As a sanity check, I attempted to install the Confluent JDBC connector plugin without using confluent-hub, per this docker-compose.yml. However, I still see this error:
[2021-07-17 02:19:19,538] INFO Adding admin resources to main listener (org.apache.kafka.connect.runtime.rest.RestServer:241)
[2021-07-17 02:19:20,009] ERROR Stopping due to error (org.apache.kafka.connect.cli.ConnectDistributed:86)
java.lang.NoClassDefFoundError: Could not initialize class org.eclipse.jetty.http.MimeTypes$Type
at org.eclipse.jetty.http.MimeTypes.<clinit>(MimeTypes.java:175)
at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:895)
at org.eclipse.jetty.servlet.ServletContextHandler.doStart(ServletContextHandler.java:288)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:73)
at org.apache.kafka.connect.runtime.rest.RestServer.initializeResources(RestServer.java:305)
at org.apache.kafka.connect.runtime.Connect.start(Connect.java:55)
at org.apache.kafka.connect.cli.ConnectDistributed.startConnect(ConnectDistributed.java:140)
at org.apache.kafka.connect.cli.ConnectDistributed.main(ConnectDistributed.java:80)
[2021-07-17 02:19:20,020] INFO Kafka Connect stopping (org.apache.kafka.connect.runtime.Connect:67)
which results in the connector to stop, with the same behaviour observed above:
[2021-07-17 02:19:24,689] INFO [Producer clientId=producer-1] Closing the Kafka producer with timeoutMillis = 9223372036854775807 ms. (org.apache.kafka.clients.producer.KafkaProducer:1204)
[2021-07-17 02:19:24,694] INFO Metrics scheduler closed (org.apache.kafka.common.metrics.Metrics:659)
[2021-07-17 02:19:24,694] INFO Closing reporter org.apache.kafka.common.metrics.JmxReporter (org.apache.kafka.common.metrics.Metrics:663)
[2021-07-17 02:19:24,695] INFO Metrics reporters closed (org.apache.kafka.common.metrics.Metrics:669)
[2021-07-17 02:19:24,698] INFO App info kafka.producer for producer-1 unregistered (org.apache.kafka.common.utils.AppInfoParser:83)
[2021-07-17 02:19:24,699] INFO Metrics scheduler closed (org.apache.kafka.common.metrics.Metrics:659)
[2021-07-17 02:19:24,700] INFO Closing reporter org.apache.kafka.common.metrics.JmxReporter (org.apache.kafka.common.metrics.Metrics:663)
[2021-07-17 02:19:24,701] INFO Metrics reporters closed (org.apache.kafka.common.metrics.Metrics:669)
[2021-07-17 02:19:24,709] INFO App info kafka.consumer for consumer-kafka-connect-1 unregistered (org.apache.kafka.common.utils.AppInfoParser:83)
[2021-07-17 02:19:24,710] INFO Stopped KafkaBasedLog for topic _connect-offsets (org.apache.kafka.connect.util.KafkaBasedLog:237)
[2021-07-17 02:19:24,710] INFO Stopped KafkaOffsetBackingStore (org.apache.kafka.connect.storage.KafkaOffsetBackingStore:159)
[2021-07-17 02:19:24,711] INFO Metrics scheduler closed (org.apache.kafka.common.metrics.Metrics:659)
[2021-07-17 02:19:24,712] INFO Closing reporter org.apache.kafka.common.metrics.JmxReporter (org.apache.kafka.common.metrics.Metrics:663)
[2021-07-17 02:19:24,713] INFO Metrics reporters closed (org.apache.kafka.common.metrics.Metrics:669)
[2021-07-17 02:19:24,717] INFO App info kafka.connect for kafka-connect:8083 unregistered (org.apache.kafka.common.utils.AppInfoParser:83)
[2021-07-17 02:19:24,718] INFO Worker stopped (org.apache.kafka.connect.runtime.Worker:230)
[2021-07-17 02:19:24,723] INFO App info kafka.admin.client for adminclient-8 unregistered (org.apache.kafka.common.utils.AppInfoParser:83)
[2021-07-17 02:19:24,732] INFO Metrics scheduler closed (org.apache.kafka.common.metrics.Metrics:659)
[2021-07-17 02:19:24,733] INFO Closing reporter org.apache.kafka.common.metrics.JmxReporter (org.apache.kafka.common.metrics.Metrics:663)
[2021-07-17 02:19:24,733] INFO Metrics reporters closed (org.apache.kafka.common.metrics.Metrics:669)
[2021-07-17 02:19:24,734] INFO [Worker clientId=connect-1, groupId=kafka-connect] Herder stopped (org.apache.kafka.connect.runtime.distributed.DistributedHerder:321)
[2021-07-17 02:19:24,736] INFO [Worker clientId=connect-1, groupId=kafka-connect] Herder stopped (org.apache.kafka.connect.runtime.distributed.DistributedHerder:738)
[2021-07-17 02:19:24,736] INFO Kafka Connect stopped (org.apache.kafka.connect.runtime.Connect:72)
Full logs are here.
So, it certainly seems that not even Confluent plugins can run properly?