In WSO2 EI 6.6, proxy stopped working abruptly. upon analyzing observed an error in the wso2 carbon log "GC Overhead limit exceeded", after this error nothing happening in the EI.
Proxy logic is to get the data from Sql server table and form an xml and send it to an external API. Proxy runs every 5 mins interval and in every interval maximum of 5 records will be pushed to an API.
After restarting the wso2 carbon services, proxy are started working. currently we are restarting the services every 3 days to avoid this issue.
Need to know how to identify the potential issue and resolve this.
This mean the JVM has run out of allocated memory. There can be many reasons for this. For example, if you haven't allocated enough memory to the JVM you can easily run out of memory. If that's not the case you need to analyze a memory dump and see what's occupying the memory causing it to fill up.
Generally, when you see the mentioned error the JVM automatically creates a heap dump(heap-dump.hprof) in the <EI_HOME>/repository/logs directory. You can try analyzing the dump to find the root cause. If the server doesn't generate a memory dump, manually take a memory dump when it's occupied than the expected level and analyze it.
Related
I see a degradation in response times within myapplications. After a server restart, response times are acceptable. However, after some time, which depends on the workload on the system, the response times degrade and the server has to be restarted to return to good performance.
Are you monitoring the Java heap usage with verbose garbage collection (GC) logs?
The behavior you describe can happen if the heap has enough free space after a restart, then gradually fills with long-lived objects as the workload runs. This may be caused by the heap simply being too small, or the application may have a memory leak, using heap and not releasing it for collection when the associated work is completed. When there is not enough free heap space, the application work slows down because the JVM spends excessive time running GC.
You can learn more about Java GC troubleshooting in our documentation
https://www.eclipse.org/openj9/docs/vgclog/
You can also open a support case to get assistance from WebSphere/Java troubleshooting experts, if you have a support arrangement with IBM.
I created and ran a simple SpringBoot application to accept some requests. I used jconsole to check the Heap Memory Usage and I saw this periodic increase followed by GC, I don't know the reason for the increases. Are there any Objects keep being created (because I think the instances are imported to container when the application starts)?
Spring boot has background processes which may consume your resources despite on absent requests to your app, for example jobs, etc.
Those spikes are expected and regular for any Java app based on any more less complex framework. GC algorithm depends on your jvm version, but could be overridden. The graph shows normal situation, from time to time memory consumed for some activities and after some time GC wake up and do the cleaning.
In case if you want to check what exactly objects caused memory spike you may try to use Java Flight Recorder or regular heap dump analysis using Eclipse memory analyser.
For current case Java Flight Recorder would be more convenient and suitable.
I am using Windows Azure SDK 2.2 and have created an Azure cloud service that uses an in-role cache.
I have 2 instances of the service running under normal conditions.
When the services scales (up to 3 instances, or back down to 2 instances), I get lots of DataCacheExceptions. These are often accompanied by Azure db connection failures from the process going in inside the cache. (If I don't find the entry I want in the cache, I get it from the db and put it into the cache. All standard stuff.)
I have implemented retry processes on the cache gets and puts, and use the ReliableSqlConnection object with a retry process for db connection using the Transient Fault Handling application block.
The retry process uses a fixed interval retrying every second for 5 tries.
The failures are typically;
Microsoft.ApplicationServer.Caching.DataCacheException: ErrorCode:SubStatus:There is a temporary failure. Please retry later
Any idea why the scaling might cause these exceptions?
Should I try a less aggressive retry policy?
Any help appreciated.
I have also noticed that I am getting a high percentage (> 70%) cache miss rate and when the system is struggling, there is high cpu utilisation (> 80%).
Well, I haven't been able to find out any reason for the errors I am seeing, but I have 'fixed' the problem, sort of!
When looking at the last few days processing stats, it is clear the high cpu usage corresponds with the cloud service having 'problems'. I have changed the service to use two medium instances instead of two small instances.
This seems to have solved the problem, and the service has been running quite happily, low cpu usage, low memory usage, no exceptions.
So, whilst still not discovering what the source of the problems were, I seem to have overcome them by providing a bigger environment for the service to run in.
