[jira] [Commented] (FLINK-4439) Error message KafkaConsumer08 when all 'bootstrap.servers' are invalid

["Robert Metzger (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-4439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15429735#comment-15429735 ] 

Robert Metzger commented on FLINK-4439:
---------------------------------------

In my opinion, the logging is pretty good.
There's a log message at WARN level:
{code}
2016-08-21 15:22:30 WARN  FlinkKafkaConsumerBase:290 - Error communicating with broker inexistentKafkHost:9092 to find partitions for [testTopic].class java.nio.channels.ClosedChannelException. Message: null
{code}

and the stack trace is at debug level.

I'm not sure if failing fast is a good solution: Maybe its just a temporary issue with the broker, or the client can not contact the broker.

> Error message KafkaConsumer08 when all 'bootstrap.servers' are invalid
> ----------------------------------------------------------------------
>
>                 Key: FLINK-4439
>                 URL: https://issues.apache.org/jira/browse/FLINK-4439
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming Connectors
>    Affects Versions: 1.0.3
>            Reporter: Gheorghe Gheorghe
>            Priority: Minor
>
> The "flink-connector-kafka-0.8_2"  is logging the following error when all 'bootstrap.servers' are invalid when passed to the FlinkKafkaConsumer08. 
> See stacktrace: 
> {code:title=stacktrace|borderStyle=solid}
> 2016-08-21 15:22:30 WARN  FlinkKafkaConsumerBase:290 - Error communicating with broker inexistentKafkHost:9092 to find partitions for [testTopic].class java.nio.channels.ClosedChannelException. Message: null
> 2016-08-21 15:22:30 DEBUG FlinkKafkaConsumerBase:292 - Detailed trace
> java.nio.channels.ClosedChannelException
> 	at kafka.network.BlockingChannel.send(BlockingChannel.scala:100)
> 	at kafka.consumer.SimpleConsumer.liftedTree1$1(SimpleConsumer.scala:78)
> 	at kafka.consumer.SimpleConsumer.kafka$consumer$SimpleConsumer$$sendRequest(SimpleConsumer.scala:68)
> 	at kafka.consumer.SimpleConsumer.send(SimpleConsumer.scala:91)
> 	at kafka.javaapi.consumer.SimpleConsumer.send(SimpleConsumer.scala:68)
> 	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer08.getPartitionsForTopic(FlinkKafkaConsumer08.java:264)
> 	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer08.<init>(FlinkKafkaConsumer08.java:193)
> 	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer08.<init>(FlinkKafkaConsumer08.java:164)
> 	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer08.<init>(FlinkKafkaConsumer08.java:131)
> 	at MetricsFromKafka$.main(MetricsFromKafka.scala:38)
> 	at MetricsFromKafka.main(MetricsFromKafka.scala)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:497)
> 	at sbt.Run.invokeMain(Run.scala:67)
> 	at sbt.Run.run0(Run.scala:61)
> 	at sbt.Run.sbt$Run$$execute$1(Run.scala:51)
> 	at sbt.Run$$anonfun$run$1.apply$mcV$sp(Run.scala:55)
> 	at sbt.Run$$anonfun$run$1.apply(Run.scala:55)
> 	at sbt.Run$$anonfun$run$1.apply(Run.scala:55)
> 	at sbt.Logger$$anon$4.apply(Logger.scala:84)
> 	at sbt.TrapExit$App.run(TrapExit.scala:248)
> 	at java.lang.Thread.run(Thread.java:745)
> {code}
> In the above stackrace it is hard to figure out that the actual servers provided as a config cannot be resolved to a valid ip address. Moreover the flink kafka consumer will try all of those servers one by one and failing to get partition information.
> The suggested improvement is to fail fast and announce the user that the servers provided in the 'boostrap.servers' config are invalid. If at least one server is valid then the exception should not be thrown. 



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