Azure Kafka Bootstrap broker disconnected - spring-boot

Question

I try to create an Apache Kafka connection to Azure event hubs with reactor kafka in a spring boot application. At first I followed the official Azure tutorial to set up Azure event hubs and the spring backend: https://learn.microsoft.com/en-us/azure/developer/java/spring-framework/configure-spring-cloud-stream-binder-java-app-kafka-azure-event-hub
Everything worked fine and I created some more advanced services.
However when trying to get reactor kafka working with Azure event hubs, it doesn't work. When the consumer is triggered it cannot consume any messages and the following is logged:
com.test.Application : Started Application in 10.442 seconds (JVM running for 10.771)
o.a.k.c.c.internals.AbstractCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Discovered group coordinator mynamespacename.servicebus.windows.net:9093 (id: 2147483647 rack: null)
o.a.k.c.c.internals.AbstractCoordinator : [Consumer clientId=test-client-0, groupId=$Default] (Re-)joining group
o.a.k.c.c.internals.AbstractCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Successfully joined group with generation Generation{generationId=30, memberId='mynamespacename.servicebus.windows.net:c:$default:I:test-client-0-33016d4334614aa8b9b7bf3fd5e1023e', protocol='range'}
o.a.k.c.c.internals.ConsumerCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Finished assignment for group at generation 30: {mynamespacename.servicebus.windows.net:c:$default:I:test-client-0-33016d4334614aa8b9b7bf3fd5e1023e=Assignment(partitions=[my-event-hub-0])}
o.a.k.c.c.internals.AbstractCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Successfully synced group in generation Generation{generationId=30, memberId='mynamespacename.servicebus.windows.net:c:$default:I:test-client-0-33016d4334614aa8b9b7bf3fd5e1023e', protocol='range'}
o.a.k.c.c.internals.ConsumerCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Notifying assignor about the new Assignment(partitions=[my-event-hub-0])
o.a.k.c.c.internals.ConsumerCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Adding newly assigned partitions: my-event-hub-0
o.a.k.c.c.internals.ConsumerCoordinator : [Consumer clientId=test-client-0, groupId=$Default] Setting offset for partition my-event-hub-0 to the committed offset FetchPosition{offset=17, offsetEpoch=Optional.empty, currentLeader=LeaderAndEpoch{leader=Optional[mynamespacename.servicebus.windows.net:9093 (id: 0 rack: null)], epoch=absent}}
o.s.k.l.KafkaMessageListenerContainer : $Default: partitions assigned: [my-event-hub-0]
o.a.k.clients.consumer.ConsumerConfig : ConsumerConfig values:
allow.auto.create.topics = true
auto.commit.interval.ms = 5000
auto.offset.reset = latest
bootstrap.servers = [mynamespacename.servicebus.windows.net:9093]
check.crcs = true
client.dns.lookup = use_all_dns_ips
client.id = test-client
client.rack =
connections.max.idle.ms = 540000
default.api.timeout.ms = 60000
enable.auto.commit = false
exclude.internal.topics = true
fetch.max.bytes = 52428800
fetch.max.wait.ms = 500
fetch.min.bytes = 1
group.id = $Default
group.instance.id = null
heartbeat.interval.ms = 3000
interceptor.classes = []
internal.leave.group.on.close = true
internal.throw.on.fetch.stable.offset.unsupported = false
isolation.level = read_uncommitted
key.deserializer = class org.springframework.kafka.support.serializer.JsonDeserializer
max.partition.fetch.bytes = 1048576
max.poll.interval.ms = 300000
max.poll.records = 500
metadata.max.age.ms = 300000
metric.reporters = []
metrics.num.samples = 2
metrics.recording.level = INFO
metrics.sample.window.ms = 30000
partition.assignment.strategy = [class org.apache.kafka.clients.consumer.RangeAssignor]
receive.buffer.bytes = 65536
reconnect.backoff.max.ms = 1000
reconnect.backoff.ms = 50
request.timeout.ms = 30000
