Set better defaults for Solr max heap size to prevent OOMs

[seanhamlin]

Whenever Solr runs out of heap space, the result is fairly catastrophic:

Caused by: java.lang.OutOfMemoryError: Java heap space

2022-08-29 23:06:21.232 WARN  (qtp1543148593-73) [   x:core] o.e.j.s.HttpChannel /solr/core/select
java.lang.OutOfMemoryError: Java heap space

The pod enters a weird endless cycle of the solr process being killed by Java, which in turn causes the health check to fail, so the pod is restarted, which leads to consuming all the RAM (again) ... on and on.

The defaults for the environment variable are from the upstream Solr image https://solr.apache.org/guide/7_0/taking-solr-to-production.html#memory-and-gc-settings

SOLR_JAVA_MEM="-Xmx512m"

Proposed change

Where there is not an override, to default the environment variable to

SOLR_JAVA_MEM="-Xms128m -Xmx2g"

Perhaps something like this in an entrypoint?

DEFAULT_SOLR_JAVA_MEM="-Xms128m -Xmx2g"
SOLR_JAVA_MEM="${SOLR_JAVA_MEM:-$DEFAULT_SOLR_JAVA_MEM}" 

So a minimum of 128MB, and a max of 2GB RAM.

If there is an environment variable override, to prefer that (similar to now).

[nicksantamaria]

According to the docs there should be a variable SOLR_JAVA_MEM which I can not find anywhere in this repo. Is there some magic that uses this variable, or are the docs incorrect?

Upon more reading it looks like this envvar is consumed by solr itself, and isn't specific to the container image.