This example is showcasing an eventually consistent, fault-tolerant, event sourced system following the CQRS (Command-Query-Responsibility-Segregation) principle consisting of two individual microservices using romshark/eventlog as both an event database and communication bus. The producer service produces events of objects being put into a virtual pile, while the consumer service consumes them and projects the current state of the pile onto its dgraph-io/badger key-value database. The producer service also projects the world onto its own database to transactionally check for invariants (preventing take events from being commited when there aren't enough objects in the pile). The system uses OCC (Optimistic Concurrency Control) to enforce invariants and keep the log in a consistent and valid state.
- Run the eventlog in in-memory mode:
eventlog inmem -http-host :9090 - Run the consumer:
cd cmd/consumer && go run main.go -log-addr :9090 - Run the producer:
cd cmd/producer && go run main.go -log-addr :9090 - Optionally, you can use
-db-diron both the consumer and producer to make them use an actual persistent database, otherwise they will use an in-memory database by default.-db-logwill enable more detailed database debug logs.
The order in which the services are run isn't important, the system will automatically try to (re)connect to the log indefinitely.