sensor

Sensor Simulation

This service simulates a sensor which measures the filling of a container. The sensor simulation is built with Quarkus and publishes information about the measured filling to a Kafka topic.

Run

To run a sensor in Quarkus development mode without the need to separate build and run, you can use the Quarkus plugin via the Maven wrapper.

./mvnw quarkus:dev \
    -Dquarkus.http.port=<port> \
    -Dsensor.id=<sensor-id>

Kafka Topic and Sent Information

The measured information is regularly published to the Kafka topic sensors. Each message which a sensor published includes a sensorId of the sensor which published the message, a dateTime of when the message was produced and a filling which is a percentage of how much liquid is left in the measured container.

Published Messages

To see the published messages, you can locate the file kafka-console-consumer.sh, go to its folder and execute ./kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic sensors --from-beginning. In our example of running Kafka via the provided docker-compose.yml, you have to exec into the started Kafa container with docker-compose exec kafka bash. After starting a sensor simulation, you can execute the following command:

./bin/kafka-console-consumer.sh \
    --bootstrap-server localhost:9092 \
    --topic sensors \
    --from-beginning \
    --max-messages 10

Run Multiple Sensors Simultaneously

To run several sensors simultaneously, each sensor needs an own ID and each sensor has to run on a unique port.

Custom Port

Usually, each sensor application start on port 8080. However, several applications cannot run on the same port. To easily modify the port of each sensor, the port can be set via the config property quarkus.http.port=<port>. This system property can also be set during startup with Maven's -D flag. The application can therefore be started in the development mode with:

./mvnw quarkus:dev \
    -Dquarkus.http.port=<port>

Custom Sensor ID

Generally, each sensor has a random UUID as its ID. However, it is also possible to set a custom ID via the config property sensor.id=<sensor-id>. This is also possible during startup with Maven's -D flag. The application can therefore be started in the development mode with:

./mvnw quarkus:dev \
    -Dsensor.id=<sensor-id>

Run Sensor in Production Mode

To create a .jar of the sensor application, you have to package the whole application with the Maven Wrapper.

./mvnw package

It produces the quarkus-run.jar file in the target/quarkus-app/ directory. It can be run like any other .jar and equipped with properties via the -D flag.

java \
    -Dquarkus.http.port=<port> \
    -Dsensor.id=<sensor-id> \
    -jar target/quarkus-app/quarkus-run.jar

Be aware that the packaged application is 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 application is then runnable using java -jar target/quarkus-app/quarkus-run.jar. (do not forget port and sensor id).

Run Sensor as Native Executable

To achieve a blazingly fast startup and an application with a smaller footprint, you can run the application as a native executable. You can create a native executable using:

./mvnw package -Pnative

Or, if you don't have GraalVM installed, you can run the native executable build in a container using:

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

You can then execute your native executable with ./target/sensor-1.0-SNAPSHOT-runner and also provide it properties via the -D flag.

./target/sensor-1.0-SNAPSHOT-runner \
    -Dquarkus.http.port=<port> \
    -Dsensor.id=<sensor-id>

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