from time to time jboss serwer throws "An unhandled exception has occurred:
java.lang.OutOfMemoryError: Java heap space".
Could you please explain me how it works?
A few infromation:
Jboss is running all the time in standalone mode on Windows.
From standalone.conf "JAVA_OPTS=-Xms1G -Xmx1G -XX:MaxPermSize=256M"
I deploy ~50MB war file, after tests I remove it.
What is possible cause of this Java heap space exception?
Should I restart server between following deploys?
Is there any command to clean heap space?
If I understand corectly increasing of -Xmx argument will not help. It will only delay the appearance of the exception. Right?
Thanks in advance
What is possible cause of this Java heap space exception?
On the face of it, the explanation is simple. The JVM has run out of heap space, and the GC is unable to reclaim enough space to continue.
But what caused the JVM to get into that state?
There are a number of possible explanations, but they mostly fall into three classes:
Your application has a memory leak.
Repeated deploys are causing memory to leak.
There are no memory leaks, but occasionally your application is getting a request that simply needs too much memory.
Should I restart server between following deploys?
That may help if the deploys are causing the leaks. If not, it won't.
Is there any command to clean heap space?
There is no command that will do this. The JVM will already have run a "full" GC before throwing the OOME.
If I understand corectly increasing of -Xmx argument will not help. It will only delay the appearance of the exception. Right?
That depends. If the root cause is #3 above, then increasing the heap size may solve the problem. But if the root cause is #1 or #2, then tweaking the heap size will (at best) cause the JVM to survive longer between crashes.
My recommendation is to start by treating this as a "normal" (cause #1) memory leak, and use a memory profiler to identify and fix leaks that are likely to build over time.
If / when you can definitively eliminate cause #1, consider the others.
I absolutely agree with the answer from Stephen C, i just want to show you a possible way how you can analyse it.
A minimal tool for monitoring the memory is jstat and comes with JDK.
After starting JBoss you can start monitoring the memory and GC with
jstat -gc <JBOSS_PID> 2s
The output can then be loaded for example in an excel.
Now when you recognize something strange happens with the memory, take a heap dump:
jcmd <JBOSS_PID> GC.heap_dump <filename>
jcmd also comes with JDK.
You can than load the heap dump into MAT and analyse it. It takes some practice and patience to work with MAT. They also have a good Tutorial. You can also compare heap dumps in MAT.
I also suggest you add XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=<path>" to your JAVA_OPTS.
Please increase the MaxPermSize variable and check it will work.
JAVA_OPTS=-Xms1G -Xmx1G -XX:MaxPermSize=512M
Related
I am programming a Java application allowing to minimize any boolean expression using QuineMcCluskey methodology. When I compile my code, I have an OutOfMemory Error with the message "Java heap space"!
If I understand, the exception may have several origins:
The memory space allocated to the JVM heap is insufficient to create the objects required by the application.
A memory leak prevents the garbage collector from releasing objects that are yet unused but still have references. Thus these objects are never released and occupy more and more space in the pile until occupying all the available space.
...
I know that use a profiling tool may be necessary to analyze the contents of the memory of the JVM and determine the origin of the memory consumption. But how use thoses tools ? Have I to modify xmx and xms data ? What could be the consequences if I change them ?
(I know also that it is necessary to optimize my code).
What are the different debugging steps ?
Furthermore, this application has to be use by lot of users (so by diferent computers...)
As you can see, I have lot of questions about this problem (I am a novice lol)... That's why I create this post.. I would like to resolve this problem by the better way and also, learn good reflexes.
Thank you!
Increasing of the memory is NOT the solution, unless you have unlimited resources!
If that happens in production or any machine other than your own, you can force the JVM which runs your service to generate a dump file which you can then download and analyse by adding VM flag -XX:+HeapDumpOnOutOfMemoryError to your jvm.conf file.
That is pretty useful when the machine that runs the app becomes unresponsive so no JMX connections could be made in order to run Oracle's JMC (or similar) monitoring tools. If you are for some reason able to get to the VM you can run the flight recording and try to analyse which method is causing the OOM.
Check here how to use flight recording.
