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Spring Boot and SAGA EIP Example

This example shows how to work with Apache Camel Saga using Spring Boot and Narayana LRA Coordinator to manage long running actions

How it works

There are 4 services as participants of the Saga:

  • payment-service: it emulates a real payment transaction and it will be used by both flight-service and train-service

  • flight-service: it emulates the booking of a flight ticket and it uses the payment-service to execute a payment transaction

  • train-service: it emulates the reservation of a train seat and it uses the payment-service to execute a payment transaction

  • app: is the starting point and it emulates a user that starts the transaction to buy both flight and train tickets

The starting point is a REST endpoint that creates a request for a new reservation and there is 15% probability that the payment service fails.

Logical view

logic diagram

Compensating a failure

compesate diagram

Technical view

tech diagram

The communication between services and LRA coordinator (blue connectors) is via HTTP protocol, so every service expose REST endpoints called by the LRA, moreover it calls LRA via REST endpoint

The communication between services (red connectors) is via AMQ broker (using OPENWIRE protocol), implemented using Camel JMS component and RequestReply EIP obtaining a synchronous behavior using asynchronous protocol

Analyzing logs

In the logs there will be all the messages about the execution of the service.

First the app starts the saga LRA, passing the id to the entry point REST

#local environment
curl -X POST http://localhost:8084/api/saga?id=1

#Openshift cluster
curl -X POST "http://$(oc get route camel-example-spring-boot-saga-app -o go-template --template='{{.spec.host}}')/api/saga?id=1"

in the log

Executing saga #1 with LRA http://localhost:8080/lra-coordinator/0_ffff7f000001_8aad_62d16f11_2

where the URL contains the id of the LRA and the number of the saga is the value of the parameter passed to the rest in the starting point

We’re expecting that if the payment is ok, the message in the payment service will be:

Paying train for order #1

Payment train done for order #1 with payment transaction xxxxx

Payment flight done for order #1 with payment transaction xxxxx

the value of the payment transaction is the JMSCorrelationID used in the RequestReply EIP in the payment service

If the random failure occurs, the log in the payment service will be

Payment flight for saga #65 fails!

Payment for order #65 has been cancelled

It means that the compensation for the payment has been called, so we expect that in the flight service there will be a log

Flight purchase #65 has been cancelled due to payment failure

in the train service

Train purchase #65 has been cancelled due to payment failure

in the app

Transaction http://localhost:8080/lra-coordinator/0_ffff7f000001_8aad_62d16f11_74 has been cancelled due to flight or train failure

Running on Openshift cluster

Requirements

  • oc client installed (guide)

  • already logged in into cluster (running oc login)

  • destination project already created (running oc new-project my-project)

Run installation script

# if the cluster is enabled to create Persistent Volume Claims
./install-ocp.sh

# otherwise in ephemeral mode
./install-ocp-ephemeral.sh
Red Hat Developer Sandbox usage example

Go to https://developers.redhat.com/developer-sandbox/get-started after login, click on Start using your sandbox button.

Then login into the Openshift and copy the command login clicking on the link Copy Login Command in the OpenShift console (the command will be something similar to oc login --token=sha256~xxxx --server=https://api.sandbox-xxxx.openshiftapps.com:6443).

Select your project oc project xxxxxx-dev

Run that command on the terminal and then run the installation script ./install-ocp-ephemeral.sh

Check OCP generated resources

it will generate all the necessary PODs:

  • amq-broker

  • lra-coordinator

  • camel-example-spring-boot-saga-app

  • camel-example-spring-boot-saga-flight

  • camel-example-spring-boot-saga-payment

  • camel-example-spring-boot-saga-train

wait for all the pods to be ready:

# all running pods
oc get pods -l csbexample=saga

# only services
oc get pods -l csbexample=saga -l provider=jkube

tail logs of the application:

oc logs -f deploymentconfig/camel-example-spring-boot-saga-payment

Running on local environment

Requirements

  • docker compose installed (guide)

Run script to execute services locally

./run-local.sh

It will generate all the necessary Docker containers and java processes, logs are stored in the .log files, and process id in the .pid files

Run script to stop services locally

./stop-local.sh

This command will kill the running processes, remove the PID files and stop the containers; the log files will be left

Using Camel components

Apache Camel provides 200+ components which you can use to integrate and route messages between many systems and data formats. To use any of these Camel components, add the component as a dependency to your project.

Help and contributions

If you hit any problem using Camel or have some feedback, then please let us know.

We also love contributors, so get involved :-)

The Camel riders!