Please update log4-over-slf4j to at least 1.7.21:

https://github.com/javamelody/javamelody/issues/566

the log4j-over-slf4j-1.7.7.jar brought by jenkins 2.60.3 makes it impossible to install monitoring-plugin when jenkins running in tomcat.

env. tomcat-8.0.43-28.2 on sles 12 sp2 x64.

java.lang.NoSuchMethodError: net.bull.javamelody.Log4JAppender.setThreshold(Lorg/apache/log4j/Priority;)V

        at net.bull.javamelody.Log4JAppender.<init>(Log4JAppender.java:42)

        at net.bull.javamelody.Log4JAppender.<clinit>(Log4JAppender.java:34)

        at net.bull.javamelody.FilterContext.initLogs(FilterContext.java:313)

        at net.bull.javamelody.FilterContext.<init>(FilterContext.java:95)

        at net.bull.javamelody.MonitoringFilter.init(MonitoringFilter.java:142)

        at net.bull.javamelody.PluginMonitoringFilter.init(PluginMonitoringFilter.java:45)

        at org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.init(HudsonMonitoringFilter.java:61)

        at hudson.util.PluginServletFilter.addFilter(PluginServletFilter.java:111)

        at org.jvnet.hudson.plugins.monitoring.PluginImpl.start(PluginImpl.java:118)

        at hudson.ClassicPluginStrategy.startPlugin(ClassicPluginStrategy.java:534)

        at hudson.ClassicPluginStrategy.load(ClassicPluginStrategy.java:523)

Caused: java.io.IOException: Failed to initialize

        at hudson.ClassicPluginStrategy.load(ClassicPluginStrategy.java:526)

        at hudson.PluginManager.dynamicLoad(PluginManager.java:865)

Caused: java.io.IOException: Failed to install monitoring plugin

        at hudson.PluginManager.dynamicLoad(PluginManager.java:874)

        at hudson.PluginManager.dynamicLoad(PluginManager.java:813)

        at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1889)

Caused: java.io.IOException: Failed to dynamically deploy this plugin

        at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1893)

        at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1651)

        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)

        at java.util.concurrent.FutureTask.run(FutureTask.java:266)

        at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:110)

        at java.lang.Thread.run(Thread.java:748)