I want to use mbeans on startup of j2ee application to check if all the MDBs are running and jms specification has been activated.
Any pointers will be very helpful
The only way I know of to do this would be to use the ServerEndpointControl MBean. This is a Liberty specific MBean for controlling the input sources for work into the runtime. This can also be used to get status on http listeners.
The best place to find the Javadoc for the MBean is here. To find out if an MBean is running you call the isPaused method providing the MDB name which is defined as:
ApplicationName#ModuleName#BeanName
if the MDB is running it'll return false.
Related
We have an application that makes use of Spring Kafka's non blocking retries via the RetryableTopic annotation.
We are in the middle of upgrading spring-kafka from 2.8.4 to 2.9.0.
We have several SpringBootTests that makes use of EmbeddedKafka. Each of these tests are marked with DirtyContext and AutoConfigureMockMvc
After upgrading, the first test would run fine, but the later test would fail to start the application with
Constructor threw exception; nested exception is java.lang.IllegalStateException: Only one 'RetryTopicConfigurationSupport' is allowed
I understand that the RetryTopicConfigurationSupport tries to ensures only one instance of itself is ever instantiated. So in the use case of running multiple unit tests, which includes multiple different SpringBootTests, how do we avoid hitting this problem?
I have tried marking the context dirty, but of course that didn't solve the problem as RetryTopicConfigurationSupport is using a static variable to track whether it has been instantiated before or not.
I have tried NOT marking the ContextDirty, but the later tests would fail to start the application because the Port is already in use.
Appreciate any advise!
Looks like this problem has been addressed in spring-kafka 3.0 and backported to 2.9.3
https://github.com/spring-projects/spring-kafka/issues/2477
The pprof package documentation says
The package is typically only imported for the side effect of registering its HTTP handlers. The handled paths all begin with /debug/pprof/."
The documentation says if you already have an http server running you don't need to start another one but if you are not using DefaultServeMux, you will have to register handlers with the mux you are using.
Shouldn't I always use a separate port for pprof? Is it okay to use the same port that I am using for prometheus metrics?
net/http/pprof is a convenience package. It always registers handlers on DefaultServeMux, because DefaultServeMux is a global variable that it can actually do that with.
If you want to serve pprof results on some other ServeMux there's really nothing to it; all it takes is calling runtime/pprof.StartCPUProfile(w) with an http.ResponseWriter and then sleeping, or calling p.WriteTo(w, debug) on a runtime/pprof.Profile object. You can look at the source of net/http/pprof to see how it does it.
In a slightly better universe, net/http/pprof would have a RegisterHandlers(*http.ServeMux) function that could be used anywhere, you would be able to import it without anything being registered implicitly, and there would be another package (say net/http/pprof/sugar) that did nothing except call pprof.RegisterHandlers(http.DefaultServeMux) in its init. However, we don't live in that universe.
IBM WAS: 8.5.5 Version
On JSP pages have & tags, I receive below error
Error 500: java.lang.Exception: java.lang.VerifyError: JVMVRFY012
stack shape inconsistent; class=com/ibm/_jsp/_desktop,
method=_jspx_meth_c_set_0(Ljavax/servlet/jsp/PageContext;)Z, pc=73;
Type Mismatch, argument 1 in signature
org/apache/jasper/el/ELContextWrapper.:(Ljavax/el/ELContext;Ljavax/el/FunctionMapper;)V
does not match Exception Details:
Location:
com/ibm/_jsp/_desktop._jspx_meth_c_set_0(Ljavax/servlet/jsp/PageContext;)Z
#73: JBinvokespecial Reason: Type
'org/apache/jasper/runtime/ProtectedFunctionMapper' (current frame,
stack[8]) is not assignable to 'javax/el/FunctionMapper'
Current Frame: bci: #73 flags: { } locals: { 'com/ibm/_jsp/_desktop',
'javax/servlet/jsp/PageContext', 'javax/servlet/jsp/JspWriter',
'org/apache/taglibs/standard/tag/rt/core/SetTag' } stack: {
'org/apache/taglibs/standard/tag/rt/core/SetTag', 'uninitialized',
'uninitialized', 'java/lang/String', 'javax/el/ExpressionFactory',
'uninitialized', 'uninitialized', 'javax/el/ELContext',
'org/apache/jasper/runtime/ProtectedFunctionMapper' } Stackmap Table:
append_frame(#128,Object[#127],Object[#231],integer)
On reading https://www.ibm.com/support/pages/ibm-java-linux-howto-resolving-javalangverifyerror-jvmvrfy012-stack-shape-inconsistent, understand that the reason could be
code is compiled against a different library than the one being used at runtime
a class tries to extend a class declared as final
a method tries to override a super method that is declared as final
a wrong argument is passed to a method
It does look to be #4 - but the same code works in Tomcat and does not work in IBM WAS and am unsure why WAS is passing an incorrect argument. Any suggestions on how we can resolve this issue?
