kafka appender: When kafka server is down, application can't start

## Description

I use kafka appender to send logs to kafka server. When kafka server is down, if I start my application at this time, the kafka appender would attemp to connect to kafka continually. and then application has been hang-up.

I think that the failure of log component should not affect application startup and execution .

## Configuration

**Version:** 2.20.0

**Operating system:** all

**JDK:** 17
## Logs

```
load hp-soa system properties file -> /data/hp-soa/config/system-config.properties
2023-08-05 02:14:25.005 INFO [main] o.a.d.spring.boot.context.event.WelcomeLogoApplicationListener#onApplicationEvent(L:64) -> [DUBBO]

:: Dubbo (v3.2.4) : https://github.com/apache/dubbo
:: Discuss group : dev@dubbo.apache.org
, dubbo version: 3.2.4, current host: 192.168.59.1
2023-08-05 02:14:25.079 INFO [background-preinit] o.h.v.internal.util.Version#(L:21) -> HV000001: Hibernate Validator 8.0.1.Final
2023-08-05 02:14:27.948 INFO [main] o.a.k.common.config.AbstractConfig#logAll(L:369) -> ProducerConfig values:
acks = -1
auto.include.jmx.reporter = true
batch.size = 0
bootstrap.servers = [192.168.56.23:9092]
buffer.memory = 33554432
client.dns.lookup = use_all_dns_ips
client.id = producer-1
compression.type = none
connections.max.idle.ms = 540000
delivery.timeout.ms = 120000
enable.idempotence = true
interceptor.classes = []
key.serializer = class org.apache.kafka.common.serialization.ByteArraySerializer
linger.ms = 0
max.block.ms = 60000
max.in.flight.requests.per.connection = 5
max.request.size = 1048576
metadata.max.age.ms = 300000
metadata.max.idle.ms = 300000
metric.reporters = []
metrics.num.samples = 2
metrics.recording.level = INFO
metrics.sample.window.ms = 30000
partitioner.adaptive.partitioning.enable = true
partitioner.availability.timeout.ms = 0
partitioner.class = null
partitioner.ignore.keys = false
receive.buffer.bytes = 32768
reconnect.backoff.max.ms = 1000
reconnect.backoff.ms = 50
request.timeout.ms = 30000
retries = 2147483647
retry.backoff.ms = 100
sasl.client.callback.handler.class = null
sasl.jaas.config = [hidden]
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.connect.timeout.ms = null
sasl.login.read.timeout.ms = 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.login.retry.backoff.max.ms = 10000
sasl.login.retry.backoff.ms = 100
sasl.mechanism = GSSAPI
sasl.oauthbearer.clock.skew.seconds = 30
sasl.oauthbearer.expected.audience = null
sasl.oauthbearer.expected.issuer = null
sasl.oauthbearer.jwks.endpoint.refresh.ms = 3600000
sasl.oauthbearer.jwks.endpoint.retry.backoff.max.ms = 10000
sasl.oauthbearer.jwks.endpoint.retry.backoff.ms = 100
sasl.oauthbearer.jwks.endpoint.url = null
sasl.oauthbearer.scope.claim.name = scope
sasl.oauthbearer.sub.claim.name = sub
sasl.oauthbearer.token.endpoint.url = null
security.protocol = PLAINTEXT
security.providers = null
send.buffer.bytes = 131072
socket.connection.setup.timeout.max.ms = 30000
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
transaction.timeout.ms = 60000
transactional.id = null
value.serializer = class org.apache.kafka.common.serialization.ByteArraySerializer

2023-08-05 02:14:28.008 INFO [main] o.a.k.clients.producer.KafkaProducer#configureTransactionState(L:596) -> [Producer clientId=producer-1] Instantiated an idempotent producer.
2023-08-05 02:14:36.186 INFO [main] o.a.k.common.config.AbstractConfig#logUnused(L:378) -> These configurations '[sasl.jaas.config]' were supplied but are not used yet.
2023-08-05 02:14:36.190 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:119) -> Kafka version: 3.5.0
2023-08-05 02:14:36.191 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:120) -> Kafka commitId: c97b88d5db4de28d
2023-08-05 02:14:36.191 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:121) -> Kafka startTimeMs: 1691172876187
2023-08-05 02:14:36.194 INFO [main] o.a.k.common.config.AbstractConfig#logAll(L:369) -> ProducerConfig values:
acks = -1
auto.include.jmx.reporter = true
batch.size = 0
bootstrap.servers = [192.168.56.23:9092]
buffer.memory = 33554432
client.dns.lookup = use_all_dns_ips
client.id = producer-2
compression.type = none
connections.max.idle.ms = 540000
delivery.timeout.ms = 120000
enable.idempotence = true
interceptor.classes = []
key.serializer = class org.apache.kafka.common.serialization.ByteArraySerializer
linger.ms = 0
max.block.ms = 60000
max.in.flight.requests.per.connection = 5
max.request.size = 1048576
metadata.max.age.ms = 300000
metadata.max.idle.ms = 300000
metric.reporters = []
metrics.num.samples = 2
metrics.recording.level = INFO
metrics.sample.window.ms = 30000
partitioner.adaptive.partitioning.enable = true
partitioner.availability.timeout.ms = 0
partitioner.class = null
partitioner.ignore.keys = false
receive.buffer.bytes = 32768
reconnect.backoff.max.ms = 1000
reconnect.backoff.ms = 50
request.timeout.ms = 30000
retries = 2147483647
retry.backoff.ms = 100
sasl.client.callback.handler.class = null
sasl.jaas.config = [hidden]
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.connect.timeout.ms = null
sasl.login.read.timeout.ms = 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.login.retry.backoff.max.ms = 10000
sasl.login.retry.backoff.ms = 100
sasl.mechanism = GSSAPI
sasl.oauthbearer.clock.skew.seconds = 30
sasl.oauthbearer.expected.audience = null
sasl.oauthbearer.expected.issuer = null
sasl.oauthbearer.jwks.endpoint.refresh.ms = 3600000
sasl.oauthbearer.jwks.endpoint.retry.backoff.max.ms = 10000
sasl.oauthbearer.jwks.endpoint.retry.backoff.ms = 100
sasl.oauthbearer.jwks.endpoint.url = null
sasl.oauthbearer.scope.claim.name = scope
sasl.oauthbearer.sub.claim.name = sub
sasl.oauthbearer.token.endpoint.url = null
security.protocol = PLAINTEXT
security.providers = null
send.buffer.bytes = 131072
socket.connection.setup.timeout.max.ms = 30000
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
transaction.timeout.ms = 60000
transactional.id = null
value.serializer = class org.apache.kafka.common.serialization.ByteArraySerializer

2023-08-05 02:14:36.196 INFO [main] o.a.k.clients.producer.KafkaProducer#configureTransactionState(L:596) -> [Producer clientId=producer-2] Instantiated an idempotent producer.
2023-08-05 02:14:36.213 INFO [main] o.a.k.common.config.AbstractConfig#logUnused(L:378) -> These configurations '[sasl.jaas.config]' were supplied but are not used yet.
2023-08-05 02:14:36.214 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:119) -> Kafka version: 3.5.0
2023-08-05 02:14:36.214 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:120) -> Kafka commitId: c97b88d5db4de28d
2023-08-05 02:14:36.214 INFO [main] o.a.k.common.utils.AppInfoParser$AppInfo#(L:121) -> Kafka startTimeMs: 1691172876214

. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v3.1.2)

