java.lang.ClassCastException: io.netty.channel.epoll.EpollEventLoopGroup cannot be cast to io.netty.channel.EventLoopGroup

[mateen-dar]

Setting up Kafka Connect with Redis 6
v 0.0.2.11
Confluent version v 6.0.0

java.lang.ClassCastException: io.netty.channel.epoll.EpollEventLoopGroup cannot be cast to io.netty.channel.EventLoopGroup\n\t
at io.lettuce.core.resource.DefaultEventLoopGroupProvider.getOrCreate(DefaultEventLoopGroupProvider.java:119)\n\t
at io.lettuce.core.resource.DefaultEventLoopGroupProvider.allocate(DefaultEventLoopGroupProvider.java:65)\n\t
at io.lettuce.core.AbstractRedisClient.getEventLoopGroup(AbstractRedisClient.java:187)\n\t
at io.lettuce.core.AbstractRedisClient.channelType(AbstractRedisClient.java:173)\n\t
at io.lettuce.core.RedisClient.getConnectionBuilder(RedisClient.java:343)\n\t
at io.lettuce.core.RedisClient.connectStatefulAsync(RedisClient.java:291)\n\t
at io.lettuce.core.RedisClient.connectStandaloneAsync(RedisClient.java:274)\n\t
at io.lettuce.core.RedisClient.connect(RedisClient.java:207)\n\t
at com.github.jcustenborder.kafka.connect.redis.RedisSessionFactoryImpl$RedisSessionImpl.create(RedisSessionFactoryImpl.java:166)\n\t
at com.github.jcustenborder.kafka.connect.redis.RedisSessionFactoryImpl.create(RedisSessionFactoryImpl.java:52)\n\t
at com.github.jcustenborder.kafka.connect.redis.RedisSinkTask.start(RedisSinkTask.java:73)\n\t
at org.apache.kafka.connect.runtime.WorkerSinkTask.initializeAndStart(WorkerSinkTask.java:302)\n\t
at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:193)\n\t
at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:185)\n\t
at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:235)\n\t
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)\n\t
at java.util.concurrent.FutureTask.run(FutureTask.java:266)\n\t
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\t
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\t
at java.lang.Thread.run(Thread.java:748)\n"

[jruaux]

Having the same issue with Confluent Platform 6.1.0 and it also happens with this other Redis connector: https://github.com/jaredpetersen/kafka-connect-redis
I'm guessing it's a class loader issue introduced in Confluent 6.

[jcustenborder]

Sorry I just noticed this. It's most likely cause plugin isolation pulls in the classpath from the connect worker. I'll look into a patch shortly.

[jcustenborder]

Ok did a little research. It looks like we (I work at Confluent) have changed the version of netty a couple times. Classpath isolation inherits the classpath from the worker so that means this is the version we're getting each time. Easiest workaround you for my connector and https://github.com/jaredpetersen/kafka-connect-redis would be to see if there is a compatible version of lettuce that uses a compatible version of netty and recompile against that. I'll take a deeper look tomorrow. Sorry for the delayed response. I didn't see the notification come in from @mateen-dar.

./confluent-6.1.0/share/java/kafka/netty-all-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-buffer-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-codec-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-codec-http2-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-codec-http-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-codec-socks-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-common-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-handler-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-handler-proxy-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-resolver-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-tcnative-boringssl-static-2.0.34.Final.jar
./confluent-6.1.0/share/java/kafka/netty-transport-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-transport-native-epoll-4.1.51.Final.jar
./confluent-6.1.0/share/java/kafka/netty-transport-native-epoll-4.1.51.Final-linux-x86_64.jar
./confluent-6.1.0/share/java/kafka/netty-transport-native-unix-common-4.1.51.Final.jar

./confluent-6.0.1/share/java/kafka/netty-all-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-buffer-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-codec-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-common-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-handler-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-resolver-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-tcnative-boringssl-static-2.0.30.Final.jar
./confluent-6.0.1/share/java/kafka/netty-transport-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-transport-native-epoll-4.1.50.Final.jar
./confluent-6.0.1/share/java/kafka/netty-transport-native-unix-common-4.1.50.Final.jar

[jruaux]

I tried with older versions of Lettuce (5.2.1, 5.3.3, 6.0.0) with varying versions of Netty to no avail. Did you have any luck?

[jonathanfox82]

Any workaround for this issue?

[jcustenborder]

Try removing the netty jars from the connector. That seems to do it.

[jonathanfox82]

Perfect thanks.

[DenysFaure]

Hi guys,
Any news on this issue?

[jcustenborder]

The workaround above seems to work. I will be releasing a new version soon

[jruaux]

The workaround worked for me:

<dependency>
    <groupId>io.lettuce</groupId>
    <artifactId>lettuce-core</artifactId>
    <version>6.0.2.RELEASE</version>
    <exclusions>
        <exclusion>
            <groupId>io.netty</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>

[DenysFaure]

Are there any plans to update docker image https://hub.docker.com/r/jcustenborder/kafka-connect-all ?

[jcustenborder]

@DenysFaure I updated that docker image for you. Going forward I'm not going to be deprecating that docker image. I would recommend moving to my cp-kafka-connect or my cp-server-connect-operator. These images are tagged based on the version of the Confluent platform they are using. This allows me to support several versions of connect workers for Confluent Platform and Confluent Operator installs.