Warning in JanusGraph 1.0.0 about missing class which did not occur in 0.6.3

[mrckzgl]

After upgrade from 0.6.3 to 1.0.0 we see this warning at the first query of the graph:

[Ruby-0-Thread-6: importers/lib/TaskQueueManager.rb:90] WARN org.reflections8.Reflections - could not get type for name org.apache.tinkerpop.gremlin.server.GraphManager from any class loader
org.reflections8.ReflectionsException: could not get type for name org.apache.tinkerpop.gremlin.server.GraphManager
	at org.reflections8.ReflectionUtils.forName(ReflectionUtils.java:412)
	at org.reflections8.Reflections.expandSuperTypes(Reflections.java:421)
	at org.reflections8.Reflections.<init>(Reflections.java:158)
	at org.reflections8.Reflections.<init>(Reflections.java:200)
	at org.reflections8.Reflections.<init>(Reflections.java:173)
	at org.janusgraph.graphdb.util.JanusGraphTraverserUtil.<clinit>(JanusGraphTraverserUtil.java:35)
	at org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphMultiQueryStep.registerTraverser(JanusGraphMultiQueryStep.java:119)
	at org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphMultiQueryStep.processNextStart(JanusGraphMultiQueryStep.java:112)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:155)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.hasNext(ExpandableStepIterator.java:47)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.NoOpBarrierStep.processAllStarts(NoOpBarrierStep.java:67)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.NoOpBarrierStep.processNextStart(NoOpBarrierStep.java:56)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:155)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:55)
	at org.apache.tinkerpop.gremlin.process.traversal.step.map.ScalarMapStep.processNextStart(ScalarMapStep.java:39)
	at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:155)
	at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:192)
	at org.jruby.dist/org.jruby.javasupport.ext.JavaUtil$Iterator.each(JavaUtil.java:113)
	at org.jruby.dist/org.jruby.javasupport.ext.JavaUtil$Iterator$INVOKER$s$0$0$each.call(JavaUtil$Iterator$INVOKER$s$0$0$each.gen)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:485)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:210)
	at org.jruby.dist/org.jruby.RubyEnumerable.callEach(RubyEnumerable.java:87)
	at org.jruby.dist/org.jruby.RubyEnumerable.to_a(RubyEnumerable.java:453)
	at org.jruby.dist/org.jruby.RubyEnumerable$INVOKER$s$to_a.call(RubyEnumerable$INVOKER$s$to_a.gen)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:474)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:195)
	at org.jruby.dist/org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:350)
	at org.jruby.dist/org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:66)
	at org.jruby.dist/org.jruby.ir.interpreter.InterpreterEngine.interpret(InterpreterEngine.java:82)
	at org.jruby.dist/org.jruby.internal.runtime.methods.InterpretedIRMethod.INTERPRET_METHOD(InterpretedIRMethod.java:204)
	at org.jruby.dist/org.jruby.internal.runtime.methods.InterpretedIRMethod.call(InterpretedIRMethod.java:191)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:495)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:244)
	at org.jruby.dist/org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:318)
	at org.jruby.dist/org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:66)
	at org.jruby.dist/org.jruby.ir.interpreter.InterpreterEngine.interpret(InterpreterEngine.java:76)
	at org.jruby.dist/org.jruby.internal.runtime.methods.InterpretedIRMethod.INTERPRET_METHOD(InterpretedIRMethod.java:167)
	at org.jruby.dist/org.jruby.internal.runtime.methods.InterpretedIRMethod.call(InterpretedIRMethod.java:146)
	at org.jruby.dist/org.jruby.RubyClass.finvokeWithRefinements(RubyClass.java:505)
	at org.jruby.dist/org.jruby.RubyBasicObject.send(RubyBasicObject.java:1642)
	at org.jruby.dist/org.jruby.RubyKernel.send(RubyKernel.java:2303)
	at org.jruby.dist/org.jruby.RubyKernel$INVOKER$s$send.call(RubyKernel$INVOKER$s$send.gen)
	at org.jruby.dist/org.jruby.internal.runtime.methods.JavaMethod$JavaMethodOneOrNBlock.call(JavaMethod.java:422)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:495)
	at org.jruby.dist/org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:244)
	at org.jruby.dist/org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:318)
	at org.jruby.dist/org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:66)
	at org.jruby.dist/org.jruby.ir.interpreter.Interpreter.INTERPRET_BLOCK(Interpreter.java:116)
	at org.jruby.dist/org.jruby.runtime.InterpretedIRBlockBody.commonYieldPath(InterpretedIRBlockBody.java:135)
	at org.jruby.dist/org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:66)
	at org.jruby.dist/org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:58)
	at org.jruby.dist/org.jruby.runtime.Block.call(Block.java:143)
	at org.jruby.dist/org.jruby.RubyProc.call(RubyProc.java:357)
	at org.jruby.dist/org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:110)
	at java.base/java.lang.Thread.run(Thread.java:1589)
Caused by: java.lang.ClassNotFoundException: org.apache.tinkerpop.gremlin.server.GraphManager
	at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	at org.reflections8.ReflectionUtils.forName(ReflectionUtils.java:410)
	... 54 more

The cuplrit seems this code:

janusgraph/janusgraph-core/src/main/java/org/janusgraph/graphdb/util/JanusGraphTraverserUtil.java

Lines 34 to 40 in ab3a801

	for(String packageToScan : Arrays.asList("org.apache.tinkerpop", "org.janusgraph")){
	Reflections reflections = new Reflections(packageToScan);
	Set<Class<? extends Traverser>> subTypesOfTraverser = reflections.getSubTypesOf(Traverser.class);
	for (Class<?> traverserType : subTypesOfTraverser) {
	addTraverserClass(traverserType);
	}
	}

we include the following jars and their dependencies (via lock_jar JRuby gem):

jar 'org.janusgraph:janusgraph-berkeleyje:1.0.0'
jar 'org.janusgraph:janusgraph-lucene:1.0.0'
jar 'org.slf4j:slf4j-simple:1.7.36'

This warning did not appear in version 0.6.3. I would like this to be confirmed as a bug to open an issue on the tracker.

best

[FlorianHockmann]

@porunov Do you have any idea about this one? Seems like you added the mentioned code in this commit.

[mrckzgl]

For completeness, this seems to be the same issue as here: #4349

[porunov]

Thanks for bringing it up. I answered about these warnings in the original discussion: #4349 (comment)

In short: it is fine that you see these warnings and they are harmless. We do need to refactor the way we plug-in Hadoop functionality to not expect these classes in the classpath.

I will close this discussion as a duplicate discussion.