[jira] [Created] (KAFKA-5736) Improve error message in Connect when all kafka brokers are down

["Konstantine Karantasis (JIRA)" <ji...@apache.org>]

Konstantine Karantasis created KAFKA-5736:
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             Summary: Improve error message in Connect when all kafka brokers are down
                 Key: KAFKA-5736
                 URL: https://issues.apache.org/jira/browse/KAFKA-5736
             Project: Kafka
          Issue Type: Bug
          Components: KafkaConnect
    Affects Versions: 0.11.0.0
            Reporter: Konstantine Karantasis
            Assignee: Konstantine Karantasis
             Fix For: 0.11.0.1




Currently when all the Kafka brokers are down, Kafka Connect is failing with a pretty unintuitive message when it tries to, for instance, reconfigure tasks. 

Example output: 
{code:java}
[2017-08-15 19:12:09,959] ERROR Failed to reconfigure connector's tasks, retrying after backoff: (org.apache.kafka.connect.runtime.distributed.DistributedHerder)
java.lang.IllegalArgumentException: CircularIterator can only be used on non-empty lists
    at org.apache.kafka.common.utils.CircularIterator.<init>(CircularIterator.java:29)
    at org.apache.kafka.clients.consumer.RoundRobinAssignor.assign(RoundRobinAssignor.java:61)
    at org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor.assign(AbstractPartitionAssignor.java:68)
    at 

... (connector code)

    at org.apache.kafka.connect.runtime.Worker.connectorTaskConfigs(Worker.java:230)
{code}

The error message needs to be improved, since its root cause is the absence kafka brokers for assignment. 



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