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Add saga example
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‎.github/dependabot.yml

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- "/openapi-contract-first"
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- "/platform-http-security-keycloak"
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- "/rest-json"
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- "/saga"
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- "/timer-log-kotlin"
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- "/timer-log-main"
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- "/timer-log"

‎.github/generate-test-groups.groovy

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// Distribute example projects across a bounded set of test groups and output as JSON
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new File(".").eachFileRecurse { file ->
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if (file.getName() == "pom.xml") {
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if (file.getName() == "pom.xml" && file.getParentFile().getParentFile().getName() == ".") {
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if (GROUPS[groupId] == null) {
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GROUPS[groupId] = [:]
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GROUPS[groupId].name = "group-${String.format("%02d", groupId + 1)}"

‎.gitignore

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# Quarkus
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quarkus.log*
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# Saga
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payment.*
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flight.*
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train.*
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app.*
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‎docs/modules/ROOT/attachments/examples.json

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"description": "Demonstrates how to create a REST service using the Camel REST DSL and Jackson.",
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"link": "https://github.com/apache/camel-quarkus-examples/tree/main/rest-json"
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},
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{
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"title": "Saga and LRA",
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"description": "Shows how to use saga and lra",
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"link": "https://github.com/apache/camel-quarkus-examples/tree/main/saga"
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},
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{
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"title": "Timer Hello World",
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"description": "Uses the Camel timer component to output a Hello world message to the console",

‎saga/README.adoc

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= Saga and LRA: A Camel Quarkus example
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:cq-example-description: An example that shows how to use saga and lra
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{cq-description}
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TIP: Check the https://camel.apache.org/camel-quarkus/latest/first-steps.html[Camel Quarkus User guide] for prerequisites
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and other general information.
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=== How it works
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There are 4 services as participants of the Saga:
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- payment-service: it emulates a real payment transaction and it will be used by both flight-service and train-service
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- flight-service: it emulates the booking of a flight ticket and it uses the payment-service to execute a payment transaction
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- train-service: it emulates the reservation of a train seat and it uses the payment-service to execute a payment transaction
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- app: is the starting point and it emulates a user that starts the transaction to buy both flight and train tickets
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The starting point is a REST endpoint that creates a request for a new reservation
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and there is 15% probability that the payment service fails.
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==== Logical view
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image::doc-resources/logic-diagram.png[]
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==== Compensating a failure
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image::doc-resources/compesate-diagram.png[]
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==== Technical view
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image::doc-resources/tech-diagram.png[]
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The communication between services and LRA coordinator (blue connectors) is via HTTP protocol,
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so every service expose REST endpoints called by the LRA, moreover it calls LRA via REST endpoint
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The communication between services (red connectors) is via AMQ broker (using OPENWIRE protocol),
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implemented using Camel JMS component and RequestReply EIP
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obtaining a synchronous behavior using asynchronous protocol
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==== Analyzing logs
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In the logs there will be all the messages about the execution of the service.
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First the app starts the saga LRA, passing the id to the entry point REST
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[source,shell]
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----
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curl -X POST http://localhost:8084/api/saga?id=1
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----
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in the log
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[source]
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----
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Executing saga #1 with LRA http://localhost:8080/lra-coordinator/0_ffff7f000001_8aad_62d16f11_2
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----
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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
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We're expecting that if the payment is ok, the message in the payment service will be:
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[source]
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----
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Paying train for order #1
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Payment train done for order #1 with payment transaction xxxxx
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Payment flight done for order #1 with payment transaction xxxxx
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----
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the value of the payment transaction is the `JMSCorrelationID` used in the RequestReply EIP in the payment service
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If the random failure occurs, the log in the payment service will be
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[source]
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----
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Payment flight for saga #65 fails!
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Payment for order #65 has been cancelled
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----
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It means that the compensation for the payment has been called, so we expect that in the flight service there will be a log
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[source]
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----
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Flight purchase #65 has been cancelled due to payment failure
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----
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in the train service
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[source]
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----
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Train purchase #65 has been cancelled due to payment failure
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----
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in the app
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[source]
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----
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Transaction http://localhost:8080/lra-coordinator/0_ffff7f000001_8aad_62d16f11_74 has been cancelled due to flight or train failure
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----
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=== Package and run the application
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Once you are done with developing you may want to package and run the application.
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TIP: Find more details about the JVM mode and Native mode in the Package and run section of
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https://camel.apache.org/camel-quarkus/latest/first-steps.html#_package_and_run_the_application[Camel Quarkus User guide]
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==== External systems
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Start Artemis:
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[source, shell]
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----
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docker run --name artemis \
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-e AMQ_USER=admin -e AMQ_PASSWORD=admin \
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-d -p 61616:61616 \
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quay.io/artemiscloud/activemq-artemis-broker
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----
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Start Narayana LRA Coordinator Server:
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[source, shell]
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----
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docker run --network host -e QUARKUS_HTTP_PORT=8080 quay.io/jbosstm/lra-coordinator:latest
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----
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==== JVM mode
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[source,shell]
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----
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$ mvn clean package
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----
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==== Native mode
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IMPORTANT: Native mode requires having GraalVM and other tools installed. Please check the Prerequisites section
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of https://camel.apache.org/camel-quarkus/latest/first-steps.html#_prerequisites[Camel Quarkus User guide].
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To prepare a native executable using GraalVM, run the following command:
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[source,shell]
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----
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$ mvn clean package -Pnative
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----
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==== Run script to execute services locally
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[source,shell]
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----
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./run.sh
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----
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It will generate all the java processes and start in dev mode, logs are stored in the `.log` files, and process id in the `.pid` files
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==== Run script to stop services locally
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[source,shell]
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----
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./stop.sh
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----
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This command will kill the running processes, remove the PID files; the log files will be left
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== Feedback
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Please report bugs and propose improvements via https://github.com/apache/camel-quarkus/issues[GitHub issues of Camel Quarkus] project.

‎saga/doc-resources/compesate-diagram.png

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‎saga/doc-resources/logic-diagram.png

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‎saga/doc-resources/tech-diagram.png

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