安装
介绍
- Broker:消息中间件处理节点,一个 Kafka 节点就是一个 broker,多个 broker 可以组成一个 Kafka 集群。
- Topic:一类消息,例如 page view 日志、click 日志等都可以以 topic 的形式存在,Kafka 集群能够同时负责多个 topic 的分发。
- Partition:topic 物理上的分组,一个 topic 可以分为多个 partition,每个 partition 是一个有序的队列。
- Segment:partition 物理上由多个 segment 组成,下面 2.2 和 2.3 有详细说明。
- offset:每个 partition 都由一系列有序的、不可变的消息组成,这些消息被连续的追加到 partition 中。partition 中的每个消息都有一个连续的序列号叫做 offset,用于 partition 唯一标识一条消息。
::: tip kafka partition 和 consumer 数目关系
- 如果 consumer 比 partition 多是浪费,因为 kafka 的设计是在一个 partition 上是不允许并发的,所以 consumer 数不要大于 partition 数 。
- 如果 consumer 比 partition 少,一个 consumer 会对应于多个 partitions,这里主要合理分配 consumer 数和 partition 数,否则会导致 partition 里面的数据被取的不均匀 。最好 partiton 数目是 consumer 数目的整数倍,所以 partition 数目很重要,比如取 24,就很容易设定 consumer 数目 。
- 如果 consumer 从多个 partition 读到数据,不保证数据间的顺序性,kafka 只保证在一个 partition 上数据是有序的,但多个 partition,根据你读的顺序会有不同
- 增减 consumer,broker,partition 会导致 rebalance,所以 rebalance 后 consumer 对应的 partition 会发生变化
:::
快速开始
在 .NET Core 项目中安装组件
Install-Package Confluent.Kafka
开源地址:https://github.com/confluentinc/confluent-kafka-dotnet
添加IKafkaService
服务接口
public interface IKafkaService
{
/// <summary>
/// 发送消息至指定主题
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="topicName"></param>
/// <param name="message"></param>
/// <returns></returns>
Task PublishAsync<TMessage>(string topicName, TMessage message) where TMessage : class;
/// <summary>
/// 从指定主题订阅消息
/// </summary>
/// <typeparam name="TMessage"></typeparam>
/// <param name="topics"></param>
/// <param name="messageFunc"></param>
/// <param name="cancellationToken"></param>
/// <returns></returns>
Task SubscribeAsync<TMessage>(IEnumerable<string> topics, Action<TMessage> messageFunc, CancellationToken cancellationToken) where TMessage : class;
}
实现IKafkaService
public class KafkaService : IKafkaService
{
public async Task PublishAsync<TMessage>(string topicName, TMessage message) where TMessage : class
{
var config = new ProducerConfig
{
BootstrapServers = "127.0.0.1:9092"
};
using var producer = new ProducerBuilder<string, string>(config).Build();
await producer.ProduceAsync(topicName, new Message<string, string>
{
Key = Guid.NewGuid().ToString(),
Value = message.SerializeToJson()
});
}
public async Task SubscribeAsync<TMessage>(IEnumerable<string> topics, Action<TMessage> messageFunc, CancellationToken cancellationToken) where TMessage : class
{
var config = new ConsumerConfig
{
BootstrapServers = "127.0.0.1:9092",
GroupId = "consumer",
EnableAutoCommit = false,
StatisticsIntervalMs = 5000,
SessionTimeoutMs = 6000,
AutoOffsetReset = AutoOffsetReset.Earliest,
EnablePartitionEof = true
};
//const int commitPeriod = 5;
using var consumer = new ConsumerBuilder<Ignore, string>(config)
.SetErrorHandler((_, e) =>
{
Console.WriteLine($"Error: {e.Reason}");
})
.SetStatisticsHandler((_, json) =>
{
Console.WriteLine($" - {DateTime.Now:yyyy-MM-dd HH:mm:ss} > 消息监听中..");
})
.SetPartitionsAssignedHandler((c, partitions) =>
{
string partitionsStr = string.Join(", ", partitions);
Console.WriteLine($" - 分配的 kafka 分区: {partitionsStr}");
})
.SetPartitionsRevokedHandler((c, partitions) =>
{
string partitionsStr = string.Join(", ", partitions);
Console.WriteLine($" - 回收了 kafka 的分区: {partitionsStr}");
})
.Build();
consumer.Subscribe(topics);
try
{
while (true)
{
try
{
var consumeResult = consumer.Consume(cancellationToken);
Console.WriteLine($"Consumed message '{consumeResult.Message?.Value}' at: '{consumeResult?.TopicPartitionOffset}'.");
if (consumeResult.IsPartitionEOF)
{
Console.WriteLine($" - {DateTime.Now:yyyy-MM-dd HH:mm:ss} 已经到底了:{consumeResult.Topic}, partition {consumeResult.Partition}, offset {consumeResult.Offset}.");
continue;
}
TMessage messageResult = null;
try
{
messageResult = JsonConvert.DeserializeObject<TMessage>(consumeResult.Message.Value);
}
catch (Exception ex)
{
var errorMessage = $" - {DateTime.Now:yyyy-MM-dd HH:mm:ss}【Exception 消息反序列化失败,Value:{consumeResult.Message.Value}】 :{ex.StackTrace?.ToString()}";
Console.WriteLine(errorMessage);
messageResult = null;
}
if (messageResult != null/* && consumeResult.Offset % commitPeriod == 0*/)
{
messageFunc(messageResult);
try
{
consumer.Commit(consumeResult);
}
catch (KafkaException e)
{
Console.WriteLine(e.Message);
}
}
}
catch (ConsumeException e)
{
Console.WriteLine($"Consume error: {e.Error.Reason}");
}
}
}
catch (OperationCanceledException)
{
Console.WriteLine("Closing consumer.");
consumer.Close();
}
await Task.CompletedTask;
}
}
注入IKafkaService
