.NET Kafka Client

This is a .NET implementation of a client for Kafka using C# for Kafka 0.8. It provides for an implementation that covers most basic functionalities to include a simple Producer and Consumer.

Producer

The Producer can send one or more messages to Kafka in both a synchronous and asynchronous fashion.

Producer Usage

var producerConfig1 = new ProducerConfig();
producerConfig1.ProducerType = ProducerTypes.Async; // (or sync)
// ...
// other configuration settings (described below)
// ...
producerConfig1.Brokers = new List<BrokerConfiguration>
           {
              new BrokerConfiguration
                  {
                     BrokerId = 0, Host = "localhost", Port = 9092
                  }
          };
producerConfig1.KeySerializer = typeof(StringEncoder).AssemblyQualifiedName;
producerConfig1.Serializer = typeof(StringEncoder).AssemblyQualifiedName;
using (var producer1 = new Producer<string, string>(producerConfig1))
    producer1.Send(new KeyedMessage<string, string>(topic, "test", "test1"));
}

Producer Configuration Options

XML parameter name / Config class parameter name	Default value	Description
Brokers /Brokers	-	This is for bootstrapping and the producer will only use it for getting metadata (topics, partitions and replicas). The socket connections for sending the actual data will be established based on the broker information returned in the metadata.
partitioner /PartitionerClass	DefaultPartitioner	The partitioner class for partitioning messages amongst sub-topics. The default partitioner is based on the hash of the key.
type /ProducerType	Sync	This parameter specifies whether the messages are sent asynchronously in a background thread. Valid values are async for asynchronous send and sync for synchronous send. By setting the producer to async we allow batching together of requests (which is great for throughput) but open the possibility of a failure of the client machine dropping unsent data.
compressionCodec /CompressionCodec	None	This parameter allows you to specify the compression codec for all data generated by this producer.
compressedTopics / CompressedTopics	Empty string list	This parameter allows you to set whether compression should be turned on for particular topics. If the compression codec is anything other than NoCompressionCodec, enable compression only for specified topics if any. If the list of compressed topics is empty, then enable the specified compression codec for all topics. If the compression codec is NoCompressionCodec, compression is disabled for all topics
messageSendMaxRetries / MessageSendMaxRetries	3	This property will cause the producer to automatically retry a failed send request. This property specifies the number of retries when such failures occur. Note that setting a non-zero value here can lead to duplicates in the case of network errors that cause a message to be sent but the acknowledgement to be lost.
retryBackoffMs / RetryBackoffMs	100	Before each retry, the producer refreshes the metadata of relevant topics to see if a new leader has been elected. Since leader election takes a bit of time, this property specifies the amount of time that the producer waits before refreshing the metadata.
topicMetadataRefreshIntervalMs / TopicMetadataRefreshIntervalMs	600 * 1000	The producer generally refreshes the topic metadata from brokers when there is a failure (partition missing, leader not available...). It will also poll regularly (default: every 10min so 600000ms). If you set this to a negative value, metadata will only get refreshed on failure. If you set this to zero, the metadata will get refreshed after each message sent (not recommended). Important note: the refresh happen only AFTER the message is sent, so if the producer never sends a message the metadata is never refreshed
queueBufferingMaxMs / QueueBufferingMaxMs	5000	Maximum time to buffer data when using async mode. For example a setting of 100 will try to batch together 100ms of messages to send at once. This will improve throughput but adds message delivery latency due to the buffering.
queueBufferingMaxMessages / QueueBufferingMaxMessages	10000	The maximum number of unsent messages that can be queued up the producer when using async mode before either the producer must be blocked or data must be dropped.
queueEnqueueTimeoutMs / QueueEnqueueTimeoutMs	-1	The amount of time to block before dropping messages when running in async mode and the buffer has reached queue.buffering.max.messages. If set to 0 events will be enqueued immediately or dropped if the queue is full (the producer send call will never block). If set to -1 the producer will block indefinitely and never willingly drop a send.
batchNumMessages / BatchNumMessages	200	The number of messages to send in one batch when using async mode. The producer will wait until either this number of messages are ready to send or queue.buffer.max.ms is reached.
sendBufferBytes /SendBufferBytes	100 * 1024	Socket write buffer size
clientId / ClientId	""	The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request.
requestRequiredAcks / RequestRequiredAcks	0	This value controls when a produce request is considered completed. Specifically, how many other brokers must have committed the data to their log and acknowledged this to the leader? Typical values are 0, which means that the producer never waits for an acknowledgement from the broker (the same behavior as 0.7). This option provides the lowest latency but the weakest durability guarantees (some data will be lost when a server fails). 1, which means that the producer gets an acknowledgement after the leader replica has received the data. This option provides better durability as the client waits until the server acknowledges the request as successful (only messages that were written to the now-dead leader but not yet replicated will be lost). -1, which means that the producer gets an acknowledgement after all in-sync replicas have received the data. This option provides the best durability, we guarantee that no messages will be lost as long as at least one in sync replica remains.
requestTimeoutMs / RequestTimeoutMs	10000	The amount of time the broker will wait trying to meet the request.required.acks requirement before sending back an error to the client.
serializer / Serializer	kafka.serializer. DefaultEncoder	he serializer class for messages. The default encoder takes a byte[] and returns the same byte[].
keySerializer / KeySerializer	-	The serializer class for keys (defaults to the same as for messages if nothing is given).

