It’s a common issue with Magento 2 , after a while Elasticsearch will crashed if it could not find enuaf RAM.

Why this should happen? when ES started it try to use all RAM to save it data. all thing will be okay but when Apache or PHP needs to more RAM based on their processed they can not find memory because that Elasticsearch will crashed.

How we can set limit on Elasticsearch prepossess. it’s easy just follow this setup:

1- open /etc/elasticsearch/jvm.options by nano or vim

2- check -Xms4g and -Xmx4g are commented or not.

3 : please comment them.

4: Create new file on this directory : nano /etc/elasticsearch/jvm.options.d/heat.options

the file name is optional but extension .options is essential

5: put below line and save file

-Xms1g
-Xmx4g

Xms1g : show we set minmum RAM to 1 Gig

Xmx1g : show we put maxmum RAM to 4 Gig

after thos setup you need to restart Elasticsearch :

sudo service elasticsearch restart

reference : elastic.co/guide/en/elasticsearch/reference/7.16/advanced-configuration.html#set-jvm-heap-size