Table of Contents

KEFCore: KafkaDbContext

KafkaDbContext is a special class which helps to define the DbContext and use Entity Framework Core provider for Apache Kafka:

  • KafkaDbContext inherits from DbContext: to define the model, and/or creating the database, see getting started in the docs and KEFCore usage
  • KafkaDbContext defines the following properties:
    • KeySerDesSelectorType: the .NET type to be used to allocate an external serializer for Apache Kafka record key
    • ValueSerDesSelectorType: the .NET type to be used to allocate an external serializer for Apache Kafka record value
    • ValueContainerType: the .NET type to be used to allocate an external container class for Apache Kafka record value
    • UseNameMatching: set to false to avoid Entity matching based on Name
    • BootstrapServers: the server hosting the broker of Apache Kafka
    • ApplicationId: the application identifier used to identify the context
    • DatabaseName: the user defined name which declares the database name, it is used to prepend every Topic which belongs to this database
    • DefaultNumPartitions: the default number of partitions used when topics are created for each entity
    • DefaultReplicationFactor: the replication factor to use when data are stored in Apache Kafka
    • DefaultConsumerInstances: the consumer instances to be allocated when UseCompactedReplicator is true
    • UsePersistentStorage: set to true to use a persistent storage between multiple application startup
    • UseEnumeratorWithPrefetch: set to true to prefer enumerator instances able to do a prefetch on data speeding up execution, used if UseKNetStreams is true and UseCompactedReplicator is false
    • UseByteBufferDataTransfer: set to true to prefer data exchange in serializer instances
    • UseDeletePolicyForTopic: set to true to enable delete cleanup policy
    • UseCompactedReplicator: Use KNetCompactedReplicator instead of Apache Kafka Streams to manage data to or from topics
    • UseKNetStreams: Use KNet version of Apache Kafka Streams instead of standard Apache Kafka Streams, used if UseCompactedReplicator is false
    • ConsumerConfig: parameters to use for Producer
    • ProducerConfig: parameters to use for Producer
    • StreamsConfig: parameters to use for Apche Kafka Streams application
    • TopicConfig: parameters to use on topic creation for each entity
    • OnChangeEvent: handler to receive change events from back-end

How to use KafkaDbContext class

The most simple example of usage can be found in KEFCore usage. By default, KafkaDbContext automatically manages OnConfiguring method of DbContext:

  • KafkaDbContext checks the mandatory options like BootstrapServers and DbName
  • KafkaDbContext setup the options needed to use an Apache Kafka cluster:
    • default ConsumerConfig can be overridden using ConsumerConfig property of KafkaDbContext
    • default ProducerConfig can be overridden using ProducerConfig property of KafkaDbContext
    • default StreamsConfig can be overridden using StreamsConfig property of KafkaDbContext
    • default TopicConfig can be overridden using TopicConfig property of KafkaDbContext

Default ConsumerConfig

Over the Apache Kafka defaults it applies:

  • EnableAutoCommit is true
  • AutoOffsetReset set to EARLIEST
  • AllowAutoCreateTopics set to false

Default ProducerConfig

Does not change anything over the Apache Kafka defaults

Default StreamsConfig

Does not change anything over the Apache Kafka defaults

Default TopicConfig

Over the Apache Kafka defaults it applies:

  • DeleteRetentionMs set to 100 ms
  • MinCleanableDirtyRatio set to 0.01
  • SegmentMs set to 100 ms
  • RetentionBytes set to 1073741824 bytes (1 Gb)