logging in java agents is not trivial in WildFly / EAP
by John Mazzitelli
<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=org.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.
---
[1] $ cat JavaAgent.java
import java.util.logging.*;
public class JavaAgent {
private static final Logger log = Logger.getLogger(JavaAgent.class.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*
2 months, 2 weeks
Inventory API question
by Austin Kuo
I was creating 2 different resource types with the same http client at the
same time.
But one succeed, the other failed with the response 400 and body:
{
"errorMsg" : "The transaction has already been closed"
}
Is it not allowed to do so?
Austin.
3 months
logging in java agents is not trivial in WildFly / EAP
by Mark Ambrose
>>> ... this means problems still need to be overcome when
>>> putting java agents in host controllers for EAP 7.0 domain mode.
>>> </tl;dr>
Is a solution to these problems for when putting java agents in host
controllers for EAP 7.0 domain mode known?
...
[Host Controller] 16:16:33,937 INFO [org.jboss.as.host.controller]
(Controller Boot Thread) WFLYHC0023: Starting server TestServer1a
16:16:33,968 INFO [org.jboss.as.process.Server:TestServer1a.status]
(ProcessController-threads - 3) WFLYPC0018: Starting process
'Server:TestServer1a'
[Server:TestServer1a] Could not load Logmanager
"org.jboss.logmanager.LogManager"
[Server:TestServer1a] java.lang.ClassNotFoundException:
org.jboss.logmanager.LogManager
[Server:TestServer1a] at
java.net.URLClassLoader.findClass(URLClassLoader.java:382)
...
Thanks,
Mark Ambrose
3 months
need a briefing on what the hawkular agent is now doing with respect to inventory
by John Mazzitelli
Joel,
Now that the new inventory-into-metrics is in master and released, I need to know what you did :-D I suspect others will want to know what you did too.
Is it possible for you to write something up or have a 15-minute Blue Jeans session to discuss how inventory is stored in H-Metrics?
I am going to need to know this because I have to implement it in GoLang for HOSA, unless you want to do it :)
--John Mazz
3 months
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by John Mazzitelli
I had a couple peeps ask me if they can run HOSA without needing to run it inside an OpenShift cluster (presumably to collect metrics from Prometheus and Jolokia-JMX endpoints that are also running outside of OpenShift). The answer is "yes" and if you are interested, here is a quick how-to.
First get a config.yaml used to configure HOSA (that's the wget command below - it just grabs the example config from github) and then run "docker run" to launch HOSA:
$ wget -O /tmp/config.yaml https://raw.githubusercontent.com/hawkular/hawkular-openshift-agent/maste...
$ docker run --net=host -v /tmp/config.yaml:/config.yaml hawkular/hawkular-openshift-agent --config=/config.yaml
This assumes you have Hawkular-Metrics server (or a full Hawkular-Services server) running on 127.0.0.1 listening to port 8080. If not, just edit config.yaml to point to your server. You can edit that config.yaml however you want.
By default, HOSA itself is a Prometheus endpoint and will collect its own metrics and store them (see config.yaml for its endpoints definitions). So by running HOSA you will automatically start getting "prometheus" data stored into your H-Metrics. You can add more endpoint definitions to the config to tell HOSA to collect from your own Prometheus and Jolokia-JMX endpoints.
You don't have to use docker - if you build the go executable locally (git clone the HOSA repo and "make build") you can run the executable directly. But it's easier to just docker run - no need to git clone, no need to install Go, no need to build anything.
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Hi, can you recommend a cool site that will help with transportation of things?
by Qwerty Qwerty
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essay
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I needed to write an essay on career goals for scholarships but I just didn't understand how to do it on my own. I had never written an essay before and I was no good at it. So I found information about that career goal essay for scholarships https://essayservice.com/blog/guide-on-career-goals-essay website and it came in handy for me. Because I immediately understood how to do it. So I wrote a great essay thanks to this article
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