Kafka基础教程（三）：C#使用Kafka消息队列

　　接上篇Kafka的安装，我安装的Kafka集群地址：192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092，所以这里直接使用这个集群来演示

　　首先创建一个项目，演示采用的是控制台（.net core 3.1），然后使用Nuget安装 Confluent.Kafka 包：

　　

　　上面的截图中有Confluent.Kafka的源码地址，感兴趣的可以去看看：https://github.com/confluentinc/confluent-kafka-dotnet/

　　

　　消息发布

　　先直接上Demo　　

    static void Main(string[] args)
    {
        ProducerConfig config = new ProducerConfig();
        config.BootstrapServers = "192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092";
        var builder = new ProducerBuilder<string, object>(config);
        builder.SetValueSerializer(new KafkaConverter());//设置序列化方式
        var producer = builder.Build();
        producer.Produce("test", new Message<string, object>() { Key = "Test", Value = "hello world" }); 

　　　　  Console.ReadKey();
    }

　　上述代码执行后，就可以使用上一节提到的kafkatool工具查看到消息了。

　　1、消息发布需要使用生产者对象，它由ProducerBuilder<,>类构造，有两个泛型参数，第一个是路由Key的类型，第二个是消息的类型，开发过程中，我们多数使用ProducerBuilder<string, object>或者ProducerBuilder<string, string>。

　　2、ProducerBuilder<string, object>在实例化时需要一个配置参数，这个配置参数是一个集合（IEnumerable<KeyValuePair<string, string>>），ProducerConfig其实是实现了这个集合接口的一个类型，在旧版本的Confluent.Kafka中，是没有这个ProducerConfig类型的，之前都是使用Dictionary<string,string>来构建ProducerBuilder<string, object>，比如上面的Demo，其实也可以写成：　　

    static void Main(string[] args)
    {
        Dictionary<string, string> config = new Dictionary<string, string>();
        config["bootstrap.servers"]= "192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092";
        var builder = new ProducerBuilder<string, object>(config);
        builder.SetValueSerializer(new KafkaConverter());//设置序列化方式
        var producer = builder.Build();
        producer.Produce("test", new Message<string, object>() { Key = "Test", Value = "hello world" });

        Console.ReadKey();
    }

　　这两种方式是一样的效果，只是ProducerConfig对象最终也是生成一个KeyValuePair<string, string>集合，ProducerConfig中的属性都会有一个Key与它对应，比如上面的ProducerConfig的BootstrapServers属性最终会映射成bootstrap.servers，表示Kafka集群地址，多个地址之间使用逗号分隔。

　　其他配置信息可以参考官方配置文档：https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md

　　3、Confluent.Kafka还要求提供一个实现了ISerializer<TValue>或者IAsyncSerializer<TValue>接口的序列化类型，比如上面的Demo中的KafkaConverter：　　

    public class KafkaConverter : ISerializer<object>
    {
        /// <summary>
        /// 序列化数据成字节
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public byte[] Serialize(object data, SerializationContext context)
        {
            var json = JsonConvert.SerializeObject(data);
            return Encoding.UTF8.GetBytes(json);
        }
    }

 　　这里我采用的是Json格式序列化，需要使用Nuget安装Newtonsoft.Json。

　　4、发布消息使用Produce方法，它有几个重载，还有几个异步发布方法。第一个参数是topic，如果想指定Partition，需要使用TopicPartition对象，第二个参数是消息，它是Message<TKey, TValue>类型，Key即路由，Value就是我们的消息，消息会经过ISerializer<TValue>接口序列化之后发送到Kafka，第三个参数是Action<DeliveryReport<TKey, TValue>>类型的委托，它是异步执行的，其实是发布的结果通知。

　　消息消费

　　先直接上Demo

    static void Main(string[] args)
    {
        ConsumerConfig config = new ConsumerConfig();
        config.BootstrapServers = "192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092";
        config.GroupId = "group.1";
        config.AutoOffsetReset = AutoOffsetReset.Earliest;
        config.EnableAutoCommit = false;

        var builder = new ConsumerBuilder<string, object>(config);
        builder.SetValueDeserializer(new KafkaConverter());//设置反序列化方式
        var consumer = builder.Build();
        consumer.Subscribe("test");//订阅消息使用Subscribe方法
        //consumer.Assign(new TopicPartition("test", new Partition(1)));//从指定的Partition订阅消息使用Assign方法

        while (true)
        {
            var result = consumer.Consume();
            Console.WriteLine($"recieve message:{result.Message.Value}");
            consumer.Commit(result);//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
        }
    }

　　1、和消息发布一样，消费者的构建是通过ConsumerBuilder<, >对象来完成的，同样也有一个ConsumerConfig配置对象，它在旧版本中也是不存在的，旧版本中也是使用Dictionary<string,string>来实现的，比如上面的例子等价于：

    static void Main(string[] args)
    {
        Dictionary<string, string> config = new Dictionary<string, string>();
        config["bootstrap.servers"] = "192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092";
        config["group.id"] = "group.1";
        config["auto.offset.reset"] = "earliest";
        config["enable.auto.commit"] = "false";

        var builder = new ConsumerBuilder<string, object>(config);
        builder.SetValueDeserializer(new KafkaConverter());//设置反序列化方式
        var consumer = builder.Build();
        consumer.Subscribe("test");//订阅消息使用Subscribe方法
        //consumer.Assign(new TopicPartition("test", new Partition(1)));//从指定的Partition订阅消息使用Assign方法

        while (true)
        {
            var result = consumer.Consume();
            Console.WriteLine($"recieve message:{result.Message.Value}");
            consumer.Commit(result);//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
        }
    }

