CODEWITHSUNDEEP
spring-boot
Robin Sun
Robin Sun

Reputation: 1618

Why SpringBoot continues to consume a lot of memory even after the load test is done

My website is a SpringBoot application deployed in Linux server. I add JMX so that I can monitor this website by JVisualVM. I run it as below:

nohup java -Djava.rmi.server.hostname=10.25.161.45 -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.port=22222 -jar sms-web.jar &

I start load test and I can see that the memory consume is escalating very fast, as the red rectangle shows here. This is understandable because there are a lot of TCP connections establised and disposed while in load test. But after the load test is done, it still continues to consume a lot of memeory, sometimes to 800MB, as you can see in the green rectangle. What happens under the cover? Why it consums so much memory?

Edit: Is there any way for JVM to do a through GC to release a lot of memory?

enter image description here

Upvotes: 1

Views: 2230

Answers (1)

Dimitri Mestdagh
Dimitri Mestdagh

Reputation: 44685

This is quite normal behaviour for any Java application. As long as your application is running, objects will be created, even when it's not being used (threadpools being checked/refreshed, ...).

That means that it's only normal that heap memory goes up over time. However, when necessary, the garbage collector will run, and will destroy any objects that are no longer in use. That's why you can see a clear memory usage drop at certain times.

Now, the garbage collector will only run when necessary. This process often happens when your memory in use (blue line) is getting close to the memory that is allowed to be used (orange line).

This explains two things:

  1. It explains the zigzag lines during your loadtest, which means many objects were being created and being destroyed afterwards by the garbage collector.
  2. It explains why your application can use more than 800MB of memory before freeing anything, because there was still more memory it allowed to be consumed.

Now, if you think it's problematic that your application allows about 1GB (or more) memory to be consumed, you'll have to play around with your JVM settings, and perhaps reduce the -Xmx parameter to a reasonable amount. Make sure to run some loadtests afterwards, to see how your application behaves when reducing the maximum allowed memory, as it could have a higher impact on the performance of your application since the garbage collector would have to run more often.

Upvotes: 1

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