Maybe someone had the same problem.
I use Weblogic at work. So, we have two small applications on it. And today it stopped writing logs(all logs stopped writing at the same time). Then, after three hours it writes in log “JVM called WLS shutdown hook. The server will force shutdown now” and shutdown. After start everything works fine.
But I want to understand, why this situation happened
Thanks
This happens when System.exit(int) is called. Check if some of the deployed components call System.exit instead of throwing an Exception. This also can be due to the JVM taking up the OS signals.Set the -Xrs option in the startup scripts in JAVA_OPTIONS if you are using Sun JDK.It reduces use of operating-system signals by the JVM.
Related
I've created an SNMP listener application for one of our servers that runs as a service and passively listens for any SNMP message alerts sent from another server, and when one is received is sends out a page/email to appropriate staff. I followeda few online tutorials for setting up the application as a windows service since it needs to run constantly and won't require input/interaction from a user, or interaction with any GUI/desktop applications.
For some reason, when I install the application as a service, it installs correctly, but doesn't actually seem to be working. When SNMP messages are sent to the server nothing happens. However, in my app.publish folder there's an SNMPTrapper.exe application,and if I run that exe on its own, then everything works fine. For the time being I'm using a workaround so that the Onstart section of the code for the service basically just launches the SNMPTrapper.exe application, and when the service is stopped, it finds and kills the SNMPTrapper.exe process. At this point though, the service itself doesn't seem to be working/doing anything. It's essentially just a way to get the SNMPTrapper.exe application launched.
Does anyone know what the issue may be? In some of the tutorials I've read through they outline how to setup polling intervals for the service, but I don't think that would be applicable since this service will essentially just run constantly to listen for new messages, it won't need to check for anything at a regular interval.
Right now pretty much all of my code is executed in Sub Main() except for a few function calls.
Any help would be greatly appreciated.
You don’t state how you’re doing any of this. For a windows service you get two messages from the system: OnStart and OnStop. The job of OnStart is to set up all the required code to do the job, then exit. It doesn’t take part in the work so you need a Task or Thread setting up to do that. The Task or Thread should loop until it gets a message, passed by OnStop, that we’re done. If you want a service that you can test from the command line then your Main routine needs to do exactly the same setup, then wait for a key to be pressed before sending an OnStop.
(As an aside, you ARE remembering to start the service once you have installed it?)
Are container-registered IHostedService's started in parallell or sequential?
Are the startups waited on before accepting incoming request?
If the startup crashes, how can this be detected? It seem to swallow this.
If a service crashes during operation, can it be configured to restart automatically?
I think I can answer most of these myself after some research:
They seem to start in the sequence they are registered, and not in parallell.
StartAsync is not waited on and requests are handled before StartAsync is completed (which can be mitigated with a custom middleware).
If StartAsync crashes it will go unnoticed (which I read somewhere should apparently be fixed for a future release).
If crashing during operation this will also go unnoticed and I haven't found a way to restart them with config, though it should be fairly easy to make a custom manager to restart them.
For various reasons I need to use HttpWebRequest instead of the built-in WWW class to call out to web services in our Unity project. I'm finding that Request.EndGetResponse hangs under certain circumstances. The issue is exacerbated when the debugger is attached--it does happen from time to time without the debugger, but happens close to 100% of the time when the debugger is attached. It is only happening when I'm calling a web service using HTTPS.
I plugged in Wireshark to look at the two traces. Oddly, the trace when the debugger is attached includes a "Handshake Failure" where the trace without the debugger does not. The other interesting thing is that the trace that works includes two [FIN, ACK] messages presumably from other failed attempts.
Ultimately I think I'm running into some known issues with the Mono 2.6 threadpool. That said, I don't understand what EndGetResponse is doing that could cause it to hang--I thought this was a synchronous operation. I also don't understand how attaching the debugger could affect the issue.
If there are any mono experts out there, I'd appreciate any insight!
My problem is, that I am running a webapp on Tomcat7 on a 2GB 2Core VPS and when the app crashes with heapoverflow exception Tomcat doesn't start or stop. When I try to access it via the browser it just hangs.
If I try to stop it looks like it stops but if I do it repeatedly it is supposed to throw an exception because it's already stopped, but this is not the case. Only after 15 minutes am I able to start it up again.
I know that I should solve the heapoverflow problem, but the thing is I am simply not able as the framework I am using turned out to be nod thread safe and I have to create a new instance of a memory heavy object for every request :( I tried to come round the problem by adding some basic controller which only allows certain amount of objects to be created and the rest of the request are redirected to a Sorry-page. Since it is for a UNI project and the main goal is not being able to serve hundreds of users it's not important to make the framework thread safe.
Still I need to know why Tomcat does it after it crashes. Also it would help if you would have a better idea how to limit the number of these objects being in the memory at the same time.
++++++++++
At the moment the only solution I can see is to get say 2GB of more RAM so I will be able to serve some 15-20 users at a time.
Generally after tomcat crashes with out of memory error it is in unusable state and the process has to be killed either manually or by using
catalina.sh stop -force
For a discussion on how to prevent those out of memory errors see
Dealing with "java.lang.OutOfMemoryError: PermGen space" error
Though ultimately you may need to throw more hardware at the problem.
This might also come handy:
Can I auto restart tomcat jvm on out of memory exception
I have an app and it fails randomly sometimes because my internet is not so fast (my app uses the webbrowser). How can I make my app restart itself it it fails? Or make my app click button1 on my form if it fails.
I have had similar problems in the past. I solved it by using scheduled tasks to start the app on a regular basis. On Startup the new version would attempt to stop the old version and if that failed, (because it was hung) it would kill the process of the old program.