,在需要使用的地方直接调用即可。
public class MessageService : IMessageService, ITransientDependency
{
private readonly IKafkaService _kafkaService;
public MessageService(IKafkaService kafkaService)
{
_kafkaService = kafkaService;
}
public async Task RequestTraceAdded(XxxEventData eventData)
{
await _kafkaService.PublishAsync(eventData.TopicName, eventData);
}
}
以上相当于一个生产者,当我们消息队列发出后,还需一个消费者进行消费,所以可以使用一个控制台项目接收消息来处理业务。
var cts = new CancellationTokenSource();
Console.CancelKeyPress += (_, e) =>
{
e.Cancel = true;
cts.Cancel();
};
await kafkaService.SubscribeAsync<XxxEventData>(topics, async (eventData) =>
{
// Your logic
Console.WriteLine($" - {eventData.EventTime:yyyy-MM-dd HH:mm:ss} 【{eventData.TopicName}】- > 已处理");
}, cts.Token);
在IKafkaService
中已经写了订阅消息的接口,这里也是注入后直接使用即可。
生产者消费者示例
生产者
static async Task Main(string[] args)
{
if (args.Length != 2)
{
Console.WriteLine("Usage: .. brokerList topicName");
// 127.0.0.1:9092 helloTopic
return;
}
var brokerList = args.First();
var topicName = args.Last();
var config = new ProducerConfig { BootstrapServers = brokerList };
using var producer = new ProducerBuilder<string, string>(config).Build();
Console.WriteLine("\n-----------------------------------------------------------------------");
Console.WriteLine($"Producer {producer.Name} producing on topic {topicName}.");
Console.WriteLine("-----------------------------------------------------------------------");
Console.WriteLine("To create a kafka message with UTF-8 encoded key and value:");
Console.WriteLine("> key value<Enter>");
Console.WriteLine("To create a kafka message with a null key and UTF-8 encoded value:");
Console.WriteLine("> value<enter>");
Console.WriteLine("Ctrl-C to quit.\n");
var cancelled = false;
Console.CancelKeyPress += (_, e) =>
{
e.Cancel = true;
cancelled = true;
};
while (!cancelled)
{
Console.Write("> ");
var text = string.Empty;
try
{
text = Console.ReadLine();
}
catch (IOException)
{
break;
}
if (string.IsNullOrWhiteSpace(text))
{
break;
}
var key = string.Empty;
var val = text;
var index = text.IndexOf(" ");
if (index != -1)
{
key = text.Substring(0, index);
val = text.Substring(index + 1);
}
try
{
var deliveryResult = await producer.ProduceAsync(topicName, new Message<string, string>
{
Key = key,
Value = val
});
Console.WriteLine($"delivered to: {deliveryResult.TopicPartitionOffset}");
}
catch (ProduceException<string, string> e)
{
Console.WriteLine($"failed to deliver message: {e.Message} [{e.Error.Code}]");
}
}
}
消费者
static void Main(string[] args)
{
if (args.Length != 2)
{
Console.WriteLine("Usage: .. brokerList topicName");
// 127.0.0.1:9092 helloTopic
return;
}
var brokerList = args.First();
var topicName = args.Last();
Console.WriteLine($"Started consumer, Ctrl-C to stop consuming");
var cts = new CancellationTokenSource();
Console.CancelKeyPress += (_, e) =>
{
e.Cancel = true;
cts.Cancel();
};
var config = new ConsumerConfig
{
BootstrapServers = brokerList,
GroupId = "consumer",
EnableAutoCommit = false,
StatisticsIntervalMs = 5000,
SessionTimeoutMs = 6000,
AutoOffsetReset = AutoOffsetReset.Earliest,
EnablePartitionEof = true
};
const int commitPeriod = 5;
using var consumer = new ConsumerBuilder<Ignore, string>(config)
.SetErrorHandler((_, e) =>
{
Console.WriteLine($"Error: {e.Reason}");
})
.SetStatisticsHandler((_, json) =>
{
Console.WriteLine($" - {DateTime.Now:yyyy-MM-dd HH:mm:ss} > monitoring..");
//Console.WriteLine($"Statistics: {json}");
})
.SetPartitionsAssignedHandler((c, partitions) =>
{
Console.WriteLine($"Assigned partitions: [{string.Join(", ", partitions)}]");
})
.SetPartitionsRevokedHandler((c, partitions) =>
{
Console.WriteLine($"Revoking assignment: [{string.Join(", ", partitions)}]");
})
.Build();
consumer.Subscribe(topicName);
try
{
while (true)
{
try
{
var consumeResult = consumer.Consume(cts.Token);
if (consumeResult.IsPartitionEOF)
{
Console.WriteLine($"Reached end of topic {consumeResult.Topic}, partition {consumeResult.Partition}, offset {consumeResult.Offset}.");
continue;
}
Console.WriteLine($"Received message at {consumeResult.TopicPartitionOffset}: {consumeResult.Message.Value}");
if (consumeResult.Offset % commitPeriod == 0)
{
try
{
consumer.Commit(consumeResult);
}
catch (KafkaException e)
{
Console.WriteLine($"Commit error: {e.Error.Reason}");
}
}
}
catch (ConsumeException e)
{
Console.WriteLine($"Consume error: {e.Error.Reason}");
}
}
}
catch (OperationCanceledException)
{
Console.WriteLine("Closing consumer.");
consumer.Close();
}
}