wait_timeout.sh

#!/bin/bash
#
# Wait for the system load to hit a set level. Can be used in init
# scripts to avoid insane load spikes. Use the return value to abort
# starting processes if the load remains too high.
# 
# wait_timeout.sh 4 || exit 0

# Default sleep interval in seconds.
SLEEP=30

# How many sleeps before we give up?
TIMEOUT=10

# Unless we get a CLI param, wait until the system load is 2(.something) or lower.
typeset -i TARGET=${1:-2}

if [ $TARGET -eq 0 ]; then
  typeset -i TARGET=2
fi

echo "Waiting until the system load reaches $TARGET. Will give up after $((SLEEP * $TIMEOUT)) seconds."

typeset -i COUNT=0
typeset -i LOAD=$(cut -d. -f1 < /proc/loadavg)
while [ $LOAD -gt $TARGET ]; do
  if [ $COUNT -gt $TIMEOUT ]; then
    echo "Reached the timeout of $((SLEEP * $TIMEOUT)) seconds, giving up."
    exit 1
  fi
  echo "Current load $LOAD is above $TARGET, sleeping for $SLEEP seconds..."
  sleep $SLEEP
  typeset -i LOAD=$(cut -d. -f1 < /proc/loadavg)
  COUNT=$(($COUNT+1))
done

echo "Current load $LOAD is below $TARGET, continuing."
exit 0