--Late news!!! I noticed this morning that from about 06:30, the cpu usage started to climb, along with the time taken for the service to process as it should. Errors started appearing and I had to restart the service at 10:30 to get things back to 'normal'. Also, when restarting the service, the OnRoleRun process threw loads of DataCacheExceptions before it started running again, 45 minutes later.
Now all seems well again, and I will monitor for the next hours/days...
There seems to be no explanation for this, remote desktop to the instances show no exceptions in the event log, other logging is not showing application problems, so I am still stumped.
I implemented a web application to start the Tomcat service works very quickly, but spending hours and when more users are entering is getting slow (up to 15 users approx.).
Checking RAM usage statistics (20%), CPU (25%)
Server Features:
RAM 8GB
Processor i7
Windows Server 2008 64bit
Tomcat 7
MySql 5.0
Struts2
-Xms1024m
-Xmx1024m
PermGen = 1024
MaxPernGen = 1024
I do not use Web server, we publish directly on Tomcat.
Entering midnight slowness is still maintained (only 1 user online)
The solution I have is to restart the Tomcat service and response time is again excellent.
Is there anyone who has experienced this issue? Any clue would be appreciated.
Not enough details provided. Need more information :(
Use htop or top to find memory and CPU usage per process & per thread.
CPU
A constant 25% CPU usage in a 4 cores system can indicate that a single-core application/thread is running 100% CPU on the only core it is able to use.
Which application is eating the CPU ?
Memory
20% memory is ~1.6GB. It is a bit more than I expect for an idle server running only tomcat + mysql. The -Xms1024 tells tomcat to preallocate 1GB memory so that explains it.
Change tomcat settings to -Xms512 and -Xmx2048. Watch tomcat memory usage while you throw some users at it. If it keeps growing until it reaches 2GB... then freezes, that can indicate a memory leak.
Disk
Use df -h to check disk usage. A full partition can make the issues you are experiencing.
Filesystem Size Used Avail Usage% Mounted on
/cygdrive/c 149G 149G 414M 100% /
(If you just discovered in this example that my laptop is running out of space. You're doing it right :D)
Logs
Logs are awesome. Yet they have a bad habit to fill up the disk. Check logs disk usage. Are logs being written/erased/rotated properly when new users connect ? Does erasing logs fix the issue ? (copy them somewhere for future analysis before you erase them)
If not. Logs are STILL awesome. They have the good habit to help you track bugs. Check tomcat logs. You may want to set logging level to debug. What happens last when the website die ? Any useful error message ? Do user connections are still received and accepted by tomcat ?
Application
I suppose that the 25% CPU goes to tomcat (and not mysql). Tomcat doesn't fail by itself. The application running on it must be failing. Try removing the application from tomcat (you can eventually put an hello world instead). Can tomcat keep working overnight without your application ? It probably can, in which case the fault is on the application.
Enable full debug logging in your application and try to track the issue. Run it straight from eclipse in debug mode and throw users at it. Does it fail consistently in the same way ?
If yes, hit "pause" in the eclipse debugger and check what the application is doing. Look at the piece of code each thread is currently running + its call stack. Repeat that a few times. If there is a deadlock, an infinite loop, or similar, you can find it this way.
You will have found the issue by now if you are lucky. If not, you're unfortunate and it's a tricky bug that might be deep inside the application. That can get tricky to trace. Determination will lead to success. Good luck =)
For performance related issue, we need to follow the given rules:
You can equalize and emphasize the size of xms and xmx for effectiveness.
-Xms2048m
-Xmx2048m
You can also enable the PermGen to be garbage collected.
-XX:+UseConcMarkSweepGC -XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled
If the page changes too frequently to make this option logical, try temporarily caching the dynamic content, so that it doesn't need to be regenerated over and over again. Any techniques you can use to cache work that's already been done instead of doing it again should be used - this is the key to achieving the best Tomcat performance.
If there any database related issue, then can follow sql query perfomance tuning
rotating the Catalina.out log file, without restarting Tomcat.
In details,There are two ways.
