TL;DR this is a regression vs 5.17.6 It appears to me (code inspection) to be caused by commit e5970172 / AMQ-7426
activemq-all-5.18.3.jar(as far as I can tell, erroneously) includes a META-INF/services/org.slf4j.spi.SLF4JServiceProvider file specifying org.apache.logging.slf4j.SLF4JServiceProvider (aka logging-log4j2/log4j-slf4j2-impl/src/main/java/org/apache/logging/slf4j/SLF4JServiceProvider.java) rather than allowing/requiring the application to configure it. This looks to me to be just be the default because org.apache.logging:log4j-slf4j-impl is included, even though it's declared optional. ------------- Workarounds: Delete META-INF/services/org.slf4j.spi.SLF4JServiceProvider from activemq-all-5.18.3.jar Downgrade to activemq-all-5.17.6.jar Include log4j2 in the classpath ------------- Attempting to upgrade a project from 5.16.x, which does not otherwise include log4j2, I dropped in 5.18.3 and see the following exceptions: Exception occurred: java.lang.ClassNotFoundException (to be caught at: org.slf4j.LoggerFactory.bind(), line=208 bci=86)"thread=AlertClientSettingsProvider", jdk.internal.loader.BuiltinClassLoader.loadClass(), line=581 bci=19 AlertClientSettingsProvider[1] where [1] jdk.internal.loader.BuiltinClassLoader.loadClass (BuiltinClassLoader.java:581) [2] jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass (ClassLoaders.java:178) [3] java.lang.ClassLoader.loadClass (ClassLoader.java:522) [4] org.apache.logging.slf4j.SLF4JServiceProvider.initialize (SLF4JServiceProvider.java:53) [5] org.slf4j.LoggerFactory.bind (LoggerFactory.java:195) [6] org.slf4j.LoggerFactory.performInitialization (LoggerFactory.java:182) [7] org.slf4j.LoggerFactory.getProvider (LoggerFactory.java:490) [8] org.slf4j.LoggerFactory.getILoggerFactory (LoggerFactory.java:476) [9] org.slf4j.LoggerFactory.getLogger (LoggerFactory.java:425) [10] org.slf4j.LoggerFactory.getLogger (LoggerFactory.java:451) [11] org.apache.activemq.broker.BrokerService.<clinit> (BrokerService.java:139) <application stack snipped> AlertClientSettingsProvider[1] locals Method arguments: cn = "org.apache.logging.log4j.Logger" resolve = false causing: Exception occurred: java.lang.NoClassDefFoundError (to be caught at: java.util.concurrent.FutureTask.runAndReset(), line=307 bci=55)"thread=AlertClientSettingsProvider", org.slf4j.LoggerFactory.getProvider(), line=492 bci=33 AlertClientSettingsProvider[1] where [1] org.slf4j.LoggerFactory.getProvider (LoggerFactory.java:492) [2] org.slf4j.LoggerFactory.getILoggerFactory (LoggerFactory.java:476) [3] org.slf4j.LoggerFactory.getLogger (LoggerFactory.java:425) [4] org.slf4j.LoggerFactory.getLogger (LoggerFactory.java:451) [5] org.apache.activemq.broker.BrokerService.<clinit> (BrokerService.java:139) <application stack snipped> (Instantiation of BrokerService fails and the application goes away) -------------
