We are running druid cluster using Docker on Azure, and we're using Azure Blob Storage as the deep storage. We've noticed there is a

solr

process running in coordinator container. Does anyone know what is the role of

solr

process inside the Druid coordinator? It seems to be consuming quite a lot of CPU. Is there some druid configuration we can use to control this process and its cpu usage?

we don't use

solr

as part of Druid, is it possible this was added to your docker containers some other way?

I don't think so. It seems the parent process of

solr

is the coordinator process:

PID    PPID COMMAND         COMMAND
1747821   10455 solr            ./solr
  10455   10401 java            /usr/bin/java --add-exports=java.base/jdk.internal.misc=ALL-UNNAMED --add-exports=java.base/jdk.internal.ref=ALL-UNNAMED --add-opens=java.base/java.nio=ALL-UNNAMED --add-opens=java.base/sun.nio.ch=ALL-UNNAMED --add-opens=jdk.management/com.sun.management.internal=ALL-UNNAMED -server -XX:+ExitOnOutOfMemoryError -XX:+UseG1GC -Duser.timezone=UTC -Dfile.encoding=UTF-8 -Djava.io.tmpdir=var/tmp -Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager -Dderby.stream.error.file=var/druid/derby.log -Xmx256m -Xms256m -XX:MaxNewSize=250m -XX:NewSize=250m -XX:MaxDirectMemorySize=1280m -Dlogfilename=coordinator -XX:+UseG1GC -XX:+ExitOnOutOfMemoryError -cp /tmp/conf/druid/cluster/_common:/tmp/conf/druid/cluster/master/coordinator-overlord:lib/*: org.apache.druid.cli.Main server coordinator

not that i can see; there is no reference to

solr

in our code (just searched the apache/druid repository). there is a

solr-solrj

library pulled as part of the extension

druid-ranger-security

but it just seems to be coming in as a dependency. i do not see code that actually launches a

solr

process

We're using a private image off of the

apache/druid:25.0.0

image. Our private image has benign changes (adding config files), and runs

./druid.sh coordinator

at the end. We can reproduce it by using azure for deep storage.

very odd since the image doesn't have solr on it-- i tried

find / -name solr