore, string> msg, TimeSpan.FromSeconds(1)))
{
Console.WriteLine($"Topic: {msg.Topic} Partition: {msg.Partition} Offset: {msg.Offset} {msg.Value}");
}
}
}
}
static void Main(string[] args)
{
var config = new ConsumerConfig {
GroupId = "test-consumer",
BootstrapServers = "localhost:9092",
AutoOffsetReset = AutoOffsetResetType.Earliest
};
Console.Write("Topic to suscribe in this session:");
var topic = Console.ReadLine();
using (var consumer = new Consumer <Ignore, string>(config)){
consumer.Subscribe(topic);
var consumig = true;
consumer.OnError += (_, e) => consumig = !e.IsFatal;
while (true)
{
try{
var consumeReport = consumer.Consume();
Console.WriteLine($"Consumed message: '{consumeReport.Value}' at: '{consumeReport.TopicPartitionOffset}'");
}catch (ConsumeException e) {
Console.WriteLine($"Error: {e.Error?.Reason}");
}
}
}
}
/// <summary>
/// In this example
/// - offsets are manually committed.
/// - consumer.Consume is used to consume messages.
/// (all other events are still handled by event handlers)
/// - no extra thread is created for the Poll (Consume) loop.
/// </summary>
public static void Run_Consume(string brokerList, List <string> topics)
{
var config = new Dictionary <string, object>
{
{ "bootstrap.servers", brokerList },
{ "group.id", "csharp-consumer" },
{ "enable.auto.commit", false },
{ "statistics.interval.ms", 60000 },
{ "session.timeout.ms", 6000 },
{ "auto.offset.reset", "smallest" }
};
using (var consumer = new Consumer <Ignore, string>(config, null, new StringDeserializer(Encoding.UTF8)))
{
// Note: All event handlers are called on the main thread.
consumer.OnPartitionEOF += (_, end)
=> Console.WriteLine($"Reached end of topic {end.Topic} partition {end.Partition}, next message will be at offset {end.Offset}");
consumer.OnError += (_, error)
=> Console.WriteLine($"Error: {error}");
// Raised on deserialization errors or when a consumed message has an error != NoError.
consumer.OnConsumeError += (_, error)
=> Console.WriteLine($"Consume error: {error}");
// Raised when the consumer is assigned a new set of partitions.
consumer.OnPartitionsAssigned += (_, partitions) =>
{
Console.WriteLine($"Assigned partitions: [{string.Join(", ", partitions)}], member id: {consumer.MemberId}");
// If you don't add a handler to the OnPartitionsAssigned event,
// the below .Assign call happens automatically. If you do, you
// must call .Assign explicitly in order for the consumer to
// start consuming messages.
consumer.Assign(partitions);
};
// Raised when the consumer's current assignment set has been revoked.
consumer.OnPartitionsRevoked += (_, partitions) =>
{
Console.WriteLine($"Revoked partitions: [{string.Join(", ", partitions)}]");
// If you don't add a handler to the OnPartitionsRevoked event,
// the below .Unassign call happens automatically. If you do,
// you must call .Unassign explicitly in order for the consumer
// to stop consuming messages from it's previously assigned
// partitions.
consumer.Unassign();
};
consumer.OnStatistics += (_, json)
=> Console.WriteLine($"Statistics: {json}");
consumer.Subscribe(topics);
Console.WriteLine($"Started consumer, Ctrl-C to stop consuming");
var cancelled = false;
Console.CancelKeyPress += (_, e) => {
e.Cancel = true; // prevent the process from terminating.
cancelled = true;
};
while (!cancelled)
{
if (!consumer.Consume(out Message <Ignore, string> msg, TimeSpan.FromMilliseconds(100)))
{
continue;
}
Console.WriteLine($"Topic: {msg.Topic} Partition: {msg.Partition} Offset: {msg.Offset} {msg.Value}");
if (msg.Offset % 5 == 0)
{
var committedOffsets = consumer.CommitAsync(msg).Result;
Console.WriteLine($"Committed offset: {committedOffsets}");
}
}
}
}