　　实际上，它和ProducerConfig一样也是一个KeyValuePair<string, string>集合，它的属性最终都会有一个Key与它对应。其他配置信息可以参考官方配置文档：https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md

　　这里顺带提一下这个例子用到的几个配置：　　

   BootstrapServers：Kafka集群地址，多个地址之间使用逗号分隔。
　　GroupId：消费者的Group，注意了，Kafka以Group的形式消费消息，一个消息只会被同一Group中的一个消费者消费，另外，一般的，同一Group中的消费者应该实现相同的逻辑
　　EnableAutoCommit：是否自动提交，如果设置成true，那么消费者接收到消息就相当于被消费了，我们可以设置成false，然后在我们处理完逻辑之后手动提交。
　　AutoOffsetReset：自动重置offset的行为，默认是Latest，这是kafka读取数据的策略，有三个可选值：Latest，Earliest，Error，个人推荐使用Earliest　　　　

 　　关于AutoOffsetReset配置，这里再提一点　　

　　Latest：当各分区下有已提交的offset时，从提交的offset开始消费；无提交的offset时，消费新产生的该分区下的数据
　　Earliest：当各分区下有已提交的offset时，从提交的offset开始消费；无提交的offset时，从头开始消费
　　Error：topic各分区都存在已提交的offset时，从offset后开始消费；只要有一个分区不存在已提交的offset，则抛出异常

　　上面几句话说得有点蒙，举个例子：

　　当有一个消费者连接到Kafka，那这个消费者该从哪个位置开始消费呢？

　　首先，我们知道Kafka的消费者以群组Group的形式去消费，Kafka会记录每个Group在每个Partition中的到哪个位置，也就是offset。　　

　　当有消费者连接到Kafka要消费消息是，如果这个消费者所在的群组Group之前有消费过并提交过offset（也就是存在offset记录），那么这个消费者就从这个offset的位置开始消费，这一点Latest，Earliest，Error三个配置的行为是一样的。

　　但是如果连接的消费者所在的群组是一个新的群组时（也就是不存在offset记录），Latest，Earliest，Error三个配置表现出不一样的行为：

　　Latest：从连接到Kafka那一刻开始消费之后产生的消息，之前发布的消息不在消费，这也是默认的行为

　　Earliest：从offset最小值（如果消息全部有效的话，那就是最开头）处开始消费，也就是说会消费连接到Kafka之前发布的消息

　　Error：简单暴力的抛出异常

　　2、生产消息需要序列化，消费消息就需要反序列化了，我们需要提供一个实现了IDeserializer<TValue>接口的类型，比如上面的例子采用Json序列化：　　

    public class KafkaConverter : IDeserializer<object>
    {/// <summary>
        /// 反序列化字节数据成实体数据
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public object Deserialize(ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
        {
            if (isNull) return null;

            var json = Encoding.UTF8.GetString(data.ToArray());
            try
            {
                return JsonConvert.DeserializeObject(json);
            }
            catch
            {
                return json;
            }
        }
    }

 　　3、Kafka是发布/订阅方式的消息队列，Confluent.Kafka提供了两个订阅的方法：Subscribe和Assign

　　Subscribe：从一个或者多个topic订阅消息

　　Assign：从一个或者多个topic的指定partition中订阅消息

　　另外，Confluent.Kafka还提供了两个取消订阅的方法：Unsubscribe和Unassign

　　4、获取消息使用Consume方法，方法返回一个ConsumeResult<TKey, TValue>对象，我们要的消息就在这个对象中，它还包含offset等等其他信息。

　　另外，Consume方法会导致当前线程阻塞，直至有获取到消息可以消费，或者超时。

　　5、如果我们创建消费者时，设置了EnableAutoCommit=false，那么我们就需要手动调用Commit方法提交消息，切记。

 　　

　　完整的Demo例子

　　上面有提到，生产消息需要一个实现序列化消息接口的对象，而消费消息需要一个实现了反序列化接口的对象，这两者建议用同一个类实现，于是一个完整的实现类：　　

    public class KafkaConverter : ISerializer<object>, IDeserializer<object>
    {
        /// <summary>
        /// 序列化数据成字节
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public byte[] Serialize(object data, SerializationContext context)
        {
            var json = JsonConvert.SerializeObject(data);
            return Encoding.UTF8.GetBytes(json);
        }
        /// <summary>
        /// 反序列化字节数据成实体数据
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public object Deserialize(ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
        {
            if (isNull) return null;

            var json = Encoding.UTF8.GetString(data.ToArray());
            try
            {
                return JsonConvert.DeserializeObject(json);
            }
            catch
            {
                return json;
            }
        }
    }

