memory-limit.sh

#!/bin/bash
# by spiritlhl
# from https://github.com/spiritLHLS/Oracle-server-keep-alive-script

if [[ -d "/usr/share/locale/en_US.UTF-8" ]]; then
  export LANG=en_US.UTF-8
  export LC_ALL=en_US.UTF-8
  export LANGUAGE=en_US.UTF-8
else
  export LANG=C.UTF-8
  export LC_ALL=C.UTF-8
  export LANGUAGE=C.UTF-8
fi
pid_file=/tmp/memory-limit.pid
if [ -e "${pid_file}" ]; then
  # 如果 PID 文件存在，则读取其中的 PID
  pid=$(cat "${pid_file}")
  # 检查该 PID 是否对应一个正在运行的进程
  if ps -p "${pid}" >/dev/null; then
    echo "Error: Another instance of memory-limit.sh is already running with PID ${pid}"
    exit 1
  fi
  # 如果 PID 文件存在，但对应的进程已经停止运行，删除 PID 文件
  rm "${pid_file}"
  rm /dev/shm/file
fi
echo $$ >"${pid_file}"

while true; do
  mem_total=$(free | awk '/Mem/ {print $2}')
  mem_used=$(free | awk '/Mem/ {print $3}')
  mem_usage=$(echo "scale=2; $mem_used/$mem_total * 100.0" | bc)
  if [ $(echo "$mem_usage < 25" | bc) -eq 1 ]; then
    target_mem_usage=$(echo "scale=0; $mem_total * 0.25 / 1" | bc)
    echo "target_mem_usage: $target_mem_usage"
    stress_mem=$(echo "$target_mem_usage - $mem_used" | bc)
    echo "stress_mem: $stress_mem"
    stress_mem_in_mb=$(echo "scale=0; $stress_mem / 1024" | bc)
    echo "stress_mem_in_mb: $stress_mem_in_mb"
    fallocate -l "${stress_mem_in_mb}M" /dev/shm/file
    sleep 300
    rm /dev/shm/file
  else
    sleep 300
  fi
done

rm "${pid_file}"