[KAFKA-5229] Reflections logs excessive warnings when scanning classpaths

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.0.0, 0.10.0.1, 0.10.1.0, 0.10.1.1, 0.10.2.0, 0.10.2.1
• Fix Version/s: 0.11.0.0
• Component/s: connect
• Labels: newbie
• Assignee: Bharat Viswanadham
• Reporter: Ewen Cheslack-Postava
• Created: 12/May/17 22:04
• Updated: 25/Jul/17 11:11
• Resolved: 01/Jun/17 20:47

Description

We use Reflections to scan the classpath for available plugins (connectors, converters, transformations), but when doing so Reflections tends to generate a lot of log noise like this:

[2017-05-12 14:59:48,224] WARN could not get type for name org.jboss.netty.channel.SimpleChannelHandler from any class loader (org.reflections.Reflections:396)
org.reflections.ReflectionsException: could not get type for name org.jboss.netty.channel.SimpleChannelHandler
	at org.reflections.ReflectionUtils.forName(ReflectionUtils.java:390)
	at org.reflections.Reflections.expandSuperTypes(Reflections.java:381)
	at org.reflections.Reflections.<init>(Reflections.java:126)
	at org.apache.kafka.connect.runtime.PluginDiscovery.scanClasspathForPlugins(PluginDiscovery.java:68)
	at org.apache.kafka.connect.runtime.AbstractHerder$1.run(AbstractHerder.java:391)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: org.jboss.netty.channel.SimpleChannelHandler
	at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
	at org.reflections.ReflectionUtils.forName(ReflectionUtils.java:388)
	... 5 more

Despite being benign, these warnings worry users, especially first time users.

We should either a) see if we can get Reflections to turn off these specific warnings via some config or b) make Reflections only log at > WARN by default in our log4j config. (b) is probably safe since we should only be seeing these at startup and I don't think I've seen any actual issue logged at WARN.

Issue Links

• links to: GitHub Pull Request #3072