　　一个完整的Demo例子如下：　　

    static void Main(string[] args)
    {
        var bootstrapServers = "192.168.209.133:9092,192.168.209.134:9092,192.168.209.135:9092";
        var group1 = "group.1";
        var group2 = "group.2";
        var topic = "test";

        new Thread(() =>
        {
            ConsumerConfig config = new ConsumerConfig();
            config.BootstrapServers = bootstrapServers;
            config.GroupId = group1;
            config.AutoOffsetReset = AutoOffsetReset.Earliest;
            config.EnableAutoCommit = false;

            var builder = new ConsumerBuilder<string, object>(config);
            builder.SetValueDeserializer(new KafkaConverter());//设置反序列化方式
            var consumer = builder.Build();
            //consumer.Subscribe(topic);//订阅消息使用Subscribe方法
            consumer.Assign(new TopicPartition(topic, new Partition(0)));//从指定的Partition订阅消息使用Assign方法

            while (true)
            {
                var result = consumer.Consume();
                Console.WriteLine($"{group1} recieve message:{result.Message.Value}");
                consumer.Commit(result);//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
            }

        }).Start();

        new Thread(() =>
        {
            ConsumerConfig config = new ConsumerConfig();
            config.BootstrapServers = bootstrapServers;
            config.GroupId = group2;
            config.AutoOffsetReset = AutoOffsetReset.Earliest;
            config.EnableAutoCommit = false;

            var builder = new ConsumerBuilder<string, object>(config);
            builder.SetValueDeserializer(new KafkaConverter());//设置反序列化方式
            var consumer = builder.Build();
            //consumer.Subscribe(topic);//订阅消息使用Subscribe方法
            consumer.Assign(new TopicPartition(topic, new Partition(1)));//从指定的Partition订阅消息使用Assign方法

            while (true)
            {
                var result = consumer.Consume();
                Console.WriteLine($"{group2} recieve message:{result.Message.Value}");
                consumer.Commit(result);//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
            }

        }).Start();

        int index = 0;
        ProducerConfig config = new ProducerConfig();
        config.BootstrapServers = bootstrapServers;
        var builder = new ProducerBuilder<string, object>(config);
        builder.SetValueSerializer(new KafkaConverter());//设置序列化方式
        var producer = builder.Build();
        while (true)
        {
            Console.Write("请输入消息:");
            var line = Console.ReadLine();

            int partition = index % 3;
            var topicPartition = new TopicPartition(topic, new Partition(partition));
            producer.Produce(topicPartition, new Message<string, object>() { Key = "Test", Value = line });

            index++;
        }
    }

　　封装使用

　　这里做一个简单的封装，使用几个常用的配置以方便使用，当然，还是要使用nuget安装 Confluent.Kafka 和 Newtonsoft.Json两个包，具体几个类如下：　　

　　

    public abstract class KafkaBaseOptions
    {
        /// <summary>
        /// 服务器地址
        /// </summary>
        public string[] BootstrapServers { get; set; }
    }

　　

    public class KafkaConsumer : IDisposable
    {
        ConsumerBuilder<string, object> builder;
        List<IConsumer<string, object>> consumers;
        bool disposed = false;

        /// <summary>
        /// kafka服务节点
        /// </summary>
        public string BootstrapServers { get; private set; }
        /// <summary>
        /// 群组
        /// </summary>
        public string GroupId { get; private set; }
        /// <summary>
        /// 是否允许自动提交（enable.auto.commit）
        /// </summary>
        public bool EnableAutoCommit { get; set; } = false;

        /// <summary>
        /// 异常事件
        /// </summary>
        public event Action<object, Exception> ErrorHandler;
        /// <summary>
        /// 统计事件
        /// </summary>
        public event Action<object, string> StatisticsHandler;
        /// <summary>
        /// 日志事件
        /// </summary>
        public event Action<object, KafkaLogMessage> LogHandler;

        public KafkaConsumer(string groupId, params string[] bootstrapServers)
        {
            if (bootstrapServers == null || bootstrapServers.Length == 0)
            {
                throw new Exception("at least one server must be assigned");
            }

            this.GroupId = groupId;
            this.BootstrapServers = string.Join(",", bootstrapServers);
            this.consumers = new List<IConsumer<string, object>>();
        }

        #region Private
        /// <summary>
        /// 创建消费者生成器
        /// </summary>
        private void CreateConsumerBuilder()
        {
            if (disposed)
            {
                throw new ObjectDisposedException(nameof(KafkaConsumer));
            }

            if (builder == null)
            {
                lock (this)
                {
                    if (builder == null)
                    {
                        ConsumerConfig config = new ConsumerConfig();
                        config.BootstrapServers = BootstrapServers;
                        config.GroupId = GroupId;
                        config.AutoOffsetReset = AutoOffsetReset.Earliest;
                        config.EnableAutoCommit = EnableAutoCommit;
                        //config.EnableAutoOffsetStore = true;
                        //config.IsolationLevel = IsolationLevel.ReadCommitted;
                        //config.MaxPollIntervalMs = 10000;


