A bash script and systemd files for periodically logging memory use on a host

log-memory-usage.service

[Unit]
Description=Log memory usage and top processes on an EC2 instance running Amazon Linux 2023

[Service]
Type=oneshot
ExecStartPre=/usr/bin/mkdir -p /home/ec2-user/memlog
ExecStart=/home/ec2-user/log_memory_usage.sh /home/ec2-user/memlog/memory_summary.log /home/ec2-user/memlog/top_processes.log
StandardOutput=journal
StandardError=journal
User=ec2-user

log-memory-usage.timer

[Unit]
Description=Run memory usage logger every minute during working hours

[Timer]
OnCalendar=Mon..Fri *-*-* 08:00..18:00:00
Persistent=true

[Install]
WantedBy=timers.target

log_memory_usage.sh

#!/bin/bash

if [ -z "$2" ]; then
	echo "Usage: $0 <memory_summary_log_file> <top_processes_log_file>"
	exit 1
fi

MEM_SUMMARY_FILE="$1"
TOP_PROCESSES_FILE="$2"

CURRENT_TIMESTAMP=$(date)

# Get total and used memory in MiB and calculate percentage
# Use awk to pick up the second line of free -m output and format it
MEM_INFO=$(free -m | awk 'NR==2{printf "%sMiB %.2f%%", $3, $3/$2*100}')

# Output to memory summary file
echo "$CURRENT_TIMESTAMP Total Used Memory: $MEM_INFO" >>"$MEM_SUMMARY_FILE"

# Output to top processes file
echo "$CURRENT_TIMESTAMP" >>"$TOP_PROCESSES_FILE"
# Use if-else in awk to print header for the first line
ps aux --sort -rss | head -n 11 | awk '{if(NR==1) print $1, $11, "%MEM"; else print $1, $11, $4}' >>"$TOP_PROCESSES_FILE"

logger "Memory summary logged to $MEM_SUMMARY_FILE"
logger "Top processes logged to $TOP_PROCESSES_FILE"