How to set heap size for wildfly inside Docker container?

When using docker-compose set environment variable as follows!

environment:  - JAVA_OPTS=-server -Xms512m -Xmx2048m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -XX:+UseAdaptiveSizePolicy -XX:MaxMetaspaceSize=1024m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true-Djava.net.preferIPv4Stack=true

do not use " (quotes)!

You can pass the value of the JAVA_OPTS environment variable in the command used to run the docker container:

docker run -it --env JAVA_OPTS="-server -Xms2048m -Xmx6144m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true" jboss/wildfly

Alternatively, you can extend the standard image by creating a Dockerfile containing:

FROM jboss/wildfly:latestCOPY standalone.conf $JBOSS_HOME/bin/

and placing your modified standalone.conf in the directory next to it.

Then you can build it:

docker build -t my/wildfly:latest .

and run it:

docker run my/wildfly

I suggest you to use JAVA_TOOL_OPTIONS rather than JAVA_OPTS .Because JVM directly understand JAVA_TOOL_OPTIONS.