Sample producer configuration in App.config:

<configuration>
  <configSections>
    <section name="producer"
      type="Kafka.Client.Cfg.Sections.ProducerConfigurationSection, Kafka.Client" />
  </configSections>
  <producer type="Sync" serializer="Kafka.Client.Serializers.StringEncoder" keySerializer="Kafka.Client.Serializers.StringEncoder">
    <brokers>
      <add id="0" host="localhost" port="9092" />
    </brokers>
  </producer>
</configuration>

And invocation in application:

ProducerConfig configuration = ProducerConfig.configure("producer");

Consumer

The consumer has several functions of interest: CommitOffsets and CreateMessageStreams. CommitOffsets will commit offset that was already consumed by client. You can also configure to autocommit offsets. CreateMessageStreams creates streams from which we can read messages.

Consumer Usage

var consumerConfig1 = new ConsumerConfig("localhost", "2181", "group1");
var zkConsumerConnector1 = new ZookeeperConsumerConnector(consumerConfig1);
var topicMessageStreams1 =
    zkConsumerConnector1.CreateMessageStreams(
        new Dictionary<string, int> { { Topic, 1 } }, new StringDecoder(), new StringDecoder());

foreach (var messageAndMetadata in topicMessageStreams1[Topic][0])
{
    Console.WriteLine(messageAndMetadata.Message);
}

Consumer Configuration Options

XML parameter name / Config class parameter name	Default value	Description
groupId / GroupId	REQUIRED	A string that uniquely identifies the group of consumer processes to which this consumer belongs. By setting the same group id multiple processes indicate that they are all part of the same consumer group.
zookeeper / ZooKeeper	REQUIRED	Specifies the zookeeper locations
consumerId / ConsumerId	null	Generated automatically if not set.
socketTimeout / SocketTimeoutMs	30 * 1000	The socket timeout for network requests. The actual timeout set will be FetchWaitMaxMs + SocketTimeoutMs.
socketBufferSize / SocketReceiveBufferBytes	64 * 1024	The socket receive buffer for network requests
fetchSize / FetchMessageMaxBytes	1024 * 1024	The number of byes of messages to attempt to fetch for each topic-partition in each fetch request. These bytes will be read into memory for each partition, so this helps control the memory used by the consumer. The fetch request size must be at least as large as the maximum message size the server allows or else it is possible for the producer to send messages larger than the consumer can fetch.
numConsumerFetchers / NumConsumerFetchers	1	The number threads used to fetch data.
autoCommit / AutoCommitEnable	true	If true, periodically commit to zookeeper the offset of messages already fetched by the consumer. This committed offset will be used when the process fails as the position from which the new consumer will begin.
autoCommitInterval / AutoCommitIntervalMs	60 * 1000	The frequency in ms that the consumer offsets are committed to zookeeper.
maxQueuedChunks / QueuedMaxMessages	10	Max number of message chunks buffered for consumption. Each chunk can be up to FetchMessageMaxBytes
maxRebalanceRetries / RebalanceMaxRetries	4	When a new consumer joins a consumer group the set of consumers attempt to "rebalance" the load to assign partitions to each consumer. If the set of consumers changes while this assignment is taking place the rebalance will fail and retry. This setting controls the maximum number of attempts before giving up.
minFetchBytes / FetchMinBytes	1	The minimum amount of data the server should return for a fetch request. If insufficient data is available the request will wait for that much data to accumulate before answering the request.
maxFetchWaitMs / FetchWaitMaxMs	100	The maximum amount of time the server will block before answering the fetch request if there isn't sufficient data to immediately satisfy FetchMinBytes
rebalanceBackoffMs / RebalanceBackoffMs	2000	Backoff time between retries during rebalance.
refreshMetadataBackoffMs / RefreshLeaderBackoffMs	200	Backoff time to wait before trying to determine the leader of a partition that has just lost its leader.
autoOffsetReset / AutoOffsetReset	largest	What to do when there is no initial offset in Zookeeper or if an offset is out of range: smallest : automatically reset the offset to the smallest offset largest : automatically reset the offset to the largest offset anything else: throw exception to the consumer. If this is set to largest, the consumer may lose some messages when the number of partitions, for the topics it subscribes to, changes on the broker. To prevent data loss during partition addition, set AutoOffsetReset to smallest
consumerTimeoutMs / ConsumerTimeoutMs	-1	Throw a timeout exception to the consumer if no message is available for consumption after the specified interval
clientId / ClientId	group id value	The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request.

Sample consumer configuration in App.config:

<configuration>
  <configSections>
    <section name="consumer"
      type="Kafka.Client.Cfg.Sections.ConsumerConfigurationSection, Kafka.Client" />
  </configSections>
  <consumer groupId="group1" >
    <zookeeper>
      <servers>
        <add host="localhost" port="2181" />
      </servers>
    </zookeeper>
  </consumer>
</configuration>