Kafka S3 Sink Connector忽略bootstrap.servers连接localhost问题

我通过Docker Compose部署了Kafka、ZooKeeper以及Confluent Kafka S3 Sink Connector三个服务，但Connector（具体为connect-distributed脚本）始终尝试连接localhost:9092，忽略了配置文件中正确配置的bootstrap.servers。从调试信息可见，AdminClientConfig已加载正确的bootstrap.servers值[172.18.0.3:9092]，但后续AdminClient却持续尝试连接127.0.0.1:9092。请问这是否是Connector的Bug？

2022-08-10 16:37:30,626] INFO Creating Kafka admin client (org.apache.kafka.connect.util.ConnectUtils)
    [2022-08-10 16:37:30,634] INFO AdminClientConfig values:
            bootstrap.servers = [172.18.0.3:9092]
            client.dns.lookup = default
            client.id =
            connections.max.idle.ms = 300000
            metadata.max.age.ms = 300000
            metric.reporters = []
            metrics.num.samples = 2
            metrics.recording.level = INFO
            metrics.sample.window.ms = 30000
            receive.buffer.bytes = 65536
            reconnect.backoff.max.ms = 1000
            reconnect.backoff.ms = 50
            request.timeout.ms = 120000
            retries = 5
            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
            ssl.cipher.suites = null
            ssl.enabled.protocols = [TLSv1.2, TLSv1.1, TLSv1]
            ssl.endpoint.identification.algorithm`**gateSetaddGroup�娃**洗firstwh禁
算法 https
            ssl.key.password = null
            ssl.keymanager.algorithm = SunX509
            ssl.keystore.location = null
            ssl.keystore.password = null
            ssl.keystore.type = JKS
            ssl.protocol = TLS
            ssl.provider = null
            ssl.secure.random.implementation = null
            ssl.trustmanager.algorithm = PKIX
            ssl.truststore.location = null
            ssl.truststore.password = null
            ssl.truststore.type = JKS
     (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'config.storage.topic' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'group.id' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'status.storage.topic' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'plugin.path' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'internal.key.converter.schemas.enable' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'kafka.consumer.group.id' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'internal.key.converter' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'offset.storage.file.filename' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,747] WARN The configuration 'internal.value.converter.schemas.enable' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
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    [2022-08-10 16:37:30,748] WARN The configuration 'internal.value.converter' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,748] WARN The configuration 'offset.storage.topic' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,749] WARN The configuration 'value.converter' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,749] WARN The configuration 'key.converter' was supplied but isn't a known config. (org.apache.kafka.clients.admin.AdminClientConfig)
    [2022-08-10 16:37:30,750] INFO Kafka version: 5.4.1-ccs (org.apache.kafka.common.utils.AppInfoParser)
    [2022-08-10 16:37:30,750] INFO Kafka commitId: fd1e543386b47352 (org.apache.kafka.common.utils.AppInfoParser)
    [2022-08-10 16:37:30,751] INFO Kafka startTimeMs: 1660149450749 (org.apache.kafka.common.utils.AppInfoParser)
    [2022-08-10 16:37:31,031] WARN [AdminClient clientId=adminclient-1] Connection to node 1 (/127.0.0.1:9092) could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)

这不是Connector的Bug，核心原因是Kafka Broker的advertised.listeners配置错误。

• 原理说明：当Connector通过bootstrap.servers连接到Kafka Broker后，会从Broker获取集群元数据，其中包含Broker对外暴露的advertised.listeners地址。如果Broker的advertised.listeners配置为localhost:9092，即使Connector初始连接的是172.18.0.3:9092，后续也会切换到localhost:9092进行通信，这在Docker环境下必然失败（因为Connector容器内的localhost指向自身，而非Kafka容器）。

• 解决步骤：

  1. 修改Docker Compose中Kafka服务的配置，设置advertised.listeners为Kafka容器能被Connector访问到的地址（比如容器名称+端口，如kafka:9092，前提是Docker Compose的服务名在同一网络下可解析；或者直接用Kafka容器的固定IP）。
  2. 确保listeners配置包含容器内部可监听的地址（如PLAINTEXT://0 BV requiring以上 Raw通Tags par&），同时advertised.listeners`设置为外部服务（包括Connector）可访问的地址。
  3. 重启Kafka和Connector服务，验证连接是否正常。

补充说明：日志中那些"supplied but isn't a known config"的警告可以忽略，因为Connect的配置参数会被传递给AdminClient，但部分参数是Connect专属的，AdminClient不识别属于正常现象，不影响功能。

内容的提问来源于stack exchange，提问作者Jin Ma