                        //List<KeyValuePair<string, string>> config = new List<KeyValuePair<string, string>>();
                        //config.Add(new KeyValuePair<string, string>("bootstrap.servers", BootstrapServers));
                        //config.Add(new KeyValuePair<string, string>("group.id", GroupId));
                        //config.Add(new KeyValuePair<string, string>("auto.offset.reset", "earliest"));
                        //config.Add(new KeyValuePair<string, string>("enable.auto.commit", EnableAutoCommit.ToString().ToLower()));
                        //config.Add(new KeyValuePair<string, string>("max.poll.interval.ms", "10000"));
                        //config.Add(new KeyValuePair<string, string>("session.timeout.ms", "10000"));
                        //config.Add(new KeyValuePair<string, string>("isolation.level", "read_uncommitted"));

                        builder = new ConsumerBuilder<string, object>(config);

                        Action<Delegate, object> tryCatchWrap = (@delegate, arg) =>
                        {
                            try
                            {
                                @delegate?.DynamicInvoke(arg);
                            }
                            catch { }
                        };
                        builder.SetErrorHandler((p, e) => tryCatchWrap(ErrorHandler, new Exception(e.Reason)));
                        builder.SetStatisticsHandler((p, e) => tryCatchWrap(StatisticsHandler, e));
                        builder.SetLogHandler((p, e) => tryCatchWrap(LogHandler, new KafkaLogMessage(e)));
                        builder.SetValueDeserializer(new KafkaConverter());
                    }
                }
            }
        }
        /// <summary>
        /// 内部处理消息
        /// </summary>
        /// <param name="consumer"></param>
        /// <param name="cancellationToken"></param>
        /// <param name="action"></param>
        private void InternalListen(IConsumer<string, object> consumer, CancellationToken cancellationToken, Action<RecieveResult> action)
        {
            try
            {
                var result = consumer.Consume(cancellationToken);
                if (!cancellationToken.IsCancellationRequested)
                {
                    CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
                    if (!EnableAutoCommit && result != null)
                    {
                        cancellationTokenSource.Token.Register(() =>
                        {
                            consumer.Commit(result);
                        });
                    }
                    action?.Invoke(result == null ? null : new RecieveResult(result, cancellationTokenSource));
                }
            }
            catch { }
        }
        /// <summary>
        /// 验证消费主题和分区
        /// </summary>
        /// <param name="subscribers"></param>
        private void CheckSubscribers(params KafkaSubscriber[] subscribers)
        {
            if (subscribers == null || subscribers.Length == 0)
            {
                throw new InvalidOperationException("subscriber cann't be empty");
            }

            if (subscribers.Any(f => string.IsNullOrEmpty(f.Topic)))
            {
                throw new InvalidOperationException("topic cann't be empty");
            }
        }
        /// <summary>
        /// 设置监听主题
        /// </summary>
        /// <param name="consumer"></param>
        private void SetSubscribers(IConsumer<string, object> consumer, params KafkaSubscriber[] subscribers)
        {
            var topics = subscribers.Where(f => f.Partition == null).Select(f => f.Topic).ToArray();
            var topicPartitions = subscribers.Where(f => f.Partition != null).Select(f => new TopicPartition(f.Topic, new Partition(f.Partition.Value))).ToArray();

            if (topics.Length > 0)
            {
                consumer.Subscribe(topics);
            }

            if (topicPartitions.Length > 0)
            {
                consumer.Assign(topicPartitions);
            }
        }
        /// <summary>
        /// 创建一个消费者
        /// </summary>
        /// <param name="listenResult"></param>
        /// <param name="subscribers"></param>
        /// <returns></returns>
        private IConsumer<string, object> CreateConsumer(ListenResult listenResult, params KafkaSubscriber[] subscribers)
        {
            if (disposed)
            {
                throw new ObjectDisposedException(nameof(KafkaConsumer));
            }

            CheckSubscribers(subscribers);

            CreateConsumerBuilder();

            var consumer = builder.Build();
            listenResult.Token.Register(() =>
            {
                consumer.Dispose();
            });

            SetSubscribers(consumer, subscribers);

            consumers.Add(consumer);

            return consumer;
        }
        #endregion

        #region Listen
        /// <summary>
        /// 监听一次并阻塞当前线程，直至有消息获取或者取消获取
        /// </summary>
        /// <param name="topics"></param>
        public RecieveResult ListenOnce(params string[] topics)
        {
            return ListenOnce(topics.Select(f => new KafkaSubscriber() { Partition = null, Topic = f }).ToArray());
        }
        /// <summary>
        /// 监听一次并阻塞当前线程，直至有消息获取或者取消获取
        /// </summary>
        /// <param name="subscribers"></param>
        public RecieveResult ListenOnce(params KafkaSubscriber[] subscribers)
        {
            ListenResult listenResult = new ListenResult();
            var consumer = CreateConsumer(listenResult, subscribers);

