NPE on smallrye-metrics JsonExporter on Java 8 when empty/null tags

[davsclaus]

Notice this test error on Apache Camel where we are using smallrye metrics 3.0.3

https://ci-builds.apache.org/job/Camel/job/Apache%20Camel/job/main/121/testReport/junit/org.apache.camel.component.microprofile.metrics.message.history/MicroProfileMetricsExceptionInRouteMessageHistoryTest/testMetricsHistoryWhenRouteThrowsException/

java.lang.NullPointerException
	at java.util.TreeMap.putAll(TreeMap.java:313)
	at io.smallrye.metrics.exporters.JsonExporter.createTagsString(JsonExporter.java:350)
	at io.smallrye.metrics.exporters.JsonExporter.lambda$exportMetricsByName$5(JsonExporter.java:175)
	at java.util.HashMap.forEach(HashMap.java:1289)
	at io.smallrye.metrics.exporters.JsonExporter.exportMetricsByName(JsonExporter.java:173)
	at io.smallrye.metrics.exporters.JsonExporter.lambda$exportMetricsForMap$9(JsonExporter.java:214)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1699)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:485)
	at io.smallrye.metrics.exporters.JsonExporter.exportMetricsForMap(JsonExporter.java:215)
	at io.smallrye.metrics.exporters.JsonExporter.exportOneRegistry(JsonExporter.java:199)
	at io.smallrye.metrics.exporters.JsonExporter.exportOneScope(JsonExporter.java:71)
	at org.apache.camel.component.microprofile.metrics.message.history.MicroProfileMetricsExceptionInRouteMessageHistoryTest.testMetricsHistoryWhenRouteThrowsException(MicroProfileMetricsExceptionInRouteMessageHistoryTest.java:60)
	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:498)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)

This only happens on Java 8, the same test works on Java 11.

The unit test is here
https://github.com/apache/camel/blob/main/components/camel-microprofile/camel-microprofile-metrics/src/test/java/org/apache/camel/component/microprofile/metrics/message/history/MicroProfileMetricsExceptionInRouteMessageHistoryTest.java

[jmartisk]

I haven't really dug into it, but I assume this could happen because MP Config is not properly available when you're building the JsonExporter? See https://github.com/smallrye/smallrye-metrics/blob/3.0.3/implementation/src/main/java/io/smallrye/metrics/exporters/JsonExporter.java#L65
That would explain the null map in globalTags, which is the reason for the NPE during export.

SmallRye should be functioning properly even without MP Config being available, so this is a bug, and the globalTags needs to be set to an empty map rather than null in such case. I'll get a PR up in a jiffy.

[jmartisk]

It's also weird why MP Config doesn't seem to be working properly when the test uses Java 8. The attempt to read a config property throws this:

java.lang.NoClassDefFoundError: javax/annotation/Priority
	at io.smallrye.config.SmallRyeConfigBuilder$InterceptorWithPriority$1.getPriority(SmallRyeConfigBuilder.java:445)
	at io.smallrye.config.SmallRyeConfigBuilder$InterceptorWithPriority.<init>(SmallRyeConfigBuilder.java:453)
	at io.smallrye.config.SmallRyeConfigBuilder$InterceptorWithPriority.<init>(SmallRyeConfigBuilder.java:432)
	at io.smallrye.config.SmallRyeConfigBuilder$InterceptorWithPriority.<init>(SmallRyeConfigBuilder.java:424)
	at io.smallrye.config.SmallRyeConfigBuilder.getDefaultInterceptors(SmallRyeConfigBuilder.java:211)
	at io.smallrye.config.SmallRyeConfig.buildInterceptors(SmallRyeConfig.java:92)
	at io.smallrye.config.SmallRyeConfig.<init>(SmallRyeConfig.java:68)
	at io.smallrye.config.SmallRyeConfigBuilder.build(SmallRyeConfigBuilder.java:402)
	at io.smallrye.config.SmallRyeConfigFactory$Default.getConfigFor(SmallRyeConfigFactory.java:59)
	at io.smallrye.config.SmallRyeConfigProviderResolver.getConfig(SmallRyeConfigProviderResolver.java:76)
	at io.smallrye.config.SmallRyeConfigProviderResolver.getConfig(SmallRyeConfigProviderResolver.java:64)
	at org.eclipse.microprofile.config.ConfigProvider.getConfig(ConfigProvider.java:85)
	at io.smallrye.metrics.exporters.JsonExporter.<init>(JsonExporter.java:61)
	at org.apache.camel.component.microprofile.metrics.message.history.MicroProfileMetricsExceptionInRouteMessageHistoryTest.testMetricsHistoryWhenRouteThrowsException(MicroProfileMetricsExceptionInRouteMessageHistoryTest.java:59)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
	at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at java.util.ArrayList.forEach(ArrayList.java:1259)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at java.util.ArrayList.forEach(ArrayList.java:1259)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
	at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.execute(JUnitPlatformProvider.java:188)
	at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invokeAllTests(JUnitPlatformProvider.java:154)
	at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invoke(JUnitPlatformProvider.java:128)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:428)
	at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:162)
	at org.apache.maven.surefire.booter.ForkedBooter.run(ForkedBooter.java:562)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:548)
Caused by: java.lang.ClassNotFoundException: javax.annotation.Priority
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	... 82 more

When I add a dependency on javax.annotation-api, the test passes on 8, not sure why an additional dependency is needed on 8. I'd assume there's some magic in Camel's pom files that does this?