The first, which is more direct, is that you can rotate Catalina.out by adding a simple pipe to the log rotation tool of your choice in Catalina's startup shell script. This will look something like:
"$CATALINA_BASE"/logs/catalina.out WeaponOfChoice 2>&1 &
Simply replace "WeaponOfChoice" with your favorite log rotation tool.
The second way is less direct, but ultimately better. The best way to handle the rotation of Catalina.out is to make sure it never needs to rotate. Simply set the "swallowOutput" property to true for all Contexts in "server.xml".
This will route System.err and System.out to whatever Logging implementation you have configured, or JULI, if you haven't configured.
See more at: Tomcat Catalina Out
I experienced a very slow stock Tomcat dashboard on a clean Centos7 install and found the following cause and solution:
Slow start up times for Tomcat are often related to Java's
SecureRandom implementation. By default, it uses /dev/random as an
entropy source. This can be slow as it uses system events to gather
entropy (e.g. disk reads, key presses, etc). As the urandom manpage
states:
When the entropy pool is empty, reads from /dev/random will block until additional environmental noise is gathered.
Source: https://www.digitalocean.com/community/questions/tomcat-8-5-9-restart-is-really-slow-on-my-centos-7-2-droplet
Fix it by adding the following configuration option to your tomcat.conf or (preferred) a custom file into /tomcat/conf/conf.d/:
JAVA_OPTS="-Djava.security.egd=file:/dev/./urandom"
We encountered a similar problem, the cause was "catalina.out". It is the standard destination log file for "System.out" and "System.err". It's size kept on increasing thus slowing things down and ultimately tomcat crashed. This problem was solved by rotating "catalina.out". We were using redhat so we made a shell script to rotate "catalina.out".
Here are some links:-
Mulesoft article on catalina (also contains two methods of rotating):
Tomcat Catalina Introduction
If "catalina.out" is not the problem then try this instead:-
Mulesoft article on optimizing tomcat:
Tuning Tomcat Performance For Optimum Speed
We had a problem, which looks similar to yours. Tomcat was slow to respond, but access log showed just milliseconds for answer. The problem was streaming responses. One of our services returned real-time data that user could subscribe to. EPOLL were becoming bloated. Network requests couldn't get to the Tomcat. And whats more interesting, CPU was mostly idle (since no one could ask server to do anything) and acceptor/poller threads were sitting in WAIT, not RUNNING or IN_NATIVE.
At the time we just limited amount of such requests and everything became normal.
Disclaimer: I am more of a programmer and have little knowledge of JBOSS.
When we deployed the system, it works properly in the test environment. However in production, since there are multiple users and a lot of data are being updated/saved, some issues occurred. Double updates are being created, some functions are not working unless the server is restartedd. I'm thinking that this may be corrected by modifying whatever session or memory parameter JBOSS has. So we could prevent restarting the server every time an error occurs.
Question: What parameter or jboss configuration should we edit to accommodate multiple users and a large number of transactions.
You need to investigate the reason for your application not behaving the way you want to. Some Points you can consider :
Log request in Jboss support.
Try increasing Java heap size. (this can be done by editing entry in standalone.conf).
Try enabling gc logs to see , if your garbage is properly collected or not.
Check for memory leakage in code.
try to analyze thread dumps to check whether some of your threads are being blocked or not.
See what if you server CPU and memory Utilization is high or not.
I'm not sure what version of JBoss you are using, but if you are wanting to increase the JVM memory you can modify the following line in the run.bat file in your bin folder:
set JAVA_OPTS=%JAVA_OPTS% -Xms128m -Xmx512m
Xms = Minimum size and Xmx is Maximum size. If you think it is due to lack of resources, you may want to increase it to something like this:
set JAVA_OPTS=%JAVA_OPTS% -Xms512m -Xmx1024m
Does everything work normally with only 1 or very few users using the system? To me it seems more like a coding issue.
Check the Heap size of JVM and set it according to Machine RAM available.
You must have performance testing done before you deploy to production. You can check the behaviour of your code in performance testing using some monitoring tool or JMX tool.
Tune the paramter like Heap size, GC alogrithm, you might want to define fixed size of young generation
Tune the thread as well.
https://developer.jboss.org/wiki/ThreadPoolConfiguration?_sscc=t