            RecieveResult result = null;
            InternalListen(consumer, listenResult.Token, rr =>
            {
                result = rr;
            });
            return result;
        }
        /// <summary>
        /// 异步监听一次
        /// </summary>
        /// <param name="topics"></param>
        /// <returns></returns>
        public async Task<RecieveResult> ListenOnceAsync(params string[] topics)
        {
            return await ListenOnceAsync(topics.Select(f => new KafkaSubscriber() { Partition = null, Topic = f }).ToArray());
        }
        /// <summary>
        /// 异步监听一次
        /// </summary>
        /// <param name="subscribers"></param>
        /// <returns></returns>
        public async Task<RecieveResult> ListenOnceAsync(params KafkaSubscriber[] subscribers)
        {
            return await Task.Run(() =>
            {
                return ListenOnce(subscribers);
            });
        }
        /// <summary>
        /// 监听
        /// </summary>
        /// <param name="topics"></param>
        /// <param name="action"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public void Listen(string[] topics, Action<RecieveResult> action = null, CancellationToken cancellationToken = default)
        {
            Listen(topics.Select(f => new KafkaSubscriber() { Partition = null, Topic = f }).ToArray(), action, cancellationToken);
        }
        /// <summary>
        /// 监听
        /// </summary>
        /// <param name="subscribers"></param>
        /// <param name="action"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public void Listen(KafkaSubscriber[] subscribers, Action<RecieveResult> action = null, CancellationToken cancellationToken = default)
        {
            ListenResult result = new ListenResult();
            var consumer = CreateConsumer(result, subscribers);
            cancellationToken.Register(() =>
            {
                result.Stop();
            });
            while (!result.Stoped)
            {
                InternalListen(consumer, result.Token, action);
            }
        }
        /// <summary>
        /// 异步监听
        /// </summary>
        /// <param name="topics"></param>
        /// <param name="action"></param>
        /// <returns></returns>
        public async Task<ListenResult> ListenAsync(string[] topics, Action<RecieveResult> action = null)
        {
            return await ListenAsync(topics.Select(f => new KafkaSubscriber() { Partition = null, Topic = f }).ToArray(), action);
        }
        /// <summary>
        /// 异步监听
        /// </summary>
        /// <param name="subscribers"></param>
        /// <param name="action"></param>
        /// <returns></returns>
        public async Task<ListenResult> ListenAsync(KafkaSubscriber[] subscribers, Action<RecieveResult> action = null)
        {
            ListenResult result = new ListenResult();
            new Task(() =>
            {
                var consumer = CreateConsumer(result, subscribers);
                while (!result.Stoped)
                {
                    InternalListen(consumer, result.Token, action);
                }
            }).Start();
            return await Task.FromResult(result);
        }
        #endregion
        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            disposed = true;
            builder = null;

            foreach (var consumer in consumers)
            {
                consumer?.Close();
                consumer?.Dispose();
            }

            GC.Collect();
        }

        public static KafkaConsumer Create(string groupId, KafkaBaseOptions kafkaBaseOptions)
        {
            return new KafkaConsumer(groupId, kafkaBaseOptions.BootstrapServers);
        }
        public override string ToString()
        {
            return BootstrapServers;
        }
    }

    public class RecieveResult
    {
        CancellationTokenSource cancellationTokenSource;

        internal RecieveResult(ConsumeResult<string, object> consumeResult, CancellationTokenSource cancellationTokenSource)
        {
            this.Topic = consumeResult.Topic;
            this.Message = consumeResult.Message.Value?.ToString();
            this.Offset = consumeResult.Offset.Value;
            this.Partition = consumeResult.Partition.Value;
            this.Key = consumeResult.Message.Key;

            this.cancellationTokenSource = cancellationTokenSource;
        }

        /// <summary>
        /// Kafka消息所属的主题
        /// </summary>
        public string Topic { get; private set; }
        /// <summary>
        /// 键值
        /// </summary>
        public string Key { get; private set; }
        /// <summary>
        /// 我们需要处理的消息具体的内容
        /// </summary>
        public string Message { get; private set; }
        /// <summary>
        /// Kafka数据读取的当前位置
        /// </summary>
        public long Offset { get; private set; }
        /// <summary>
        /// 消息所在的物理分区
        /// </summary>
        public int Partition { get; private set; }

        /// <summary>
        /// 提交
        /// </summary>
        public void Commit()
        {
            if (cancellationTokenSource == null || cancellationTokenSource.IsCancellationRequested) return;

            cancellationTokenSource.Cancel();
            cancellationTokenSource.Dispose();
            cancellationTokenSource = null;
        }
    }
    public class ListenResult : IDisposable
    {
        CancellationTokenSource cancellationTokenSource;

        /// <summary>
        /// CancellationToken
        /// </summary>
        public CancellationToken Token { get { return cancellationTokenSource.Token; } }
        /// <summary>
        /// 是否已停止
        /// </summary>
        public bool Stoped { get { return cancellationTokenSource.IsCancellationRequested; } }

        public ListenResult()
        {
            cancellationTokenSource = new CancellationTokenSource();
        }

        /// <summary>
        /// 停止监听
        /// </summary>
        public void Stop()
        {
            cancellationTokenSource.Cancel();
        }

        public void Dispose()
        {
            Stop();
        }
    }

　　

    public class KafkaConverter : ISerializer<object>, IDeserializer<object>
    {
        /// <summary>
        /// 序列化数据成字节
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public byte[] Serialize(object data, SerializationContext context)
        {
            var json = JsonConvert.SerializeObject(data);
            return Encoding.UTF8.GetBytes(json);
        }
        /// <summary>
        /// 反序列化字节数据成实体数据
        /// </summary>
        /// <param name="data"></param>
        /// <param name="context"></param>
        /// <returns></returns>
        public object Deserialize(ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
        {
            if (isNull) return null;

            var json = Encoding.UTF8.GetString(data.ToArray());
            try
            {
                return JsonConvert.DeserializeObject(json);
            }
            catch
            {
                return json;
            }
        }
    }

