Re: [Hawkular-dev] logging in java agents is not trivial in WildFly / EAP

I've copied James Perkins, who is the WildFly logging component lead. Brian Stansberry Manager, Senior Principal Software Engineer Red Hat On Fri, Sep 29, 2017 at 3:35 AM, Thomas Heute <theute(a)redhat.com&gt; wrote: > Adding Dimitris and Brian (It relates to https://issues.jboss.org/br > owse/WFCORE-2526 ) > > (Mazz I have a question below) > > On Thu, Sep 28, 2017 at 5:29 PM, John Mazzitelli <mazz(a)redhat.com&gt; wrote: > >> <tl;dr> >> No matter if a java agent uses JBoss Logging or simply relies on the >> JRE's own Java logging, it still won't work in WildFly/EAP unless you set >> additional things to environment variables in standalone.conf. So no matter >> what logging is used, this means problems still need to be overcome when >> putting java agents in host controllers for EAP 7.0 domain mode. >> </tl;dr> >> >> I am looking at how Java Agents should log messages when attached to >> WildFly or EAP. I want to see if there is a way to implement a Java Agent >> and NOT have to set any special JAVA_OPTS values to pass to the VM to get >> it to work. >> >> Turns out, it is not a trivial issue. >> >> I wrote a silly little test agent [1] just to see what would happen if >> it simply logs a message using *java* logging and spins a thread logging a >> message every second again using *java* logging. So, no extra third party >> logging libraries, just using java.util.logging classes that are in the JRE >> already. >> >> Adding just -javaagent to JAVA_OPTS (in standalone.conf, add something >> like "-javaagent:/where/it/is/ja.jar=foo=bar") is no good, the server >> bombs with this error, presumably because my agent already started logging >> using java logger: >> >> Caused by: java.util.concurrent.ExecutionException: >> java.lang.IllegalStateException: WFLYLOG0078: The logging subsystem >> requires the log manager to be org.jboss.logmanager.LogManager. The >> subsystem has not be initialized and cannot be used. To use JBoss Log >> Manager you must add the system property "java.util.logging.manager" and >> set it to "org.jboss.logmanager.LogManager" >> >> Well, catch-22, because if I set java.util.logging.manager=org.jboss.logmanager.LogManager >> in JAVA_OPTS, this happens when the test agent tries to log: >> >> Could not load Logmanager "org.jboss.logmanager.LogManager" >> java.lang.ClassNotFoundException: org.jboss.logmanager.LogManager >> >> which then falls back to java logging, which then causes the server to >> bomb again because it wants JBoss Logging. >> >> If I set this in standalone.conf: >> >> JBOSS_MODULES_SYSTEM_PKGS="org.jboss.byteman,org.jboss.logmanager" >> >> the java agent still gets this error: >> >> Could not load Logmanager "org.jboss.logmanager.LogManager" >> java.lang.ClassNotFoundException: org.jboss.logmanager.LogManager >> >> which is then followed by jboss modules error which causes the server to >> again to fail to start: >> >> WARNING: Failed to load the specified log manager class >> org.jboss.logmanager.LogManager >> Exception in thread "main" java.lang.NoClassDefFoundError: >> org/jboss/logmanager/Level >> ... >> at org.jboss.modules.Module.run(Module.java:320) >> >> The ONLY way to get the server to start properly with this java agent >> installed (EVEN WITH the agent using ONLY java logging), you have to do all >> of the above plus add this to JAVA_OPTS: >> >> -Xbootclasspath/p:$JBOSS_HOME/modules/system/layers/base/org >> /jboss/logmanager/main/jboss-logmanager-2.0.4.Final.jar >> >> So, in short, you need to add "-Djava.util.logging.manager=o >> rg.jboss.logmanager.LogManager" to JAVA_OPTS, you need to add >> ",org.jboss.logmanager" to JBOSS_MODULES_SYSTEM_PKGS, and you need to add >> that -Xbootclasspath to JAVA_OPTS just to get a javaagent to work even if >> the javaagent simply uses nothing more than standard java logging. >> > > That's for WF-Core 2.x (as in EAP 7.0), how about WF-Core 3 (as in EAP > 7.1) ? IIRC you also need some of those ugliness ? > > Thomas > > > >> >> --- >> >> [1] $ cat JavaAgent.java >> import java.util.logging.*; >> public class JavaAgent { >> private static final Logger log = Logger.getLogger(JavaAgent.cla >> ss.getName()); >> public static void premain(String args) { >> log.severe("log in premain: " + args); >> new Thread(new Runnable() { >> public void run() { >> while (true) { >> try { >> Thread.sleep(1000); >> log.severe("log in premain loop: " + args); >> } catch (Exception e) { >> return; >> } >> } >> } >> }).start(); >> } >> } >> >> To build it: >> >> $ echo "Premain-Class: JavaAgent" > manifest.mf >> $ javac JavaAgent.java >> $ jar cvfm ja.jar manifest.mf JavaAgent* >> >> _______________________________________________ >> hawkular-dev mailing list >> hawkular-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hawkular-dev >> > >