2023-08-05 02:14:36.315 INFO [main] o.s.b.SpringApplication#logStartupProfileInfo(L:634) -> No active profile set, falling back to 1 default profile: "default"
2023-08-05 02:14:38.701 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:38.701 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:38.706 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:38.706 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:38.707 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:38.707 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:40.829 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:40.829 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:40.829 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:40.829 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:40.830 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:40.830 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:42.936 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:42.936 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:42.937 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:43.016 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:43.017 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:43.018 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:45.144 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:45.145 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:45.146 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:45.279 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:45.280 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:45.280 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:47.557 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:47.557 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:47.558 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:47.742 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:47.743 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:47.744 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:50.274 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:50.275 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:50.276 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:50.463 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:50.464 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:50.464 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:53.146 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:53.146 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:53.147 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:53.394 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:53.395 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:53.396 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:56.341 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:56.342 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:56.343 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:56.346 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:56.347 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:56.347 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:59.213 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:14:59.214 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:59.215 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:14:59.570 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:14:59.571 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:14:59.572 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:02.167 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:02.168 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:02.169 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:02.451 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:02.452 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:02.453 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:05.344 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:05.345 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:05.346 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:05.477 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:05.477 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:05.478 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:08.323 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:08.324 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:08.325 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:08.348 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:08.349 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:08.349 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:11.397 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:11.397 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:11.398 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:11.419 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:11.420 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:11.421 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:14.378 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:14.379 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:14.380 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:14.595 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:14.596 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:14.596 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:17.217 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:17.218 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:17.218 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:17.682 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:17.683 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:17.683 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:20.142 INFO [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-1] Node -1 disconnected.
2023-08-05 02:15:20.142 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-1] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:20.143 WARN [kafka-producer-network-thread | producer-1] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-1] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
2023-08-05 02:15:20.652 INFO [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#handleDisconnections(L:977) -> [Producer clientId=producer-2] Node -1 disconnected.
2023-08-05 02:15:20.652 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient#processDisconnection(L:814) -> [Producer clientId=producer-2] Connection to node -1 (/192.168.56.23:9092) could not be established. Broker may not be available.
2023-08-05 02:15:20.653 WARN [kafka-producer-network-thread | producer-2] o.a.k.clients.NetworkClient$DefaultMetadataUpdater#handleServerDisconnect(L:1105) -> [Producer clientId=producer-2] Bootstrap broker 192.168.56.23:9092 (id: -1 rack: null) disconnected
```

## Reproduction

Just shutdown kafka server and start application.