And check this for heap dump analysis preview
It is possible to increase heap size allocated by the JVM by using command line options Here we have 3 options
-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size
java -Xms16m -Xmx64m ClassName
It is also possible to increase heap size allocated by the JVM in eclipse directly In eclipse IDE goto
Run---->Run Configurations---->Arguments
And set VM arguments
I have a java application running on tomcat with xmx=2GB
I see memory consumption slowly raises on tomcat, exceeding the 2GB heap limit.
Going through this forum I know that there more than just the heap consuming the memory.
The problem is that memory keeps raising above 3 and even 4GB until no more memory is available on the machine, and I need to restart tomcat.
Looking at the GC log, I see that the heap does not exceed 2GB.
My question is how can I find and analyze the memory been used.
Also, can it be code related?
It is obviously some kind of leak, but I don't know how to locate and fix it, or even identify the source (my code, tomcat, etc).
Thanks
Maayan
Since it is more likely to be a memory leak in your code than in tomcat, I'd start here.
Create a heap dump using JMap, and try to analyze it using a tool like the Eclipe Memory Analyzer
How to identify the issue when java OutOfMemoryError or stackoverflow comes in production. By which reason it is coming or why the server is down.
For example I am developing an application which is lived on production and UAT. Instantly on production java OutOfMemoryError or stackoverflow.
Then how can we track this issue, by which reason it has happened ? Is there any technique that can tell me by which code flow this is happening ?
Please explain it. I have faced this issue many times.
If you face it in production and you cannot really reason about it from stacktraces or logs, you need to analyze what was in there.
Get the VM to dump on OOM
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath="/tmp"
And use that for analysis. The memory analyzer tool (http://eclipse.org/mat/) is a good standalone program for this analysis.
The Oracle docs:- Troubleshooting Memory Leaks has detailed explanation on it:
This error is thrown when there is insufficient space to allocate an
object in the Java heap or in a particular area of the heap. The
garbage collector cannot make any further space available to
accommodate a new object, and the heap cannot be expanded further.
.....
An early step to diagnose an OutOfMemoryError is to determine what the
error means. Does it mean that the Java heap is full, or does it mean
that the native heap is full? To help you answer this question, the
following subsections explain some of the possible error messages,
with reference to the detail part of the message:
Exception in thread "main": java.lang.OutOfMemoryError: Java heap
space
See 3.1.1 Detail Message: Java heap space.
Exception in thread "main": java.lang.OutOfMemoryError: PermGen space
See 3.1.2 Detail Message: PermGen space.
Exception in thread "main": java.lang.OutOfMemoryError: Requested
array size exceeds VM limit
See 3.1.3 Detail Message: Requested array size exceeds VM limit.
Exception in thread "main": java.lang.OutOfMemoryError: request
bytes for . Out of swap space?
See 3.1.4 Detail Message: request bytes for . Out of
swap space?.
Exception in thread "main": java.lang.OutOfMemoryError:
(Native method)
See 3.1.5 Detail Message: (Native method).
UPDATE:-
You can download the HotSpot VM source code from OpenJDK. If you want to monitor and track the memory footprint of your Java Heap spaces ie, the young generation and old generation spaces is to enable verbose GC from your HotSpot VM. You may add the following parameters within your JVM start-up arguments:
-verbose:gc –XX:+PrintGCDetails –XX:+PrintGCTimeStamps –Xloggc:<app path>/gc.log
You can use jvisualvm to manage your process at the runtime.
You can see memory, heap space, objects etc ...
This program is located in your bin directory of your JDK.
It's best to try to reproduce the problem in place where you are free to debug it - on dev server or on your local machine. Then try to debug, look for recursive invocations, heap size and what objects are being created. Unfortunately it's not always easy to reproduce prod env (with it's load and so on) on local machine, therefore finding the root cause of such error might be a challenge.
The amount of memory given to Java process is specified at startup. memory divided into separate areas, heap and permgen being the most familiar sub-areas.
