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This repository is deprecated and replaced by light-kafka for Event Sourcing and CQRS with Kafka Streams and Interactive Queries.

An eventual consistency framework implementation based on event sourcing, CQRS and Kafka on top of light-4j. It is based on the open source project eventuate-local from Chris Richardson

When building microservices, there are two major patterns are used for service to service communication.

Synchronous, Request/Response Communication

In light-4j, this means to use Client module to call other services in the request/response fashion regardless light-rest-4j, light-graphql-4j or light-hybrid-4j is used.

Asynchronous, Message-Based Communication

The eventual consistency framework light-eventuate-4j is designed to facilitate asynchronous communication between services built on top of light-rest-4j, light-grahpql-4j and light-hybrid-4j. Service communication is through events and every service maintains its own aggregates to serve consumer independently.

Which Style to Choose

For pros and cons of each communication patterns, please see here

Why light-eventuate-4j

For microservices implementation, developing business transactions that updates entities owned by multiple services is a challenge, as is implementing queries that retrieve data from multiple services; For complicated application that has too many services interact with each other, it is essential to choose asynchronous message-based style for service communication and transaction management with eventual consistency.

Once you've decided that asynchronous message-based communication is best for your use case, you need to make some architecture decision to choose the best of combination of frameworks to build your microservices.

Light-eventuate-4j is the best framework to enable messaging-based service communication. It is based on event sourcing and CQRS on top of Kafka message broker. You can build your services with light-rest-4j, light-graphql-4j or light-hybrid-4j and they are all seamlessly integrated with light-eventuate-4j framework which provides event store and event producing and consuming client for services built on top of other light-4j frameworks.

light-eventuate-4j components:

light-4j, light-rest-4j, light-graphql-4j and light-hybrid-4j provide platforms to build microservices in REST, Graphql and Hybrid/RPC style.
Mysql for event store to persist events
Zookeeper is used to manage Kafka cluster
Apache Kafka is used as message brokers for publishing/subscribing events
A console/admin UI to monitor the message broker and communication between services
A hybrid command server to host all hybrid command services in case light-hybrid-4j is used
A hybrid query server to host all hybrid query services in case light-hybrid-4j is used
A RESTful CDC server that is responsible to publish events to Kafka from event store if light-rest-4j is used.
A hybrid CDC service that is responsible to publish events to Kafka from event store if light-hybrid-4j is used.