　　

    public class KafkaMessage
    {
        /// <summary>
        /// 主题
        /// </summary>
        public string Topic { get; set; }
        /// <summary>
        /// 分区，不指定分区即交给kafka指定分区
        /// </summary>
        public int? Partition { get; set; }
        /// <summary>
        /// 键值
        /// </summary>
        public string Key { get; set; }
        /// <summary>
        /// 消息
        /// </summary>
        public object Message { get; set; }
    }

　　

    public class KafkaProducer : IDisposable
    {
        /// <summary>
        /// 负责生成producer
        /// </summary>
        ProducerBuilder<string, object> builder;
        ConcurrentQueue<IProducer<string, object>> producers;
        bool disposed = false;

        /// <summary>
        /// kafka服务节点
        /// </summary>
        public string BootstrapServers { get; private set; }
        /// <summary>
        /// Flush超时时间(ms)
        /// </summary>
        public int FlushTimeOut { get; set; } = 10000;
        /// <summary>
        /// 保留发布者数
        /// </summary>
        public int InitializeCount { get; set; } = 5;
        /// <summary>
        /// 默认的消息键值
        /// </summary>
        public string DefaultKey { get; set; }
        /// <summary>
        /// 默认的主题
        /// </summary>
        public string DefaultTopic { get; set; }
        /// <summary>
        /// 异常事件
        /// </summary>
        public event Action<object, Exception> ErrorHandler;
        /// <summary>
        /// 统计事件
        /// </summary>
        public event Action<object, string> StatisticsHandler;
        /// <summary>
        /// 日志事件
        /// </summary>
        public event Action<object, KafkaLogMessage> LogHandler;

        public KafkaProducer(params string[] bootstrapServers)
        {
            if (bootstrapServers == null || bootstrapServers.Length == 0)
            {
                throw new Exception("at least one server must be assigned");
            }

            this.BootstrapServers = string.Join(",", bootstrapServers);
            producers = new ConcurrentQueue<IProducer<string, object>>();
        }

        #region Private
        /// <summary>
        /// producer构造器
        /// </summary>
        /// <returns></returns>
        private ProducerBuilder<string, object> CreateProducerBuilder()
        {
            if (builder == null)
            {
                lock (this)
                {
                    if (builder == null)
                    {
                        ProducerConfig config = new ProducerConfig();
                        config.BootstrapServers = BootstrapServers;

                        //var config = new KeyValuePair<string, string>[] { new KeyValuePair<string, string>("bootstrap.servers", BootstrapServers) };

                        builder = new ProducerBuilder<string, object>(config);
                        Action<Delegate, object> tryCatchWrap = (@delegate, arg) =>
                        {
                            try
                            {
                                @delegate?.DynamicInvoke(arg);
                            }
                            catch { }
                        };
                        builder.SetErrorHandler((p, e) => tryCatchWrap(ErrorHandler, new Exception(e.Reason)));
                        builder.SetStatisticsHandler((p, e) => tryCatchWrap(StatisticsHandler, e));
                        builder.SetLogHandler((p, e) => tryCatchWrap(LogHandler, new KafkaLogMessage(e)));
                        builder.SetValueSerializer(new KafkaConverter());
                    }
                }
            }

            return builder;
        }
        /// <summary>
        /// 租赁一个发布者
        /// </summary>
        /// <returns></returns>
        private IProducer<string, object> RentProducer()
        {
            if (disposed)
            {
                throw new ObjectDisposedException(nameof(KafkaProducer));
            }

            IProducer<string, object> producer;
            lock (producers)
            {
                if (!producers.TryDequeue(out producer) || producer == null)
                {
                    CreateProducerBuilder();
                    producer = builder.Build();
                }
            }
            return producer;
        }
        /// <summary>
        /// 返回保存发布者
        /// </summary>
        /// <param name="producer"></param>
        private void ReturnProducer(IProducer<string, object> producer)
        {
            if (disposed) return;

            lock (producers)
            {
                if (producers.Count < InitializeCount && producer != null)
                {
                    producers.Enqueue(producer);
                }
                else
                {
                    producer?.Dispose();
                }
            }
        }
        #endregion

