Skip to content

Saga Pattern Realization With Eventuate Tram

This project includes an example implementation of the Saga pattern using the Eventuate Tram and Eventuate Tram Sagas framework. The example application represents a travel application that consists of three backend services: TravelService, HotelService and FlightService. For simplicity reasons, only the workflow for booking a trip has been implemented.

Start the Application

  1. Run ./gradlew clean build

  2. Execute docker-compose up

  3. Requesting trip bookings is now possible. Either use curl commands, the provided TravelApplication.json insomnia file, which includes different trip booking requests, or access the Swagger UI of the different services:

Service
URL to Swagger UI
TravelService http://localhost:8090/swagger-ui.html
HotelService http://localhost:8081/swagger-ui.html
FlightService http://localhost:8082/swagger-ui.html

An example for such a request:

TravelRequest
{
    "duration":
    {
        "start":"2021-12-01",
        "end":"2021-12-12"
    },
    "start":
    {
        "country":"Scotland",
        "city":"Stirling"
    },
    "destination":
    {
        "country":"Sweden",
        "city":"Stockholm"
    },
    "travellerName": "Max Mustermann",
    "boardType":"breakfast",
    "customerId":"1"
}

To simulate a Saga that fails because no hotel or no flight is available, use one of the following Strings as destination country in the trip booking request: 

"Provoke hotel failure"

"Provoke flight failure"

The services also provide a health and an info endpoint that show some information about the system like that the DB is up and running. These endpoints can be accessed via:

Service
URL to health endpoint
URL to info endpoint
TravelService http://localhost:8090/api/travel/monitor/health http://localhost:8090/api/travel/monitor/info
HotelService http://localhost:8081/api/hotels/monitor/health http://localhost:8081/api/hotels/monitor/info
FlightService http://localhost:8082/api/flights/monitor/health http://localhost:8082/api/flights/monitor/info

If you are on Windows or Mac, you sometimes have to replace localhost with the default IP of your docker machine (use docker-machine ip default to get this default IP).

Stop the Application

To stop the application and remove the created containers, execute the following command: 

docker-compose down --remove-orphans

Monitor the Application

MySQL Database

The eventuate database, with its different tables, can be accessed with the following information, which is also included in the docker-compose.yaml file:
Username: mysqluser | Password: mysqlpw

Log Files

Each service provides a log that contains some information about it. The logs can be accessed using the name of the relevant container. The different logs can be accessed using the following commands:

Log of Command to execute
TravelService docker logs travelservice_eventuate
HotelService docker logs hotelservice_eventuate
FlightService docker logs flightservice_eventuate

By using the --follow supplement, it will be continued to stream the service's output to the console.

The logging level can be changed in the respective application.properties file.

Zipkin

The services include the necessary gradle dependencies to enable distributed tracing with Zipkin when using the Eventuate Tram framework.

The Zipkin UI can be accessed via http://localhost:9411/zipkin/

Metrics of the CDC Service

Eventuate's CDC Service publishes some metrics like the number of processed messages.

The metrics can be accessed via http://localhost:8099/actuator/prometheus

EventuateTram_Implementations/EventuateTram

Last update: 2022-02-15
Back to top