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KafkaDbContext
Describe what is and how use KafkaDbContext class from Entity Framework Core provider for Apache Kafka™

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)