Limit MongoDB memusage. Original src [https://www.techpaste.com/2016/04/limit-mongodb-memory-usage/]

mongodb_memory_limiter.sh

#!/usr/bin/env bash
# Script to limit mongoDB memory usage.
# Author: TechPaste.Com
############################################

export _arg="$1"
if [ -z "$_arg" ]
then
    echo "Memory to Allocate is empty"
    echo "Usage: ./mongodb_memory_limiter.sh 1536"
    echo "Note: Here 1536 is 1536 MB of RAM"
    exit 1;
fi

_check_tools() {
    _cmd=$1
    command -v $_cmd >/dev/null 2>&1 || { echo >&2 "Script requires $_cmd but it's not in path or not installed. Aborting."; exit 1; }

}
_pre_setup() {

    _check_tools ps
    _check_tools pmap
    _check_tools cgcreate
    _check_tools sync
    _check_tools cgclassify
    _check_tools tail
    _check_tools free

    memaloc=`echo "$(($_arg * 1024 * 1024))"`
    mongopid=`ps -eaf | grep mongod |grep -v grep | awk -F" " '{print $2}'`
    if [[ $mongopid == "" ]]; then

    echo " Mongo DB is not running. Please start the Mongo DB service first.";
    echo "Example start command: mongod --fork --dbpath /data/db/ --logpath /opt/mongodb/mongodb.log"
    exit 1;

    fi
    echo
    echo "Mongo DB Process: "
    echo
    echo "########################################################"
    ps -eaf | grep mongod |grep -v grep
    echo "########################################################"
    echo "Current MongoDB RAM usage:"
    echo "$(( `pmap -x $mongopid | tail -1 | awk -F" " '{print $3}'` ))KB= $(( `pmap -x $mongopid | tail -1 | awk -F" " '{print $3}'` / 1024 ))MB"
    echo "########################################################"
    echo
}

_mem_setup() {
    echo
    echo "1. Creating control group :MongoLimitGroup."
    echo
    echo "Running cgcreate -g memory:MongoLimitGroup"
    cgcreate -g memory:MongoLimitGroup
    echo
    echo "2. Specifying $memaloc bytes memory needs to be allocated for this group"
    echo
    echo "echo $memaloc > /sys/fs/cgroup/memory/MongoLimitGroup/memory.limit_in_bytes"
    echo $memaloc > /sys/fs/cgroup/memory/MongoLimitGroup/memory.limit_in_bytes
    echo
    echo "3. Dropping pages already stayed in cache..."
    echo
    echo "sync; echo 3 > /proc/sys/vm/drop_caches"
    sync; echo 3 > /proc/sys/vm/drop_caches
    echo
    echo "4. Assigning a server to be created for control group"
    echo
    echo "cgclassify -g memory:MongoLimitGroup $mongopid"
    cgclassify -g memory:MongoLimitGroup $mongopid
    echo
    echo "########################################################"
    echo "Post Setup MongoDB RAM usage:"
    echo "$(( `pmap -x $mongopid | tail -1 | awk -F" " '{print $3}'` ))KB= $(( `pmap -x $mongopid | tail -1 | awk -F" " '{print $3}'` / 1024 ))MB"
    echo "########################################################"
}

main() {
    _pre_setup
    _mem_setup
}

main