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https://github.com/eventuate-tram/eventuate-tram-core-examples-basic

Basic examples for Eventuate Tram
https://github.com/eventuate-tram/eventuate-tram-core-examples-basic

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Basic examples for Eventuate Tram

Host: GitHub
URL: https://github.com/eventuate-tram/eventuate-tram-core-examples-basic
Owner: eventuate-tram
License: other
Created: 2017-07-30T04:20:29.000Z (over 7 years ago)
Default Branch: master
Last Pushed: 2024-09-25T09:12:27.000Z (3 months ago)
Last Synced: 2024-12-25T23:06:42.216Z (9 days ago)
Language: Java
Size: 307 KB
Stars: 43
Watchers: 10
Forks: 33
Open Issues: 12
Metadata Files:
- Readme: README.adoc
- License: LICENSE.md

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README

= Eventuate Tram basic examples

image::https://eventuate.io/i/logo.gif[]

This project is part of http://eventuate.io[Eventuate], which is a microservices collaboration platform.
It consists of a basic set of Spring Boot-based examples that show how to use https://github.com/eventuate-tram/eventuate-tram-core[Eventuate Tram], which is a framework for https://microservices.io/patterns/data/transactional-outbox.html[transactional messaging].
Eventuate Tram sends and receives messages as part of a database transaction, which maintains data consistency.
It ensures that your application atomically updates the database and sends messages.
Eventuate Tram also ensures that your https://microservices.io/patterns/communication-style/idempotent-consumer.html[message handlers are idempotent].

== About the examples

There are the following examples:

* Messaging - sending and receiving messages
* Event publishing/subscribing - publishing of and subscribing to domain events
* Command/async reply - sending commands and receiving replies

Each example has a producer service and at least one consumer service.

== Supported databases and message brokers

The examples support a variety of databases and message brokers:

* Databases: MySQL, PostgreSQL
* Message brokers: Apache Kafka, RabbitMQ, and ActiveMQ

There are the following Gradle properties that specify which infrastructure services to use:

* `messageBroker` - specifies the messageBroker, which can be `kafka`, `rabbitmq`, or `activemq`. It defaults to `kafka`.
* `database` - specifies the database, which can be `mysql` or `postgres`. It defaults to `mysql`.
* `mode` - specifies how the https://eventuate.io/docs/manual/eventuate-tram/latest/cdc-configuration.html[`Eventuate CDC` service] reads the transactional outbox table. It defaults to `binlog` for MySql and `wal` for Postgres. It can also be set to `polling` for Postgres.

Various Gradle tasks for building, and running the services can be configured with these properties.
For example,

[source,shell]
----
./gradlew -P messageBroker=activemq -P database=postgres someTask
----

executes `someTask` using Postgres and ActiveMQ.

== Running the infrastructure services

Before running the examples, you need to start the infrastructure services:

[source,shell]
----
$ ./gradlew startServices -P messageBroker=kafka -P database=mysql
----

Similarly, you can stop the services by running:

[source,shell]
----
$ ./gradlew stopServices -P messageBroker=kafka -P database=mysql
----

== About the messaging examples

The examples are in the link:messages[messages directory].
There are two services:

* `eventuate-tram-examples-basic-message-producer` - a service that implements a `POST /produce` endpoint that sends a message to a channel
* `eventuate-tram-examples-basic-message-consumer` - a service that subscribes the channel

This command starts the producer:

[source,shell]
----
$ ./gradlew :messages:eventuate-tram-examples-basic-message-producer:bootRun
----

This command starts the consumer:

[source,shell]
----
$ ./gradlew :messages:eventuate-tram-examples-basic-message-consumer:bootRun
----

You can then send a message to the producer:

[source,shell]
----
$ http POST localhost:8080/produce accountId=101
----

You should see a `2024-04-02 13:42:29.644 INFO 66525 --- [pool-1-thread-1] i.e.t.e.b.e.subscriber.MessageHandler : Got message ...` log entry in the consumer.

=== About the event publishing/subscribing examples

These examples are in the link:events[events directory].
There are three services:

* `eventuate-tram-examples-basic-event-publisher` - a service that implements a `POST /publish` endpoint publishes an event to a channel
* `eventuate-tram-examples-basic-event-subscriber` - a service that subscribes to the event channel
* `eventuate-tram-examples-basic-event-cqrs-subscriber` - a subscriber service that does NOT use the (relational) database to implement message handler idempotency

The following command starts the producer:

[source,shell]
----
$ ./gradlew :events:eventuate-tram-examples-basic-event-publisher:bootRun
----

This command starts the subscriber:

[source,shell]
----
$ ./gradlew :events:eventuate-tram-examples-basic-event-subscriber:bootRun
----

This command starts the CQRS subscriber:

[source,shell]
----
$ ./gradlew :events:eventuate-tram-examples-basic-event-crqs:subscriber:bootRun
----

This command triggers the publishing of event:

[source,shell]
----
$ http POST localhost:8080/publish accountId=10 amount=12
----

== About the command/async reply examples

These examples are in the link:commands[commands directory].
There are two services:

* `eventuate-tram-examples-basic-command-producer` - a service that implements a `POST /send` endpoint sends a command to a channel
* `eventuate-tram-examples-basic-command-consumer` - a service that subscribes to a command channel and sends a reply

This command starts the producer:

[source,shell]
----
$ ./gradlew :commands:eventuate-tram-examples-basic-command-producer:bootRun
----

This command starts the consumer:

[source,shell]
----
$ ./gradlew :commands:eventuate-tram-examples-basic-command-consumer:bootRun
----

You can then send a command to the consumer:

[source,shell]
----
$ http POST localhost:8080/send customerId=101
----

== Runnning the tests

After starting the infrastructure services, you can also run the tests:

[source,shell]
----
$ ./gradlew build
----

== For more information

Please read the http://eventuate.io/tram/gettingstarted.html[Eventuate Tram getting started guide] or look at the http://eventuate.io/exampleapps.html[examples].