available-stock-processor project

This project uses Quarkus, the Supersonic Subatomic Java Framework, and KafkaStreams.

If you want to learn more about Quarkus, please visit its website: https://quarkus.io/ . Or KafkaStreams: https://kafka.apache.org/documentation/streams/ .

Application

This app runs a KafkaStreams topology which consumes orders and shipments (from topics of the same name) and produces a stream of stock reservations per product SKU.

Logic

• The "warehouse", represented by the stock-levels topic, is the master of stock and periodically updates absolute stock levels per SKU.
• New customer orders and shipments create and release reservations on existing stock for each product SKU and quantity ordered.

Assumptions

• Updates to stock-levels per SKU always supersede previous updates. (Lots of things can happen in the warehouse to change stock-levels.)
• reserved-stock per SKU, resulting from orders and shipments, will be used to modify in real time the latest stock-levels.

(The reserved-stock-processor project: https://github.com/merlante/reserved-stock-processor does this last bit, producing a real time stream of stock reservations.)

Quickstart

Requirements

• A kafka cluster configured to use OAUTHBEARER authentication.
• A service account with OAUTHBEARER credentials and an oauth token endpoint.

The following topics are required in your kafka cluster for this app to run:

• stock-levels
• reserved-stock

Run

To run the app, add the following vars to your environment:

export BOOTSTRAP_SERVERS=<KAFKA_BOOTSTRAP_SERVERS>
export CLIENT_ID=<KAFKA_CLIENT_ID>
export CLIENT_SECRET=<KAFKA_CLIENT_SECRET>
export TOKEN_ENDPOINT_URI=<OAUTH_TOKEN_ENDPOINT_URI>

Then run one of the ./mvnw commands, below, e.g.

./mvnw compile quarkus:dev

The app will connect to your kafka cluster and consume and produce records from topics, according to its KafkaStreams topology, until it is exited.

Running the application in dev mode

You can run your application in dev mode that enables live coding using:

./mvnw compile quarkus:dev

NOTE: Quarkus now ships with a Dev UI, which is available in dev mode only at http://localhost:8080/q/dev/.

Packaging and running the application

The application can be packaged using:

./mvnw package

It produces the quarkus-run.jar file in the target/quarkus-app/ directory.

The application is now runnable using java -jar target/quarkus-app/quarkus-run.jar.

Be aware that it’s not an über-jar as the dependencies are copied into the target/quarkus-app/lib/ directory.

If you want to build an über-jar, execute the following command:

./mvnw package -Dquarkus.package.type=uber-jar

The über-jar is runnable using java -jar target/available-stock-processor-<maven_version>-runner.jar.

Creating a native executable

You can create a native executable using:

./mvnw package -Pnative

Or, if you don't have GraalVM installed, and/or you want to build for a different native target (e.g. building for linux when running on a mac), you can run the native executable build in a container using:

./mvnw package -Pnative -Dquarkus.native.container-build=true

Use this command (or the next variation) if you want to build an executable suitable for running in a linux-based docker image (see below).

If you want to specify that docker is the container runtime, rather than podman, the default, do:

./mvnw package -Pnative -Dnative-image.container-runtime=docker -Dquarkus.native.container-build=true

You can then execute your native executable with: ./target/available-stock-processor-1.0.0-SNAPSHOT-runner

If you want to learn more about building native executables, please consult https://quarkus.io/guides/maven-tooling.html.

Running in docker

Build

Jvm image build (if you ran ./mvnw package [...] without -Pnative):

docker build -f src/main/docker/Dockerfile.jvm -t [repo_name]available-stock-processor .

Native image build (if you ran ./mvnw package -Pnative [...]):

docker build -f src/main/docker/Dockerfile.native -t [repo_name]available-stock-processor .

[repo_name] could be something like "quay.io/myaccount/", with quay.io being a pushable remote repository at quay.io, or it can be blank, with only a local name of, say, "available-stock-processor", needed.

To push to a remote:

docker push [repo_name]available-stock-processor .

Run

docker run --rm [repo_name]available-stock-processor .

Related guides

• Apache Kafka Streams (guide): Implement stream processing applications based on Apache Kafka