While you specify the maximum size of the heap allowed for this particular process via -Xmx,
the corresponding parameter for permgen is -XX:MaxPermSize. 90% of the Java apps seem to require between 64 and 512 MB of permgen to work properly. In order to find your limits, experiment a bit.
to solve this issue you have change your VM arguments
-Xms256m -Xmx1024m -XX:+DisableExplicitGC -Dcom.sun.management.jmxremote
-XX:PermSize=256m -XX:MaxPermSize=512m
add above two line in VM argument i am sure you will not face this problem any more
to know more about go to OutOfMemory
Low memory configuration :-
It is possible that you have estimate less memory for your application for example your application need 2 Gb of memory but you have configured only 512 Mb so here you will get an OOME(Out-of-memory errors )
Due to Memoryleak :-
Memory leak is responsible for decreasing the available memory for heap and can lead to out of memory error for more read What is a Memory Leak in java?
Memory fragmentation :-
It is possible that there may be space in heap but it may be not contiguous . And heap needs compaction . Rearrange its memory.
Excess GC overhead :-
Some JVM implementations, such as the Oracle HotSpot, will throw an out-of-memory error when GC overhead becomes too great. This feature is designed to prevent near-constant garbage collection—for example, spending more than 90% of execution time on garbage collection while freeing less than 2% of memory. Configuring a larger heap is most likely to fix this issue, but if not you’ll need to analyze memory usage using a heap dump
Allocating over-sized temporary objects:-
Program logic that attempts to allocate overly large temporary objects. Since the JVM can’t satisfy the request, an out-of-memory error is triggered and the transaction will be aborted. This can be difficult to diagnose, as no heap dump or allocation-analysis tool will highlight the problem. You can only identify the area of code triggering the error, and once discovered, fix or remove the cause of the problem.
for more pls visit my site
http://all-about-java-and-weblogic-server.blogspot.com/2014/02/main-causes-of-out-of-memory-errors-in.html
I have used Thread Pool for New IO server design . I have used newFixedThreadPool as a Executors factory method for thread pool creation. My server is throwing Exception when i execute my server for 20 to 30 minute . how to handle this exception.
java.lang.OutOfMemoryError: Java heap space
Obviously you are using too much memory, so now you need to find out why. Without your source it is very hard to to say what is wrong, but even with source it can be problematic when the program start to become complex.
What I have found helpful is to take memory dumps and look at them in tools such as Memory Analyzer (MAT). It can even compare several dumps to see what kind of objects are allocated. When you get an idea of what objects exists which you don't think should be there you can use the tool to see what roots it has (which objects has a reference to it).
To get a memory dump form a running java program use jmap -dump:format=b,file=heap.bin and to automatically get a memory dump when your program gets and OutOfMemoryError you can run it with java -XX:+HeapDumpOnOutOfMemoryError failing.java.Program
normally its java -Xms5m -Xmx15m MyApp
-Xms set initial Java heap size
-Xmx set maximum Java heap size
and in eclipse under java run configuration as VM argument
-Xms128m
-Xmx512m
-XX:permSize=128M
-XX:MaxPermSize=384M
You can defnitely try increasing the HEAP SIZE and check if you are getting the issue.
However, I would prefer you to try profiling your application to find out why your heap size and where the memory is being consumed.
There are few Profilers available as open source you can try.
I am facing "Out Of Memory Error Exception" while running a web service application over jboss 4.2
how can I increase the memory of jboss ? and will this solve the problem ?
You should first confirm if the memory usage is not abnormal. If it is not, it is probably a good idea to increase the memory allocation. JBoss default memory allocation is rather small at the default setting.
You want to confirm that the memory shortage is heap shortage (it could be permgen etc. if it is permgen, please refer to general OOME (OutOfMemoryError) questions). If you are using Java 1.6 you just need to read the exception message to determine this.
Once you confirm it is a heap shortage, it is advisable to confirm that there is no memory leak occurring before you go for a bigger heap size. To do this, you can attach a heap monitor like visualVM and monitor heap usage under stress (for more information see this: http://olex.openlogic.com/wazi/2009/how-to-fix-memory-leaks-in-java/).
Once you are done with this, and you are sure that you have a legitimate heap shortage, you can edit run.conf (Linux) or run.bat (Windows) to allocate more heap. You can search for JAVA_OPTS and change -Xmx512m to something like -Xmx1024m.
You can increase the memory for JBoss, but make sure to find out why it uses more memory than expected to make sure the problem doesn't come back to bite you.
Set this in your shell before launching JBoss while experimenting:
JAVA_OPTS="-Xms512m -Xmx1024m"