Kafka Connect 0.11 / 3.3.0 docker has a LOT of WARN at start

[Stephane Maarek]

It seems that due to the new plugins capabilities, a lot of the reflection is failing. I'm not sure of the extent of the impact, and if the problems lies with Kafka connect code itself, or the way the confluent docker image is packed up.

echo "===> Launching ... "

+ echo '===> Launching ... '

===> Launching ...

exec /etc/confluent/docker/launch

+ exec /etc/confluent/docker/launch

===> Launching kafka-connect ...

SLF4J: Class path contains multiple SLF4J bindings.

SLF4J: Found binding in [jar:file:/usr/share/java/kafka/slf4j-log4j12-1.7.25.jar!/org/slf4j/impl/StaticLoggerBinder.

class]

SLF4J: Found binding in [jar:file:/usr/share/java/kafka-connect-hdfs/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticL

oggerBinder.class]

SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.

SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]

[2017-08-21 01:41:14,927] WARN could not create Vfs.Dir from url. ignoring the exception and continuing (org.reflect

ions.Reflections)

org.reflections.ReflectionsException: could not create Vfs.Dir from url, no matching UrlType was found [file:/usr/sh

are/java/confluent-support-metrics/*]

either use fromURL(final URL url, final List<UrlType> urlTypes) or use the static setDefaultURLTypes(final List<UrlT

ype> urlTypes) or addDefaultURLTypes(UrlType urlType) with your specialized UrlType.

                 at org.reflections.vfs.Vfs.fromURL(Vfs.java:109)

        at org.reflections.vfs.Vfs.fromURL(Vfs.java:91)

        at org.reflections.Reflections.scan(Reflections.java:240)

        at org.reflections.Reflections.scan(Reflections.java:202)

        at org.reflections.Reflections.<init>(Reflections.java:123)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanPluginPath(DelegatingClassLoader.jav

a:221)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanUrlsAndAddPlugins(DelegatingClassLoa

der.java:198)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.initLoaders(DelegatingClassLoader.java:1

59)

        at org.apache.kafka.connect.runtime.isolation.Plugins.<init>(Plugins.java:47)

        at org.apache.kafka.connect.cli.ConnectDistributed.main(ConnectDistributed.java:63)

[2017-08-21 01:41:16,982] WARN could not create Vfs.Dir from url. ignoring the exception and continuing (org.reflect

ions.Reflections)

org.reflections.ReflectionsException: could not create Vfs.Dir from url, no matching UrlType was found [file:/etc/ka

fka-connect/jars/*]

either use fromURL(final URL url, final List<UrlType> urlTypes) or use the static setDefaultURLTypes(final List<UrlT

ype> urlTypes) or addDefaultURLTypes(UrlType urlType) with your specialized UrlType.

        at org.reflections.vfs.Vfs.fromURL(Vfs.java:109)

        at org.reflections.vfs.Vfs.fromURL(Vfs.java:91)

        at org.reflections.Reflections.scan(Reflections.java:240)

        at org.reflections.Reflections.scan(Reflections.java:202)

        at org.reflections.Reflections.<init>(Reflections.java:123)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanPluginPath(DelegatingClassLoader.jav

a:221)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanUrlsAndAddPlugins(DelegatingClassLoa

der.java:198)

        at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.initLoaders(DelegatingClassLoader.java:1

59)

        at org.apache.kafka.connect.runtime.isolation.Plugins.<init>(Plugins.java:47)

        at org.apache.kafka.connect.cli.ConnectDistributed.main(ConnectDistributed.java:63

Etc etc... getting a ton of those. 

[Konstantine Karantasis]

Currently, the log4j properties template for the connect image does not have a setting that defaults to ERROR level for org.reflections (as is the case in the log4j properties in AK).

Currently, this is solved by explicitly adding

-e CONNECT_LOG4J_LOGGERS=org.reflections=ERROR

to your docker run command that starts Connect.
 
I have updated the docs to mention this additional parameter, and the changes will be reflected shortly here:

http://docs.confluent.io/current/cp-docker-images/docs/quickstart.html#installing-running-docker

- Konstantine 

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[Stephane Maarek]

Thanks Konstantine. That's helpful, and yes should be included as default in the docker images as well. In the meantime I'll keep that environment variable solution, thanks!

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