        #region Publish
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="key"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void PublishWithKey(string key, object message, Action<DeliveryResult> callback = null)
        {
            Publish(DefaultTopic, null, key, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="partition"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void PublishWithKey(int? partition, string key, object message, Action<DeliveryResult> callback = null)
        {
            Publish(DefaultTopic, partition, key, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void PublishWithKey(string topic, string key, object message, Action<DeliveryResult> callback = null)
        {
            Publish(topic, null, key, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void Publish(object message, Action<DeliveryResult> callback = null)
        {
            Publish(DefaultTopic, null, DefaultKey, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="partition"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void Publish(int? partition, object message, Action<DeliveryResult> callback = null)
        {
            Publish(DefaultTopic, partition, DefaultKey, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void Publish(string topic, object message, Action<DeliveryResult> callback = null)
        {
            Publish(topic, null, DefaultKey, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="partition"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void Publish(string topic, int? partition, object message, Action<DeliveryResult> callback = null)
        {
            Publish(topic, partition, DefaultKey, message, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="partition"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        /// <param name="callback"></param>
        public void Publish(string topic, int? partition, string key, object message, Action<DeliveryResult> callback = null)
        {
            Publish(new KafkaMessage() { Key = key, Message = message, Partition = partition, Topic = topic }, callback);
        }
        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="kafkaMessage"></param>
        /// <param name="callback"></param>
        public void Publish(KafkaMessage kafkaMessage, Action<DeliveryResult> callback = null)
        {
            if (string.IsNullOrEmpty(kafkaMessage.Topic))
            {
                throw new ArgumentException("topic can not be empty", nameof(kafkaMessage.Topic));
            }
            if (string.IsNullOrEmpty(kafkaMessage.Key))
            {
                throw new ArgumentException("key can not be empty", nameof(kafkaMessage.Key));
            }

            var producer = RentProducer();
            if (kafkaMessage.Partition == null)
            {
                producer.Produce(kafkaMessage.Topic, new Message<string, object>() { Key = kafkaMessage.Key, Value = kafkaMessage.Message }, dr => callback?.Invoke(new DeliveryResult(dr)));
            }
            else
            {
                var topicPartition = new TopicPartition(kafkaMessage.Topic, new Partition(kafkaMessage.Partition.Value));
                producer.Produce(topicPartition, new Message<string, object>() { Key = kafkaMessage.Key, Value = kafkaMessage.Message }, dr => callback?.Invoke(new DeliveryResult(dr)));
            }

            producer.Flush(TimeSpan.FromMilliseconds(FlushTimeOut));

            ReturnProducer(producer);
        }
        #endregion

        #region PublishAsync
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="key"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishWithKeyAsync(string key, object message)
        {
            return await PublishAsync(DefaultTopic, null, key, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="partition"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishWithKeyAsync(int? partition, string key, object message)
        {
            return await PublishAsync(DefaultTopic, partition, key, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishWithKeyAsync(string topic, string key, object message)
        {
            return await PublishAsync(topic, null, key, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishAsync(object message)
        {
            return await PublishAsync(DefaultTopic, null, DefaultKey, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="partition"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishAsync(int? partition, object message)
        {
            return await PublishAsync(DefaultTopic, partition, DefaultKey, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishAsync(string topic, object message)
        {
            return await PublishAsync(topic, null, DefaultKey, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="partition"></param>
        /// <param name="message"></param>
        public async Task<DeliveryResult> PublishAsync(string topic, int? partition, object message)
        {
            return await PublishAsync(topic, partition, DefaultKey, message);
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="partition"></param>
        /// <param name="key"></param>
        /// <param name="message"></param>
        /// <returns></returns>
        public async Task<DeliveryResult> PublishAsync(string topic, int? partition, string key, object message)
        {
            return await PublishAsync(new KafkaMessage() { Key = key, Message = message, Partition = partition, Topic = topic });
        }
        /// <summary>
        /// 异步发送消息
        /// </summary>
        /// <param name="kafkaMessage"></param>
        /// <returns></returns>
        public async Task<DeliveryResult> PublishAsync(KafkaMessage kafkaMessage)
        {
            if (string.IsNullOrEmpty(kafkaMessage.Topic))
            {
                throw new ArgumentException("topic can not be empty", nameof(kafkaMessage.Topic));
            }
            if (string.IsNullOrEmpty(kafkaMessage.Key))
            {
                throw new ArgumentException("key can not be empty", nameof(kafkaMessage.Key));
            }

            var producer = RentProducer();
            DeliveryResult<string, object> deliveryResult;
            if (kafkaMessage.Partition == null)
            {
                deliveryResult = await producer.ProduceAsync(kafkaMessage.Topic, new Message<string, object>() { Key = kafkaMessage.Key, Value = kafkaMessage.Message });
            }
            else
            {
                var topicPartition = new TopicPartition(kafkaMessage.Topic, new Partition(kafkaMessage.Partition.Value));
                deliveryResult = await producer.ProduceAsync(topicPartition, new Message<string, object>() { Key = kafkaMessage.Key, Value = kafkaMessage.Message });
            }

            producer.Flush(new TimeSpan(0, 0, 0, 0, FlushTimeOut));

            ReturnProducer(producer);

            return new DeliveryResult(deliveryResult);
        }

        #endregion

        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            disposed = true;
            while (producers.Count > 0)
            {
                IProducer<string, object> producer;
                producers.TryDequeue(out producer);
                producer?.Dispose();
            }
            GC.Collect();
        }

        public static KafkaProducer Create(KafkaBaseOptions kafkaBaseOptions)
        {
            return new KafkaProducer(kafkaBaseOptions.BootstrapServers);
        }
        public override string ToString()
        {
            return BootstrapServers;
        }
    }

    public class DeliveryResult
    {
        internal DeliveryResult(DeliveryResult<string, object> deliveryResult)
        {
            this.Topic = deliveryResult.Topic;
            this.Partition = deliveryResult.Partition.Value;
            this.Offset = deliveryResult.Offset.Value;
            switch (deliveryResult.Status)
            {
                case PersistenceStatus.NotPersisted: this.Status = DeliveryResultStatus.NotPersisted; break;
                case PersistenceStatus.Persisted: this.Status = DeliveryResultStatus.Persisted; break;
                case PersistenceStatus.PossiblyPersisted: this.Status = DeliveryResultStatus.PossiblyPersisted; break;
            }
            this.Key = deliveryResult.Key;
            this.Message = deliveryResult.Value;

            if (deliveryResult is DeliveryReport<string, object>)
            {
                var dr = deliveryResult as DeliveryReport<string, object>;
                this.IsError = dr.Error.IsError;
                this.Reason = dr.Error.Reason;
            }
        }

