Mongo uses too much memory and is automatically shut down by the system

background ：

There is an online application for mongo(v 4.4.4), Generally, the system business volume is relatively small , There is no problem with the system , Recently, the system business volume has suddenly increased . Find out mongo Hang up , After reboot , The next day I hung up again .

screening ：

cd /var/log
grep "mongod" messages

Conclusion ：

From the query results, we can see , “Out of memory: Kill process 24567 (mongod)”, Express mongod Too much memory , System auto kill fall mongo 了 .

Access to information （In-Memory Storage Engine — MongoDB Manual）,mongo The default maximum memory of the storage engine is server memory 50%-1GB, Other services are deployed on my server , Occupy 50% Memory -1GB This will cause the server to run out of memory . So the Mongo kill .

Solution ：

Sure By setting cacheSizeGB, Set the maximum memory used by the cache .