retry.backoff.ms = 100
sasl.client.callback.handler.class = null
sasl.jaas.config = null
sasl.kerberos.kinit.cmd = /usr/bin/kinit
sasl.kerberos.min.time.before.relogin = 60000
sasl.kerberos.service.name = null
sasl.kerberos.ticket.renew.jitter = 0.05
sasl.kerberos.ticket.renew.window.factor = 0.8
sasl.login.callback.handler.class = null
sasl.login.class = null
sasl.login.refresh.buffer.seconds = 300
sasl.login.refresh.min.period.seconds = 60
sasl.login.refresh.window.factor = 0.8
sasl.login.refresh.window.jitter = 0.05
sasl.mechanism = GSSAPI
security.protocol = PLAINTEXT
security.providers = null
send.buffer.bytes = 131072
session.timeout.ms = 10000
socket.connection.setup.timeout.max.ms = 127000
socket.connection.setup.timeout.ms = 10000
ssl.cipher.suites = null
ssl.enabled.protocols = [TLSv1.2, TLSv1.3]
ssl.endpoint.identification.algorithm = https
ssl.engine.factory.class = null
ssl.key.password = null
ssl.keymanager.algorithm = SunX509
ssl.keystore.certificate.chain = null
ssl.keystore.key = null
ssl.keystore.location = null
ssl.keystore.password = null
ssl.keystore.type = JKS
ssl.protocol = TLSv1.3
ssl.provider = null
ssl.secure.random.implementation = null
ssl.trustmanager.algorithm = PKIX
ssl.truststore.certificates = null
ssl.truststore.location = null
ssl.truststore.password = null
ssl.truststore.type = JKS
value.deserializer = class org.apache.kafka.common.serialization.StringDeserializer
o.a.kafka.common.utils.AppInfoParser : Kafka version: 2.7.1
o.a.kafka.common.utils.AppInfoParser : Kafka commitId: 61dbce85d0d41457
o.a.kafka.common.utils.AppInfoParser : Kafka startTimeMs: 1629919378494
r.k.r.internals.ConsumerEventLoop : SubscribeEvent
o.a.k.clients.consumer.KafkaConsumer : [Consumer clientId=test-client, groupId=$Default] Subscribed to topic(s): my-event-hub
org.apache.kafka.clients.NetworkClient : [Consumer clientId=test-client, groupId=$Default] Bootstrap broker mynamespacename.servicebus.windows.net:9093 (id: -1 rack: null) disconnected
org.apache.kafka.clients.NetworkClient : [Consumer clientId=test-client, groupId=$Default] Bootstrap broker mynamespacename.servicebus.windows.net:9093 (id: -1 rack: null) disconnected
The following is the code:
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Flux;
import reactor.kafka.receiver.KafkaReceiver;
import reactor.kafka.receiver.ReceiverOptions;
import reactor.kafka.receiver.ReceiverRecord;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
#Slf4j
#Service
public class StreamConsumer {
public Flux<Object> consumeMessages() {
Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "mynamespacename.servicebus.windows.net:9093");
props.put(ConsumerConfig.CLIENT_ID_CONFIG, "test-client");
props.put(ConsumerConfig.GROUP_ID_CONFIG, "$Default");
props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, org.springframework.kafka.support.serializer.JsonDeserializer.class);
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, org.apache.kafka.common.serialization.StringDeserializer.class);
ReceiverOptions<String, Object> receiverOptions = ReceiverOptions.create(props);
ReceiverOptions<String, Object> options = receiverOptions.subscription(Collections.singleton(KafkaConstants.KAFKA_TOPIC))
.addAssignListener(partitions -> log.debug("onPartitionsAssigned {}", partitions))
.addRevokeListener(partitions -> log.debug("onPartitionsRevoked {}", partitions));
Flux<ReceiverRecord<String, Object>> kafkaFlux = KafkaReceiver.create(options).receive();
return kafkaFlux.map(x -> "Test");
}
}
The reactor code uses the same topic and group id constants. As the client logs a broken connection:
[Consumer clientId=test-client, groupId=$Default] Bootstrap broker mynamespacename.servicebus.windows.net:9093 (id: -1 rack: null) disconnected
I assume that there is a configuration missing to connect the consumer properly to Azure event hubs.