        /// <summary>
        /// 是否异常
        /// </summary>
        public bool IsError { get; private set; }
        /// <summary>
        /// 异常原因
        /// </summary>
        public string Reason { get; private set; }
        /// <summary>
        /// 主题
        /// </summary>
        public string Topic { get; private set; }
        /// <summary>
        /// 分区
        /// </summary>
        public int Partition { get; private set; }
        /// <summary>
        /// 偏移
        /// </summary>
        public long Offset { get; private set; }
        /// <summary>
        /// 状态
        /// </summary>
        public DeliveryResultStatus Status { get; private set; }
        /// <summary>
        /// 消息键值
        /// </summary>
        public string Key { get; private set; }
        /// <summary>
        /// 消息
        /// </summary>
        public object Message { get; private set; }
    }
    public enum DeliveryResultStatus
    {
        /// <summary>
        /// 消息提交失败
        /// </summary>
        NotPersisted = 0,
        /// <summary>
        /// 消息已提交，是否成功未知
        /// </summary>
        PossiblyPersisted = 1,
        /// <summary>
        /// 消息提交成功
        /// </summary>
        Persisted = 2
    }
    public class KafkaLogMessage
    {
        internal KafkaLogMessage(LogMessage logMessage)
        {
            this.Name = logMessage.Name;
            this.Facility = logMessage.Facility;
            this.Message = logMessage.Message;

            switch (logMessage.Level)
            {
                case SyslogLevel.Emergency: this.Level = LogLevel.Emergency; break;
                case SyslogLevel.Alert: this.Level = LogLevel.Alert; break;
                case SyslogLevel.Critical: this.Level = LogLevel.Critical; break;
                case SyslogLevel.Error: this.Level = LogLevel.Error; break;
                case SyslogLevel.Warning: this.Level = LogLevel.Warning; break;
                case SyslogLevel.Notice: this.Level = LogLevel.Notice; break;
                case SyslogLevel.Info: this.Level = LogLevel.Info; break;
                case SyslogLevel.Debug: this.Level = LogLevel.Debug; break;
            }
        }
        /// <summary>
        /// 名称
        /// </summary>
        public string Name { get; private set; }
        /// <summary>
        /// 级别
        /// </summary>
        public LogLevel Level { get; private set; }
        /// <summary>
        /// 装置
        /// </summary>
        public string Facility { get; private set; }
        /// <summary>
        /// 信息
        /// </summary>
        public string Message { get; private set; }

        public enum LogLevel
        {
            Emergency = 0,
            Alert = 1,
            Critical = 2,
            Error = 3,
            Warning = 4,
            Notice = 5,
            Info = 6,
            Debug = 7
        }
    }

　　

    public class KafkaSubscriber
    {
        /// <summary>
        /// 主题
        /// </summary>
        public string Topic { get; set; }
        /// <summary>
        /// 分区
        /// </summary>
        public int? Partition { get; set; }
    }

　　使用方法，比如上面的Demo例子：　　

    class Program
    {
        static void Main(string[] args)
        {
            var bootstrapServers = new string[] { "192.168.209.133:9092", "192.168.209.134:9092", "192.168.209.135:9092" };
            var group1 = "group.1";
            var group2 = "group.2";
            var topic = "test";

            {
                KafkaConsumer consumer = new KafkaConsumer(group1, bootstrapServers);
                consumer.EnableAutoCommit = false;
                consumer.ListenAsync(new KafkaSubscriber[] { new KafkaSubscriber() { Topic = topic, Partition = 0 } }, result =>
                {
                    Console.WriteLine($"{group1} recieve message:{result.Message}");
                    result.Commit();//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
                }).Wait();
            }

            {
                KafkaConsumer consumer = new KafkaConsumer(group2, bootstrapServers);
                consumer.EnableAutoCommit = false;
                consumer.ListenAsync(new KafkaSubscriber[] { new KafkaSubscriber() { Topic = topic, Partition = 1 } }, result =>
                {
                    Console.WriteLine($"{group2} recieve message:{result.Message}");
                    result.Commit();//手动提交，如果上面的EnableAutoCommit=true表示自动提交，则无需调用Commit方法
                }).Wait();
            }

            KafkaProducer producer = new KafkaProducer(bootstrapServers);

            int index = 0;
            while (true)
            {
                Console.Write("请输入消息:");
                var line = Console.ReadLine();

                int partition = index % 3;
                producer.Publish(topic, partition, "Test", line);
                index++;
            }
        }
    }