新建一个.net core类库项目
安装第三方依赖库，如下图所示：
41.png
新建一个SUPKafkaTopicConsumer类
这是用来创建并初始化消费者，接下来看看这个类里面包含了什么。
- 首先声明一个委托，用来接收订阅消息
public delegate void OnReceivedHandle(object data);
初始化消费者，构造函数中传入kafka地址，以及要订阅的组groupId，另外注入了log4net记录日志信息。
init()方法用来初始化，新建一个消费者，具体代码如下。
public class SUPKafkaTopicConsumer<TKey, TValue>
{
private IConsumer<TKey, TValue> consumer;
private SUPLogger logger_;
private string BootStrapServer;
private string GroupId;
public SUPKafkaTopicConsumer(string bootStrapServer, string groupId, SUPLogger logger = null)
{
BootStrapServer = bootStrapServer;
GroupId = groupId;
logger_ = logger;
}
public bool Init()
{
try
{
var conf = new ConsumerConfig
{
GroupId = GroupId,
BootstrapServers = BootStrapServer,
AutoOffsetReset = AutoOffsetReset.Earliest,
EnableAutoCommit = false // 设置非自动偏移，业务逻辑完成后手动处理偏移，防止数据丢失
};
consumer = new ConsumerBuilder<TKey, TValue>(conf)
.SetErrorHandler((_, e) => Console.WriteLine($"Error: {e.Reason}"))
.Build();
return true;
}
catch (Exception ex)
{
throw;
}
}
- 定义回调事件，用以处理用户自定义方法。
public event OnReceivedHandle onReceivedHandle;
- 定义一个订阅的方法，传入topic，以及是否需要提交偏移量。
其实看init()方法中我把EnableAutoCommit=false，取消了自动提交，让应用程序决定何时提交 偏移量，为什么这么做呢？
自动提交虽然方便，但是也有一些弊端，自动提交的弊端是通过间隔时间。 一般是默认5s提交时间间隔，在最近一次提交之后的 3s发生了再均衡，再均衡之后，消费者从最后一次提交的偏移量位置开始读取消息。这个时候偏移量已经落后 了 3s，所以在这 3s 内到达的消息会被重复处理。可以通过修改提交时间间隔来更频繁地提交偏移量，减小可能出现重复消息的时间窗，不过这种情况是无也完全避免的 。
大部分开发者通过控制偏移量提交时间来消除丢失消息的可能性，井在发生再均衡时减少 重复消息的数量。消费者 API提供了另一种提交偏移量的方式 ， 开发者可以在必要的时候 提交当前偏移盘，而不是基于时间间隔。
public void Subscribe(string topic, bool isCommit)
{
try
{
if (consumer != null)
{
consumer.Subscribe(topic);
while (true)
{
var consume = consumer.Consume();
if (onReceivedHandle != null)
{
onReceivedHandle(consume);
if (isCommit)
{
consumer.Commit(consume);
}
}
}
}
}
catch (Exception ex)
{
//consumer.Close();
throw ex;
}
}
- 取消订阅
public void UnSubscribe()
{
if (consumer != null)
{
consumer.Unsubscribe();
}
}
新建生产者类
- 首先定义了ISUPKafkaProducer<Tkey, TValue>接口，包含四个方法
public interface ISUPKafkaProducer<Tkey,TValue>
{
ISendResult Send(Tkey key, TValue value, string topic,Action<DeliveryReport<Tkey, TValue>> sendCallBack = null);
ISendResult Send(Tkey key, TValue value, TopicPartition topicPartition, Action<DeliveryReport<Tkey, TValue>> sendCallBack = null);
ISendResult AsyncSend(Tkey key, TValue value,string topic);
ISendResult AsyncSend(Tkey key, TValue value, TopicPartition topicPartition);
}
- 接口的实现，初始化过程类似消费者
internal class SUPKafkaTopicProducer<Tkey, TValue> : ISUPKafkaProducer<Tkey, TValue>
{
private IProducer<Tkey, TValue> producer;
private SUPLogger logger_;
private string m_bootStrapServer;
public SUPKafkaTopicProducer(string bootStrapServer,SUPLogger logger = null)
{
m_bootStrapServer = bootStrapServer;
logger_ = logger;
}
public bool Init()
{
try
{
var config = new ProducerConfig
{
BootstrapServers = m_bootStrapServer
};
producer = new ProducerBuilder<Tkey, TValue>(config)
.SetErrorHandler((producer, error) =>
{
logger_.Fatal(string.Format("Kafka Error Handler {0},ErrorCode:{2},Reason:{3}",
m_bootStrapServer, error.Code, error.Reason));
})
.SetLogHandler((producer, msg) =>
{
logger_.Info(string.Format("Kafka Log Handler {0}-{1},Name:{2},Message:{3}",
m_bootStrapServer, msg.Name, msg.Message));
})
.Build();
return true;
}
catch (Exception ex)
{
throw ex;
}
}
实现继承至ISUPKafkaProducer<Tkey, TValue>的方法
public ISendResult Send(Tkey key, TValue value,string topic, Action<DeliveryReport<Tkey, TValue>> sendCallBack = null)
{
try
{
if (producer != null)
{
var message = new Message<Tkey, TValue>
{
Value = value,
Key = key
};
producer.Produce(topic, message, sendCallBack);
return new SendResult(true);