You may want to explore Servlet/JSP version compatibility.
WAS: 8.5.5 reference
Servlet 3.0
JSP 2.2
If you happen to be using Spring Boot:
2.2.x and 2.1.x require Servlet 3.1+
2.0.x supports Servlet 3.0
This looks like a cross-linkage between the javax.el library in your application and the version packaged in the server. When using PARENT_LAST, any Java EE APIs you include in the application are loaded twice, once from the server and once from the application (because the application loader doesn't delegate that load to its parents). Depending on the other classes/packages in play, you can have an instance in which a class ends up directly referencing one instance of the class and indirectly (through some other reference) referencing the other instance, and the JVM will throw a VerifyError in that scenario.
The easiest answer: If you are not 200% sure you NEED the version of the javax.el classes in the app, remove them, and this specific error should be impossible. If you are definitely dependent on that version, then it becomes trickier, as it might require adding additional stuff to the application (to avoid picking stuff up from the server), or it may be that this specific library simply can't be safely overridden with PARENT_LAST loading. That analysis would require a deeper look at the error stack and possibly a dive into detail trace of the class loading.
I want to use a console command from this bundle within my controller: http://knpbundles.com/dizda/CloudBackupBundle
The developer proposes cronjobs, however I want to use the command to backup my database from within my controller.
How would I do that?
I am getting this error message when i simply try to register this command as a service:
You have requested a non-existent service "backupcommandservice".
Thanks for the help!
commands don't quite work that way. Per the note on http://symfony.com/doc/current/cookbook/console/console_command.html#register-commands-in-the-service-container
registering a command as a service doesn't do much other than control location and dependency injection.
if you want to call a command: http://symfony.com/doc/current/components/console/introduction.html#calling-an-existing-command
that being said you shouldn't call commands from within a controller since you're basically asking to wait for this command to finish executing before you return a response. You'd be better off just sending a request to a queue box (for example beanstalk) and have a worker perform the job.
I have many servlets in a web applicaton; for some stange reason, only and only one of them always fails in initialization with the following error trace:-
00000045 ServletWrappe E SRVE0100E: Did not realize init() exception thrown by servlet MyServletX: java.lang.NullPointerException
at com.ibm.ws.webcontainer.WebAppPmiListener.onServletStartInit(WebAppPmiListener.java:120)
at com.ibm.ws.webcontainer.webapp.FireOnServletStartInit.fireEvent(WebAppEventSource.java:237)
at com.ibm.ws.webcontainer.util.EventListeners.fireEvent(EventListeners.java:48)
at com.ibm.ws.webcontainer.webapp.WebAppEventSource.onServletStartInit(WebAppEventSource.java:105)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.init(ServletWrapper.java:261)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:444)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:2841)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:220)
at com.ibm.ws.webcontainer.VirtualHost.handleRequest(VirtualHost.java:204)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:1681)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:77)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:421)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:367)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:94)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.requestComplete(WorkQueueManager.java:548)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.attemptIO(WorkQueueManager.java:601)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.workerRun(WorkQueueManager.java:934)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager$Worker.run(WorkQueueManager.java:1021)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1332)
I could not figure out if there is anything extra ordinary with this servlet. There is no init() method in this servlet and it extends HTTPServlet. Any idea what could be reason? I am using websphere server 6.0.x. How to get more debugging information in this case?
Well I don't know still cause of above error, but this is how it started working strangely:- i) Re-applied recommended fixes by IBM for my WAS version (especially there are IBM JDK upgrade related fix patches) ii) created a new profile of server iii) Install web application to new profile and it started working.
I don't think this is a product issue.
To debug this problem what i would suggest is to place a simple servlet (kind of Hello World) and deploy it to the server and see what happens.
initialization does not necessarily mean init() method alone.
If you have a static block in your servlet, if you have any variables that are initialized they would all be part of the initialization activity.
Look at the FFDC logs that were generated when this error occurred and that should provide you with clues.
As bkail mentioned, also ensure that yo have the latest fixpacks just to eliminate known problems with the product.
if the hello world servlet works, suggest you place hte servlet code here along with the SystemOut and System Err logs that correspond to this issue along with the relevant FFDC logs and i am sure most of us will be able to help you out with this
HTH
Manglu