Eclipse Paho Kotlin MqttClient.subscribe() endless loop - spring-boot

Question

I am using the latest version of Eclipse Paho in a Kotlin Spring Boot app to read from an MQTT topic over websockets. I am successfully connecting to the server, but when I try to subscribe, I am getting into an endless loop using MqttClient.subscribe().
#PostConstruct
fun connectToDigitalMortar() {
val FUNCTION_NAME = "connectToDigitalMortar()"
logger.info { "$FUNCTION_NAME: entering" }
val clientId = UUID.randomUUID().toString()
val url = "wss://${digitalMortarIngestorConfig.mqtt.host}:${digitalMortarIngestorConfig.mqtt.port}/ws"
val client: IMqttClient = MqttClient(
url,
clientId
)
val options = MqttConnectionOptions()
options.isAutomaticReconnect = true
options.isCleanStart = true
options.connectionTimeout = 10
options.userName = digitalMortarIngestorConfig.mqtt.username
options.password = digitalMortarIngestorConfig.mqtt.password.toByteArray()
options.socketFactory = InsecureTrustManager.getInsecureSocketFactory()
logger.info { "$FUNCTION_NAME: connecting to $url" }
var errorAction = ""
try {
errorAction = "client.connect()"
client.connect(options)
errorAction = "client.subscribe()"
client.subscribe(
digitalMortarIngestorConfig.mqtt.topic,
0,
object : IMqttMessageListener {
override fun messageArrived(topic: String?, mqttMessage: MqttMessage?) {
messageConsumer(topic, mqttMessage)
}
}
)
} catch (exc: Exception) {
logger.error { "$FUNCTION_NAME: exception encountered on $errorAction - $exc" }
}
fun messageConsumer(topic: String?, mqttMessage: MqttMessage?) {
logger.info { "messageConsumer(): Message received - ${objectMapper.writeValueAsString(mqttMessage)} " }
}
Here is the log:
2022-08-20 11:45:11.177 ERROR 24023 --- [ main] o.s.boot.SpringApplication : Application run failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'digitalMortarPahoMqttClient': Invocation of init method failed; nested exception is java.lang.StackOverflowError
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:160) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:440) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1796) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:955) ~[spring-beans-5.3.22.jar:5.3.22]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.22.jar:5.3.22]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.22.jar:5.3.22]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-2.7.2.jar:2.7.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-2.7.2.jar:2.7.2]
at com.dsg.innovation.digitalmortaringestor.InnovationDigitalMortarIngestorApplicationKt.main(InnovationDigitalMortarIngestorApplication.kt:13) ~[classes/:na]
Caused by: java.lang.StackOverflowError: null
at org.eclipse.paho.mqttv5.client.MqttClient.subscribe(MqttClient.java:525) ~[org.eclipse.paho.mqttv5.client-1.2.5.jar:na]
at org.eclipse.paho.mqttv5.client.MqttClient.subscribe(MqttClient.java:525) ~[org.eclipse.paho.mqttv5.client-1.2.5.jar:na]
at org.eclipse.paho.mqttv5.client.MqttClient.subscribe(MqttClient.java:525) ~[org.eclipse.paho.mqttv5.client-1.2.5.jar:na]
...
Any ideas what I am doing wrong?