}
else
{
return new SendResult(true, "没有初始化生产者");
}
}
catch (Exception ex)
{
throw ex;
}
}
public ISendResult Send(Tkey key, TValue value, TopicPartition topicPartition, Action<DeliveryReport<Tkey, TValue>> sendCallBack = null)
{
try
{
if (producer != null)
{
var message = new Message<Tkey, TValue>
{
Value = value,
Key = key
};
producer.Produce(topicPartition, message, sendCallBack);
return new SendResult(true);
}
else
{
return new SendResult(true, "没有初始化生产者");
}
}
catch (Exception ex)
{
throw ex;
}
}
public ISendResult AsyncSend(Tkey key, TValue value,string topic)
{
try
{
if (producer != null)
{
var message = new Message<Tkey, TValue>
{
Value = value,
Key = key
};
var deliveryReport = producer.ProduceAsync(topic, message);
deliveryReport.ContinueWith(task =>
{
Console.WriteLine("Producer: " + producer.Name + "\r\nTopic: " + topic + "\r\nPartition: " + task.Result.Partition + "\r\nOffset: " + task.Result.Offset);
});
producer.Flush(TimeSpan.FromSeconds(10));
return new SendResult(true);
}
else
{
return new SendResult(true, "没有初始化生产者");
}
}
catch (Exception ex)
{
throw ex;
}
}
public ISendResult AsyncSend(Tkey key, TValue value, TopicPartition topicPartition)
{
try
{
if (producer != null)
{
var message = new Message<Tkey, TValue>
{
Value = value,
Key = key
};
var deliveryReport = producer.ProduceAsync(topicPartition, message);
deliveryReport.ContinueWith(task =>
{
Console.WriteLine("Producer: " + producer.Name + "\r\nTopic: " + topicPartition.Topic + "\r\nPartition: " + task.Result.Partition + "\r\nOffset: " + task.Result.Offset);
});
producer.Flush(TimeSpan.FromSeconds(10));
return new SendResult(true);
}
else
{
return new SendResult(true, "没有初始化生产者");
}
}
catch (Exception ex)
{
throw ex;
}
}
新建一个SUPKafkaMessageCenter类
这个类是对外开放的，我们利用这个类来管理生产者和消费者，看下代码非常简单。
public static class SUPKafkaMessageCenter<Tkey, TValue>
{
private static SUPLogger logger = null;
static SUPKafkaMessageCenter()
{
SUPLoggerManager.Configure();
logger = new SUPLogger("KafkaCenter");
}
/// <summary>
/// 创建生产者
/// </summary>
/// <param name="bootstrapServer"></param>
/// <param name="topicName"></param>
/// <returns></returns>
public static ISUPKafkaProducer<Tkey, TValue> CreateTopicProducer(string bootstrapServer)
{
if (string.IsNullOrEmpty(bootstrapServer))
{
return null;
}
var producer = new SUPKafkaTopicProducer<Tkey, TValue>(bootstrapServer, logger);
if (!producer.Init())
{
return null;
}
return producer;
}
/// <summary>
/// 创建消费者
/// </summary>
/// <param name="bootstrapServer"></param>
/// <param name="groupId"></param>
/// <returns></returns>
public static SUPKafkaTopicConsumer<Tkey, TValue> CreateTopicConsumer(string bootstrapServer, string groupId= "default-consumer-group")
{
if (string.IsNullOrEmpty(bootstrapServer))
{
return null;
}
var consumer = new SUPKafkaTopicConsumer<Tkey, TValue>(bootstrapServer, groupId,logger);
if (!consumer.Init())
{
return null;
}
return consumer;
}
测试
新建一个测试的控制台程序，调用代码如下
- 消费者
var consumer = SUPKafkaMessageCenter<string, string>.CreateTopicConsumer("localhost:9092");
//绑定接收信息，回调函数
consumer.onReceivedHandle += CallBack;
var topics = new List<string>();
topics.Add("kafka-default-topic");
topics.Add("test");
//订阅主题
consumer.Subscribe(topics, false);
- 生产者
ISUPKafkaProducer<string, string> kafkaCenter = SUPKafkaMessageCenter<string, string>.CreateTopicProducer("localhost:9092");
kafkaCenter.Send(i.ToString(), "", "kafka-default-topic",deliveryReport =>{...});
除了上面写的这些方法，其实对于kafka还有很多功能，比如topic的增删改查，我把它认为是管理类的，这里就不贴代码了，有兴趣的朋友可以进gitee上下载来看看。https://gitee.com/zhanwei103/Kafka.Net
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