If you are running Graylog in a Docker Container or Docker-Compose, you will sooner or late experience, that the Graylog-Server will use most of it’s heap space, which is set to 4Gi by default.

Assuming your Docker-Host has some more Memory to spare, you can increase the Heap Size by using an environment variable.

Set the -Xms to you desired minimum used memory and -Xmx to the allowed maximum.

services:
	graylog:
    	hostname: "server"
        image: "${GRAYLOG_IMAGE:-graylog/graylog:6.0}"
        ...  
		environment:
			# Xms: minimum allocated memory
			# Xmx: maximum allocated memory
			GRAYLOG_SERVER_JAVA_OPTS: "-Xms2g -Xmx8g -XX:NewRatio=1 -server -XX:+ResizeTLAB -XX:-OmitStackTraceInFastThrow"
        ports:
        ...  

Now restart the containers

docker compose up -d

and your Graylog-Server should now be able to use more memory.