CODEWITHSUNDEEP
javadockerheap-memory
Tung Nguyen
Tung Nguyen

Reputation: 1924

How to set Java heap size (Xms/Xmx) inside Docker container?

As of raising this question, Docker looks to be new enough to not have answers to this question on the net. The only place I found is this article in which the author is saying it is hard, and that's it.

Upvotes: 61

Views: 154377

Answers (8)

Ram Pratap
Ram Pratap

Reputation: 520

I am little late on the question, I will use @Fritz Duchardt answer.

But if someone is struggling and getting "Invalid initial heap size" , then we should have two separate args for -Xms ans -Xmx as below :

"java","-Xms256m","-Xmx1G","-Dspring.profiles.active=${ENV}","-jar","app-0.0.1-SNAPSHOT.jar"

Upvotes: 0

Muhammad Tariq
Muhammad Tariq

Reputation: 4634

You can set the Xms and Xmx values in the dockerfile using the following way as well.

ENTRYPOINT ["java", "-Xms128M ", "-Xmx256M", "-jar", "your-precious-service-1.0.0.jar"]

You can also ignore the Xms value and just set the Xmx value.

ENTRYPOINT ["java", "-Xmx256M", "-jar", "your-precious-service-1.0.0.jar"]

For more info please read : https://akobor.me/posts/heap-size-and-resource-limits-in-kubernetes-for-jvm-applications

Upvotes: 3

Fritz Duchardt
Fritz Duchardt

Reputation: 11860

Update: Regarding this discussion, Java has upped there game regarding container support. Nowadays (or since JVM version 10 to be more exact), the JVM is smart enough to figure out whether it is running in a container, and if yes, how much memory it is limited to.

So, rather than setting fixed limits when starting your JVM, which you then have to change in line with changes to your container limits (resource limits in the K8s world), simply do nothing and let the JVM work out limits for itself.

Without any extra configuration, the JVM will set the maximum heap size to 25% of the allocated memory. Since this is frugal, you might want to ramp that up a bit by setting the -XX:MaxRAMPercentage attribute. Also, there is -XX:InitialRAMPercentage for initial heap size and -XX:MinRAMPercentage for containers with less than 96MB RAM.

For more information on the topic, here is an excellent overview.

Upvotes: 46

Riswan chatholi
Riswan chatholi

Reputation: 159

you can do it by specifying java options environment in docker compose file 

env: 
  - name: _JAVA_OPTIONS
    value: "-Xmx1g"

it will change the heap size.

Upvotes: 10

jbarrueta
jbarrueta

Reputation: 5175

I agree that it depends on what container you're using. If you are using the official Tomcat image, it looks like it's simple enough, you will need to pass the JAVA_OPTS environment variable with your heap settings:

docker run --rm -e JAVA_OPTS='-Xmx1g' tomcat

See How to set JVM parameters?

Upvotes: 50

hawkeye
hawkeye

Reputation: 35692

Note that in a docker-compose.yml file - you'll need to leave out the double-quotes:

  environment:
  - JVM_OPTS=-Xmx12g -Xms12g -XX:MaxPermSize=1024m

or

  environment:
  - CATALINA_OPTS=-Xmx12g -Xms12g -XX:MaxPermSize=1024m

Upvotes: 58

occasl
occasl

Reputation: 5454

You can also just place those settings in your image so something like the following would exist in your Dockerfile:

ENV JAVA_OPTS="-XX:PermSize=1024m -XX:MaxPermSize=512m"

Upvotes: 23

Mark O'Connor
Mark O'Connor

Reputation: 77951

It all depends how your Java application is packaged and how it's configuration files are exposed using Docker.

For example the official tomcat image states that the configuration file is available in the default location: /usr/local/tomcat/conf/

So easy to override entire directory or just one configuration file:

docker run -it --rm -p 8080:8080 -v $PWD/catalina.properties:/usr/local/tomcat/conf/catalina.properties tomcat:8.0

Upvotes: 6

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